When is your camera’s high ISO too high? That’s a difficult question to answer. I think it depends on your tolerance for high ISO images, the subject of the photograph, and how the photo is eventually going to be viewed. If you’re a photographer then hopefully you have a pretty good understanding of what ISO is and how it’s used. Basically, it’s your camera sensor’s sensitivity to light and it generally corresponds to film speed (what we called ASA). The higher the ISO the more sensitivity to light, which allows photographers to shoot in darker conditions. But there is a tradeoff—photography has always been about compromise.
The downside is, with higher ISO, more noise (what we called film grain) starts to appear in your image—especially in the shadows. Modern digital cameras have really improved in this area and are capable of producing acceptable results at a really high ISO. For instance, a few years ago, my shot of the abandoned house pictured above would have been almost impossible given the shooting conditions I faced: I couldn’t get into the house with a tripod, I was shooting handheld through a broken window, and the interior was really dark. I needed an aperture of f/13 for maximum depth-of-field which pushed my ISO to a whopping 12,800.
Even now an ISO of 12,800 makes me shudder. However, my Canon EOS 5D Mark IV full-frame DSLR handles high ISO and dynamic range very well. This is a high-resolution image that will easily print large and still keep its detail. How is that possible with an ISO of 12,800? First, it’s a dark gritty image of urban decay with deep shadows I never intended to raise in post. Raising (lightening) dark shadows of high ISO photos increases digital noise (grain). Second, I have some tolerance for noise in gritty, urban images like this—it increases the grittiness factor. Finally—viewers will see this on the web or from a distance if printed large.
Technical Field Notes: I took this photo with my Canon EOS 5D Mark IV 30.4MP full-frame DSLR and Canon EF 16-35mm f/4L IS USM ultra wide-angle zoom lens. My camera settings were: 1/25s handheld @ f/13 ISO 12,800 @ 35mm. My lens has IS so a shutter speed of 1/25s was sufficient. I needed an aperture of f/13 for maximum depth-of-field and the auto-ISO self-selected for 12,800 (the maximum ISO I’m willing to shoot with on this camera). I intentionally left the deep, mysterious shadows and blown highlights as they were for dramatic effect. This shot would not have been possible without using a very high ISO. SFD