High ISO, or Needs Must When the Devil Drives

Digital SLR manufacturers seem to have abandoned the quest to cram as many millions of pixels onto the sensor as they can. Now the preference is to ensure that the pixels are of the highest quality, so that the sensor sensitivity can be jacked up to almost hysterical levels.

Experienced photographers can probably skip this bit: ISO is derived from film, where films with high ISO ratings were more sensitive to light. So photos could be taken in lower light levels than with lower ISO ratings. This usually came at a cost in terms of “grain” in the film: higher ISO shots were perceived to be of lower quality than lower ISO shots. With digital cameras, the same exists. ISO is sensitivity to light. The effect is achieved by ramping up the power to the image sensor in the camera. With more power (or “gain”) at the sensor, the amount of light required to allow the pixel to be sensed decreases. Consequently, the probability of a false sensing increases. Where a pixel is fired but there is no light, this is viewed on the image as a random colour of pixel, and is referred to as “noise”. While Digital SLR manufacturers are pushing for headline ISO ratings, their view of what constitutes “acceptable noise” differs from Digital SLR users…

For me, there are two thresholds: “detectable noise”, where you can see the noise in the image, and “acceptable noise”, above which the noise is having such a disruptive effect on the image that it”s essentially unusable.

For the entry-level dSLR I had, Canon”s 350d, “detectable” was somewhere between 200 and 400, depending on conditions. “acceptable” peaked at around 800. The 5d raises the detectable noise level massively: 640 is attainable with no problem. Acceptable is up to ISO 1250. By contrast, a pocket digital camera”s “acceptable” level is 400.

Karen Douglas in a shot that would have been impossible without an ultra-sensitive camera

So, I found myself at a function in a room that was essentially dark. Clearly, my own threshold was going to have to be raised. I had with me a Canon EOS 1d MkIII. I’ve taken shots with this at ISO 1000 where there wasn’t any detectable noise, so I went for it, pushed it. Turns out that ISO 2500 was entirely usable. Some ISO 2000 shots taken a few days later showed little noise, but slightly diluted colours that could be fixed in post-production.

So, the 1 series proves its worth.

And for those of you wondering why this makes a difference? Well, the difference is that not only do I get to use the ISO to facilitate a greater level of creativity, but also I can sometimes get shots that for me have acceptable noise, but which on other cameras are an horrific mesh of mashed colours.