Panorama Tutorial by Barninga

8/8/2019 Panorama Tutorial by Barninga

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Barninga's panorama tutorial

A foreword A panorama is an image made of several pics, stitched together. This technique allows very

detailed images at resolutions that no camera can give. Panoramas are also very effective,

due to their particular format: their height/width ratio is much smaller than the common ratios

found in the digital photography field. While most digital cameras take pics with a 2/3 or 3/4

ratio, panoramas usually have a ratio smaller than 1/3: 1/5 or 1/6, and even 1/7 or 1/8 arequite common values.

Panoramas are rather easy to create in the digital field, while traditional film pics would

require technical means and skills that only very expert photographers can have: therefore

this guide is oriented to digital image processing. However, taking the pics with a traditional

camera and scanning them allows the pics to be assembled into a panorama just as if they

had been taken with a digital equipment. Thus, panorama concepts apply, after all, to

traditional photography also.

This tutorial is not a complete and comprehensive guide to panorama images. It's just a

tutorial. Not a really quick one, maybe, but it addresses the basic aspects, in the effort togive suggestions about how to get the most out of a bunch of carefully taken shots, and

avoid common errors and problems.

I am not a professional photographer and, to make things even worse, English is not my own

language; so, i apologize in advance for any errors and ambiguities this document may

contain.

Taking the pics It is obvious, but it is anyway worth the while saying:

in order to compose a panorama image, the single

pics must partially overlap (see image). The wider the

overlapping area, the better the result. In some

cases, it is still possible to stitch the pics even if they

overlap just a little, however, as a general rule, they

should overlap by 1/3, or at least 1/4 of their width (or

height) to get optimal results.

Page 1 of 22

Note how the leftmost part of the pic on the right

overlaps the rightmost part of the pic on the left.



Some useful suggestions

Vertical vs. horizontal panoramas

Pics can be taken panning horizontally or vertically; in both cases, however, it is important

to pan following an horizontal or vertical axis with the maximum possible precision. For

example, while taking the pics for an horizontal panorama, the horizon line should be at the

same height in all the shots (see also: “Tripod shooting”, pg. 3). If not, you'll get a wavy

panorama, and you'll have to crop a thicker border, at the risk to lose important details and

parts of the image we originally planned to get.

Vertical vs. horizontal camera position

The camera itself can be held in horizontal (landscape) or vertical (portrait) position. There's

not an optimal choice for all situations, anyway it is clear that shooting in landscape mode

requires less pics to cover the whole width of the view. However, the panorama image will

be little in height and, more than likely, you'll have to take two rows of pics, instead of one, to

properly compose the view. Needless to say, the bottom portion of any pic in the upper row

must overlap with the top portion of the corresponding pic in the lower row.

Frame slant

Besides following an horizontal or vertical axis, it is important not to slant the pics. Many

stitching softwares correctly handle perspective distortions caused by the panning

movement of the camera and modify the pics accordingly, so that objects boundaries match

perfectly; however programs often assume that the pics have the same slant: even little

angles of rotation can cause ghost effects (see also: “Attention needed”, pg. 5) in

overlapping areas.

The panning movement

Most of the times, you will stay (or place the tripod) in a place that offers a good view overthe scene, and take the pics from there. This means that the camera will rotate following

your face, or on the tripod head: these two different situations can lead to significantly

different results, since, in order to avoid parallax errors (and therefore perspective changes

between the pics; see also: “Parallax errors”, pg. 11), the lens should rotate on its nodal

point , that is the point where the light rays converge and flip over; it is usually located near

the center of the lens barrel. Now, using a tripod does not ensure, per se, that the lens

rotates on its nodal point; on the other hand, freehand shooting will certainly guarantee that

the lens does not rotate on its nodal point.

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An example of a wavy panorama. The camera was not moved along a horizontal path; it will be difficult to properly crop it without losing

important details.



Parallax errors, if not excessive, are usually

managed quite well by stitching programs,

which apply more or less noticeable

deformations to horizontal and vertical lines

to make them properly match across the

shots. Therefore, objects in panoramas can

have a sort of “fish-eye lens” look. The

higher the parallax error, the more

noticeable the deformation; in addition, near

objects are more affected than far ones.

Therefore, if the panorama foreground

features near objects, it is particularly

important to find the nodal point of the lens;

if this is not possible, shooting with a tripod will usually give better results.

Tripod shooting

Usually, only pro tripod heads allow sliding the camera back

and forth, and side to side, to bring the nodal point of the lens

exactly above the pivot axis of the tripod head itself. Anyway,

here's a simple method to find the nodal point of a lens:

✔ First, the lens must be centered on the pivot rod of the

tripod. This can be done easily, by looking at the lens

from its front side, after mounting the camera on the

tripod: the lens is centered when its vertical diameter is

aligned with the pivot rod of the tripod. Now, you have to

locate two vertical lines, like two poles or street lamps,

placed at different distances from the camera. Looking

in the viewfinder,

pan the camera until both the objects appear in

the frame. Then, keep on panning: if the

distance between the two objects remains the

same as you pan the camera, the lens is

rotating on its nodal point. If the distance

changes (that's the effect of a parallax error),

slide the camera to the front or to the rear and

repeat the test, until you find the correct

placement.

