Everything You Need to Know About ISO

Along with the aperture and shutter speed, ISO is one of the three fundamental components that controls light and exposure, but many people don’t quite get it. This video will help answer all your ISO questions.

I teach a photography course to sophomore students here in Japan and I always find it quite easy to explain what the aperture is and how it works, as well as the impact that shutter speed has on light entering your camera. But when it comes to explaining ISO, I often get more than a few blank stares coming back at me from students who look like I’ve just hit them over the head with a wet slab of salmon sashimi.

I always find that the easiest way to explain ISO to my students is to simply let them take photos using different ISO settings and then have them compare the results. However, even though this method of teaching ISO is effective in that they can see the level of noise and grain increasing as they gradually up their ISO settings on each shot, I’m certain they still don’t actually understand why it’s happening.

This video by Phlearn explains things very clearly and succinctly and even uses some Star Wars figures to get the point across. Who doesn’t love a bit of Darth Vader in a photography tutorial? So if you want to get out of shooting in auto mode, or you want to understand exactly what ISO is and how it works in conjunction with the aperture and shutter speed, then this video perfectly simplifies and demystifies things.

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I honestly expected more from this article. Is this really everything I need to know about ISO? Maybe it should be named "Basic introduction to ISO" or "Hey, I just found a YouTube video and wrote an 'article' by embedding the video in it" instead...

Chris Kennedy's picture

Everything huh? How about the more you increase your ISO generally the more highlight retention/details you can also keep? It's not a drastic change but when used in uncontrolled shooting conditions with mixed lighting it's also something to keep in mind.

Everything a beginner needs to know about ISO

Juan Carlos Munoz-Mateos's picture

Very misleading. Comparing the noise of shots taken not only with different ISO but also with different shutter speeds and/or apertures is totally pointless when evaluating the impact of ISO on noise. If you close your aperture or increase your shutter speed, and increase the ISO to brighten up the image, the noise will be higher not because of the higher ISO, but because you're letting less light on the detector. That's not ISO's fault!

A proper test would be to take several shots with the same aperture and shutter speed but different ISO, then put the images at the same brightness level in post and compare the noise. For some sensors the noise will be roughly similar; for others like Canon ones the noise will be lower at higher ISOs, up to a certain ISO beyond which the noise doesn't decrease any more.

I'm very curious about that - I have read a few times that in certain circumstances (or with certain sensor types?) pushing up the ISO can decrease noise. I cannot get my head around that...can you tell me more about it? Thanks.