OFFON

SHUTTER PRioRiTy ModE

Av mode Aperture priority is labelled Av on the Mode dial. While it directly sets the aperture, it indirectly affects the shutter speed, too

Tv mode Shutter Priority mode is marked as Tv on the Mode dial – it stands for Time value and gives you complete control over shutter speed

The Canon Magazine 87

ALL ABOUT SHUTTER SpEEd

hen it comes to shooting a subject where shutter speed

is critical, it makes a lot of sense to use Shutter priority (Tv) mode. Imagine you want to photograph a fast-moving subject, such as motorbike. You turn the Main dial to the right to increase shutter speed and keep going until the shutter speed hits its fastest point. You take your shots but when you review them every single one is too dark. Why?

This is where Shutter Priority mode can catch you out, if you are not careful. While it allowed you to select a very fast shutter speed, it had no aperture it could match it with for a correct exposure, and the result was an underexposed shot. Of course, the camera did warn you – the maximum aperture display was flashing in the viewfinder – but it didn’t actually prevent you from taking the shot.

Had you heeded the warning you could either have dropped the shutter speed or increased ISO until the maximum aperture figure stopped

flashing. However, if you ignored the warning then your shot would inevitably have been underexposed.

It’s for this reason I prefer to use Av (Aperture Priority) mode, even for action. I set the aperture I want, based on how much depth-of-field I think the image needs, and then check the shutter speed. If it’s too slow for the subject, I have the choice of either opening the aperture up more (if I can) or increasing ISO. Usually I’ll increase ISO; for me, this makes more sense as I can make a creative decision on aperture first, and then alter the settings to get the shutter speed I need.

However, if you want to work in Shutter Priority mode and set a specific shutter speed, make sure the maximum aperture displayed in the viewfinder isn’t flashing on and off. If it is, take the shutter speed back a stop or two, or increase ISO. There are two other things you can do to help in this situation, depending on the Canon model you own. We explore these below...

f your camera has a Safety Shift option then using it is one

way of avoiding setting the wrong exposure in Shutter priority (Tv) mode. Not all Canons boast this function, but most mid-range, high-end enthusiast and pro models do.

Essentially, Safety Shift overrides your exposure if you exceed the camera’s limits in shutter speed or aperture. For example, if you are shooting in Tv and set a shutter speed

faster or slower than the correct exposure can cope with, when you take the shot the camera will automatically change the shutter speed to give you a correct exposure.

You can also set ISO Safety Shift so that, if you try to set a shutter speed that’s too high for the maximum aperture, then the camera will automatically increase ISO sensitivity to balance the exposure. However it can only work within the limits of ISO at

either end of the sensitivity scale.

If your camera doesn’t have Safety Shift then you can set Auto ISO, which ensures that, should you exceed the exposure limits of shutter speed/aperture, the camera will set an ISO to bring the exposure triangle together for a correct exposure.

However, Safety Shift and Auto ISO come with a warning: while they may stop you from

accidentally setting values that don’t deliver a balanced exposure, you are also losing some control because the shutter speed, ISO or aperture the camera selects may not be what you want for your image.

What’s on the Tv?What to know when using Shutter Priority mode

Avoid accidental exposure errors to achieve correct exposures

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Safety Shift and Auto ISO settings