It is also important that the camera rotates along a

vertical or horizontal path (see also: “Vertical vs.

horizontal panoramas”, pg. 2): when using a tripod,

this can be achieved by leveling it. Many tripod heads

incorporate bubble levels along two of their sides:

when both the air bubbles are centered, the head is

perfectly horizontal. Unfortunately, such a leveling

system is not suitable for panoramas, since you could

Page 3 of 22

These two pics do overlap, but the parallax error, caused by their

different pespective, will make the stitching very difficult, or

impossible at all (see also “Parallax errors”, below).

Check that the vertical diameter of the

lens is aligned with the pivot rod.

If the camera rotates on the lens nodal point (yellow),

the distance "D" between the red and blue poles

remains constant while panning.



need to change the vertical angle of the head to take more than one row of pics (or you

could take a vertical panorama); in addition, since the camera rotates, one horizontal shot is

not enough: the head must follow a horizontal (or vertical) path along the whole panning

movement. What you need is a perfectly vertical pivot rod: a simple and cheap bubble

leveler is the perfect tool.

✔

Stick the bubble level to the side of the pivot rod andadjust the rod position until the air bubble of the level is

centered; then, move the level around the rod by

approximately 90° and adjust the rod again. For a

perfect vertical alignment you'll probably have to repeat

this procedure a couple of times or more, particularly if

the tripod is placed on an inclined surface.

Once the placements of the lens and the pivot rod are done,

you are ready to shoot. Start at one end of the view: when

shooting a horizontal panorama you can start, for example,

with the leftmost frame of the upper row. Before shooting, lookcarefully in the viewfinder to locate a detailed and clearly

recognizable object on the right of the frame. After shooting, pan right until that object can be

seen on the left of the frame: this ensures that the two shots will overlap. Repeat this simple

procedure until you take the rightmost shot of the row and take note of how many you shot.

Now, pan down: locate a reference object near the bottom of the frame and pan unitl it

appears to be near the top of the frame. Locate a new reference near the left side of the pic

and shoot; then pan left until the reference is near the right side of the frame. You just have

to repeat the steps done for the first row, but, this time, move from right to left. Shoot as

many pics as you shot for the first row; if a third row of images is needed, all you have to is

to iterate the process once more.

Freehand shooting

When shooting without a tripod, things don't change so much. Basically, you lose the

guarantee of panning along a vertical or horizontal path and keeping the camera perfectly

horizontal or vertical. However, with some additional care, very good results can still be

achieved.

✔ The object taken as a reference for

panning steps can be used also as areference for the vertical positioning

of the camera. You should take care

that it remains at the same distance

from the top and bottom sides of the

frame. If you are shooting a vertical

panorama, check that the reference

object remains at the same distance

from the left and right sides of the

frame while moving the camera.

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The corner of the roof (circled in red) is a good reference point for

both horizontal panning and vertical alignment.

To ensure that the pivot rod of the

tripod is vertical, do several checks around it using a bubble leveler.



✔ In horizontal panoramas, it is a good idea to follow the horizon line only if it is...

horizontal: the sea is good, a hill is not and will produce a wavy panorama.

✔ If the camera has both a viewfinder and LCD screen, the best option is always to use

the viewfinder. Sticking the camera to your face will help to keep it steady and you will

also get a better view of small details. This way the lens will rotate more near its

nodal point, than it would if kept 20 or 30 cm. far from your eyes. This means reducedparallax errors (see also: “The panning movement”, pg. 2).

✔ If the view is not too wide (say, no more than 90-100°), place yourself facing its

center; then rotate your head and/or torso to pan from one extremity to the opposite

one, without leaving your position. Keep in mind that this could lead to lowering the

camera near the extremities of the view, if it is wider than that angle. For extra large

panoramas (from 100 to 360°), it's better to start by facing one extremity and, after

each shot, move your feet, slightly, following the panning direction, just enough to be

facing the next portion of view to catch, keeping your heels in place. The goal is to

rotate yourself as if you had a pivot axis going from our neck to our heels.

Camera aided panning

Some digital cameras allow you to overlay, in the LCD screen, an extremity of the last phototaken and the current view, allowing a “live” of how the two shot will overlap. Though

apparently this feature looks like the perfect solution, it has several limits that can prevent

achieving the goal:

✔ Usually, only horizontal panning is supported, and only in one direction (left to right).

✔ Only landscape mode shooting is supported.

✔ It does not avoid parallax errors (see also: “The panning movement”, pg. 2).

So, in most situations, freehand shooting with some care is the only way to take the pics.

Camera aided panning can be effective after finding the nodal point of the lens.

