Metering and exposure are not easy companions. While they appear to work well together on the surface, metering can fool you into underexposing. Here are some experiments that show you how to control exposure and use it creatively, especially in aperture priority mode.
There’s a lot of nonsense written about camera exposure modes. I roll my eyes when I hear people have to use manual mode. It’s purely poppy. Understanding how manual mode works is one thing. However, being told you have to use it is another thing.
I’m a fan of aperture priority. It does a lot of the heavy lifting for photographers. Its great advantage is that the machine will expose the image according to the metering way. An equally big disadvantage is that the machine will automatically expose according to the metering. Let me explain.
If you don’t know, this mode allows the photographer to set the aperture and the camera to automatically adjust the shutter speed. Turning the mode dial to A (Av on Canon) gives the photographer quick control over the camera’s settings.
When shooting events like weddings, I always use aperture priority. Why? Due to the constantly changing lighting conditions and the fast speed of the camera make up for that. It can go from the 60th to the 2,000th much faster than I can turn a dial in manual mode.
Furthermore, the camera places restrictions on exposure settings that are not present in shutter priority or manual modes, making it less likely that I accidentally shot an incorrect exposure. “What,” I hear you gasp, “can an experienced professional photographer make a mistake?” You should believe it, and it can happen to anyone. Admittedly, the risks in doing so have been reduced since switching to mirrorless; I was able to see both the histogram and a close-up representation through the viewfinder before I pressed the shutter button. That support is limited by both the widest and smallest apertures, though. I was able to set the aperture to its maximum and still get the correct exposure.
Furthermore, aperture priority is a great way to learn how counterintuitively metering and exposure work together. That’s why I’m using it for the following experiments.
Test one
With your camera set to ISO 100 (200 if you’re using Micro Four Thirds), in aperture-priority mode, try shooting at the widest and narrowest apertures in a dimly-lit room. On a standard kit lens, this can be f/3.5 and f/22, respectively. Exposure will be the same at each pole, although you may have trouble holding the camera at the narrowest aperture because the shutter is open for so long.
Experiment two
Now do the same in shutter priority. At one pole, the image will be pure white and at the other extreme, very dark. The correct exposure will cover an area somewhere between the two extremes.
In shutter priority mode, the camera is limited by the longest and shortest shutter speeds. That range is from 60 seconds to 1/32,000 of a second on my camera, though yours may vary from that range. So it can make your photos overexposed or underexposed accidentally and catastrophically.
Experiment three
Next, while indoors, set your camera to take correctly exposed photos in manual mode. Then step outside into daylight. How long does it take you to adjust the settings to get the correct exposure? Try again in aperture priority mode. Now, the correct exposure will be obtained instantly.
Test Four
However, there is a problem to overcome with that approach. Metering can trick the camera into exposing it incorrectly.
Your camera expects the world – on average – to be a specific brightness. The sky is bright, the ground is darker, and there is a mixture of tones. This is a simple interpretation, but on average it assumes that the world has a medium tone, commonly referred to as medium gray or 18% gray.
Make sure your camera is set to full-frame metering. This is called matrix, multi, many, multiple segments, multiple samples, evaluation, or ESP, depending on the brand of your camera.
In aperture-priority mode, take photos of common outdoor scenes, such as a park or a tree-lined street. The image must be exposed correctly. Now, fill the frame with something white, like a piece of paper. You may have to draw an X on it first for the camera to focus. Look at the photo on your back screen. It will appear gray. Your camera has been fooled by all that whiteness. It expected the frame to have medium tones and not pure white, so it reduced the exposure accordingly.
To override metering, you must add positive exposure compensation to brighten the image. This may require pressing a button marked +/- and rotating the main dial, known as the command dial on some cameras. Also, if your camera is equipped with a second dial, turn it clockwise. You should see an indicator in the viewfinder showing that exposure is increasing. Rotate it to about +1.7 and take a picture of the piece of paper again. It must not appear white. Exact exposure compensation may vary from camera to camera.
What does this mean in the real world? If you are shooting a scene that is too bright, such as snow, a sunny sea, or bright sand, you need to add positive exposure compensation to brighten the image, otherwise the camera will make the image too dark. Brightening a photo with a bright scene may seem a bit counter-intuitive, but it’s what you have to do. I apply exposure compensation to almost every photo I take, which is why I only bought a camera with two dials.
Test year
The exact opposite is shooting something black. Set exposure compensation to zero and fill the frame with something completely black, such as the back of a camera bag. Look at the picture. Again, it looks gray, not black. This time, you must dial negative exposure compensation. Try -1.7. So if you’re taking a photo in a dark room and you want to show that shadow in the image, you’d have to adjust the exposure compensation negatively to make all those shadows look dark.
Experiment six
You can use under and over exposure creatively. In dimly lit rooms, use bright lights to illuminate the subject. Or, if you’re outside, look for streams of sunlight shining through the shadows of trees or buildings. Dial in low light even further until the shadows turn black and bright highlights have medium tones.
Test Seven
Now, look for a very bright scene with a dark element. Adjust the overexposure until the scene is almost white and the dark element moves into the midrange.
Test Eight
The sensors on the camera allow different intervals to correct exposure errors. If your camera has a bit of a flaw, and especially if you shoot raw, you can usually fix it in post-processing, although you’re better off trying to fix it right in. camera. However, if you push it too far, you will lose detail and possibly create noise when brightening the image. So it’s good to know how far you can push the exposure in either direction and still get good results. Try taking multiple shots of the same scene. Increase and decrease exposure. How far can you push it in both directions while still getting acceptable results in processing?
This article is just a superficial assessment of the exposure, and there’s a lot more to it than I’ve included in this short article. Please post your test results in the comments. Please feel free to ask any questions there. In addition, Fstoppers has A great course is available that will help you understand other aspects of exposure and the necessary camera techniques. Many of the writers here also run hands-on workshops, and you should check to see if there are workshops near you.
