The first thing you typically learn about ISO in photography is that your ISO is your camera sensor’s sensitivity to light. The higher the ISO, the more grain we’ll have in our photos. We all got that right? Awesome. But here’s 2 things you didn’t know about ISO.
Let’s make sure we’re on the same page first.
SETTING THE ISO
Say we want to have full creative control in our photography. Who doesn’t want that right?
In order to do this, we’ll usually twist our camera mode dial right on over to Manual Mode. This way, we’ll have control over the Aperture, Shutter Speed and ISO.
Notice the order I put those in?
Speaking for myself, I know when I’m working to get a creative look in my photos, I’ll usually start with Aperture or Shutter Speed, never ISO.
The reason for this is that I always want to choose as low an ISO as possible to avoid any unnecessary grain in my photos because the higher the ISO the more grain we’ll have in our photos. But we already knew that.
So after selecting my desired Aperture and Shutter Speed, I’ll only touch my ISO if necessary. Usually, on a bright day, I’ll try to keep it between ISO 100 and ISO 400. Notice the nice sets of digits there?
I’ll explain what I mean in a second.
So to summarize, ISO is typically the last exposure setting that I’ll set. The only reason I’ll ever increase my ISO is when my scene is simply too dark for the other settings to adjust for. For example, in Astrophotography I’ll usually bump my ISO up to ISO 1600 to ensure I get that bright Milky Way core shining through my photo. Other than that, it basically stays between ISO 100 and 400.
But why am I choosing those numbers?
THE FIRST THING YOU DIDN’T KNOW ABOUT ISO
Native ISOs
Remember how I brought up the sets of digits I was using? Well, I was referring to the nice full Stops of ISO 100 and ISO 400. If you’re curious to learn more about Stops, check out this post.
Typically, DSLR cameras allow you to change your ISO in thirds of Stops.
For example, going from ISO 100 to ISO 200 is a full Stop. This means we are letting in twice as much light when we jump from ISO 100 to ISO 200.
But, our DSLR will allow us to adjust this in thirds So if we wanted, we could bump up our ISO by one-third to ISO 125, or by two-thirds to ISO 160 before reaching the full stop of ISO 200.
I know it’s a little tricky, but when you get home today, pick up that DSLR and play around with ISO and you’ll see what I mean.
I usually don’t use ISO 125 or 160 though and here’s why.
Every DSLR camera has a native ISO. For my camera it’s ISO 100. This means when I take a shot at ISO 100, my camera’s sensitivity to light is actually at ISO 100. Every full stop after that like ISO 200, ISO 400 and so on are also native ISOs.
Stay with me here!
However, if I take a shot at ISO 125, what the camera is actually doing is shooting at ISO 100 and then digitally brightening the image to ISO 125.
So, it’s actually better to bump up a full Stop to the next native ISO, like ISO 200, rather than shoot at ISO 125.
It’s not really a big difference unless you’re blowing up your photos as huge prints, but you never know what might turn out to be a beautiful print down the road. So for good practice, I always try to shoot at native ISOs.
THE SECOND THING YOU DIDN’T KNOW ABOUT ISO
ISO affects Dynamic Range
Raising your ISO is going to reduce the overall colour and dynamic range in your photos. What the heck does this mean?
Think of an HDR (or high dynamic range) photo. Usually, when we see images that are considered HDR, we associate them with having lots of colour and tones. Sometimes even too much. But basically, dynamic range is the amount of light intensity from the highlights to the shadows in a photo.
But how does dynamic range tie in with ISO?
Well, the lower your ISO (like ISO 200), the more dynamic range you’ll have in your photo. The higher the ISO (like ISO 6400) the less dynamic range you’ll have in your photo.
The reason why you lose dynamic range with higher ISOs is because the higher the ISO, the more your camera will be clipping the highlights and the shadows. Images with high ISOs just don’t have that pop and look rather flat.
So, to maximize your dynamic range (in other words to get as much range in colour and tone as you can in your photo) use the lowest possible ISO.
SUMMARY
ISO does more than just affect the amount of grain in your photos.
- Sticking with native ISOs like ISO 100, 200, 400 and so on will ensure the best possible image quality as opposed to ISOs like 160, 320, 640 and so on. Do check your DSLRs native ISO though as yours may be different from mine.
- Staying with as low an ISO as possible will produce a photo with much more dynamic range than an image with a high ISO
If you knew these things already, you’re amazing and you get a virtual high-five. If you’ve read a few of my posts, you know I don’t hand those out too often. (I wish the winky face didn’t look so cheesy, otherwise I’d insert it here).
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These are the tips that gave me creative control over my photos. Now, I actually understand how to use my DSLR to get the feeling I want and capture the moment each and every time!
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One more from one of our recent adventures for the road!
David Sweetman
After moving from 35mm SLR I am finding it difficult to adjust to a DSLR, I find it hard to make the adjustments that came naturall with my old SLR, purely because the DSLR is so powerful in its adjustments, but what i have just read hear has put me back on track, so I’m going to play. with a 35mm I would have been pretty much stuck with the 100ASA or ISO of the film that was in the camera, and worked around it, thank this is a good tip, and it makes sense.
Claire
Hi David,
I’ve just returned from my visit to see Mickey in Florida. My apologies for the delay.
That’s the trick though! Keep playing and soon your DSLR will become natural for you too. It just makes my day to hear that this article has put you back on track. Thanks very kindly David and best of luck with your new DSLR.
So then, what is the benefit of the higher ISO’s in DSLR cameras? When is it beneficial to use the higher ISO’s like 12,800 and higher?
Hey Kim,
In my experience, I like using a higher ISO for Astrophotography, so that would be the benefit of DSLRs having higher ISOs for me.
Staying on that topic, Astrophotography would be a great one to use ISO 12,800 for. Check out some of Alyn Wallace’s work where he uses that ISO here.
Hello you teaching are quiet good to me, it is really encouraging how to use my Canon EOS 4000D Camera.
That’s wonderful news! Wishing you wonderful adventures to come with your Canon camera!