When Does ISO Matter?

Modern cameras have amazing high-ISO capabilities. Back in the days of film, ISO 400 was considered high-ISO by many (including Fujifilm, who designated all their ISO 400 films with the letter “H” for high-speed), and ISO 1600 was ultra-high-ISO, used only out of absolute necessity or by the brave who wanted a certain gritty look. Nowadays some photographers don’t even think of ISO 1600 as a high-ISO setting, and don’t think twice about using it. For many, high-ISO doesn’t really begin until ISO 3200, and ultra-high-ISO doesn’t begin until you go above ISO 6400. It’s really unbelievable!

The real question is this: when does ISO matter? Since modern cameras make such good-looking images at incredibly high sensitivities, when should you start considering image quality degradation? When is a certain ISO setting too high? That’s what I want to answer.

Of course, since this is the Fuji X Weekly blog, I’m discussing Fujifilm X cameras, specifically X-Trans III. This won’t apply 100% to other cameras, but it’s still relevant to some degree no matter the camera make and model. If you are reading this with another camera in mind, take everything said here with a small grain of salt.

I did a little experiment just to better understand all of this ISO stuff. I already knew the answer from experience even before beginning the experiment, but I wanted to see if my instincts matched reality. I captured a few sets of identical pictures, all straight-out-of-camera JPEGs from a Fujifilm X-T20, using ISO 400 and ISO 6400. I made sure that all of the settings were the same between the identical pictures except for ISO and shutter speed. This isn’t 100% scientific, but it’s a controlled-enough test to draw some conclusions about ISO capabilities.

Here are the original pictures:

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ISO 6400

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ISO 400 – my Velvia recipe

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ISO 6400

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ISO 6400

There’s not a lot that can be learned by looking at the above images, other than when viewing images on the web the ISO doesn’t matter whatsoever because it’s incredibly difficult to spot the differences even when comparing side-by-side. In real life nobody does side-by-side comparisons, that’s pretty much an internet-only thing, so it would be impossible to tell if a picture was captured using a low-ISO or high-ISO just by looking at it on your screen. We need to look much closer to really gain anything from this test. Below are some crops from the above images.

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ISO 400

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ISO 6400

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ISO 400

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ISO 6400

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ISO 400

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ISO 6400

If you study the color crops carefully, you’ll notice that the ISO 400 images are cleaner, sharper and have just a hair more dynamic range, but the differences are quite small and subtle. You really have to look carefully to find them. With the black-and-white image, the differences are even less obvious, and I actually prefer the ISO 6400 version, as it seems to have a more film-like quality. Looking at the crops clarifies things a little, but what kind of conclusions can we really draw?

My opinion with regards to color photography and ISO is this: if I’m printing smaller than 16″ x 24″ or displaying the pictures on the web, I don’t find any practical difference between base ISO and ISO 6400. Even ISO 12800 can be acceptable, especially if I’m not going to print the picture. If I’m going to print 16″ x 24″ or larger, a lower ISO is better, preferably less than ISO 3200, but it’s not a big deal to use up to ISO 6400. The ISO that I select does not make a huge difference to the outcome of the image, so I don’t worry a whole lot about it. Put more simply, if I print large, it’s preferable but not critical that I use a lower ISO, and if I don’t print large it doesn’t matter at all.

My opinion with regards to black-and-white photography and ISO is this: the ISO doesn’t matter much at all no matter how large I’m printing, and I often prefer (just by a little) high-ISO over low-ISO because it looks more analog. I freely use without hesitation any ISO up to 12800. Thanks to the Acros film simulation, Fujifilm X cameras are some of the best monochrome cameras on the market, and with that film simulation, often times the higher the ISO the better.

These are, of course, my opinions, and not everyone is going to agree with them, and that’s perfectly alright. Find what works for you. Use a higher ISO or lower ISO if that’s what you need for your pictures, because, after all, they’re your pictures. I’m not here to judge your camera setting choices, only to offer mine, which I’m hoping is helpful to some of you. I hope that this article makes sense and clarifies some things regarding high-ISO on Fujifilm X cameras.

Below is a video that I made on this topic:

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2 comments

  1. Khürt Williams · 11 Days Ago

    There’s not a lot that can be learned by looking at the above images, other than when viewing images on the web the ISO doesn’t matter whatsoever because it’s incredibly difficult to spot the differences even when comparing side-by-side.

    The modern sensors in these camera bodies are incredible and we all benefit by not worrying about ISO noise as much as we did several years ago.

    Liked by 1 person

    • Ritchie Roesch · 11 Days Ago

      It’s amazing how far digital camera technology has come. What cameras now are capable of would have seemed impossible 15 years ago.

      Like

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