dss grey image/gimp dark image?

[jonnydreads]

hi all, when ive stacked in dss the image comes out greyish, which ive read is normal, but when I open the file in gimp its really dark, is that normal too? how can I get it back to grey, it was easier to manipulate when it was in dss

[wxsatuser]

If it's the Autosave tif it will be very dark, needs stretching.

[jonnydreads]

when the term stretching is used does that refer to colour levels...?

[wxsatuser]

Normally the whole image would have a curve applied to it.
You should be able to see that curve in DSS, it's under the image.

[Thalestris24]

13 minutes ago, jonnydreads said:

when the term stretching is used does that refer to colour levels...?

Levels and Curves in Gimp (and other packages). If stretching doesn't solve the problem, it could be that your images are underexposed.

Louise

[The Admiral]

2 hours ago, jonnydreads said:

when the term stretching is used does that refer to colour levels...?

In astrophotography, stretching is a term used for greatly increasing the contrast of the image, in a way to keep the sky almost black, and the brightest bits clearly revealed. This is done using curves and levels, as Louise said. This can be done with specialist astro processing software, or Photoshop, or Gimp. A quick Goggle can bring up a range of advice. This looks like it might give you the guidance you are after. https://astrobackyard.com/deep-sky-image-processing/

Ian

[jonnydreads]

Just now, The Admiral said:

In astrophotography, stretching is a term used for greatly increasing the contrast of the image, in a way to keep the sky almost black, and the brightest bits clearly revealed. This is done using curves and levels, as Louise said. This can be done with specialist astro processing software, or Photoshop, or Gimp. A quick Goggle can bring up a range of advice. This looks like it might give you the guidance you are after. https://astrobackyard.com/deep-sky-image-processing/

Ian

Thankyou 

[The Admiral]

16 minutes ago, jonnydreads said:

Thankyou 

Hmm, looking at it I'm not sure how much help the link will give. But if you Goggle 'astrophotography and gimp', you should be able to come up with something useful.

Ian

[happy-kat]

The website budgetastro.net Doug has a good set of videos to follow for DSS and Photoshop and most of what he does you can do using GIMP.

[FaDG]

4 hours ago, jonnydreads said:

but when I open the file in gimp its really dark, is that normal too?

I've read that GIMP doesn't correctly handle 64 bits TIFF, which is the output format of DSS. 

Actually, i feel that the very desaturated look of DSS output is hard to recover, even using other tools, as the image seems quire noisy once saturation is pumped up. 

 

[Thalestris24]

3 minutes ago, FaDG said:

I've read that GIMP doesn't correctly handle 64 bits TIFF, which is the output format of DSS. 

Actually, i feel that the very desaturated look of DSS output is hard to recover, even using other tools, as the image seems quire noisy once saturation is pumped up. 

 

I think the default dss output is 32 bit floating point but you can save an image as 16 bit which is what I usually do.

Louise

[FaDG]

Sorry Louise, my bad. 

I think that GIMP has issues with 16 bits TIFFs, it only supports correctly 8 bit ones. 

The standard message I get is:""The image you are loading has 16 bits per channel. GIMP can only handle 8 bit, so it will be converted for you. Information will be lost because of this conversion."

GIMP 2.10 SHOULD handle them, but this is not always the case. 

[Starlight 1]

Gimp 2.9 is that  64 bit .

[Thalestris24]

Don't confuse 32/64bit apps with image bit depth...

[Starlight 1]

9 minutes ago, Thalestris24 said:

Don't confuse 32/64bit apps with image bit depth...

its got 64 bit gamma and linear floating point  what is that for.

[Thalestris24]

If in doubt - read the docs!

https://www.gimp.org/release-notes/gimp-2.10.html