Over the days leading up to the 25th of December I’d like to give something to everyone who stops by my blog. These tips cover camera settings, flash, lighting, software and gear. I’ll be providing a pair of tips each day until 25th December.

#25 – No automatic exposure lock with spot metering

no automatic exposure lock spot metering

EOS cameras don’t automatically lock exposure when set to spot metering, unlike evaluative metering. This often causes photographers a few problems as they explore the more advanced capabilities of their cameras.

no automatic exposure lock spot metering

The EOS 7D Mark II displays an exclamation mark on the screen as a reminder when spot metering is selected.

Evaluative metering + ONE SHOT AF = automatic exposure lock

There’s one combination of focus mode and metering pattern that automatically locks exposure, evaluative and one shot AF. Any time you use AI Servo AF, there’s no automatic lock. When you use one shot AF with spot, partial or centre-weighted metering there no automatic lock.

This is important since most people start out – or forever stay – using one shot AF with evaluative metering, and use the focus lock and recompose technique. So they aim at a face, focus lock – which also locks the exposure – and the recompose. Using evaluative metering is fine, but with a change to spot metering exposure seems a bit more random.

I see so many recommendations to use spot metering for accuracy, yes it’s accurate, but for many “less advanced” photographers this is a step too far. Interestingly, Canon has started to consider that this might be a concern with some of it’s advanced cameras, so the EOS 6D Mark II and EOS R have a custom setting to enable auto exposure lock with any, or none, of the metering modes when using one shot AF.

no automatic exposure lock spot metering

Let’s imagine your subject is a perfect mid-toned object to the left of the frame, and behind it is a totally dark background. Using evaluative metering and one-shot, you’d recompose by moving the camera left – you’re probably looking at the centre AF point too, half-pressing the shutter to lock the focus (and exposure) then moving the camera right to reframe, and then taking the shot. Now with spot metering, it’s all good until you move away from the mid-grey subject, and point the centre of the frame (where the spot meter measures from) at the dark background. The camera will now increase the exposure to lighten the background to mid-grey, and in doing so overexposes the mid-grey subject. It’s not just dark backgrounds, you’d have the same with white too, except underexposure would result.

Unfortunately if you use an AF point off-centre, the spot meter, and partial meter too, only measure from the centre of the frame. EOS-1D series cameras only, have the custom setting to link the spot meter to the selected AF point.

Some photographers get along just fine with spot metering because they use manual exposure. That’s full manual where they set shutter speed, aperture and ISO value. In this case they can point the spot meter at a suitable part of the frame to get a baseline exposure from, and make their settings. Since their settings are chosen deliberately, any changed composition has no effect on the exposure. Use AUTO ISO with manual though and you’ll need to remember to lock the exposure still.

How to lock exposure?

AE lock button

Exposure is locked with the AE-LOCK button, the one with the * symbol on it. You’ll see a little * symbol in the viewfinder to indicate the exposure is locked, and it stays locked while you keep half-pressure on the shutter button, or for about 6 seconds.

exposure lock with hold
Advanced cameras have ways to increase that 6-second duration, EOS -1D models can adjust the timer length, and recent advanced cameras have something called exposure lock with hold. You’ll need to talk a look in the custom controls to set AE-lock with hold. Basically once pressed the exposure is locked until you switch the camera off, or unlock it by pressing the AE-lock button again.

Not sure when you should use ONE SHOT or AI Servo AF? Let me give you some help…

This is the halfway line to fifty tips 🙂

#26 – Reduce reflections in your subjects glasses

flash reflection in glasses

If you’ve used a flash to photograph a subject wearing glasses, particularly on-camera flash you’ll almost surely have seen the reflection in the glasses. Old tricks such as removing the lenses and dulling sprays work, but are a little “invasive”. The picture above on the left shows the reflection, yet by asking the gent to lower his chin, they were avoided easily for the shot on the right a couple of frames later.

If you’re using off-camera flash then move the light a little or turn the subjects head to a slight different angle can improve the results. However if your lights are set, the subjects pose is not possible to adjust you are left with moving the glasses, or asking your subject to. When I was shooting Ed the other day I was reminded of a neat trick, ask your subject to lift the ads of the arms of their glasses up a little on their ears. This tilts the lenses down and usually makes the reflection disappear out of your shot.

flash reflection in glasses

flash reflection in glasses

The two shots of Ed above, show the difference a slight lift of the spectacle arms makes. The top shot has the reflection of my softbox, and the lower one it’s gone. It’s a good thing that Ed managed to hold his position 🙂


Here’s a few more festive fifty tips