**System Information**
iMac 27' / osX 10.8.5 / Nvidia GeForce GTX 675MX 1024MB / 16GB DDR3 Ram
**Blender Version**
Broken: Official 2.70 19e672c
Worked: Official 2.69
**Short description of error**
Seems that only affects a Mac.
Adding a value bigger than 0.0 dithering, the actual render becomes full black, but the information its still behind.
Affects Blender internal and Cycles.
Click and drag through the image shows color, alpha, Z, and more info.
Saving the render with F3 goes fine, with dither and all.
**Exact steps for others to reproduce the error**
1) Open blender in a Mac.
2) Press F12 to render default scene, make sure the render result is visible.
3) Go to "Render Options" look for the "Post-Processing" panel.
4) Add some value to the Dither slider, the rendered image should turn black.
Hope this helps, to track down this bug.
Thank you for all your dedication.