do we actually need ISO settings in still photographic cameras?

I will speak about digital cameras, since ISO is an adjustment that is readily available there.

There are many times when you simply can't use flash. Sometimes is it not allowed, such as at concerts or weddings. Sometimes the subject is so far away that flash won't do you any good.

In the modern day, ISO is considered the third leg of the exposure triad. We used to determine ISO simply by choosing a roll of film that seemed like it would suit the conditions of the shoot. Today, we can change ISO frame by frame as needed.

Take a look at this ISO 25,600 sample. The digital noise ("grain") is not so bad, is it?

http://www.flickr.com/photos/samfeinstein/83995280...

Okay, that's with a modern full format sensor, but here's ISO 3200 on a compact point and shoot Canon S100. You will have to agree that the "grain" is not really an issue.

http://www.flickr.com/photos/samfeinstein/81044631...

Flash can;t do everything and if you only use a low ISO and flash you'll get very dark backgrounds.

Here is an example:

http://flic.kr/p/d9Z9Xe

Two pictures taken one after the other ... both are using flash. Notice the ambient in the background ... on the one on the left, there is no detail in the background ... the background is very dark and gives the impression that the subject is in a pitch black room ... this can give a feeling of isolation or loneliness. Also notice how we lose part of the head in the shadows of the background (black hair on black background).

On the right, I slowed my shutter down to the lowest I felt comfortable for a hand held portrait and then bumped up the ISO until my meter told me that the background would be close to properly exposed, then I let my flashes TTL do it's thing on the subject.

Here is a better example of the right hand image:

http://flic.kr/p/dj6EFP

The thing you have to remember is that newer cameras have ridiculously good noise performance. My 5DMkII is good up to 3200 with minimal noise and the new 5DMkIII is about equivalent at ISO 12800 while my old Rebel XSi is unusable past ISO 400.

The next thing is that grain/noise is better than a blurry picture.

As a professional, I assure you that flash is often the worst lighting, unless you are working with professional gear and know how to use off-camera flash well.

Your flash won't help you if you're taking a photo of something more than a few yards away genius...

Photographers do not always want to use flash. Often it ruins the shot.