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Mastering I.S.O.

Andrea Allen
June 10, 2011 by Andrea Allen Alum

Back in the days of yore when everything was black and white, cameras used film. I.S.O. was a measure of the film’s speed. The lower the I.S.O. the less sensitive the film was to light and vice versa. Now that we’re living in the future, most folks use digital cameras rather than film. Digital cameras still have I.S.O. but now it measures the light sensitivity of a sensor instead of film.
Here’s a quick video from E. Eilding that explains it even more!

So, now that we’re clear on what I.S.O. is, let’s see what the different I.S.O. settings look like! Leave it to the Vimeo community to upload tons of I.S.O. tests. Here’s an especially good one by Amila C. Kumarasinghe. He uses a very low-light setting to take us from I.S.O. 100 to 6400 on his Canon 60D.

If you paid close attention, you’ll see that the higher the I.S.O. the more light the camera picked up, but the image started getting noisy. Digital noise makes the color black look grainy and fuzzy (noisy!). Here’s another test video from Andrew Schär that shows the noise in each of the different I.S.O. settings on a Canon 60D.

So what’s the best way to use I.S.O.? Well, you’ll typically want to choose the lowest I.S.O. that still gives you a good image. In low light situations, you’ll have to bump it up but try to stay below 3200 if you can!

If you have a camera that allows you to change your I.S.O. you’ll usually be able to access it through the menu and it will probably look something like this:

*P***Pro tip:** As you’re choosing your I.S.O. there are a few settings, even low ones, that cause more noise and you’ll want to avoid. Good ISOs: 160, 320, 640, 1250, and 2500
Avoid using: 125, 250, 500, and 1000. These ISO settings create noise and make your footage look grainy.

Keep I.S.O. in mind when you’re shooting as it’s one of the more critical settings to check before you start shooting your awesome video.

3 Comments

Erfan Al-Keilani

Very cool didn't know that, now I will try to master it!

David Esp Plus

Not always less noise the lower the ISO, it depends on the camera model. For many cameras there can instead be a Natural or Native ISO, For example on a BMCC it is well known to be 800. Lower than this causes both signal and noise to be reduced, but the signal/noise *ratio* increases. This is because at the lower ISO settings all the camera does is *digitally* scale-down the value it reads from the sensor, reducing dynamic range as a side-effect. At any non-halving or doubling ISO numbers there will additionally be quantization noise. Its only those camera models whose ISO adjustment directly affects *analog* amplification at sensor level where the "lower ISO = lower signal/noise ratio" rule applies.
Some discussions on this, found by Google:[bmcc natural iso]:
1) forum.blackmagicdesign.com/viewtopic.php?f=2&t=10892
2) dpreview.com/forums/thread/2659404#forum-post-33068233

David Esp Plus

Halving-type digital scaling-down can be done by binary division, as explained at en.wikipedia.org/wiki/Division_by_two, As example, to digitally halve a 14-bit (say) sensor reading, you would shift its binary bit sequence to the right, losing the lowest-value bit. So now it's only a 13 bit digital number. Do it again - so the overall scaling is a quarter - and you end up with only 12 bits. Fewer bits means more quantization noise. Covered (to some extent) at quora.com/What-is-ISO-in-relation-to-a-camera-and-how-does-it-affect-the-clarity-of-a-photo . Except for one comment there that ignores the whole argument. The "lowest ISO => least signal/noise" rule of thumb is not as universally applicable as it used to be. Not, at least, for the present generation of cameras.

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