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If you take pictures for yourself or your friends on Facebook, noise might not be a huge factor for you. However, if you sell your images as stock, or to paying clients, you will want to keep it to a minimum. As an image inspector for iStockphoto, I have seen all kinds of images from every type of camera, and I’ve learned that no matter what you use to record your images, there’s always a chance you’ll end up with some noise. In fact, when an image is rejected for inclusion into the collection, noise/artifacts is very often the reason. So here is a short list of some of the most common ways the dreaded artifacts might appear.

Shooting and Working in JPG

When a JPG file is saved, it compresses the data and causes some quality loss. Even if you save at the highest quality setting. If you shoot in JPG, your image is compressed even as it is being saved onto your memory card. Every time you save that file afterwards, it’s compressed a little more, and more noise appears. The damage done to your file is permanent and irreversible. This is one of the reasons, I always recommend working with RAW, but even if you can’t or don’t want to do that, you should save your file as a PSD or TIFF while you’re working on it, to avoid further compression along the way.

JPG compression will typically show up as “wrinkles” around the edges of the elements in your photo, or as square blocks.

High ISO

While some argue that ISO noise is the digital equivalent of film grain, it doesn’t change the fact that high ISO images will have a harder time making it into your stock portfolio. The exact amount of ISO noise greatly depends on your camera. Some models produce much less of it than others, even within the same brand. If you shoot in well lit environments, it won’t matter much since you’ll be able to shoot at low values always, but if you shoot a lot of dark images, you will want to research your camera’s performance.

Though digital grain is less of a problem in higher resolution cameras (simply because a huge image won’t show the noise as much, when the image is printed or scaled down), I generally recommend shooting at the lowest possible value. Preferably not going above ISO 200.

Low Light Captures

Darker parts of the image contain less data than well lit areas. If you try to brighten a dark spot in post processing, there is a good chance you’ll get noise. This is because Photoshop (or whatever you’re using) has to guess what data to put into your previously dark area, and in doing so, it ends up creating artifacts. Sometimes in the form of ‘pixel discoloration’, meaning green, red and blue dots appearing in the parts you are brightening.

The best way to avoid this, is to expose your images correctly during capture. It’s always easier to darken something (taking away data) than the other way around (adding data where there was none). If that is not an option, you can combat the noise during the processing, though you will still want to be careful not to take that too far.

Too Much Tweaking

Artifacts can come from too much processing. In stock photography, highly saturated images are very popular, but too much saturation will make little blotches appear. Also, bumping up the contrast or saturation too much can cause moire patterns/banding to appear in the gradients of your image. If your image has any blue sky in it, that’s a very good place to check for this type of noise, as is any other large one-color surface. Pay special attention to areas, where a darker shade is transitioning into a lighter one. Obviously, the way to avoid this type of noise, is to not push your post processing too far.

Upsampling

A surefire way to get noise in your images, is to upsample them. Upsampling is when you make your picture larger than it was when it came off the camera. If you shoot microstock, you should not upsample your images at all. Ever. If you also submit to macro stock collections, you may have to do it to meet the file size standards there. In that case, I recommend going about it in small steps, so you can keep an eye on the noise, and on the other danger of upsampling: Softening the focus.

Technically, when you upsample an image, again your post processing software has to guesstimate what pixels to add, where previously there were none. That’s why enlarged images tend to get soft and fuzzy. And not in that nice blanket-on-a-cool-night kind of way. If upsampling is a necessary part of your workflow, I’d recommend you invest in software that’s specialized for the purpose. Otherwise, the best suggestion is to avoid it at all costs.

Dealing with Noise

If you get a lot of noise/artifact rejections on your submitted stock photos, first try to identify where it comes from. By referring to the list above, you might be able to sleuth your way to an explanation. Once you know where the problem lies, you can take measures to counter it in the future. One exercise you could do, is to purposely try to recreate the five types of noise listed above. By doing that, you will get a much deeper understanding of just how far, you can push your camera and post processing. Training yourself to see the artifacts is a huge step, and one that can positively affect your image approval rate.

Remember: When checking your photos for noise and artifacts look at them at 100% resolution. At less than that it might not show, and if you zoom in past full resolution, you might see noise that isn’t really there.

A final note about noise removal software, such as Neat Image or Noise Ninja. These all have one major flaw: They attack noise after it has appeared. In my experience, it takes a lot of tweaking to get the software to behave. Often it will go too far, giving the photo a plastic look, smoothing out details in areas like hair, leaves etc. I have never been a fan of noise reduction software for this reason, and instead of trying to remove it after the fact, I advocate simply minimizing the noise to begin with.

Photo credit: Justin Horrocks

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