How can I stack multiple low-light exposures in Photoshop to reduce noise?
Asked 1/22/2017
4 views
2 answers
0
I want to combine several aligned shots of the same very dark scene to improve signal-to-noise, similar to astrophotography stacking. There are no stars in the frame, so I can’t rely on software that expects star alignment. What is the basic workflow in Photoshop for stacking these exposures, and how should dark frames be handled if I use them?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
2
Assuming all the layers are aligned correctly, if you select them all and create a smart object, then with it selected select layer/smart objects/stack mode/median.
For dark frames use blending mode subtract for the layer, but you would need to do this for each image before stacking them.
With modern DSLR you probably don't have much need of dark frames though, just stacking will be enough.
Hope that helps.
Originally by user60071. Source · Licensed CC BY-SA 4.0
user60071
9y ago
0
Generated from our catalog & community — verify before relying on it.
In Photoshop, the basic idea is to load the aligned exposures as layers, select them all, then convert them to a Smart Object. From there, use a stack mode to combine them.
For noise reduction, the key Photoshop commands mentioned are:
- Layer > Smart Objects > Stack Mode > Median
- Layer > Smart Objects > Stack Mode > Summation
Both are used to combine multiple frames; summation was specifically suggested as the better choice here over median.
If you also shot dark frames, subtract each dark frame from its corresponding exposure before stacking. In Photoshop, this can be done by placing the dark frame above the image and using Subtract blending. Do that correction on each image first, then stack the corrected exposures.
If your frames are already aligned and the scene is static, this is essentially the manual Photoshop version of basic noise-reduction stacking. Also note that with many modern DSLRs, dark-frame subtraction often isn’t necessary unless you have obvious fixed-pattern or hot-pixel issues; simply stacking multiple exposures may be enough to improve SNR.
Recommended products
UniqueBot
AI9y ago
Your Answer
Related Questions
Can you reduce astrophotography noise by duplicating one exposure and randomizing the noise?
Can stacking multiple exposures reduce high-ISO noise, and is there software that does it well?
What software can improve multi-image stacking for high-ISO noise reduction?
Can I stack multiple drone night photos with RGB color and dark/bias calibration on a Mac?
How stacking, ISO, and long exposures affect Milky Way astrophotography