General Question

rebbel's avatar

How, in photography, does exposure compensation work exactly?

Asked by rebbel (27099points) 2 months ago

So let’s say I’m shooting in aperture priority, with an ISO of 200,and the metering tells me the shutter speed should be 1/60th.
Watching live view I decide I think it look too underexposed, so I dial in 1ev+.
Now my question is: what happens in the camera, from a technical standpoint, when I apply that 1ev+?
It’s not ISO going to 400, right?
Neither shutter speed going to be changed to ⅓0?
Let alone a change in aperture (I’m in aperture priority, so I want a certain depth of field).
So, what’s making it go 1 stop brighter, I would like to ask.
Anyone?
Thanks in advance!

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18 Answers

Tropical_Willie's avatar

Simply it takes a longer exposure ! You have frozen the aperture.

kritiper's avatar

I agree with @Tropical_Willie The exposure needs more time to burn the image onto the film or whatever the exposure burns into on a digital camera since you aren’t using the standard/normal exposure for that shot.

zenvelo's avatar

With film, exposure compensation “pushing the film” meant treating it in the developer for longer time. The extra long time in the. He I also would bring out pparts of the negative that had received a minimal amount of light, those making a distinct picture out of less light exposure when shooting the picture.

This allowed one to shoot at a faster shutter speed, or to not open the aperture as wide there by allowing greater depth of files.

The downside was a grainier picture.

I used to use High Speed Ektachrome (400 ASA) pushed to 1600 for pictures taken in concert halls with minimal light.

dabbler's avatar

A lot of cameras can bump up the sensitivity of the sensor, at the expense of added noise.

Call_Me_Jay's avatar

exposure compensation “pushing the film” meant treating it in the developer for longer time.

No, that is not at all correct. “Exposure compensation” is a camera setting, for film and digital.

It increases or decreases exposure value (EV) compared to the meter reading. The settings are incremented units (-1, -.5, +0.5, +1.0, etc) .

-1 means decrease to half the exposure, +1 means double it.

The camera will change either aperture or shutter speed to make the change. If you are on Aperture Priority (you pick the aperture), it changes the shutter speed. In Shutter Priority the camera changes the Aperture. In P, programmed, it’s either one or both.

For example:
You are shooting a backlit person. You increase EV, telling the camera “I need more exposure. Don’t use the average, I want the darker areas lightened.”

Nikon – DSLR Basics – Exposure Compensation

Digital Photography School – How to Use Exposure Compensation to Take Control of Your Exposure

ScienceChick's avatar

Pushing the film is done when you develop the roll of film. Exposure compensation is when you don’t change the aperture, but you just increase the amount of time the shutter is open. It helps in case of too much back lighting. You’re exactly right about the aperture affecting the depth of field. In a digital camera the ISO sets how sensitive you want the sensor to light. This is set exactly as if you were using more or less light sensitive films (if you’ve ever used film… that’s where I started over 30 years ago.) The lower the ISO number, the more accurately focused the picture can be on the pixels and vice versa. You don’t want to trade the clarity of your picture when you can simply use a tripod and increase the exposure.

Call_Me_Jay's avatar

Exposure compensation is when you don’t change the aperture, but you just increase the amount of time the shutter is open

Nope, nope, nope.

Exposure Compensation is a specific term referring to a setting on a camera (or light meter). It says “EV” (Exposure Value).

It means “Override the neutral ‘correct’ exposure, I want more or less light.”

Read your instruction manuals. See the links I gave.

kruger_d's avatar

In film one can “compensate” by setting the ISO dial higher or lower than the actual film sensitivity so that the light meter reading is skewed. Some cameras even have ⅓ stops on this dial. In the 70’s exposure compensation dials were added and coupled to this function to make it more user friendly. It was still the ISO altering the light meter, but through the EC dial. EC allows one to expose for shadow or highlight detail, for dark or light subjects, basically to get a ideal exposure under conditions that make the light meter inaccurate.

Either dial can also be used to over/under expose film which allows one to use wider aperture/slower shutter speed in bright light or narrower aperture/faster shutter speed in low light. Push/pull processing darkroom can improve these less than ideal exposures. Filters improve contrast, but add graininess. Just like using Photoshop today, starting with a less that ideal exposure is, well, less than ideal.

I know this doesn’t answer your questions, but hopefully it sheds some light on why/how to use EC.

ragingloli's avatar

In 3ds max’ physical camera, it changes the ISO value, to not mess with depth of field, or motion blur.

ScienceChick's avatar

@Call_Me_Jay Please explain how lengthening the shutter opening time doesn’t increase the exposure?

Call_Me_Jay's avatar

Of course opening the shutter more increases the exposure.

But Exposure Compensation is a specific setting, like a separate dial or button. You are not touching the shutter speed or aperture setting.

You change the Exposure Compensation and the auto exposure system then adjusts shutter speed and/or aperture.

Exposure Compensation button

Exposure Compensation dial

ScienceChick's avatar

@Call_Me_Jay on a digital camera. I’m soooo much older than you. LOL.

Call_Me_Jay's avatar

I’m in my mid 50s. The Exposure Compensation setting isn’t new. It was on automatic cameras in the 70s. Even hand-held light meters often hand a similar setting.

Here it is on an Olympus OM-2N camera from 1975

ScienceChick's avatar

Oh, that’s what that thing is called? That is a button for lengthening or shortening the shutter and exactly what I was talking about. It just slightly increases or decreases the time the shutter is open.

Call_Me_Jay's avatar

That is a button for lengthening or shortening the shutter

No, it can also change the aperture.

“You change the Exposure Compensation and the auto exposure system then adjusts shutter speed and/or aperture.”

ScienceChick's avatar

The poster said he didnt’ want to aperture to change…. so…... he sets the aperture to constant, uses the button and it changes the shutter time…. that’s not hard to understand.

Call_Me_Jay's avatar

OK, correct, in aperture priority mode, exposure compensation will change the shutter speed.

In shutter priority mode it will change the aperture.

In program mode it can change both.

rebbel's avatar

Thanks so much, all who answered!
I had never before noticed that, indeed, while in aperture priority, the shutter speed gets adjusted, according to the level of exposure value I dial in.
Thanks

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