Attention needed

It should be noted that even widely overlapping shots do not guarantee, per se, a flawless

stitching. It is very important that the overlapping area contains detailed objects, or at least

elements that can be matched to merge the images in the correct position. Examples of

objects that probably will make stitching difficult if they are the only ones found in the

overlapping areas:

✔ Clouds, even if rich with lights and shadows.

✔ Water, particularly sea waves (they move!).

Page 5 of 22

A 360 degrees panorama, taken without tripod. Paying some attention to the camera movement allows to achieve good results even

when shooting freehand. The relatively long distance between the camera and the subject minimized parallax errors.



✔ Sand, unless it has very contrasted shadows.

✔ A clear blue sky and any other flat, uniform surface.

A different kind of problem may be caused by moving objects:

✔ If they are outside the overlapping areas and move along as you pan, they might

appear more than once in the panorama image. Sometimes this can be a nice surreal

effect, but most of the times it will rather be an annoyance which you'll have to get rid

of by manually editing the panorama.

✔ If, on the contrary, they are found within the overlapping areas, you'll get “ghosts”

(see also: “Some useful suggestions”, pg. 2) in the panorama, since the stitching

software will merge a moving object, as caught in one pic, with the background of

another pic. Again, you will have to work on the panorama (for example, cloning

some background) to get a clean image. However, the problem can often be

corrected on the pics before stitching them: it should be possible to copy a portion of

the background of the first pic, from the same position where the moving object

appears in the second pic, and paste it over the latter.

This is why it is often very difficult to compose a clean panorama when it contains people. It

is always better to avoid ghosts and duplicates in advance: whenever possible, the shots

should be taken so that people (or other moving subjects) appear only in one pic.

When taking 360° panoramas:

✔ It is better to avoid overlapping that the first and the last shot. This could confuse the

stitching program.

For any panorama, and particularly for views around 180° wide:

✔ It is better to take the shots from a position facing the center of the view. If you shootfrom a point significantly nearer to one of the extremities, the panorama will possibly

have an exhaggerated perspective, that will make it look weird.

Digging deeper: camera settings

Since you're about to take a series of shots which will have to be stitched together, the more

features they share, the better the result. In most cases, you'll have to choose settings that

can be considered good enough for all the shots, even if they are not the best for any of

them.

Focal length

If your lens can zoom, set the focal length to a value that allows you to catch the amount of

detail you want, in a reasonable number of pics. You'll probably have to pan along the view

of interest, trying several zoom settings. Remember that, once the focal length (zoom) has

been set, it must not be changed anymore, since this would impact focus. In addition, if you

change the zoom while taking the shots, subjects will have different dimensions and

proportions, and the stitching will not be possible at all. Some attention must be paid to the

fact that, while a very long focal length requires a very high number of pics to cover the

whole view, a very short focal length (i.e.: wide-angle) introduces some distortion in the pics,

Page 6 of 22



particularly on vertical lines: this can make the stitching process more difficult and possibly

unsuccessful, since it enhances parallax errors. Usually, if there are relatively near objects in

the view, any zoom above 50 mm (full-frame equivalent) will give good results; such

distortion will be fairly noticeable on distant objects. Thus, focal length will be far less than

an issue while taking pics, for example, of an open landscape.

Focus

In a panoramic view, there are

often objects placed at very

different distances. Choose an

appropriate subject in the view,

and focus it: all the shots will have

to be taken with that same focus

setting. If your camera allows, let it

automatically focus the subject and

then disable autofocus; if not,focus it manually. If autofocus

cannot be disabled, you can still

take the shots, but at the risk to

have different focus settings for overlapping shots: this will not necessarily add depth of field

to the panorama, but almost surely will cause the overlapping areas to be blurred if a focus

change occurs between two pics. If you need a long depth of field, the right way to get it is to

set the aperture to high values. After setting the focus, don't change the zoom, unless you

know for sure that your lens doesn't need a focus adjustment in consequence of a change in

focal length.

Exposure

A digital camera controls exposure through three parameters: shutter time, aperture and

sensibillity (ISO). Due to intrinsic technical limitations, no sensor can deal -under certain

conditions of light- with the huge excursion in lightness between darker and brighter areas in

a single frame; this is even more true when taking several shots of a wide scene. Changing

exposure to optimize every single frame seldom helps: there's the risk to obtain a panorama

that appears to be vertically striped with darker and brighter areas. Again, it's better to

experimentally find which parameters yield a mean good result for all the pics, and set the

camera manually. If the camera does not allow a full manual exposure, the best choice is toset the aperture and let the camera choose the shutter time; differences in brightness can be

somehow corrected later, before starting the stitching process. The same applies if the

camera only shoots in fully automatic mode.

