Free Photography Class #8: All about Digital Camera ISO

Learning Photography for Free #8: Beginner’s guide to Decoding ISO. It’s not hard, just not always explained well.. Read More..

What is digital camera ISO

All about Digital Camera ISO

Guess what? Short blog alert! Digital camera ISO is an important topic. However, there isn’t a whole lot more that can be said that we haven’t covered. But we will expand on our knowledge of what we already learned and provide some examples of how ISO can be used to bring our vision to life!

Digital camera ISO stands for the International Organization of Standardization. But really, that is some outdated information that originated in the time of film photography.  It is pronounced like “eye so;” and is the standard setting range that can brighten your photo at the expense of image quality.  As we learned, it’s like film sensitivity. But instead of sensor sensitivity, it is just telling the sensor how to receive the light coming into the camera from the exposure.  Although it is not technically “sensor sensitivity,” if you think of it in this way, it is much less complicated and much easier to remember what to do when the time comes to change your settings.

Base ISO- What is Camera ISO

The “base ISO” for most digital cameras is ISO 100. To get the highest picture quality possible, you want to use the lowest ISO possible (see our discussion on Exposure for examples).  It is easy to think… well I will just set my ISO to 100 all the time and forget about it, but that doesn’t always work.  The quality difference can be extremely small, almost undetectable in the lower ISO ranges. But the effect that raising your ISO can have on your pictures could be the difference between capturing exactly what you want, or a picture that is completely useless.  The biggest use of ISO is for low light situations; however, there are some other options as well.

Digital Camera ISO for Low light

In low light situations, yes ISO is an extremely useful tool.  In most situations, it may be easier to set your camera up by setting your ISO. Then your aperture, and shutter speed last. However, in low light it really depends on what you are shooting.  If you are taking images of anything in motion, I recommend setting your aperture so you capture your desired depth of field. 

From there, you want to set your shutter speed to ensure it is fast enough to freeze the motion.  Then you want to start increasing your ISO until you are at your desired lighting. Remember you can always stay safe by staying just a little darker and brightening in post processing.  Now if motion isn’t part of the equation, like landscape photography or still life images, set your ISO to 100. Then set your aperture to your desired depth of field.  After that, if you are using a tripod, you can set your shutter speed much slower. This gives you your desired brightness.  If you are handheld, you can go between ISO and shutter speed to get it just right so that you capture your subject perfectly without blurring.


Motion is going to be the game changer with ISO.  Sometimes you might be in decent lighting but can’t get your shutter speed fast enough to keep from blurring.  If you are trying to grab all that detail and can’t change your aperture, then ISO is your only option.  Once again, you would set your aperture, then the necessary shutter speed to freeze that motion. Then adjust your ISO to get your image bright enough.  You really aren’t going to see a huge difference all the way up to ISO 800. But once you start getting into double digits, the grain increases pretty significantly.  This can be fixed in post processing, but you will not gain any more detail through that process. It more or less smooths out your pictures, reducing fine details.

Artistic expression

Some individuals will use high ISOs to add the grain on purpose, creating a unique perspective on their photo or perhaps giving it a more classic photography feel.  I definitely discourage using this method, unless you are very skilled and have a thing about not using post processing. Once you take an image at a high ISO, you are stuck with that “effect.”  There isn’t a way to go back and make the picture have the high level of details it would have had using ISO 100.  You can smooth it out, but that will further reduce details. 

If you want that grain look, most post processing applications offer an option to add grain to your picture.  So, take the high detail picture, then add the amount of grain you want. At that point, you have more control of the overall quality and end product.

Still Confused? No worries!

Hey, it’s a lot to take in all at once, and as you start doing it and take your baby steps, you will learn it. If you need a training aid, or just something to carry around with you for learning to challenging yourself, here is a link to some waterproof cheat sheet cards. Before you know it, you’ll be leaving them at home or handing them to a friend for them to learn with, you got this!

That’s a wrap!

And that is it ladies and gentlemen!  You are now graduates of ISO and just need to get out there and start experimenting.  I will say I recently had a situation where I was regularly updating my ISO for the same shoot.  An event that was in 4pm light outside, in a wide-open field.  So, when my back was to the sun, many of my subjects were lit very well by beautiful amber sunlight, but when I turned around, subjects were shaded since the sun was blocked by a building, there was virtually no light. 

Since I was maintaining my field of view and had to have a fast shutter speed to keep from blurring, I had to use ISO to adjust between these two spots.  So as little as having my back to the sun or turning around, the light changed so drastically that I was constantly having to play with my ISO to keep images clear while maintaining shutter speed and depth of field.  Properly learning to adjust on the fly is the sign of a great photographer! So, get out there and start practicing on everything and anything to get your first 10,000 pictures under your belt!

Happy shooting everyone!

Photography and writing by Jon Frederick

Jon Frederick, Lead photographer, seven11
Jon Frederick, Lead Photographer for Seven11

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