ISO Talk :-)
 

Very excited about my brand new 7D. I'm wondering if there are any rule of thumbs for choosing what ISO setting to use. I am shooting fixed at 1080/24fps/50shutter and that only leaves the aperture and ISO for adjusting exposure. I am familiar with using the aperture to expose and the side-affects of wide open and stopped down etc. What I am not familiar with is the use of the ISO settings. I would suppose that it is the equivilant of using video gain (maybe not). Thanks for the help.

The difference is that you can actually shoot at a higher ISO and get a decent image, whereas with a traditional video camera the high gain positions are pretty bad. I've shot up to 640 ISO and it is acceptable. Some people have gone higher. You probably should do some tests to see how far you think you can push it.

On the other end of things, ie., too much light, you will have to get one or more ND filters. Regular video cameras have ND filters built in. An ND .9 will get you down to the mid ranges of your lens outdoors in bright light, shooting at 100 ISO, but there may be times you want a shallower depth of field, so you might want to be able to add a .3 or even .6 on occasion.

You can go MUCH higher than 640, if you use neat video or other noise reduction software you can go all the way to 6400.

ISO 160, 320, 640, 1250 are the one to use for least amout of noise starting with the lowest, don't use 100, 125 or those in between cuz they have more noise, example: 160 is cleaner than 100 and 125, some argue that it will clip highlights because of push and pull but if you shoot manual like you are supposed to then nothing is going to clip if you exposed it properly, this is also why on the first part of that Zacuto camera shoot out, the big boys are using ISO 160 and 320 to test and not in between.

Khoi, this is very interesting. Do you happen to know why this is so?

Because the native ISO are 100, 200, 400, 800, 1600..., the intermediate ISO like 320 is actually 400 but digitally pulled 1/3 f-stop and so that is why it is cleaner than the native 400 ISO, the drawback is that it might clip your highlight if you have such a contrast in scenery so watch your highlights but if you are shooting a flat scene or low light scenes then that doesn't matter, you can clearly see the noise different between native ISO and intermediate if you hook up your camera to your HDTV and point it at a dark scenes and change your ISO and you will see that ISO 640 is cleaner than ISO 400, but there are numerous test on this already on the internet if you search for it, but I must point out that if you should mostly on bright high contrast scenes then using native ISO is better because when you have light you don't see noise and so it is better to give the highlight some headroom, I shoot in lowlight most of the time and so my brain is stuck on intermediate ISO and forgot that others might not shoot the same kind of stuff I do.

I see that there is a little bit to consider when using ISO...this is helpful stuff, Thanks!