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How To Use Exposure Compensation For Quick But Accurate Photos
In digital photography there are often a handful of different ways for doing the same thing. The basic controls of aperture, shutter speed, ISO, metering, focus modes etc. can be combined in myriad ways to suit your unique preferences as a photographer.
Today I'm going to look at a control called exposure compensation. This is something that I use a lot. You could happily get by without it, but in lots of situations it makes life easier. Why? Because it basically enables you to retain the convenience of shooting in a non-manual mode, whilst providing a concession to manual control of expsoure.
Exposure compensation in a nutshell
Exposure compensation is a control for overriding a digital camera's automatically judged expsosure, in order to correct it or produce a brighter/darker image according to taste.
In other words, when you're in Program, Aperture Priority or Shutter Priority mode, and the exposure you're getting isn't quite what you're looking for, you can change it without having to switch over to Manual mode.
The symbol for exposure compensation is the little +/- symbol that you've probably spotted on a button or in the menus. This symbol represents positive and negative expsoure value. All you have to do is dial in your chosen number of stops, of either a positive or negative value, and your pictures will be brighter/darker by that amount.
My camera allows me to dial in up to 3 stops of exposure in either direction, moving along by increments of 1/3 stop. That gives plenty of control. For instance, I might wish to brighten a scene when shooting in Aperture priority, so dial in 2/3rds of a stop positive value. If it's still too dark I could then notch it up to a whole stop, or 1.3 stops and so on.
Exposure Compensation 0:
Exposure Compensation +1:
Exposure Compensation -1:
When is exposure compensation useful?
A I've mentioned, it's a great control to use when you're set up in Aperture Priority and don't want to switch back to Manual mode. There are some subjects that feature lighting which is just a bit too tricky for digital cameras to handle.
For example, you must have photographed someone with very strong back lighting and found that their face turns out really dark, whilst the background is pretty well exposed? This happens all the time!
There is the option of switching to spot metering to read the light just on the subject's face. But then when you recompose the shot the camera takes a reading from the new area. This can be dealt with by toggling through the autofocus sensors so the focal point is aligned with the subject, when composed correctly. Alternatively you could take a spot meter reading, press AE-L/AF-L to lock the expsosure, recompose and then take the shot. But that's all a bit of a faff isn't it!?
Why not just carry on exactly as you were before - in Aperture Priority mode, with matrix metering and using the centre autofocus point - but just tweak the exposure compensation to give the best result?
There are loads of situations where this is a brilliant technique to have up your sleeve. Sometimes the reverse of the above example is the case, i.e. the subject is very brightly lit, whilst the background is really dark. The camera automatically factors in the dark background and ends up clipping the highlights on the subject. Solution? Take the exposure compensation down a stop or two.
Using exposure compensation with aperture/shutter priority and program modes
When you use exposure compensation the camera does not, obviously, gain the ability to capture a larger dynamic range. In order for a picture to appear darker or brighter the settings have to actually be changed. So which settings do get changed?
Well, if you are in aperture priority mode the shutter speed will be automatically adjusted to factor in the exposure compensation. Conversely, if you are in shutter priority it is the aperture that changes to account for the chosen amount of exposure compensation.
In other words, whichever exposure setting you are not in control of manually will be the one the camera changes automatically. When you are in program mode, the camera is free to change both aperture and shutter speed to adjust the exposure accordingly.
So, when shooting in aperture priority with positive exposure compensation, just keep an eye out for the shutter speed if you are hand-holding. It's best not to let it drop below about 1/50th second, and should always be at least the reciprocal of focal length.
Why not just shoot in in manual mode?
Good question. Manual mode is very useful in awkward light, but the vast majority of the time it's depth of field (controlled by the aperture) that I want to control more than anything. Shots that require dialling in lots of exposure compensation are the exception not the norm.
So I get the benefit of speed (most of the time), as well as some manual control when needed. If every single shot required altering the exposure compensation value, then yes, it would make more sense to use Manual mode and drop/increase shutter speed!
When the light is very dim, I'd still rather be in aperture priority than Manual mode. If my camera is struggling to produce good exposures even at the fastest aperture setting, I'd rather ramp up the ISO to 800-3200 than risk camera shake by manually dropping shutter speed below an accpetable level. So, really, exposure compensation gives me as much manual control as I actually wish to have in most situations.
How often should you use exposure compensation?
Whether you use this control at all is completely your call. As I said at the beginning, it's always best to find a system and combination of controls that works best for you.
Personally, I find myself using exposure compensation a lot. As in almost every shoot. Nearly always that involves dialling in a positive value to increase the exposure. In fact, as I'll explain below, I leave leave a certain amount of positive exposure compensation set permanently, and work from that as a base point.
Using exposure compensation to help with exposing to the right
You may well be familiar with the idea of exposing to the right. This refers to the information contained within a photograph as it's displayed on the histogram. The histogram is a graph that shows the level of detail in an image from shadows, on the far the left, through midtones and into highlights, on the far right.
Exposing to the right:
As a rule of thumb in photography, try to capture more information on the right hand side of the graph. This means the lights and highlights should, in most images, be more prominent than the dark areas. This is simply a means of recording the maximum possible amount of information.
It's extremely easy to use Curves, Levels and the Raw file conversion window to bring contrast and depth back into bright photos. On the other hand, it's very difficult to rescue details in the darks and shadows without introducing lots of noise.
Rescuing shadows creates lots of noise:
It's easy to add contrast to a shot that's already bright:
Exposure compensation is useful here because it enables us to permanently err on the side of 'overexposing'. When shooting in Manual, I would tend to nudge the reading a little bit into the positive anyway. So I set my exposure compensation to plus 1/3 or 2/3 of a stop permanently, in order to expose to the right.
I hope this has helped you get to grips with exposure compensation. It's such a useful control, as it allows you to shoot quickly and accurately. It basically increases the flexibility and control available whilst shooting in Program or Aperture Priority.
As a final caveat I just want to note that I'm not encoraging you to abandon Manual mode! Expsoure compensation simply makes the other modes even more useful. I sometimes set up a shot in Manual mode when I know the light will not be changing throughout the shoot, for example.