What exactly does "Exposure Compensation" adjust to change the exposure? Probably another stupid question, but what actually changes to adjust the exposure when using the "Exposure...

Bison Bud

Probably another stupid question, but what actually changes to adjust the exposure when using the "Exposure Compensation" feature. This is a common option and generally adjusts in 1/3rd stops, so I assume that it's actually changing the f-stop just in smaller increments. However, maybe this isn't standard and maybe even be different from camera to camera and I'd appreciate any feedback on this issue, thanks!

rwilson1942 Loc: Houston, TX

It depends on what mode you are in.
In aperture mode it changes the shutter speed.
In shutter priority it changes the aperture.
I don't know about the other options (P, A etc) since I never use them.

chaman

In Aperture Priority mode, exposure compensation affects the camera's choice of shutter speed.

In Shutter Priority mode, it affects the camera's choice of aperture.

In Program mode, the camera chooses on its own whether to implement exposure compensation using aperture or shutter speed.

If Auto ISO is enabled, then the camera also has the choice of keeping shutter speed and aperture constant, and changing the ISO instead.

Joe Blow

Bison Bud wrote:

Probably another stupid question, but what actually changes to adjust the exposure when using the "Exposure Compensation" feature. This is a common option and generally adjusts in 1/3rd stops, so I assume that it's actually changing the f-stop just in smaller increments. However, maybe this isn't standard and maybe even be different from camera to camera and I'd appreciate any feedback on this issue, thanks!

There are several reasons you might use it, but the most common is to compensate for your light source. If the subject is backlit then you want to increase your compensation so your subject is properly exposed. Similarly, a very bright light on parts of the foreground might suggest a negative compensation.

Your light meter is a basic average of the light intensity hitting the sensor. Averages don't always work with specific subjects. Using exposure compensation and multiple exposures can allow layering to produce a more pleasingly exposed picture.

To add, don't worry about asking a stupid question. My wife claims I'm an expert at asking stupid questions.

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

It's especially usefull in classic exposure situations. preventing blue snow, "black cat in the coal bin". And lessening exposure hunting in low contrast scenes.

DTran

The exposure compensation actually only changes the meter reading but since the camera makes adjustments based on the meter reading so the exposure changes.

rehess Loc: South Bend, Indiana, USA

Bison Bud wrote:

Probably another stupid question, but what actually changes to adjust the exposure when using the "Exposure Compensation" feature. This is a common option and generally adjusts in 1/3rd stops, so I assume that it's actually changing the f-stop just in smaller increments. However, maybe this isn't standard and maybe even be different from camera to camera and I'd appreciate any feedback on this issue, thanks!

My old {film} Pentax Super Program has a knob to input film speed; a dial on its outside provides exposure compensation; in essence, these are two views of the same control. I believe that is true of modern cameras also.

DTran

rehess wrote:

My old {film} Pentax Super Program has a knob to input film speed; a dial on its outside provides exposure compensation; in essence, these are two views of the same control. I believe that is true of modern cameras also.

Not true with the digital camera. The ISO setting on the film camera only changes the meter but on the digital camera it changes both the meter and the sensor gain. Changing the ISO on a film camera to a different ISO than that of the film is the same as exposure compensation but changing the ISO on a digital camera is not.

roger

Exposure compensation does the exposure "changing" for you. You can do it yourself if you want to.

Bison Bud

It makes sense that it would control the shutter speed in aperture priority and the aperture in shutter priority, but curious as to how it handles auto and program modes and whether it does indeed also manipulate ISO. It would seem to me that ISO is generally adjusted in set steps like 100, 200, etc. Wouldn't that make it difficult to adjust in 1/3 stop increments? Otherwise, why couldn't we have continuously variable ISO control as a primary setting? When I posted my original question, I thought it was most likely that the aperture was mechanically adjusted in sub-stops in all modes, regardless of the F-stop selected and shown, but I guess the computer just decides what works best. Thanks for the feedback!

Apaflo Loc: Anchorage, Alaska

Bison Bud wrote:

It makes sense that it would control the shutter s... (show quote)

Re-read the two articles by member DTran. He nail it very precisely.

Exposure Compensation biases the output of the light meter. No more and no less.

If EC is set to +1.3 the light meter will indicate 1-1/3 EV less light. That then makes anything controlled by the light meter to provide that much more exposure to "zero" the meter.

The exact opposite happens if EC is set to a minus value. The meter is biased higher and exposure will be lower.

The most significant point is that only the light meter output is directly affected. Anything and everything controlled by the light meter is affected. But EC is not directly connected separately to any of the exposure modes or to AutoISO. They all connect to the light meter output.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Bison Bud wrote:

Probably another stupid question, but what actually changes to adjust the exposure when using the "Exposure Compensation" feature. This is a common option and generally adjusts in 1/3rd stops, so I assume that it's actually changing the f-stop just in smaller increments. However, maybe this isn't standard and maybe even be different from camera to camera and I'd appreciate any feedback on this issue, thanks!

I shoot in Aperture priority at f 6.3 on my 200-500 Nikon. If my image is too light, I use the exposure compensation to set a - value, if the image is too dark, I use a + exposure compensation. I know from experience if I see a bird in flight against a bright sky I go to +3.0 to give detail to the bird, and if the bird is against a dark background I go to - settings. It takes practice but you get better the more images you take. I do not shoot in manual because my birds are constantly in different lighting conditions and I have to adjust accordingly. I have found this system works best for me. It is not for everyone. Changing the exposure compensation in aperture priority only changes my shutter speed as I am at a constant ISO, so it only effects my shutter speed.

TomV Loc: Annapolis, Maryland

Bison Bud wrote:

Probably another stupid question, but what actually changes to adjust the exposure when using the "Exposure Compensation" feature. This is a common option and generally adjusts in 1/3rd stops, so I assume that it's actually changing the f-stop just in smaller increments. However, maybe this isn't standard and maybe even be different from camera to camera and I'd appreciate any feedback on this issue, thanks!

I would use the camera manual or on-line manufacturer users guide to get the details you are looking for.

steve_stoneblossom Loc: Rhode Island, USA

This can easily be determined by running simple tests.
Run a set in each mode, aperture priority, shutter priority, auto and programmed. Take one shot with no adjustments, and one (or more) using EC. Check EXIF and see what has changed.
You might want to also run each set twice, one with and one without auto ISO enabled.
Make sure you have not set limits on any of the variables (e.g. minimum shutter speed, maximum ISO) that might affect your results.

BebuLamar

Bison Bud wrote:

It makes sense that it would control the shutter s... (show quote)

Sorry if I miss something and as you said each camera model may be a little different so which camera are you talking about. Most cameras today allow user to change both shutter speed and aperture in 1/3 stop increments. They also display information in 1/3 stop increments. However, when the camera controls the shutter speed and aperture I am quite sure that it does it continuously (which I do not like, as I want it to use the aperture and or shutter speed it displays ).