Yesterday’s Topic: JPEG And RAW File Formats Can Coexist
I have some bad news.
Your camera is not perfect.
Don’t worry, neither is mine. The saving grace to this dilemma is the Exposure Compensation (sometimes called Exposure Bias) feature on DSLRs and a lot of point and shoot cameras. It is a little button that looks like this.
The exposure compensation button works by forcing the camera to over expose or under expose, according to its current settings, by a set number of stops. Typically the range is -2 to +2 stops but some cameras will have a -5 to +5 range. Cameras are pretty similar in how the setting is activated; simply press or hold down the button and then turn one of the camera dials. I know, a lame explanation, but with is not a “How To Use Your Camera” series, it’s about taking better pictures and there are a few things you need to work out on your own.
How is the exposure compensation button handy?
It can be handy when you know the camera is going to mess up or is already messing up. As explained in the Metering Modes post, your camera is not perfect and can only meter a limited area of the view. Plus, it has to make decisions about what’s important in the frame and try to make everything come out all average. But it makes mistakes.
Take this morning scene at the local ferryboat dock. Program mode, ISO 100f/13, 1/500
This is with the camera’s default setting using evaluative metering. I could switch to spot metering and point it at the ferry to make sure the ferry is properly exposed. Instead, I have set up my camera’s rear dial to be a quick adjustment for the over or under exposure, the exposure compensation.
Here’s the same shot over exposed by one stop. Program mode, ISO 100, f/13, 1/500
Over exposed by two stop (Program mode, ISO 100, f/10, 1/320) and then three stops (Program mode, ISO 100, f/8, 1/200)
Now, swinging the other direction, we’ll under exposed by one (Program mode, ISO 100, f/14, 1/800), two (Program mode, ISO 100, f/18, 1/1000) and then three (Program mode, ISO 100, f/20, 1/1600) stops.
As you can see, that is a big difference in exposures across a swath of seven stops of light. What is most pleasing to some, in this case, might not be pleasing to others.
The over/under exposure compensation can be a quick way to correct a camera’s wrongheaded bias towards too harsh or too dull of light depending on where the main subject in an image is situated. In this example, the shot that was underexposed by one stop has a good chance to using some fill light and contrast in a computer after the fact to pull out some life in the boat while keeping the sky interesting.
This quick setting can also help insure faces aren’t hidden in darkness by shadow when all around them is bright light. It’s better to blow out the details in the surroundings than leave a face too dark.
Questions?
Next Up: A Rule Of Thumb To Help Stop Photo Blur
31 Days To Better Photography is a series written by professional photographer Peter West Carey on The Carey Adventures.Com. The series is designed to unravel the mysteries of photography so you can take better pictures. Subscribe here to receive all the update, and bonus material. Your comments are always welcome.
Yep, been toying with this feature this morning while out shooting along the coast. So much to learn. I’m guessing a polariser would help, but I don’t know. I’ll have to get one to find out. Thanks. Would be interested to see how you use fill light and contrast to bring out the one stop underexposed image :)
Thank you for this – I had hit a button by mistake on my camera and couldn’t figure out what I had done. I now know I had adjusted the exposure bias AND, thanks to you, I also know how to fix it and what it’s for.
This lesson was particularly useful to me. I live in Florida and run into backlit situations all the time. I hadn’t used the exposure compensation button. Out of curiosity, what does the AV on it stand for?
Susan,
Adjust Value? I honestly don’t know. I know on some of the Canon X model (the Rebel models) it is also used to adjust the Aperture value when in manual mode, it is likely representing Aperture Value as Canon models note that with Av on the mode dial. That would be my guess.