To start thinking about photography noise in a digital camera we have to think about film first.Back in the old days of film, you may remember buying 100 or 400 ASA film, which was all most shops seem to stock. If the light was quite poor, as often as in the UK, a 400 ASA film would mean that a photographer could get away without flash, or that the flash could be less powerful and less obvious.In theory, using a low ASA film was a good idea, because films with higher ratings were more sensitive to light because they had larger grains of light-sensitive material, and therefore the picture looked a little grainy. If you look at old photographs of dark situations – things like jazz trumpeters in nightclubs you will see that the pictures are very grainy.
1600 ISO (bear in mind this is a Canon G9 – small sensor+12Mp=lots of noise!)
Looks pretty horrible close up
200 ISO – much better
When digital cameras came along it became possible to change the sensitivity of the sensor (the digital equivalent of the film speed) between each picture. So if light was poor, you could turn the ISO up to make the camera more sensitive – basically turning up the volume of the camera. This means that in low light you can still get a reasonable shutter speed by making the camera more sensitive.
But as with film photography, the disadvantage comes in the form of graininess which is called photography noise in a digital camera – if all the pixels are turned up to maximum sensitivity, they’ll start to interfere with each other and produce a sort of mottled effect where pixels are misfiring and producing spots of either the wrong colour or the wrong intensity. This is particularly a problem with older cameras, and also smaller cameras with smaller sensors, and lots of megapixels – where the pixels are physically close together and therefore interfere with each other more. So an old bridge camera for example will be pretty bad! It is another reason why professional full frame cameras, with huge sensors are less grainy than crop sensor cameras that most of us use because the pixels are further apart.
So the disadvantage with high ISOs is that the picture becomes slightly indistinct and grainy. How high can you go?
Sadly, this is partly up to you as the photographer – grainy pictures can look great in certain circumstances – but not others. It can make a nightclub looked dangerous and interesting, but you might not want the same effect in a church interior.
Also, as we said earlier, cameras vary a lot so 1600 ISO on one camera may be perfectly usable but dreadful on another. We always recommend experimenting and taking the ISO as high as you can before it starts to look bad, this is usually at least one or two stops less than the maximum of the camera. We used to find that our old Nikon D 90 could do quite well at 2000 ISO, but the Nikon D2X, which was a higher spec camera but older could really only manage 800. Nowadays, the D 7100 Nikon looks pretty good at 3200 ISO and the D3 and D4 even higher.So the amount of photography noise depends on your camera.
The other trick in reducing the camera shake is to make the picture deliberately a little dark. After all, it’s dark right? Slightly darker exposures will look authentic and reduce the shutter speed. So a picture taken at 800 ISO and -1 stop of shutter speed will have the same shutter speed as a picture taken at 1600 ISO, but much less photography noise. You may well be able to brighten the picture in software afterwards, but often.pictures look good anyway.
The other way of reducing ISO photography noise is to use noise reduction software. We are cautious about the use of this, it is definitely not a get out of jail free card but a little noise reduction can often help. Programs like Adobe light room have pretty good noise reduction capabilities, but they do tend to soften the image slightly. There is no such thing as something for nothing in photography!
There are a few more examples to be found here in the ask PMS section of our website.It is worth pointing out that photography noise is more of a problem on plain black surfaces – so you may get away with it in a wildlife picture where the background is mottled but the photography noise can be very clear in product pictures.
Modern cameras such as the Canon 1100 D, or 650 D or the Nikon D 7100 or D50 200 seem to cope with quite high levels of ISO without much photography noise. Bridge cameras and compact cameras especially old ones like the G9 used above can be pretty bad!