I want to make a very clear point here that low ISO values can damage our photos just as bad as really high ISO. How is this possible? Well, sometimes trying to avoid the grains that the higher values produce we have to reduce the shutter speed to compensate thus getting motion blur which is really worse than a few grains we can later fix in Photoshop. Also, have in mind that exposing longer with a lower ISO value will produce more noise than shorter exposures of the same value. The longer the exposure the more noise piles up.
Being able to change this value is a major breakthrough in photography. Back in the day people would just buy a film with a certain speed (that's ISO or ASA) and try to figure out the rest according to the light conditions. Nowadays, we can change the sensor sensitivity of our cameras with one button making it possible to emulate different film speed for every shot. Why should we be afraid of using higher values then? We really shouldn't! Instead we should master this setting and use our cameras to their full extent.
Here's what we need to remember when using this setting:
- Smaller sensors produce more noise than bigger ones.
- More megapixels means more noise (comparing the same size and year of manufacturing sensors) at higher ISO values.
- Grains (or noise) will appear in the shadows or darker areas. Light areas of the photo will appear clear.
- Wider aperture lenses will give the effect of less noise because they let more light through for the sensor to capture.
- Raw files will always look noisier than the jpeg because the first ones are an exact extract of all the information the sensor delivers, whereas the latter are missing lots of the information (noise included).
Let's check out a few examples where high ISO value is more than a friend.
- Concert photos. You need to go ahead and boost your ISO so you can avoid motion blur. (click here for all the advice you need about stage shots)
- At the church. It's dark and using flash will just make your photos look bad.
- The long restaurant shoots with plenty of guests. Even though shooting with a flash is a must you still need a higher ISO to save your flash and batteries and to get some background. Also it looks better when you use flash + higher ISO so you don't overflash and get a better and more natural overall lighting. For more tips on wedding shots click here.
- Every time your speed drops below 1/60 of a second and you feel you're getting shaky images. Don't worry if you're shooting using automatic or some of the semi-automatic modes - the camera will boost the ISO for you.
- When you want to overexpose the background.
- When you want to expose the object and the background properly (e.g. night portraits with flash, freeze a certain frame in low light conditions)
Anyway, we also need to try and keep the ISO to lower settings in the following cases:
- When you have more than enough light to shoot with high shutter speeds.
- When you are going for long exposures and do not care about motion blur. Then you need lower ISO because the longer you expose the more noise you get. Noise just piles up when you expose longer.
- When you are shooting at the studio using a darker backdrop. More info on backdrops - click here.
- When you are after a higher contrast shot. You want to emphasize more the difference between shadow and light. Of course you'd need more light for such shots.
Newer cameras have wider ISO ranges that have crazy values. I rarely go over 1600 and almost never below 200. I am very pleased with the results even though I am currently using a 2009 model. So, if you've got a brand new dSLR or SLT, you might as well go ahead and test that ISO boost.
One final thing, images always look worse when you zoom in on a computer screen than on paper. Don't be too critical! Go ahead and do some printouts. I am sure you'll be more pleased with your results on paper.
All the best,