Stacking multiple sessions in Affinity Photo

[woldsman]

Hi,

I’ve stacked two sessions of data in Affinity Photo using the stacking person a and the file group option. My data is Osc using a DSLR with lights, darks, flats and biases from two separate sessions.

Affinity Photo stacked the data but what started as an OSC stack is now monochrome. I’m not sure where I’ve gone wrong. If anyone familiar with this software knows, that would be great. Otherwise I guess I can have a go at stacking using DSS. 
 

Thanks!

[Tommohawk]

Afraid I don't know Affinity at all - but why not just give it a go with with DSS and see how it looks? Just to see how DSS handles it.

[James Ritson]

On 23/04/2022 at 16:12, woldsman said:

Hi,

I’ve stacked two sessions of data in Affinity Photo using the stacking person a and the file group option. My data is Osc using a DSLR with lights, darks, flats and biases from two separate sessions.

Affinity Photo stacked the data but what started as an OSC stack is now monochrome. I’m not sure where I’ve gone wrong. If anyone familiar with this software knows, that would be great. Otherwise I guess I can have a go at stacking using DSS. 
 

Thanks!

Hi @woldsman, this sounds a bit odd—does your data appear to have colour when you first load the light frames into the Astrophotography Stack persona? Photo should infer the bayer pattern from the FIT (or RAW) metadata but if for some reason it doesn't you can change it manually by going to the RAW Options panel on the right and using the FITS Bayer Pattern dropdown to set the correct pattern manually.

Also, once the result is stacked, are you sure it doesn't just look a bit washed out (perhaps sapping some/most of the colour detail)? Photo will do a gamma-corrected view transform in 32-bit so that your exported result looks consistent—so the data is linear, but you're seeing the gamma corrected view. On top of that, it adds a Levels adjustment which does a gamma transform for initial tone stretching, plus Curves. This might just be washing your data out, but once you actually start to tone stretch using additional adjustments (or other functions like macros) you may start to see the colour.

What DSLR are you using? If you're happy to, I could take a look at the data to see if there's anything else I can suggest—I can set up a private Dropbox file request link for this, just let me know.

All the best,
James

[woldsman]

5 hours ago, James Ritson said:

Hi @woldsman, this sounds a bit odd—does your data appear to have colour when you first load the light frames into the Astrophotography Stack persona? Photo should infer the bayer pattern from the FIT (or RAW) metadata but if for some reason it doesn't you can change it manually by going to the RAW Options panel on the right and using the FITS Bayer Pattern dropdown to set the correct pattern manually.

Also, once the result is stacked, are you sure it doesn't just look a bit washed out (perhaps sapping some/most of the colour detail)? Photo will do a gamma-corrected view transform in 32-bit so that your exported result looks consistent—so the data is linear, but you're seeing the gamma corrected view. On top of that, it adds a Levels adjustment which does a gamma transform for initial tone stretching, plus Curves. This might just be washing your data out, but once you actually start to tone stretch using additional adjustments (or other functions like macros) you may start to see the colour.

What DSLR are you using? If you're happy to, I could take a look at the data to see if there's anything else I can suggest—I can set up a private Dropbox file request link for this, just let me know.

All the best,
James

Thanks for replying, James. I redid the stack setting Raw to RGGB (which I did the first time) and it’s worked! Took some time as I am using a laptop but success. This Affinity persona is really straightforward for multi-session stacking.