How to Check Image Quality

We’ve all seen examples of fantastic photography that looks great in a thumbnail or framed hanging on a wall. You may even have images of your own that compares favourably and attracts a lot of attention on-line. However, even well exposed and composed images can often fail to meet the strict criteria that makes the image suitable for commercial use. You may gain praise for the shot, but you may have a nagging feeling that it just won’t make the grade at stock photography sites. So, how do you tell if your image really does stand up to scrutiny?

Assuming your shot was professionally composed and executed, you will be able to confirm the technical quality of the image using specialist software such as Lightroom and Adobe Camera Raw (ACR). Your DSLR manufacturer may even supply you with in-house image processing software.

There are a number of checklist items that you should cover during post-processing. The image histogram, white balance, shadows / highlights, and spot removal are the usual issues that should be checked. However, you need to view your image at “actual pixels” (or 100% zoom) to really check on the quality of the image. Some may call this “pixel peeking” an out of date concept, buy you can rest assured that the stock photography agencies are scrutinizing your image to this level of detail.

Here’s what to check for:

• Image sharpness. A common cause for rejection of an image is soft image details when viewed at actual pixels. Don’t just use the sharpening slider in ACR. You want to be able to control what part of the image, and even which tonal range, gets sharpened and which does not. There are a number of great sharpening techniques out there, which are discussed on other articles. The only thing I would add here is not to rely solely on the basic sharpening tool in Photoshop.

• Chromatic Aberrations: those glowing, thin, soft blue or red hues that run along the edges of dark and light tones in your image. They may not show up when viewed normally, but you must correct any that appear when viewed at actual pixels. ACR offers a slider that can fix most of these issues, but be aware that some chromatic aberrations are so extensive that they cannot be removed.

• Compression Artifacts can ruin image quality. They basically look like smudged or noisy patches in the image. They are caused by the compression of the image to JPeg formats and are extremely difficult to fix. Make sure your image has none of these lest you will be rejected by the stock agency. Shooting in RAW format and saving to TFF will help reduce your images susceptibility to compression losses.

• Any corrections made to exposure and the tonal range can introduce noise to the image. Noise is common in point and shoot images, which use variations in ISO to control exposure. Removing noise can be very easy. Neat Image software generally works very well. However, be careful not to overcompensate with noise removal. It can make the image overly soft, and compensating with sharpening will introduce faults that are similar to compression losses.

• Checking for spot removal is essential. Hot pixels or dust on the sensor can damage the quality of an image and will almost certainly lead to rejection. The good news is that spots are very easy to fix using the spot healer or the clone stamp tool in Photoshop.

If you follow these guidelines, you should find that well composed and well exposed images will have few problems being accepted by stock photography sites.