I make many product photos for the company I work for. For this I use Canon 400D with two external flash devices Walimex CY-600K.
I've noticed an interesting effect on many of the photos I take with white background. On the resulting image there is a red/blue area visible between object and the background. The effect is strongest for black objects and also seems too decrease when I make a brighter photo. It is mostly visible only if zoomed in really close and is not a real problem for me as the resolution is quite high and the resulting images are only 500px wide.
I am just curious as to what is causing it exactly.
For the following example photo I used manual mode with these settings: 1/200 F10 ISO200:
You can see blue area left from the object and red area right from it. What is causing this?