Exposure compensation

[fadetoblack22]

Hey, I'm not sure if this is a stupid question or not.

I am having trouble understanding the need to use exposure compensation.

Why not just change the aperture or shutter speed?

If anyone could help me out with this it would be great :)

[SimonG]

That's exactly what exposure compensation does; it changes the shutter speed or aperture (depending on whether you are in Tv or Av mode) in order to correctly expose a scene that is darker (-EV) or lighter (+EV) than medium grey.

[fadetoblack22]

I thought so, but why have the option if you can change the shutter speed/aperture and have more control over the creativity of your photo?

[nphsbuckeye]

Adjusting aperture or shutter speed is textbook.

[SimonG]

I thought so, but why have the option if you can change the shutter speed/aperture and have more control over the creativity of your photo?
When you are shooting using one of the auto modes (Tv, Av) you can only set one of the exposure variables (shutter speed or aperture); the camera will then set the other variable so that the meter is centered (based on the assumption that it is exposing for medium grey). If you are shooting something lighter or darker than this, you will need to set an appropriate exposure compensation in order to adjust the camera controlled variable so that your exposure is correct. In short, you do not have control of both exposure variables when shooting in Av or Tv mode unless you are making use of exposure compensation.

[12mnkys]

like it was stated above, the exposure compensation essentially does that for you. When you shoot in Av or Tv, you are only allowed to change that one variable. If you are in Av and you are shooting at f/8 or whatever, and you wanted to underexpose the photograph, you would set your compensation lower by however many stops, and the shutter speed will automatically adjust accordingly.

in otherwords:

You are in Av set at f/8
Your camera meters the shot at f/8 and 1/60 sec as the "correct" exposure
You want the shot to be under exposed by one stop
You would set the exposure compensation to -1
Now your camera will take a shot at f/8 and 1/120 sec exposure, thus "underexposing" the shot by one stop.


Make sense?

[PhotosGuy]

In short, you do not have control of both exposure variables when shooting in Av or Tv mode unless you are making use of exposure compensation. Metering modes come into the equation, too.
Why not just change the aperture or shutter speed? Works for me, but I use manual 99% of the time. Why? This shows how the subject can affect the exposure & why manual keeps me worry free:
Post #47 (http://photography-on-the.net/forum/showpost.php?p=5191658&postcount=47)

Try manual when conditions allow. For a good starting point, first set the f-stop & shutter speed you need for the effect you want. Then the other parameter: f-stop or shutter speed. Then adjust the ISO.
Need an exposure crutch? (http://photography-on-the.net/forum/showthread.php?t=89123)

[BobOh]

I think what hasn't been clearly said here, unless I missed it, is that in either mode, Av or Tv, when you select the aperture or the shutter speed, the camera will center the pointer in the meter. If you then change the SS or aperture to attempt an EC, the camera will still center the pointer. In these 2 modes it will always center the pointer. You can, of course adjust out of a normal exposure range until the SS or aperture setting blinks in the meter (may be camera dependent), but that will be the only indication of under- or over-exposure. The needle will still be centered. If you dial in EC you can "uncenter" the pointer.

[fadetoblack22]

I think what hasn't been clearly said here, unless I missed it, is that in either mode, Av or Tv, when you select the aperture or the shutter speed, the camera will center the pointer in the meter. If you then change the SS or aperture to attempt an EC, the camera will still center the pointer. In these 2 modes it will always center the pointer. You can, of course adjust out of a normal exposure range until the SS or aperture setting blinks in the meter (may be camera dependent), but that will be the only indication of under- or over-exposure. The needle will still be centered. If you dial in EC you can "uncenter" the pointer.

Can you explain this simpler. I don't quite understand it.

Thanks for the other posts. The links are very useful.

Am I correct in thinking that Exposure Compensation can increase by less than a stop?
Like +1/3 or +2/3?

thanks

[DStanic]

If you are using Manual mode, exposure compensation (EC) does not really exist. You are in compete control of the exposure by adjusting shutter speed AND aperture.


Av mode you are controlling the aperture. The camera adjusts the shutter speed to determine the correct exposure. You are not adjusting the shutter speed.
If you take a picture in Av mode and it is too dark, you would adjust the exposure compensation to a positive value (move the needle forward). When you do this the camera decreases the shutter speed accordingly to allow more light and increase the exposure. If you take a picture and it is too bright, you can adjust the EC to a negative value, this will make the camera take the picture with a faster shutter speed, allowing less light in.

In TV mode, you are ONLY controlling the shutter speed. The camera is controlling the aperature for an automatic exposure. When you set the camera to a fast shutter speed, the camera will open up the aperature (f/2.8 for example). When you adjust it for a slower shutter speed, the camera will use a slow aperture (f/22 as an example). If you take a picture and it is too dark, adjusting the EC to a positive value will open up the aperture (from f/4 to f/2.8 for example).

It's quite simple really.. just try playing around with it. If you don't understand it fully then try shooting in full manual until you get a grasp on how SS and aperture work with the needle.

[fadetoblack22]

Yep, I get all that. If that is what the other poster was trying to say, I did not understand it that way.

[photography by trish]

It's quite simple really.. just try playing around with it. If you don't understand it fully then try shooting in full manual until you get a grasp on how SS and aperture work with the needle.

What exactly is the needle?

[fadetoblack22]

What exactly is the needle?

Its the bit that points over your exposure e.g. +2--+1--0--+1--+2
There would be a "v" over +2 if your photo was over exposed by +2.

[fadetoblack22]

Am I correct in thinking that Exposure Compensation can increase by less than a stop?
Like +1/3 or +2/3?

