One of the hardest things to overcome is rejection. This applies to all things in life of course but in microstock you will (most likely) get A LOT of it, especially when you first start out. It can be difficult to spend a few hours preparing a few items to shoot, processing them in post for a few hours, then pridefully uploading them. A few days later you get a big fat "rejected" email.
What are your options at this point?
A). Throw the camera out the window.
C). Panic and then throw the camera out the window...?
Of course there is no need to get hysterical (although enraged may be the better word for the feeling). Rejection is a part of the game. Microstock companies have thousands upon thousands of photos to sort through and although when microstock first began it was much easier to get items approved, these days they can be much more selective.
What does this mean for you? The aspiring photographer behind the lens? Quite simply you have to practice and get better, no way around it. Learn from the issues and don't hesitate to hit the forums for a bit of info from fellow photographers. At times, the forum may be brutal, but they are good teachers, if difficult ones.
I'd like to mention some of the most common rejections and how to fix or alleviate the issues.
1). Artifacting. Artifacting is the degredation of an image, seen as blocks of interpolated information.
This technical issue is commonly created by the quality settings in-camera, in post-processing, in RAW settings or scanner settings. Artifacting can also be introduced into an image from the result of other factors such as excessive level adjustments.
A little bit more about compression: The JPEG file format uses a lossy compression method. In order to make the file smaller, information is thrown away, or lost. The quality setting that most image editing programs and digital cameras have when saving JPEGs determines how much information is lost. At a certain point with lower quality settings the removal of information during the compression process can become visible in the form of compression artifacts (places in the image where too much detail has been lost). Too much JPEG compression can become visible either in the form of a general loss of detail, or grainy/patterned areas (especially in flat spaces, such as skies).
Compression artifacting can be introduced by the camera and/or by your image editing software at lower quality settings. Also, re-sizing, re-sampling, and re-saving can all degrade the quality of a JPEG image, so one should be careful about re-saving JPEGs. If for example, a photo was re-saved 4 times (even at a quality of 12 or Best) the image quality will become worse each time as pixel information is thrown out each time the file is saved. With this in mind, it is obviously best to start with the cleanest image possible. You may want to double-check your camera settings to make sure it is saving at the highest quality. If you continue to have issues you may try shooting in RAW/NEF mode, export to TIFF and then save as JPEG at the highest possible quality (level 12) with minimal or no post processing effects. Sometimes even trying a new RAW converter could be beneficial.
2). Noise (pixels of varying color where there shouldn't be): most commonly created by digital cameras, especially in darker shadows or under low-light conditions and exacerbates the compression issues mentioned above. You might want to double-check to make sure that your camera's ISO/ASA setting is at the lowest number (usually 100). In digital cameras, higher numbers (200 or 400) will always result in more noise (just as with film).