Depends on your camera iso ability. If it looks good at 1600 but bad at 3200 then set its auto limit to 1600. For camera like FF can set much higher.

you should also try shutter mode and see which fair better.

Errr.....you dont "generally" keep the iso as low as possible. As long as its within acceptable threshold, preferably keep it as high as possible for fast shutter. "Generally" low iso is desirable for non moving scene with tripod and long exposure at night as the noise tend to show at black areas.

Exposure is affected by aperture, shutter speed and iso. The key is to get the balance between them to get right exposure. Aperture for bokeh. Shutter for moving subject. Iso is just sensor sensitivity to light which affects noise. Therefore you can leave iso at auto as long the acceptable noise threshold is not exceeded.

This post has been edited by DaddyO: Mar 20 2015, 02:01 PM

Well for street photography i prefer having a high iso even if it creates bunch of noise than low. Its easier to correct the noise than having unusable blurry shots. So really depends on what you shooting.

yes. As i mentioned, a, s and iso are related to each other affecting exposure. The bigger aperture, the faster the shutter you can use while maintaining iso and exposure. Vice versa if you adjust shutter speed. You can test out by adjusting the aperture in A mode. You will see the shutter speed auto adjust to maintain same light to the sensor. However there is a limit to that due to the lens capability. Thus iso need to raise sensor sensitivity to maintain same exposure. This is rather technical with a lot of explanation to it so u need to study further on the effect of adjusting each setting.

It boils down to a lot of times people want low f aperture because it allows faster shutter speed to maximise sharpness and maintain low iso. But thats not always possible unless you spend a lot on big lens so high clean iso is important part of camera purchasing decision.

This post has been edited by DaddyO: Mar 20 2015, 03:37 PM