Diagnose 23 of 29 Processing
Over-stretched
The image is washed out and low in contrast, with a bright gray background.
- At 100 %
Empty sky reads light gray, and the histogram's hump sits well right of the left edge.
- Causes, most likely first
Stretching without black-point discipline
A stretch lifts the background along with the signal. Unless the black point comes up to the foot of the histogram, the sky ends up gray.
FixSet the black point as you stretch, keeping it just left of where the histogram begins to rise.
Stretching before gradient removal
A gradient left in the linear data is stretched along with everything else, and no single black point suits the whole frame.
FixRemove the gradient from the linear data first, then stretch.
- Looks like, but isn't
Light pollution that was never removed is brighter on one side. An over-stretched background is gray all over.
- One frame can't tell you
The finished image shows it. A screen stretch of the linear stack shows what a better stretch can reach.
- How to confirm the fix
A dark background, with the histogram's hump close to the left edge and clear of it.
- Sources
No outside source is cited here. The signature, the causes and their order are the atlas’s own, from imaging experience. The order is a judgment of likelihood; no measured frequency is behind it.
In the symptom picker
- Washed out and low in contrast, with a bright gray backgroundweight 3
- The linear stack looks fine; the problem appears when you stretchweight 2
Tools for this
- Processing Pathnot built yet
Last updated All 29 failure modes, and the symptom picker