Auto ISO?

[MikeBcos]

might be the case on higher level cameras (I have a 400D in canon) though whilst I have heard of limits for ISO I have not heard of them for things like shutter speed or aperture.

My Nikon D40 allows me to limit the ISO level when using auto, it also allows me to select the shutter speed at which it will start to increase the ISO, so if I was using my 70-300 I would probably set it so the camera started increasing the ISO at 1/125 or 1/250.

 

[rangerrick9211]

Thanks again for the replys. I appreciate the help.

 

[tsaraleksi]

To me, the auto ISO function has the same failings as any other automatic selection function, along with the same benefits. The failing is that you give up control of the exposure, with the benefit being the same-- you don't have to pick what to use. The possibility of adding too much noise to the image aside, you're going to run into issues of over or under exposure if you're shooting a hard to meter situation, etc.

As far as selecting an ISO: the first thing is to know the characteristics of each ISO-- how much noise does it have, for what situation would you consider it acceptable? For example, I might feel comfortable shooting something for a newspaper page at a much higher ISO than I would be comfortable shooting a wedding or portrait for large print. Next, figure out what you want for your other settings, or, if you're in Av or Tv, set it to whatever you like and look at how everything is responding. If the settings don't work out, change the ISO until they do or until you hit your ISO ceiling, in which case you need to change something else.

Just think of ISO as another variable like shutter speed or aperture.

Finally, to quote the Kodak box-- 100 and 200 are good for sunny days, 400 is good for overcast days and well lit interiors, 800 is good for movement in poor light, and on up (which doesn't have a correspondent Kodak comment) are there when you need them for low light movement or just very low light.