Exposure Compensation

[hamlet]

I'm wondering why we need to use the exposure compensation? Why not just use a faster or slower shutter shutter speed to overexposing or underexposing the picture as needed? Aren't these two concepts practically the same thing?

Here is a picture of poof with a white background. This picture is very easily underexposed because the camera can think it is too bright.

If i just bump up the iso to make things brighter instead of touching the exposure compensation.

 

[manaheim]

If your camera is generally reading a scene wrong and you are working in one of the automated or semi-automated modes, exposure compensation does a bulk fix to all of your shots that generally is helpful.

BTW, that shot you have there is underexposed.

 

[hamlet]

A little, yes. I have had to bump up the original by two stops.

 

[hamlet]

And exposure compensation is only useful in automatic?

 

[manaheim]

Uh, unless I'm TOTALLY misunderstanding the situation, it won't affect manual shots at all... it might affect your meter.

 

[hamlet]

What if i'm inside a sports hall and i need a fast shutter speed and my picture will be underexposed because of this shutter speed. Couldn't i just use the exposure compensation to get the correct exposure in that situation?

 

[manaheim]

What if i'm inside a sports hall and i need a fast shutter speed and my picture will be underexposed because of this shutter speed. Couldn't i just use the exposure compensation to get the correct exposure in that situation?

Exposure compensation is not magic.

If there is no light, it can't add it.

All exposure compensation does is say "Hey, internal camera meter! The operator of the camera says you're reading this scene as brighter or darker than it is by X stops. Please adjust accordingly!"

So if your every shot is dark, but you know that ...

1. There IS enough light in the room to get the shot with a reasonable shutter and aperture.
2. The camera is just "guessing wrong".

Then exposure compensation will work for you.

The shot you have is a good example. It's a picture of a darker subject (your hamster) on a whiteish or light background.

The camera looks at any "frame" and measures it based upon a certain assumption- which is basically that when it adds up all the colors and brightness, it will come up with about 50% gray. If it gets 70% gray, it adjusts the compensation and takes the shot. Exposure compensation tells the camera that it's reading the exposure wrong by whatever you set it at.

NOTE: That explanation above MAY be exactly correct, or it may not. I've never researched the ACTUAL mechanics. There are some on this site (Notably Chris Garbz) that will be able to detail this technical process EXACTLY. Consider mine illustrative, and as an illustration, it works fine.

 

[ratssass]

...sorry,but this just came to mind,

A rabbit and a hamster walk into a bar......


...sorry,just sounds like the beginning to a joke :lmao::lmao:

 

[hamlet]

I understand now. Bunny is truly wise.

 

[manaheim]

 

[pgriz]

Exposure compensation is used to override the automatic choices the camera makes in P, Aperture priority, and Shutter priority modes. The meter is programmed to adjust the exposure until it is "zeroed" at medium grey (either 18% or 12%), which is the "average" for most scenes. However, if the actual reflectance is much higher or lower, then the meter will be fooled. Say you put Poof in front of a medium grey background, and adjust the exposure until the meter is zeroed. Let's say it reads 1/60sec at f/8. You check the image and it is well exposed with a nice bell-curve of pixels centered around 125 on your histogram. Now, put Poof on a black cloth, although under the exact same lighting conditions. Now the meter sees all that dark and tries to increase the exposure so that the scene averages out to medium grey. Unfortunately, now Poof will be very overexposed. If you put Poof on a white cloth (same lighting conditions), then the opposite will happen. The camera doesn't know what the "natural" reflectance is of the scene, but you do. And because you know, you adjust the exposure compensation to override the camera's programming (in the semi-auto modes).

However, if you determine your exposure with an incident light meter, you can put the camera in manual and put in the exposure that is correct for the amount of light you have, regardless of the reflectance of the overall scene. If you don't have a incident light-meter, you can use the spot-meter function to keep the camera looking only at the portions that are relevant for the image (Poof in this case), and this will ignore the bright or dark surroundings that would otherwise throw the meter off the correct exposure.

 

[KmH]

Like pgriz says, EC is need because the in-camera light meter is calibrated based on the assumption that most scenes average out to having a reflectance of 12% to 18% gray.

Use the camera's rear LCD histogram display to determine if (and how much) EC us needed or not.

• Understanding Camera Metering
• Understanding Histograms, Part 1: Tones & Contrast
• Understanding Histograms, Part 2: Luminosity & Color

 

[hamlet]

We have rear lcd's now?

 

[hamlet]

Exposure compensation is used to override the automatic choices the camera makes in P, Aperture priority, and Shutter priority modes. The meter is programmed to adjust the exposure until it is "zeroed" at medium grey (either 18% or 12%), which is the "average" for most scenes. However, if the actual reflectance is much higher or lower, then the meter will be fooled. Say you put Poof in front of a medium grey background, and adjust the exposure until the meter is zeroed. Let's say it reads 1/60sec at f/8. You check the image and it is well exposed with a nice bell-curve of pixels centered around 125 on your histogram. Now, put Poof on a black cloth, although under the exact same lighting conditions. Now the meter sees all that dark and tries to increase the exposure so that the scene averages out to medium grey. Unfortunately, now Poof will be very overexposed. If you put Poof on a white cloth (same lighting conditions), then the opposite will happen. The camera doesn't know what the "natural" reflectance is of the scene, but you do. And because you know, you adjust the exposure compensation to override the camera's programming (in the semi-auto modes).

However, if you determine your exposure with an incident light meter, you can put the camera in manual and put in the exposure that is correct for the amount of light you have, regardless of the reflectance of the overall scene. If you don't have a incident light-meter, you can use the spot-meter function to keep the camera looking only at the portions that are relevant for the image (Poof in this case), and this will ignore the bright or dark surroundings that would otherwise throw the meter off the correct exposure.

That is a very cohesive explanation. You know? Its about time i invest in a incident light-meter. Poof is a very demanding costumer.

 

[hirejn]

If you're shooting in a programmed mode, such as P, S or A, changing a variable does not change the exposure. If you do, the camera will automatically adjust the other variables to give you the same exposure. In manual mode, changing a variable is changing the exposure. You're overriding what the camera is telling you.