White balance

White balance, from an oversimplified perspective, is a sort of digital filter that compensates

light colour casts, so that what appears white in the real world, is white in the photograph

also; all other colours are shifted accordingly. Cameras, by default, set white balance

automatically: this is no good news this time, since there can be different light colour casts in

different portions of the chosen view. For example, shadow areas often have a different cast

Page 7 of 22

The facade of this building is actually rectlinear. The shots were taken from a

short distance, with a short focal length (wideangle lens): this caused a

noticeable distortion.



from sunlit areas; once again, this can result in a striped aspect of the panorama image, with

colours changing cast and intensity. So, it is important that white balance is set manually to

an appropriate value. Most cameras offer a choiche among several predefined settings

(sunlight, neon bulbs, cloudy or sunny weather...), top cameras also allow a white balance

fine tuning: try several settings and choose the one that works better for that particular view.

When shooting in open air, it is often enough to test a single, but representative, frame of the

panorama; when shooting indoor it should be taken in account that different kind of lamps

usually emit light with different colour casts. Trying different settings for several portions of

the view and choosing the one that gives the most uniform colours throughout the view will

definitely guarantee better results.

Stitching the pics To get a good panorama image it is necessary that the pics be stitched together, correctly

overlaying the overlapping parts and blending them so that colours transition appear smooth

and natural. Theoretically, this could be done by hand, pasting each pic over its neighbour

by means of an image editing program. However, due to parallax errors (see also: “The

panning movement”, pg. 2), it is very likely that rectilinear lines need to be curved to avoidunnatural angles and/or ghost effects on pic boundaries (see also: “Some useful

suggestions”, pg. 2).

Manual stitching

When parallax errors are very small (it happens when the lens rotates on its nodal point

and/or you shoot distant subjects), stitching the pics by hand is possible and can give good

results anyway. If, for example, you have to stitch a horizontal panorama from a set of pics,

you can follow some simple steps in your preferred image editing program. The names ofthe commands needed to perform the various tasks can vary from one program to another,

but the logic remains unchanged.

✔ First of all, it is useful to open all the pics and compare then onscreen. If some of

them have different brightness or colour casts, it is better to correct them now, using

the appropriate tools (color curves, color levels, color balance, brightness, contrast).

Save the changes and close the pics (to free precious memory).

Page 8 of 22

A panorama of an underground station. The lights on the left and the neon bulbs on the right cause very different colour casts: several

tries were made taking shots of the leftmost and rightmost parts of the view with different white balance settings. However, it was not

possible to eliminate completely the yellow cast on the left, without accepting a slight greenish cast on the right.



✔ Then, create a new pic. Its height should be about 20%-30% more than the height of

the pics, while its width should be equal to the width of the pics, multiplied by their

number. You'll have to crop some width at the end, since the shots overlap.

✔ After opening the leftmost

pic of the series (assuming

you are composing ahorizontal panorama),

copy&paste it into the newly

created panorama. Position

it near the left side, centered

in height. Now, you can

close the pic.

✔ After opening the second

pic, select it all and feather

the selection by, say, 100 ormore pixels. The wider the

feather, the better the

blending; but make sure that

the feather is not wider than

the overlapping area,

otherwise you'll get a faded

out stripe where the first pic ends. Copy the selection to the clipboard and close the

pic.

✔ After pasting it to the panorama, set the opacity of the selection to less than 100%, sothat you can see the first picture through it. This will allow to match the overlapping

parts more easily. This

should be done at 100%

zoom, by searching small

and crisp details and

moving the selection so that

they match perfectly

between the two shots. A

simple way to understand if

the match is perfect, is tomove the selection around

very slightly and slowly and

see when the details you

are working on appear

perfectly focused. If, when

moving the selection, they

go out of focus and appear

slightly blurred around their

contour, take the selection

back where it was.

Page 9 of 22

Manual stitching, step 1. The opacity of the selection (pasted pic) has been set to

50%; dragging it as shown by the arrow will make the pics overlay perfectly. Note

how the boundary of the selection fades out (it is feathered by 100 px).

Manual stitching, step 2. The images match; however the selection, after

resetting its opacity to 100%, appears to be darker than the first pic. Some

adjustement of colours and brightness is needed.



✔ When satisfied with the placement of the selection, reset its opacity to 100% and

zoom out the panorama, in order to see if the colour blending is smooth enough. If

not, it's time to apply the colour tools again on the selection, until you cannot tell

anymore where one pic ends and the other starts. Finally, anchor the selection to the

panorama image (that is, make the selection become a fixed part of the image;

editing programs usually have an explicit command or menu item for this operation).

✔ The last three steps have to be iterated for all the pics (remember to save the

panorama from time to

time!); when all the shots

have been anchored to the

panorama, it's time to apply

global colour corrections as

needed.

✔ The resulting panorama may

require additionalcorrections, like, for

example, perspective,

rotation of the whole image,

rotation of portions of the

image: more on this later

(see also: “Cosmetics”,

pg. 16).

✔ Last, when everything else

is done, crop the panoramato the desired boundaries.

Unfortunately, when trying to match overlapping areas, you will probably discover what

parallax errors and ghost effects are, and how they can prevent to obtain a seamless

stitching.

Ghosts

A ghost appears as a misplaced

shadow or a semi-transparent

object.

