This question already has an answer here:
Right now I'm trying to improve the sharpness of my photos, and for that I've checking if my D7000 has some autofocus issues. Therefore I tested my 35mm f/1.8G and my 50mm f/1.4G. I figured that the autofocus for both lenses is correct, so I probably have to learn to use it in a better way.
While testing I started to read a little more (eg. here) about the correct aperture for the sharpness and I've learned of the sweet point of each lens. But even with optimized condition I encounter a blue and red gradient in the black square of my test photo.
What do you call this gradient and what is it the result of?
Example details of shot with of my 35mm prime; the only after-work I did is to crop and to set the exposure of the images (same style for each photo):
ISO 400 1/60 f/1.8:
ISO 400 1/60 f/5:
ISO 400 1/60 f/8:
You can see the blue and red gradient or shade I'm trying to learn about even better when you zoom in:
- ISO 400 1/60 f/8: