Does the Exposure Slider in Adobe Camera Raw Have Same Effect as in camera Exposure Compensation?

Question

My assumption is that the Exposure slider in ACR does NOT have the same effect as using in-camera Exposure Compensation. Am I correct?

Background: I shoot in raw. In either Aperture priority or Shutter priority, if I chimp and see that the shot is a little dark for example, I may use EC to brighten the image. When using EC, the camera will change with shutter speed (if you are in Ap priority) or the aperture (if you are in Shutter priority). But with the EC, some aspect of your shot will be affected, .e.g, if Aperture changes to make the shot brighter - it opens up the aperture and makes depth of field shallower. If shutter changes to make shot brighter, it slows the shutter down and you may have a camera shake issue. Net - using EC to make the shot brighter has other effects on the image.

But if I had a shot that was a little dark, and I left it as is in camera, and instead lightened it a little in ACR with the exposure slider ... I assume that I am brightening the exposure and AVOIDING the other effects of AP change or SH change had I used EC in camera. If this is correct, isn't using the Exposure slider in ACR a better alternative to using EC for gentle exposure tweaking?

Answer 1

When you increase exposure In-camera EC works by getting more light into the sensor (getting you more real information and hiding noise).

Post processing exposure slider works by taking the data in the image file and increasing it mathematically (adding extrapolated "fake" information and make every tiny bit of noise more visible).

Basically you get a better image if you do this in-camera, but if you can't get it right in-camera doing it in post isn't so bad

Also, you can increase ISO to get the image to be brighter without the shutter speed or aperture side effects - but if ISO is better or worse (image quality wise) than post processing depends on your camera's sensor technology.

Answer 2

Actually the best thing that EC slider in post processing can emulate - is the ISO setting. As you mentioned - EC can not change depth of field or make any changes to motion blur.

The thing what exposure compensation of your camera doing is very depending on your settings: if you're in A (Av) mode - you will change your shutter speed, in S (Tv) - apperture, in P - it will change both aperture and shutter speed. The EC of a camera is also affecting on a flash power (at least for Nikon, Olympus for example has a different approach - EC not affected on flash power).

I have noted that if you changing the exposure in post processing for a very big values (I'd say something like 3 steps or more) - you will probably get a bad colors. You will never get anything bad like this if you will increase ISO during taking a shot.

This shoot taken with a right exposure right from a camera (JPEG, ISO 5000, f/4, 1/60s):

This one is a tweaked in ACR (EC +5) and in Photoshop (EC +0.67) (RAW, ISO 100, f/4, 1/60s):

This one is popped up in Photoshop (EC +7,11) from a camera JPEG (JPEG, ISO 100, f/4, 1/60s):

As you can see the result of RAW tweaking almost the same as ISO popping. But the colors are slightly different. The result of JPEG popping is absolute garbage.

As @Nir mentioned - it is much better to make the right exposure settings while shooting and make the post processing changes as little as possible. This is why shooting in RAW is kind of a bad practice as you are not tended to make a proper pics right from your camera (of course RAW is very helpful for some implementations like getting very clean shots or retrieving a subject texture).

I'd recommend to use camera JPEG for everyday photography to keep your exposure skills up and turn on RAW for a critical shooting.

Answer 3

Exposure comensation scales all values, sliding the histogram. The exposure controls in Lightroom move parts of the histogram and reshape it. If the same control in ACR file opening works the same, then no.