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A Beginner's Guide to Why Photographers Use High ISOs

Along with aperture and shutter speed, ISO is one of the three fundamental exposure parameters, and mastering it is crucial to being able to produce successful images. If you are newer to photography, this helpful video tutorial will show you what ISO does and why photographers sometimes use high ISOs. 

Coming to you from David Bergman with Adorama TV, this great video tutorial will show you some important concepts about ISO, particularly high ISO values. A common mistake newer photographers make is sacrificing shutter speed in an attempt to keep ISO lower. It is good to try to keep the ISO as low as possible, as this gives you less noise and greater dynamic range, but if you make your shutter speed too slow, you risk introducing blur either through camera shake or subject motion blur. The important thing to remember is that there are always techniques to deal with noise from a high ISO in post, but generally, once a photo has blurring from camera shake or the motion in it, there is not much you can do to save it. It's always better to have a noisy, sharp photo than a blurry image. Check out the video above for the full rundown from Bergman. 

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15 Comments

Jan Holler's picture

ISO is not(!) an exposure parameter because it does not affect the amount of light reaching the sensor.

Paolo Bugnone's picture

...aaaaand another video where ISO explaination is wrong.
It's incredible how few people actually explain it properly.

Black Z Eddie .'s picture

Oh god, here we go again with commenters thinking ISO is not part exposure parameter. It is since it's a setting that affects the brightness of the image.

Jan Holler's picture

Well, the brightness of an image is also affected by post-processing, but no one would associate that with the exposure at the time of shooting. Talk about ISO, say that it affects the settings, but don't say that it is an exposure parameter, because it simply is not. The brightness of an image has nothing to do with the amount of light that reaches the sensor.
If we can use precise language, we should do so. Anything else will lead to misunderstandings sooner or later.

Black Z Eddie .'s picture

Well, we're talking about settings on the camera and not post processing.

Jan Holler's picture

Do we? "Along with aperture and shutter speed, ISO is one of the three fundamental exposure parameters"

Jan Holler's picture

Well, Alex, that down voting is kind of disappointing regarding the position you're in here, as, well, professional. It is correct what I elaborated. Want prove? Here it is:

https://petapixel.com/2020/03/05/iso-has-nothing-to-do-with-exposure-an-...
https://www.dpreview.com/articles/8924544559/you-probably-don-t-know-wha...

No what?

Black Z Eddie .'s picture

I was wondering when you or someone would bring up the dpreview link. smh lol

Here, I have a link also:
https://www.adobe.com/creativecloud/photography/discover/exposure-in-pho...

You are too hung up on "light reaching the sensor" broken record excuse. You are referencing input when common knowledge is referencing output. The final file. Hence, ISO plays part in the resulting exposure.

Sigh, it's like me trying to explain water is wet.

Jan Holler's picture

Just regard the ISO dial as in camera post processing, then you get the idea behind the physics. Aperture and shutter speed do control the amount if light, ISO does not. But please, feel free to believe what you want.

Black Z Eddie .'s picture

And, therein lies the problem. Your misuse or misunderstanding of terms. Post processing is in reference to changes/updates after the file is written. That's what "post" means. LOL! So, ISO is not post processing.

And, yep, me and the industry standard will continue on with the exposure triangle.

Jan Holler's picture

As a compromise, I suggest saying "exposure control" instead of -parameter (or image parameter if you want to insist on the word parameter). Just as it says in the Adobe article you mentioned. There's a reason for my insistence on precise language: if you increase the ISO, it comes at a price: noise increases, dynamic range decreases. These are variables that don't belong in the exposure equation. But feel free to understand it the way you prefer. It also doesn't matter when it comes to practical photography. At least that's true.
Edit: I did not and don't argue about the use of this so called exposure triangle. It helps to understand how to operate your camera. I just said: ISO is not an exposure parameter.

Black Z Eddie .'s picture

Man 'o man, you and your fishing expeditions.

If I've told you once, I've told you a million times, you are too hung up on light reaching the sensor angle. I'm not going to keep repeating myself, https://fstoppers.com/comment/696911

Look, you are never going to convince the world that the Earth is flat. Never.

{it's a metaphor in case that went over your head also}

Jan Holler's picture

Now that's a bit childish, don't you think?

Black Z Eddie .'s picture

No, not childish at all. I just wanted to make sure I didn't have to come back here and have to explain that, too.