✔ If a ghost is caused by a

moving subject within the

overlapping area, you can

get rid of it by erasing the

subject from one of the two

pics before anchoring the

selection. Sometimes, you

will achieve a better result

Page 10 of 22

Manual stitching, step 3. After playing a little with the colour curves tool and the

contrast tool, one could not tell anymore where the boundary between the two

pics is.

Particular of a panorama. In the pic on the left a ghost is clearly visible; on the

right, it has been amended by copying the two people from one of the two pics and pasting them into the panorama image.



by erasing portions of it from one pic and other potions from the other pic. Again,

setting the opacity of the selection to less than 100% will be of great help to work

easily with a good precision. Use a fuzzybordered eraser in order to produce erased

areas with invisible boundaries. See the image for a different, effective, strategy.

✔ If a ghost is caused by an unwanted slant of the camera, you can rotate the selection

until its inclination is suitable for a perfect match. Rotation tools, by default, rotate theselection around its center: this is usually a good choice. The program draws some

handles around the selection; the rotation is performed by dragging one of them.

Sometimes, you can get better results by rotating the selection around a different

point: many programs highlight the rotation center and allow to move it by means of

drag&drop.

Parallax errors

Parallax errors can cause misalignments between the same object in the overlapping areas

of two different shot. As said above, the result can be a ghost, particularly for rectilinear

lines. Sometimes, particularly with small subjects, they can appear in the form of duplicated

objects or broken lines:

✔ A ghost can be caused by parallax errors. The

slant of the pic is right, but some objects just

cannot be matched, because they were shot

from different perspectives. This happens,

most of the times, to long rectilinear lines

(walls, roofs, hill edges...) and has the

appearance of a faded dupe of the object.

Usually, it is convenient to deal with this kind ofghosts after the stitching is completed; if they

are disturbingly noticeable, a good way to get

rid of them is to use the clone tool with a fuzzy-

bordered brush, since it will allow to paint over

the ghost, picking colours and shapes from

some suitable portion of the image.

✔ For duplicated objects, just like for ghosts, a

simple solution can be to erase one of the two

appearances of the object. In some cases,

instead, it is possible (or necessary) to makethe two appearances overlap (almost)

perfectly, by applying to the selection the perspective tool of the image editing

program. Such tools usually display handles on the corners of the selection; by

dragging one of them, alter the shape of the selection itself, as if it were seen from a

different angle.

✔ For broken lines, the only possible solution is to apply to both the images a spherical

distortion effect or filter: it's a complex job, that seldom gives good results, since it is

quite difficult to find the right parameters for the filter, and it is usually necessary to

Page 11 of 22

In the upper part of the facade of the church, a ghost

is clearly visible. It was caused by a parallax error (see also “The panning movement”, above).



undo and redo several times the operation on both images before the lines overlap. A

stitching software can do it quickly and better.

Software stitching

Some image editing programs, like Adobe Photoshop ® , have native stitching capabilities;

some other programs, like The Gimp, can support panoramas through plugins (Panorama

Tools, http://panotools.sourceforge.net). There's plenty of stitching tools, out there on the

Internet. some are free, some require to pay a license fee. Some programs offer a complete

control of stitching operations but are quite complex to use: they usually require that you

visually set several matching point, that is, details that appear in both the overlapping areas,

and this has to be done between each shot and all of its neighbours. It is a tedious process,

but it is very effective when the shots do not overlap enough for automatic stitching. On the

other hand, some programs automate the process completely, allowing a little control on

what they're doing and no chances to improve the image they build by default.

Autostitch

Autostitch (http://www.autostitch.net) is a popular stitching program, developed at the

University of British Columbia: its demo version is free -not as in “speech”, but at least as in

“beer”- and, though not fully functional, it is capable to completely automate the stitching

process of a set of pics with really excellent results, allowing at the same time to control

several working options. It is currently developed only for MS Windows ® , but it runs

flawlessly on Linux under Wine (http://www.winehq.org); its engine powers some commercial

panorama software for MS Windows ® and MacOS ® .

Autostich's main window has a menu, whose items are:

✔ File : it allows to

load a group of

pics by doing a

multiple selection

in the File → Open

dialog box. It also

has a File → Exit

item.

✔ Edit : it allows to

control several

working settings

(Edit → Options )

✔ Stitch : it launches

the stitching job

(Stitch → Stitch ). It

must be noted that

the stitching

process also starts

automatically after loading the pics through the File menu; the Stitch command is

Page 12 of 22

Autostitch's main window. The Wine icon in the top-left corner shows that it was actually

running under Linux when the screenshot was taken.



useful to stitch again the same set of pics after changing parameters in the

Edit → Options dialog box.

✔ Help : it allows to display the Help → About window.

So, an effective way to use Autostitch can be the following one:

✔ First, set some options (but most of the times the defaults will do) in the Edit → Options window

✔ Then, through the File → Open dialog box, load the images that compose the

panorama. As said above, the process will start automatically and will produce an

image, called pano.jpg , in the same directory where the original pics are. By default,

Autostitch creates a downsized panorama: since the computing time increases as the

final size of the panorama increases, this is very useful to get a test image in a bunch

of seconds.

