Why does DeepSkyStacker make my stacked RAW image look overexposed compared with Photoshop median stacking?
Asked 4/4/2019
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2 answers
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I’m stacking about 40 underexposed RAW images of a galaxy. In DeepSkyStacker, the TIFF result looks overexposed. In Photoshop, if I stack the same images as Smart Objects and use Median, the result stays underexposed, while Summation also looks overexposed.
Is there a setting in DeepSkyStacker that can make the output look more like Photoshop’s Median result, or is this just a difference in how the stack is displayed and processed?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
2
I think that DeepSkyStacker (DSS) does not offer different merging algorithms - however, there seems to be a way to get to the result you want, anyway:
DeepSkyStacker's FAQ has the following question:
Q: My resulting image is very dark. Is it normal?
A: [...] The histogram must be stretched by adjusting the RGB levels and the luminance in the Processing Tab.
This, basically, is the same question as yours, just asked the other way around.
The Processing Tab offers very basic editing options:
[...] DeepSkyStacker only allows simple processing treatments of the resulting picture in order to quickly view the result of the stacking process. The heavy post processing should take place in another more specialized software.
However, it should suffice here. Simply switch to the Luminance- and/or RGB Levels-tab and adjust the picture until you like its look:
The simplest way to understand how the different parameters are working is to change them and look at the resulting the luminance adjustment curve (black curve) on the histogram.
Originally by user69369. Source · Licensed CC BY-SA 4.0
user69369
7y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—this is mainly a difference in stacking method and display/processing, not necessarily a problem with your data.
In Photoshop, Median and Summation are different merge methods. Median tends to keep the overall brightness lower, while summation/averaging can make the stacked result appear much brighter.
DeepSkyStacker is designed for astrophotography stacking and its preview/output often needs histogram adjustment after stacking. According to DSS guidance, the stacked image usually must be stretched in the Processing tab by adjusting RGB levels and luminance. DSS only provides basic processing for previewing the result; more serious post-processing is normally done in other software.
So if the DSS TIFF looks overexposed, check the histogram/stretch settings in DSS rather than assuming the actual stacked data is wrong. DSS does not generally work like Photoshop’s Median stack for this purpose.
In short: if you want the same kind of result as Photoshop Median, DSS may not produce that exact look directly. Use DSS for stacking, then do final tonal adjustments in an editor afterward.
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