Modern digital camera technology has blessed us with something we never used to have: noise-free, high ISO photos.
Cameras have come so far in their ability to capture images at high ISOs that camera manufacturers have started to really use this as a selling point. You'll often see modern DSLR cameras advertised as being capable of ISOs of 25,600, or even as high as 128,000. In fact it's kind of like the new megapixel (and contrary to popular belief, high megapixels aren't necessarily better). But should you really use this as a reason to purchase or not purchase a digital camera?
[ Top image early morning in Africa by Flickr user [phil h]]
The answer is a rousing maybe. There's really no question that noise free images of look better than images that have a noise. Noise is detail killing. It's distracting. It can be just plain ugly. But is that all there is to high ISOs—the ability to give us noise-free images in low light?
A little-known fact about those higher ISOs is that it's not just noise you have to worry about when you use them. You are also losing some total range and color range when you shoot at higher ISOs. What that means is that you get fewer colors, and less dynamic range between true black and true white. The result is an overall loss of image quality, and it's not just related to digital noise.
אוריה by Flickr user asafantman
High ISO alternatives
How important is that, though? Well, like so many answers to so many photography questions, it depends. It depends on your equipment, it depends on the amount of light in the scene, and it depends on how important it is to you to capture the shot without any motion blur. If for example, you were taking a picture of a cityscape at night, you don't really want to lose color or total range. You want all of those city lights to be brilliant, you want the colors to be true, and of course you want to limit the amount of noise. In a case like this, you probably want to opt for the lower ISO, because motion blur isn't going to matter so much to you. In fact some types of motion blur like car like trails might actually improve your image. So there's really no point in shooting at the higher ISO, unless for some reason you don't happen to have your tripod with you, and you have no choice.
Multiple Reflections at The Singapore River by Flickr user williamcho
Now let's look at a different example. Let's say you're indoors, and it's just as important to have the entire room well exposed as it is to have your subjects well exposed. In this situation, you may not care so much about the noise, but you might care about color. Again, you may want to consider alternatives to turning up your ISO, such as bouncing the light from an external flash off of the ceiling. That will add some diffused light to the scene, give you a good exposure, and you won't have to worry about losing any color range or total value.
A third scenario might be a scene in which depth of field isn't all that important to you. In that case, instead of turning up your ISO, you can just use a 50 mm f/1.8 prime lens, or another lens that is capable of very large apertures. You'll get a lot less depth of field and a shot like this, but the trade-off will be that you'll have better colors and better tonal range.
Now don't get me wrong, I am a fan of the higher ISO capabilities of modern digital cameras. In the early days of digital, you couldn't shoot anything at a high ISO without sacrificing a lot of quality. Today it's different. To see what I mean, compare an ISO 1600 photo from 10 years ago to an ISO 1600 photo from a modern digital camera, and you will see a huge, very noticeable difference in quality. So I'm definitely not saying you should never shoot at those higher ISOs. What I am saying is that is that even though newer model digital cameras can give you the ability to take noise-free pictures at increasingly higher ISOs, you may not want to upgrade your camera body just so you can get that tech. You may not see as much noise at those super-high ISOs, but you're still going to notice some loss in quality.
Smiles are overrated. by Flickr user Sean Molin Photography
Doing some tests
Here's what I recommend to everyone who has a digital camera. Do some testing. Set your camera up on a tripod, and take a series of images of the same subject, starting at the lowest ISO your camera offers and ending at the highest. Open each photo up on your computer and view them at 100%. It's important to be able to see the details, because that's where you're going to start to see the differences. Now decide where those differences start to become noticeable, and where they start to become intolerable. Use that information to decide on the maximum ISO that you are willing to shoot at under any given conditions. Your decision is going to be different based on the subject matter you plan to photograph—for example, the maximum ISO you'd want to use for a landscape or a macro shot is probably going to be a lot smaller than the maximum ISO you'd want to use for a portrait.
Armed with this information, you can make a decision about how high you are willing to go with your camera's ISO. But even if that value is, say, ISO 1600, don't just automatically dial up to that setting every time you are in a given shooting situation. Even if you've determined that ISO 1600 is acceptable, it's still best to shoot at the lowest possible ISO given the lighting conditions. In other words, don't bump up the ISO unless you need to. Remember that you may be losing quality even as you go from ISO 100 to ISO 400, so it's always best to shoot at lower ISOs whenever you can, and use the higher ones only when you need to.
Forty years, a gold watch and a heart attack by Flickr user hjl
Remember that megapixels should not be the benchmark for deciding when it's time to upgrade your camera, and neither should high ISOs. It's nice that those higher ISOs give us options when all else fails, but you should never rule out other strategies for taking photos in low light. Your tripod, your off-camera flash, your 50mm f/1.8 lens—those tools should always be your first line of defense in helping you achieve the best possible photos in low light conditions. When all else fails, absolutely, turn up that ISO. It is a wonderful tool that modern photographers have been given and we should be grateful. But we should also try not to forget that there are often better ways.
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