ISO tips needed

[ThatsSomeBadHatHarry]

I'm having a little difficulty finding a decent amount of information on the relevancy and function of ISO. I gather that it is higher ISO settings are for low-light situations but also can really increase the noise in the photograph. In messing around with my camera, i'm not seeing any huge differences in ISO settings that aperature and shutter speed don't handle.

I guess i'm basically asking what the function and positives/negatives are of ISO. It seems to escape me. Thanks

 

[SuPrBuGmAn]

When you are shooting in lighting that is too low for you to get a sharp image, even if you are shooting wide open(largest possible aperture), due to subject or handmovement, you can increase ISO, which will allow a faster shutterspeed. Hopefully fast enough to freeze the action, the increased noise(sometimes not so noticable, especially once resized) is the tradeoff.

You can also bump the ISO to increase the grain for artistic applications. Noise can be added in post processing, but you'll typically get a more filmlike looking noise/grain incamera.

 

[alcina]

Yup.

In general, use the lowest ISO setting possible for underwater work. Noise will increase with each step up. Some cameras handle this better than others (Canon slrs, for instance, are quite good at high ISOs).

You will notice noise at full size for sure...in web size, you might not notice it too much. Blues and blacks, shadow areas etc are the worst.

 

[Matt S.]

When your shutter speed is as slow as you can tolerate, and your aperture is wide open, and you still don't have enough light... you need a higher ISO. To put it another way, if you want to freeze action without using a flash, turn the shutter speed up and use high ISO to compensate for less light hitting the sensor.

High ISO does mean more noise but the amount depends on the camera. My camera has a lot of noise at ISO 400. A DSLR might shoot ISO 1600 relatively cleanly though.

 

[tech108diver]

I'm just hamering in what has already been said. ISO is the equivalent "film Grain" and higher ISO's while creating more image noise(specs in the picture) will allow you to get more still pics in low light with out or less use of the flash.

I have a sd700 with a Canon Brand underwater housing. and if im in the darker areas I allways opt to up the iso before going to flash, because on a little point and shoot camera like that the flash is just not up to the task of shooting sea life more then 5 feet away.