✔ Now, you can change options in the Edit → Options window and redo the stitching: it is

not necessary to load the pics again; simply select Stitch → Stitch and you're done.

✔ When you are satisfied with the result, you can set to 100% (or whatever suits your

needs) the size of the panorama (Edit → Options window) and launch the stitching

process one more time. you'll get (after a considerably longer time) the final version

of the panorama (again, called pano.jpg ), ready for cosmetic adjustments which you

will do in your preferred image editing program (see also: “Cosmetics”, pg. 16).

Page 13 of 22

Autostitch's Edit->Options window. The values shown are the startup defaults.



Autostitch's major problem is (at the time of writing) an inexistent or very poor

documentation. Several stitching options produce subtle effects and their names sound

cryptic to the non-specialist; in addition, the program has no online help. Here is a brief

description of the parameters available in the Edit → Options window: since it is empirically

derived from practice, it cannot be considered exhaustive, or trusted as being error-free.

✔ Output size : the size of the panorama can be set as an absolute value in pixels byspecifiying its height or its width; the other dimension will be calculated proportionally,

based on the original size of the pics. Alternatively, you can specify the percentage,

relative to the original size the panorama would have if the pics were stitched without

resizing. In order to save time, it is a good practice to generate a small version of the

panorama to check if some parameter change (or other adjustment) is needed.

✔ Blending method : it is the algorithm used to merge the opverlapping areas and to

smooth colour differences. Selecting "None " causes the pics to be matched and

overlaid without any colour smoothing: this option is suitable for quick tests and to

see how the pics are distorted by Autostitch in order to get perfect matches. When

producing the final version of the panorama, the best choice is "Multi-band ": it is

slower than "Linear " but produces a more accurate smoothing. The Multi-band

algorithm is influenced by two parameters, both called “Blending ”. It looks like

increasing their value causes a slightly better smoothing, but the computing time

increases considerably.

✔ Gain compensation : this option offers a way to deal with differences in brightness

among the pics. Autostitch will lighten darker pics, and darken lighter ones. Thealgorithm is controlled by two parameters, called "Gain mean " (the mean amount of

modification) and "Gain " (a measure of the difference between the mean and the

actual adjustment Autostitch will apply to the pics): higher values of "Mean " cause a

more evident modification of the brightness of the whole panorama (a value of 0 or

less produces a black image), while a higher "Sigma " will allow the software to modify

each single pic more deeply (to approximate that mean - but 0 or less produces a

white image). This option should be used with care, since it can cause

overexposition; the "Gain compensation " checkbox is unchecked by default and must

be checked to activate the algorithm.

Page 14 of 22

A panorama produced by Autostitch, with the "Blending method" option set to "None". The pic boundaries and colour differences are

clearly visible, as well as the deformations introduced to compensate parallax errors.



✔ Crop settings : these parameters allow to crop the image. Since the original pics can

be curved and stretched to compensate parallax errors, panoramas seldom have

rectlinear borders: when “Auto crop ” is checked, Autostitch builds an image that

contains the whole panorama image, and paints black the outer padding area. After a

stitching operation done with “Auto crop ” checked, the four crop settings are set with

the values chosen by the program; they can be changed and Autostitch will use the

new values in the next stitching operation, provided that “Auto crop ” is unchecked.

“Theta min ” and “Theta max ” control the horizontal amplitude of the image, in

degrees. When Autostitch is launched, they are set to -180 and 180 respectively, thus

allowing a 360° view. “Phi max ” and “Phi min ” control the vertical amplitude, again in

degrees. By default, they are set to -90 and 90 respectively, thus allowing a 180°

view. In other words, a panorama can cover a view that goes from the ground under

your feet to the sky above your head, all around you: an interesting experiment is to

use these values to check how our actual panorama is mapped into that space. Most

of the times, the best choice is to leave “Auto crop ” checked; however, reducing the

field of view, and thus causing the panorama to be cropped automatically, can avoid

to crop it manually to get rid of unwanted padding.

✔ Matching options : these parameters influence the algorithm that Autostitch uses to

detect which pics have operlapping areas and to match them. Usually the default

values work very well; however, if the program does not recognise some matches

and therefore fails to compose the panorama (this happens when overlapping areas

are not wide enough), try increasing the "SIFT image size " (in absolute values, or

percentage) and/or decreasing “Alpha ” and “Beta ”. On the other hand, if Autostitch

matches pics that should not actually match, try decreasing the "SIFT image size "

and/or increasing “Alpha ” and “Beta ”. The "Max iterations " parameter influences the

overall precision of the algorithm: the higher its value, the higher the precision (butalso the higher the time needed to complete).

