High ISO

[T&E Run]

When people say they shot 12000, 20000, 25000 ISO, how did they do it? Is it a matter of shooting in, say AV and setting the F stop and shutter, and the camera picking that ISO or what?

[SuzyView]

Well, some of the the new cameras have that capability. I think I can shoot like insane ISO 128000 or something, but I've never done it. I think I've gone to 5000 ISO on a regular basis for concerts, but I don't like the noise in the dark. Those are in custom settings.

[bacchanal]

You can shoot with a negative EC (or just underexposed shot) and push the exposure in post processing to get a higher effective ISO than you camera is capable of being set to. Of course the results will be pretty noisy.

For instance, if you shoot at ISO3200 with and EC of -1, then you add +1 exposure correction in post, you effectively have an ISO6400 shot.

Some cameras (like the 5DII and 50D and probably just about anything released in the future) can actually be set to those ridiculously high ISOs in camera.

[Pete]

Later cameras like the 5D Mk II can let you set the ISO up to 25600. For cameras without these high ISO setting, it can be "pushed" in post processing as drew points out above.

Basically, a correct exposure is made up of aperture, shutter speed, and ISO. Many people starting out in photography will simply leave their ISO set to 100 because they're not sure what it does.

When you understand that you can use ISO to extend your exposure capabilities, it becomes second nature.

Usually, people think in two exposure "dimensions" (either choosing shutter speed or aperture priority). Changing the ISO up or down allows a third "dimension", so that you can select a shutter speed and aperture that suits your purpose and then change ISO to allow that combination to give you the correct exposure for the lighting conditions.

As an example, motor racing.

Typically, you might want a shutter speed of 1/250 or 1/500 in order to freeze motion (but allow some blurring of the wheels at speed), and you also want a mid-range aperture (f/6.5 - f/10) to control your depth of field (you want the background to be blurred a bit, but you want the whole bike/car to be in focus if you can).

In overcast conditions, this combination would lead to underexposed shots - but when you increase the ISO, the correct exposure can be obtained.

The downside to high ISO is image degradation (increased "noise"). A good camera can help with this (5D is famously good at high ISO), as can noise reduction in post processing.

[T&E Run]

Thanks to all three of you. Makes since now. Good example with the motor racing Pete.

[asysin2leads]

Later cameras like the 5D Mk II can let you set the ISO up to 25600. For cameras without these high ISO setting, it can be "pushed" in post processing as drew points out above.

Basically, a correct exposure is made up of aperture, shutter speed, and ISO. Many people starting out in photography will simply leave their ISO set to 100 because they're not sure what it does.

When you understand that you can use ISO to extend your exposure capabilities, it becomes second nature.

Usually, people think in two exposure "dimensions" (either choosing shutter speed or aperture priority). Changing the ISO up or down allows a third "dimension", so that you can select a shutter speed and aperture that suits your purpose and then change ISO to allow that combination to give you the correct exposure for the lighting conditions.

As an example, motor racing.

Typically, you might want a shutter speed of 1/250 or 1/500 in order to freeze motion (but allow some blurring of the wheels at speed), and you also want a mid-range aperture (f/6.5 - f/10) to control your depth of field (you want the background to be blurred a bit, but you want the whole bike/car to be in focus if you can).

In overcast conditions, this combination would lead to underexposed shots - but when you increase the ISO, the correct exposure can be obtained.

The downside to high ISO is image degradation (increased "noise"). A good camera can help with this (5D is famously good at high ISO), as can noise reduction in post processing.

Excellent example, Pete.