Exposure compensation

[OfMikeandMen]

I am reading Scott Kelby's Digital Photography series and he keeps talking about metering off an object and then changing the exposure compensation a certain amount of stops. I realize there is an actual "exposure compensation" feature on cameras, however, if I were to increase the exposure compensation -1, couldn't I just increase the shutter speed and make the close the aperture? Like, if I was on F/8 for 1/250 sec. and I changed the compensation to -1, couldn't I just leave the compensation at 0 and go to F/11 for 1/500 sec? Or am I misunderstanding the use of compensation?

 

[480sparky]

F/8 and 1/250 to f/11 and 1/500 is -2 stops, not -1. Changing one or the other is the same as a -1 stop EC.

Depending on the Mode you're shooting in, the camera will change either the aperture, the shutter speed, or both, in order to achieve the EC you're dialing in.

 

[amolitor]

Exposure compensation is meaningless except in the context of an auto-mode of some sort. Av, Tv, Program, Auto, whatever.

It tells the camera "hey, figure out the right exposure, and then set the camera up to under/over expose by such and such an amount" instead of the normal "figure out the right exposure, and set the camera up to expose at exactly that"

It sounds to me like you're shooting manual? Exposure compensation might affect the meter you're matching, if you're doing meter-matching, but I dunno. Does it vary camera to camera, or is there a standard? It DOES seem to alter the meter which I am matching on my D3100, I guess.

 

[AaronLLockhart]

Exposure compensation is meaningless except in the context of an auto-mode of some sort. Av, Tv, Program, Auto, whatever.

It tells the camera "hey, figure out the right exposure, and then set the camera up to under/over expose by such and such an amount" instead of the normal "figure out the right exposure, and set the camera up to expose at exactly that"

It sounds to me like you're shooting manual? Exposure compensation might affect the meter you're matching, if you're doing meter-matching, but I dunno. Does it vary camera to camera, or is there a standard? It DOES seem to alter the meter which I am matching on my D3100, I guess.

I agree with this. Great points.

One question though, don't dSLR's have a tendency to over or underexpose by default? If so, couldn't exposure compensation make up for that issue? For example, I know that the D5000 underexposes by about .5 EV from default. So, could I not just bump the Exposure compensation up a notch and that would fix it?

 

[OfMikeandMen]

Exposure compensation is meaningless except in the context of an auto-mode of some sort. Av, Tv, Program, Auto, whatever.

It tells the camera "hey, figure out the right exposure, and then set the camera up to under/over expose by such and such an amount" instead of the normal "figure out the right exposure, and set the camera up to expose at exactly that"

It sounds to me like you're shooting manual? Exposure compensation might affect the meter you're matching, if you're doing meter-matching, but I dunno. Does it vary camera to camera, or is there a standard? It DOES seem to alter the meter which I am matching on my D3100, I guess.

I am shooting in manual mode. So, in other words, if Kelby says to change the EC -1 or +1, I should change either my f/stop or ss -1/+1 stop instead? God, his books are seeming more and more useless. I think I'm missing what all the hype is about. He's confused me in certain instances because I've learned better methods prior to reading him through Peterson. The only thing that's really helped, but was even discussed by Peterson, has been some composition basics. I really hope I didn't waste my money on his box set.

 

[hirejn]

To the OP's point, you're getting the hang of it. If you're in manual mode, yes, 1/500 is one stop down from 1/250 if everything else is the same, and f/11 is one stop down from f/8. But if you're in any programmed mode, remember that if you adjust one variable, the camera automatically adjusts another to keep exposure the same. In those instances, yes, you would use exposure compensation to dial down. The compensation dial doesn't apply to manual. You're controlling each variable manually.

It doesn't matter how you adjust the three legs of the exposure triangle. If the correct exposure is 1/500 @ f/5.6 and ISO 400, then there are multiple ways to go down one stop. Remember one stop is a doubling or halving of the light. So to go minus one, you could double the shutter speed to 1/1000, effectively cutting the light in half @ 5.6 and ISO 400. Or you could close the aperture to f/8 @ 1/500 and ISO 400. Or you could cut ISO to 200 @ 1/500 and f/5.6. Or you could dial -1 compensation on auto. Bringing shutter down 1/3 stop and aperture down 2/3 stop is also the same as going down one full stop. Exposure is simply the total amount of light in the photo. Minus 1 is minus 1; how you get there is up to you.

For the exposure to stay the same, two values must cancel each other out, and one remains the same. In the example, if you changed 1/500 to 1/250, you would then need to change aperture to f/8 to stay the same, or change ISO to 200. Technically, DSLRs don't overexpose or underexpose. On any programmed metering mode they expose exactly for an 18% gray average of the scene every time. You can't leave compensation on because when you point the lens somewhere else, the meter reading changes. If your camera varies, you can calibrate a hand-held meter to your camera.

 

[amolitor]

Well, first you should determine whether exposure compensation turns up in your meter when you're using manual mode.

Set EC to 0.
Point your camera someplace, "meter-match" to set the "correct exposure"
Now dial in say, -3.0 stops of EC.
Point your camera at the same place, "meter-match" and see if the "correct exposure" is about 3 stops less, or is about the same.

Now you know whether EC affects your manual mode operation at all. If it doesn't, and you continue to shoot manual, then leave EC alone and forget it.

If it DOES affect your meter, you have two choices:

- leave EC set to zero, and then "meter-match" but biasing the match up or down to suit your goals. You can either meter-match, and then adjust, or learn where your meter's stop indications are, you should be able to just dial it until the meter reads 0.7 underexposed, or whatever.

OR

- adjust your EC to suit your goals for the shot, and the meter-match to a 0 reading on the meter ("correct exposure" reading, whatever that looks like on your camera)

 

[KmH]

Nikon exposure compensation (EC) biases the light meter when using Manual mode.

If you set +1 EV of exposure compensation, in Manual mode the zero point on the light meter is now +1 EV.
No doubt, the meter scale is by default divided into 1/3 EV steps, and the longer lines on the scale represent the full 1 EV steps relative to the zero mark, so you can just use that instead of dialing in EC.

Not all D5000's will shoot the same +-.5 EV. There is manufacturing variance from camera to camera.

 

[AaronLLockhart]

Very good info, guys. Thank you both, Keith and Amolitor

 

[The_Traveler]

Where ec is incredibly useful is shooting in constantly varying light conditions with Aperture preferred.

On Nikons when Easy EC (Auto) [b4 menu] is set on , the EC is the back thumbwheel and you can click up or down the amount you want without looking at the screen or viewfinder. EC then resets to zero when the camera goes to standby.