How To Spot Visual Artifacts In Your Digital Photos

By Matthew Braga

JPEG artifacts, low-light noise and even dust can affect everything from DSLRs to camera phones. Here's how to spot and avoid problems where possible.

You've heard it before, and you'll hear it again — no two camera sensors are created equal, especially when it comes to DSLRs and camera phones. Every model captures pixels with its own quirks and problems, and some are more apparent than others. JPEG artifacts, low-light noise and even dust can affect your final image, and turn a beautiful scene into a sub-par facsimile. 



JPEG Compression

 See that fancy, mosaic pattern? That's what pixels look like with bad JPEG compression.


Not all cameras save JPEGs in the same manner, with some models using different compression algorithms than others. Most DSLRs and point-and-shoot models tend to use a decent form of compression with acceptable results, very similar to a RAW image. However, many camera phones and low-end models tend to use quick and dirty algorithms to compress their images, resulting in blocky photos with details that are difficult to discern. Keep those quality settings on max to minimize the effects as much as possible, or invest in a better camera for best results.

Color Banding

Notice the banding in the left image? 


Grain and Noise

Zoomed in, you can see the grain that a higher ISO produces. 
When a DSLR increases its ISO to compensate for a darker scene, there's often little visible noise in the resulting image. However, the poor light sensitivity of a smaller sensor means that even a slight increase in ISO can introduce a great deal of noise. Concert photos taken with cell phone cameras are a great example of this. If you're finding your pictures a little too grainy, try a better lit scene, or a camera designed with darker scenarios in mind.

Spots, Dots and Circles


 

Fuzzy, Washed-out Pictures



This is the same reason why some professional photographers debate the usefulness of filters on professional lenses, with claims that UV filters unnecessarily block light and degrade image quality. The point is, ensure you're always using good quality glass on your cameras and lenses, and avoid plastic if possible.
 
Images via Flickr user viking_79, mobile-review.com, and DPAnswers.