If you use the fully automatic setting on your camera then it will generally produce acceptable images, but it won’t get it exact. In effect you are allowing the camera to do the work and you relegate yourself to role of ‘button pusher’. Modern DSLR’s are built to deal with most situations in Auto mode but this, in itself, does not allow the photographer to be creative: The camera controls everything. The camera is, in effect, controlling the photographer rather than the photographer controlling the camera. Sure, the photographer still has control over composition but that’s it. And sometimes, even composition is dependent on other variables. So if you are happy shooting in fully auto mode then read no further…be a happy ‘button pusher’!
However, if you want to take control of the camera instead of it being in control of you it’s worth acquiring a little knowledge about what your camera can do if you take control. This allows you to spend more time taking the photograph that you want rather than ‘spinning the dials’ and settling for what the camera decides and keeping your fingers crossed that it all turns out OK.
Practical Exposure: Don’t be scared of Manual Mode:
Aperture Priority & Shutter Priority Modes
These allow the photographer to control either the size of the aperture or the speed of the shutter. Combine this with an appropriate ISO plus the correct metering and everything should come together in a correctly exposed shot. However, deciding on which aperture to set and what shutter speed to set based on the subject and the given amount of light is easier said than done, especially if you’re shooting against different backgrounds using, say, evaluative metering. In fact, you can end up spending more time ‘spinning the dials’ on your camera trying to get everything right rather than taking the shot.
Let’s take a simple example: You’re in Aperture Priority and have set evaluative metering… and after taking the shot you look at it on the back of the camera and you’re perfectly happy with it. Exposure seems fine but your creative juices tell you that your subject would look better in front of a different background. Let’s say it’s your pet dog in front of your garage. The dog is in full sun but if you moved the subject in front of the garden greenery it would be more pleasing. So you move the dog in front of the hedge. The light hasn’t changed. You still have the sun behind you falling directly onto the subject. You take the shot. You look at the back of the camera and see that the exposure is different to the first shot. You are using Evaluative metering and conditions are the same as in the first shot! You hit the Info button on the back of your camera to check things out and are surprised to see that the settings that you had for the first shot have changed (apart from the Aperture and Evaluative metering that you originally set). You have to start over again to get the shot you want, with the background you want, correctly exposed. You start spinning the dials in a frantic effort to get the correct exposure as the first shot. You’re now playing ‘Photo Roulette’!!
None of this need happen.The solution is simple.
First, switch from Evaluative metering to a different metering pattern ( I’m a great proponent of ‘spot metering’ but it’s a little more involved…more of that on another page).
Second, take the first shot again metering directly off the subject. Look at the shot on the back of the camera and, if you’re happy with the exposure, press the Info button, note the Aperture, shutter speed and ISO.
Third, switch to Manual mode, dial-in the settings you’ve noted from the first shot.
Now, here’s the thing…given the same light, if your subject moves in front of a different background your subject will be exposed just the same as in the first one BECAUSE..
SAME LIGHT…SAME EXPOSURE
If the light doesn’t change, say on a bright sunny day, and you have the sun behind you, whilst you take the shot, then it doesn’t matter where the subject is standing. If you’ve metered correctly for the subject then the subject can move around in front of different backgrounds of different colours, shapes and sizes and they will be exposed the same in each shot… because you’ve already set the parameters in the camera. You no longer have to play ‘photo roulette’ and instead can concentrate on composing photographs (in front of different backgrounds?) in the knowledge that the subject will be exposed the same in each.
Here’s a simple experiment you can try yourself to prove that it works:
Get hold of something like a child’s toy, say a teddy bear or a plastic duck or any inanimate object. Get some large pieces of paper of different colours. Place the toy in front of one of the pieces of paper in such a way that you can change the paper without moving the toy. Make sure that you have a constant light source hitting the set-up. Set your camera on a stable surface (tripod is ideal) and in Aperture priority, using Spot metering, focus on the toy whilst filling the frame with both toy and background paper. Take the shot. Check the back of your camera via the Info button, note the settings, switch to Manual mode, lock in the settings. Make sure the camera hasn’t moved, make sure the toy hasn’t moved, change the background paper. Take the shot. Repeat with all different background papers.
Here’s the thing…the toy will be exposed exactly the same in each shot regardless of the change in background. because: SAME LIGHT…SAME EXPOSURE
If you tried this little experiment from start to finish in Aperture Priority using e.g. Evaluative metering you would probably be surprised at the differences in exposure for each shot. So why do different metering patterns affect the final exposure so much? It’s to do with area coverage of the pattern and whether or not the camera’s built-in algorithms take over. Check the link Same Light…Same Exposure
Meter The Light 