✔ Orientation settings : if “Auto Straighten ” is checked, Autostitch tries to straighten out

wavy panoramas (see also: “Vertical vs. horizontal panoramas”, pg. 2). The three

related parameters “Theta ”, “Phi ” and “Psi ” can modify the shape of the image, when

the default result is not satisfactory. Positive values of “Theta ” rotate the panorama

counterclockwise, while negative values rotate clockwise; the image is also slightly

curved like an upside-down U. Positive values of “Phi ” bend the panorama like an

upside-down U, while negative values bend it like a U. Positive values of “ Psi ” rotate

the panorama clockwise; its persective is slightly curved on the right side, while it is a

bit enlarged on the left side. Negative values of “Psi ” rotate the image

counterclockwise; its persective is slightly curved on the left side, while it is a bit

enlarged on the right side. “Theta ”, “Phi ” and “Psi ” work even if “Auto straighten ” is

not checked, but their effect is dimmed. These parameters can be useful to correct

wavy panoramas.

✔ Image rotation : the default choice, “None ”, is suitable for pics that were taken with the

camera in landscape orientation. If the pics were taken with the camera in portrait

position, or upside down, this option should be set accordingly.

Page 15 of 22



✔ System memory : Autostitch should be able to detect how much RAM is installed, so

this parameter is useful mainly when not all the installed memory is available. It

forces the software to split the panorama image in smaller chunks and perform

matching and blending operations on them. If Autostitch aborts the creation of the

panorama with an "Out of memory " error, decreasing this parameter can help.

✔ JPEG quality : this options affects the quality of the panorama, in terms of tradeoff

between size and loss of detail (Jpeg is a lossy compression algorithm). The higherthe value, the better the quality. Autostitch's default is 75; if you plan to print the

panorama in big formats, it's better to set it to 95 at least.

Cosmetics When the panorama has been composed, it may need some cosmetic work, even if built

automatically by a stitching software. Very probably, as said before, it will need to be

cropped. Some more work could be necessary to correct some stitching glitches.

Ghosts

Ghosts can appear also in automatically stitched panoramas. They can be amended as

described about manual stitching (see also: “Ghosts”, pg. 10).

Mismatches

Mismatches usually occur between

portions of more or less long lines

and area boundaries; they are due

to parallax errors (see also:“Parallax errors”, pg. 11). They

appear as broken lines or lines

with discontinuities and steps.

Most of the times, mismatches, if

not too wide, can be amended by

means of the rotation tool.

✔ Using the freehand select

tool with a suitable feather

value, select an area

Page 16 of 22

An incorrect setting of the "Image rotation" option can produce weird results. Here "None" was set, instead of "Clockwise".

Particular of a panorama. A mismatch, found in the overlapping area between two pics, is circled red.



around a portion of the mistmatching line. The selction should be done so that the

selected area:

✔ Has more or less a triangular shape, with one of the sides centered where the

dicontinuity is and the opposite vertex lying on the line itself;

✔ Is long and wide

enough to makeunevident a slight

rotation of the line;

✔ Does not include

parts of the image

that must not be

moved together with

the selected portion

of mismatching line.

✔ Copy&paste the selection:this guarantees that the

image will not have blank

areas when the rotation is

done.

✔ Activate the rotation tool

and click on the (pasted)

selection, then drag and

drop the rotation center over

the vertex at the opposite of the discontinuity point.

✔ Rotate the selection until the mismatching edges of the line are close enough to

make the line look continuous.

✔ Anchor the selection.

✔ If needed, retouch the line where you just made continuous (it may appear a bit

blurred).

It is not so easy to get a clean and good result at the first try, so don't be discouraged. Undo

the changes and try selecting the area with a different feather value and different

boundaries. Patience and experience are the keys.

Missing panorama areas

Sometimes, panoramas happen to have missing areas, which usually get filled with a

padding colour by the stitching program.

✔ If the overlapping areas are not wide enough and the pics have to be curved or

stretched to compensate parallax errors, an empty area between the pics can

appear. It has usually a triangular shape, like a cone fitted into the image from one of

its sides. A missing area can also be caused by an incorrect horizontal (or verical)

alignment of the pics: usually it can be cropped out, but if this causes an excessive

crop of the whole image, then it is worth the while to try to amend it.

Page 17 of 22

The mismatch point has been selected into a triangular selection (outlined in

yellow). The rotation tool has been applied on the selection, and the rotation

center (outlined in blue) has been dragged on the selection vertex opposite to the

mismatch point. After rotating the selection according to the blue arrow, the

mismatch is no more noticeable (red outline).



✔ If the missing area is

not too big, and

particularly if its

actual content should

not be uniformly

coloured, it can be

amended with the

clone tool. Set a point

in the middle of a

similar area as the

origin, and start

brushing the missing

area. Use a fuzzy-

bordered brush and

change the origin

point often. An

accurate work can

make the amended

area perfectly

integrated in its environment.

✔ When the area is quite extended, better results can be achieved through

copy&paste. Use the freehand selection tool, with a high feather value (more

than 30 pixels, if possible), to select a small area having similarities with what

should actually be in the missing area. Copy the selection, and then paste it

into the missing area.