If so, when people say about metering off your hand and reducing your meter reading by say 2/3 of a stop, is that one of the uses for exp. comp. in manual mode?



Can someone help me with this question please? :)

[SkipD]

Am I correct in thinking that Exposure Compensation can increase by less than a stop? Like +1/3 or +2/3?

If so, when people say about metering off your hand and reducing your meter reading by say 2/3 of a stop, is that one of the uses for exp. comp. in manual mode?Can someone help me with this question please? :)As said in at least one post above, Exposure Compensation DOES NOT WORK in Manual mode.

Exposure Compensation is used to force the camera to "adjust" its meter reading when in the automated exposure control modes (at least the P, Av, and Tv modes - I don't know about the "picture" modes).

I don't know about the third-stop adjustments, as I rarely use P, Av, or Tv modes. I shoot mostly in M mode where I have total control over my exposures. I also use a handheld meter most of the time - just the way I worked long before all this camera automation (autofocus and auto exposure) came to be.

[fadetoblack22]

As said in at least one post above, Exposure Compensation DOES NOT WORK in Manual mode.

Exposure Compensation is used to force the camera to "adjust" its meter reading when in the automated exposure control modes (at least the P, Av, and Tv modes - I don't know about the "picture" modes).

I don't know about the third-stop adjustments, as I rarely use P, Av, or Tv modes. I shoot mostly in M mode where I have total control over my exposures. I also use a handheld meter most of the time - just the way I worked long before all this camera automation (autofocus and auto exposure) came to be.

On this page it explains how to meter off your hand: http://goingmanual.com/photo/tutorials.php?tutid=64#18

It says about reducing the reducing the meter reading by 2/3 stop and to have a correct exposure. How is it reduced by 2/3 of a stop?

thanks

[SimonG]

For the default camera settings, each click of exposure compensation is a correction of 1/3 EV... just try it out and you will quickly see what is happening if you watch the camera's meter.

[fadetoblack22]

For the default camera settings, each click of exposure compensation is a correction of 1/3 EV... just try it out and you will quickly see what is happening if you watch the camera's meter.

But I was just told that expsoure comp can't be used in manual, so that is why I was wondering how the 1/3 steps were used when exposing off a hand.

[SkipD]

On this page it explains how to meter off your hand: http://goingmanual.com/photo/tutorials.php?tutid=64#18

It says about reducing the reducing the meter reading by 2/3 stop and to have a correct exposure. How is it reduced by 2/3 of a stop?

thanksFrom the link you provided, I copied the following and added some highlighting:

Using auto or semi auto settings when the scene is difficult to meter will result in an incorrect exposure. You have the options of using the exposure compensation feature of your camera or possibly locking the exposure in an area that is correctly exposed. The method that offers the most control is manual.

On Canon SLR's that I have handled (which leaves out the 1D and 1Ds families), Exposure Compensation works ONLY in the auto or semi-auto exposure modes (such as P, Tv, or Av). You can use the camera's meter while in Manual, of course, but the EC feature does not even turn on if the dial is in the M position.

[tzalman]

That article you linked to is plain wrong. If you meter off your hand, you have to increase exposure, not reduce it. I'll try to explain: Let's say you meter off a grey card (as explained in the article) and the indicated correct exposure is f/8 and 1/250. Use your hand instead and the meter will tell you that the advised exposure is f/8 and 1/400 (assuming your hand is 2/3 of a stop brighter than 18% grey, like that author's). That is because the meter is trying to make a photo of your hand come out 18%, which is darker than your hand really is. In order to do this it advises you to let less light enter the camera by changing the speed from 1/250 to 1/400 - 2/3 of a stop faster. In order to get the correct exposure you have to understand why the meter is giving bad advise and increase your exposure by 2/3.

BTW, unless your have changed the default menu setting, each click of the wheel changing either aperture or shutter speed is a change of 1/3 of a stop.

When you shoot in M, at the bottom of the viewfinder there is a scale that goes from -2 to +2. Fiddle with aperture and speed until the needle is on the 0 in the middle and your camera is set to the exposure advised by the meter. To increase that exposure by 2/3 of a stop, change either aperture or speed or both until the needle is 2 hash marks to the right of 0.

[fadetoblack22]

That article you linked to is plain wrong. If you meter off your hand, you have to increase exposure, not reduce it. I'll try to explain: Let's say you meter off a grey card (as explained in the article) and the indicated correct exposure is f/8 and 1/250. Use your hand instead and the meter will tell you that the advised exposure is f/8 and 1/400 (assuming your hand is 2/3 of a stop brighter than 18% grey, like that author's). That is because the meter is trying to make a photo of your hand come out 18%, which is darker than your hand really is. In order to do this it advises you to let less light enter the camera by changing the speed from 1/250 to 1/400 - 2/3 of a stop faster. In order to get the correct exposure you have to understand why the meter is giving bad advise and increase your exposure by 2/3.

BTW, unless your have changed the default menu setting, each click of the wheel changing either aperture or shutter speed is a change of 1/3 of a stop.

When you shoot in M, at the bottom of the viewfinder there is a scale that goes from -2 to +2. Fiddle with aperture and speed until the needle is on the 0 in the middle and your camera is set to the exposure advised by the meter. To increase that exposure by 2/3 of a stop, change either aperture or speed or both until the needle is 2 hash marks to the right of 0.

Thanks. The bit I was confused about was that I know the exp. comp. increases by 1/3 of a stop each time, but I thought aperture + shutter speed were one stop. Thanks, that has cleared that up. I should know, yes, but I have not had my camera for the last 2 months because it is being fixed and they somehow forgot about it. I am trying to learn everything I can while its gone :)