I am from a time when changing ISO meant rewinding the film I was currently using, and replacing it with one of a different speed. If that film was ISO 400 or above, there was a very good chance: the prints or transparencies would look pretty grainy.
Back then though, I didn’t know it as ISO, it was called ASA but was pretty much the same thing.
In the digital age, that grain has been replaced by noise. The large dye clouds of film, replaced by amplified pixels. The end result, however, is similar, or is it?
Some changes in photographic technology seem to happen at breakneck pace, others slowly, almost imperceptibly. High ISO noise is one of the latter. That’s because it’s actually a combination of evolving technologies that have reduced its importance in day to day photography. Today I am going to give you my opinion on why high ISO no longer matters.
The Story Of ISO Noise
Early digital sensors were noisy. Stray above 800 ISO and that noise became very obvious. However, the early days of digital photography were dominated by the “pixels war”, a relentless race to produce cameras with more and more resolution.
As we know now, whilst sensor size is important, it is pixel density that is the main driving factor of noise. Whilst sensors increased in resolution, they did not increase in size, being fixed to three main types, M4/3, APS-C and the much more expensive Full Frame.
That kind of changed in 2006 when Nikon announced the D3. Rather than chase 18 or even 24mp on full frame, they went with 12mp but with significantly better high ISO performance than any camera before it. Photographers called it “black gold” and it was a huge success. But the detente in the megapixel wars didn't last long and soon noise became an issue again.
Today, however, whilst megapixels continue to increase, sensor technology and a number of other factors have conspired to make ISO much less relevant to our photography, here’s why.
Image Stabilisation
Optical stabilisation of lenses has been around for a long time and has become increasingly good. However, it is now combined with both sensor and digital stabilisation to give us up to 7 stops of exposure. Assuming we were shooting in low light and the minimum shutter speed to avoid camera shake was 1/250th, with these combined stabilisation techniques, we can bring that shutter speed down to ¼ or even ½ second, all without raising the ISO.
That’s a huge advantage particularly for sports and wildlife photographers, whose longer lenses often have significantly slower apertures. It means many of us can walk cities at night and get good quality images without having to bump the ISO up too high.
Sensor Technology
There is no doubt that sensor technology has moved on dramatically. In a recent video I made, I looked at two images, one from a Nikon D2X shot in 2007 at 1000 ISO and one from a Sony a7RV shot at 12800. The D2X was 12mp, the Sony 61mp, yet the noise levels looked broadly similar. So 20 years of improving sensor technology has given 4-5 stops improvement in noise levels.
You can add in the fact that modern sensors have better dynamic range, meaning we do not have to push them so far in editing to raise shadows – a very common cause of visual noise in images.
There are also stacked sensors and dual native ISO sensors. The latter will have two base ISO, perhaps one at 100 and one at 2500, both giving broadly similar noise levels for the correct exposure. These have been particularly good for video shooters where noise can be very difficult to control. Indeed, the Sony a7SIII, a video centric mirrorless camera has dual native ISOs of 640 and 12800. It also has only 12mp giving a very low pixel density. There are other cameras that are more hybrid that adopt the same approach, dual native ISO with a reduced sensor resolution giving good video and still images at ultra high ISOs.
AI Denoise
The last element in this triangle of technological improvements has been the introduction of AI noise reduction tools. Until recently, noise reduction has been a weak link in high ISO shots. This is both in camera and in editing.
In camera, noise reduction could be applied to JPEG files in varying degrees. However as you had no control over it, it often left you with a smeary mess of an image.
Editing apps like Photoshop and Lightroom gave you control of the noise reduction tools both for Jpegs and RAWs, but were still prone to causing images to smear if pushed too far. You could spend hours pushing the noise, detail and sharpening sliders trying to find a decent balance, often without much success.
AI denoise has changed that for good. It first came to my attention last year when editing some low light shots taken in Bangkok. I was photographing Tuk Tuks both still and moving. This meant I needed a decent shutter speed to freeze them. Despite an f/1.8 prime, the ISO was still topping out at 12800 on my Sony a7Rv.
In Lightroom the images were clearly noisy. Not horrendous but not the sort of thing that you would want to print large. However, when I ran them through the Lightroom denoise, I was blown away. Lightroom had removed 95% of the noise yet maintained the sharpness and detail of the image. This is no fluke, I tried the denoise on multiple images with the same results.
It takes a little time, depending on both the power of your computer and your Internet connection but the end result has, to my mind, revolutionized high ISO shooting.
Lightroom is not the only tool that does this now, I have also tried it using DXO Photolab and DXO Pureraw, with the latter giving even better results than Lightroom. The great thing about it is that it can also breathe new life into older images. The noisy D2X image at 1000 ISO had the same result, a very usable image.
There are some times when we might want to have a little noise in our images, perhaps a gritty landscape or a street documentary style image. However, the majority of the time, noise is a distraction, a subtle yet obvious degradation of the image.
Today however, as far as I am concerned, high ISO is an irrelevance for pretty much every shot I take. Whilst I will generally try to keep the ISO as low as possible, I know that when I need it, I can push it a lot higher and still get great results.
