Understanding the ISO performance limits of your camera will help you achieve the best quality images possible. As you use higher ISO values the images become less sharp i.e. noisy/grainy. This blog post will provide you with an approach to choosing the maximum ISO acceptable for your camera.
In December 2020, after purchasing a Nikon Z6ii Mirrorless Camera, I performed an
ISO Study comparing Z6ii to the Olympus E-5 DSLR I had been using for over eight years. Over that period there had been significant improvements in sensor performance. Now, over 1 1/2 years later, I wanted to repeat the test a little more scientifically. I searched online and found two test charts that better allowed me to evaluate possible color shifts and loss of sharpness at higher ISOs than what I used in the original ISO Study.
Here are links to my test charts [Color Chart and Resolution Chart]. The charts both are open source and can be used for personal use only. I printed the two charts on 8.5 x 11 matte finish photo paper, at 600 dpi, using an Epson Sure Color P800 Photo Printer. However, printing at 300 dpi on any color photo printer will work. Using the photo printer allows you to obtain a high-quality print. I then mounted the cards side by side on a piece of foam board.
{Note: Many of the photos displayed in this post can be double-click
to see them larger on your screen}
Using the set up pictured (above), I took multiple photos changing the ISO. The use of the umbrella light, with a 3200K incandescent photoflood lamp allowed for constant lighting throughout the test. It’s important to have constant lighting so you get consistent results from photo to photo. Any brightly lit area should work well.
For the test photos rather than using Automatic White Balance as I normally do, I set the camera White Balance to 3200K, to ensure the most accurate colors. (See Comparison below) Sometimes Auto White Balance just doesn’t get the right setting.
Using the Nikon Z 28-70mm f/4 S kit lens, I placed the camera about 28 inches from the test charts. I chose this distance so that the subject would fill the frame. I used the following camera settings: Aperture Mode, f/8 with a focal length of 50mm. I chose f/8 as it is often the sharpest setting for most lenses. I then took a series of photos using the following ISO settings: 100, 200, 400, 800, 1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6400, 8000, 10,000, 12,800,16,000, 20,000, and 25,600.
Using a photo editing program*, I did a side-by-side comparison viewing the left side of the Test Chart at 1:1 (100%) for any color change. There were no apparent appreciable color shifts at any of the ISO’s tested. However, it can be easily seen that the ISO 25,600 setting has a lot more noise than ISO 100. (See Photos below)
*Any photo editing program will work, I used Capture One.
{For simplicity, a limited the number of photos taken
during the testing that are presented here}
I then did a side-by-side comparison, viewing the right side of the Test Chart at 1:1 (100%) for any change in sharpness. The sharpness remained reasonably consistent (IMHO) from ISO 100-6400 and can be easily used with minimal post-processing*. ISO 6400-12,800 would require more post-processing. Above, ISO 12,800-25,600, extensive post-processing would be required. As I will likely not use these higher settings in my photography, I’ve set my camera’s maximum ISO to 6400. Selecting the maximum ISO for your camera is entirely up to your judgment. It depends on how much fuzziness you are willing to accept and how much post-processing you want to perform?
(*minimal post-processing: using very little photo sharpening/clarity techniques beyond what is applied automatically by the photo processing software)
At ISO 8000-25,600, results are presented below:
My advice is if you want to understand the ISO limits of your camera, you could repeat the testing I have outlined above or visit dpreview.com which provides reviews for many old and new cameras. The ISO performance information is usually under the Noise and Noise Reduction section part of their reviews.
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