How to underexpose/overexpose

[scott1120]

a shot. I shoot aperture priority most of the time, how would I underexpose an image? Do I just close down the aperture? Example: If shooting outdoors with sun at f/11 would changing to f/16 or f/22 give me underexposed image? When would I use Exposure Compensation button?

[Daniel Bates]

Yes, shooting at f/16 or f/22 would give you an underexposed picture as long as the shutter speed and ISO stay constant. In Av, you will have to ride exposusre compensation to under or over expose an image; in manual, you can change ISO, aperture, or shutter speed independently to do the same.

[zepp]

Originally Posted by scott1120

Example: If shooting outdoors with sun at f/11 would changing to f/16 or f/22 give me underexposed image? When would I use Exposure Compensation button?

When shooting in a program mode, such as aperture priority, changing the user selectable setting, aperture in your example, will adjust the other setting, shutter speed, to give you the same amount of light/time hitting the sensor. It's only when adjusting the aperture to an extreme that an appropriate shutter speed might not be able to be selected by the camera to make an equal exposure. In this case you get an unintentional over or underexposed picture as far as the meter is concerned.

To intentionally under or overexpose a meter reading, while using a program mode, use the exposure compensation function of the camera.

Here's an example of how a meter might be fooled and how to make a corrective setting...

Your shooting out in bright overcast sky conditions where the majority of the frame is filled by the sky. The camera meter is going to give you a meter reading trying to render the image a neutral gray. If your wanting the sky to be bright as your eyes see it you would dial in + exposure compensation letting more light hit the sensor making the image brighter. The opposite is true for a dark image. Flash exposure compensation works the same way.

As Daniel said, you can also use manual control, and dial in the exact exposure you want.

Example... I'm in spot meter mode and my subject is wearing white shirt which is read by the meter. If I want the shirt to be exposed as white and not a dingy white/gray, I adjust my exposure settings, aperture/shutter speed combination, to read about two stops overexposed.

It's all in your hands, as the photographer, to create the image, exposure included, the way you want your viewer to see it.

[josphy]

Aperture Priority mode is going to even everything out for you, so if you change the aperture one way or the other, it will adjust the shutter speed accordingly, and you'll still end up with the same exposure.

For what you are trying to do -- underexpose or overexpose -- use the Exposure Compensation.

Or, you can also shoot in manual mode and then as long as you keep the shutter speed the same, opening or closing the aperture will result in over or under exposure.

[raevyncent]

If manual is still a bit , um , scary for you ( I have no idea of your level of expertise), using the exposure compensation button/setting/adjustment on your camera in a semi-auto mode like aperture or shutter priority is a good way to learn what setting create which results. Try shooting an image with a large varience in brightness( like a backlit subject or a shaded subject on a bright day) on the camera metering, then compensate both up and down 1/3 to 1/2 stop at a time to a full 1 1/2- 2 stops both under and over exposed. Do this on a tripod so the camera metering stays consistant, and note down what reading the camera selects for each exposure compensation. It is one of the easiest ways to transition yourself to shooting manual without needing to always meter the scene.

Anthony

[Hogleg 44]

Then too, you could frame and read the camera setting while in AV mode, then switch to manual, and set the shutter speed to give the exposure you want, reframe and shoot.

[scott1120]

Thanks guys. I am still trying to new this camera. On my Canon I could shoot in manual, probably because I could see the difference in the viewfinder. Granted I have not played with manual much with the Nikon. But everything I have been shooting lately AV is just fine. But then again If I am not happy with my shots in AV there is not since switching to manual.