Depending on thecharacteristics of its

content, it may be

possible to paste the

same selection

multiple times in

order to cover wider

and wider portions of

the missing area.

Sometimes, it may be

better to select adifferent area after

pasting the formerly

selected one a

couple of times. If the

boundaries of the

pasted area do not

integrate too well within the environment, decreasing its opacity can help.

Page 18 of 22

A missing area is visible on the bottom of the image. There are also some mismatches on the floor lines, and a ghost (barely visible) under the trees with

yellow leafs.

All the glitches have been amended using the clone tool with a fuzzy-bordered

brush.



✔ If an entire pic is missing, usually the only solution is to import it by hand into the

panorama, using the colour tools and the perspective tool to integrate it seamlessly

(see also: “Manual stitching”, pg. 8).

Perspective

The correction of parallax errors often

requires that the images be stretched

and deformed. This may cause vertical

lines to have a relevant slope: this is not

necessarily bad, since it gives the

panorama a perspective that somehow

recalls pics taken with extreme

wideangle lenses. However, if the

perspective effect is excessive, it can

be corrected in an image editing

program by means of the perspective

tool (see also: “Parallax errors”, pg. 11).

Striped colours

When the pics have different colour casts, wide and uniformly coloured areas may result

striped, even if the stitching is done automatically and blending algorithms are applied.

Unfortunately this defect is not easy to correct, but a try is worth the while: a good editing

program offers some chance.

✔

With a contiguous regions selection tool (usually they have a magic wand as icon),select the whole area of interest. Such tools are guided by a parameter, usually

called “treshold”, that sets the tolerance to variations in colour used to determine

what a contiguous region is. Basically, if the area doesn't get selected completely, the

treshold should be increased. On the other hand, if the selected portion of image

goes beyond the area of interest, the treshold should be decreased. Selection tools

also take a feather value, that makes the selected area boundaries more or less

feathered: for this task, there's not an optimal feather value. If the area is on its own,

like a blue sky above a mountain horizon, chances are that a few pixels feather (5-10)

be the best choice. If the area is somehow integrated in an environment, like a

meadow surrounded by trees, a wider feathered border (15-30 pixels) can fit.✔ Once the area is selected, set a new foreground colour by clicking within the area

itself with the eyedropper tool.

✔ Then, create a new transparent layer and make it the active layer: the selection

should now be defined and active on it.

✔ Using the floodfill tool, fill the selected area (on the new layer) with the new

foreground colour.

✔ Now, change the layer opacity to make it semi-transparent. This will cause the colour

of the whole area appear more uniform.

Page 19 of 22

An example of perspective correction, done (pic on the right) using the

perspective tool.



✔ If the result is not good enough, the procedure can be repeated choosing a different

colour (with the eyedropper tool) from the area on the original layer; setting the right

opacity for all the newly created layers will give good chances to achieve the goal.

✔ In order to save the image, flattening will be required, since Jpeg format does not

support layers: editing programs usually have a “Flatten image ” or “Merge down ”

menu item.

Conclusion These notes, due to their shortness, cannot address every issue pertaining panoramas,

however I hope that they can be of some help: after all they show that some attention and

patience can be enough to get surprisingly good results. Skills, as always, come through

experimenting: it is not necessary to go to the most beautiful place in the world to take your

first panorama; your garden, the street where you live, even your living room can be

appropriate to begin. Start taking panoramas made of just two or three pics; try several ways

to photograph the same view (with and without tripod, in portrait and landscape position,focusing at different distances...) and compare the results. Learning is a neverending

process.

This tutorial is open to corrections, additions and refinements suggested by anyone.

Thanks for reading, and happy panning.

Stefano Barni – http://barninga.deviantart.com

Page 20 of 22



Index

Barninga's panorama tutorial..................................................................................................1

A foreword..........................................................................................................................1

Taking the pics...................................................................................................................1

Some useful suggestions...............................................................................................2

Vertical vs. horizontal panoramas..............................................................................2

Vertical vs. horizontal camera position.......................................................................2

Frame slant................................................................................................................2

The panning movement..................................................................................................2

Tripod shooting..........................................................................................................3

Freehand shooting.....................................................................................................4

Camera aided panning...............................................................................................5

Attention needed............................................................................................................5

Digging deeper: camera settings....................................................................................6

Focal length...............................................................................................................6

Focus.........................................................................................................................7

Exposure....................................................................................................................7

White balance............................................................................................................7

Stitching the pics................................................................................................................8

Manual stitching.............................................................................................................8

Ghosts.....................................................................................................................10

Page 21 of 22



Parallax errors..........................................................................................................11

Software stitching.........................................................................................................12

Autostitch.................................................................................................................12

Cosmetics.........................................................................................................................16

Ghosts..........................................................................................................................16

Mismatches..................................................................................................................16

Missing panorama areas..............................................................................................17

Perspective..................................................................................................................19

Striped colours.............................................................................................................19

Conclusion........................................................................................................................20

Index.....................................................................................................................................21

Page 22 of 22

Documents

Panorama Tutorial by Barninga