GIMP image quality

[Dazzyt66]

Hi,

I’ve been experimenting processing stacked .tif images from DSS.

Whilst I can get fairly decent processing done in StarTools from the output tif of DSS, if I use GIMP to try and do anything, even basic levelling, it just looks ‘blocky’ i.e. far less initial image quality. Even if I just mess around with windows picture editor I get better results than GIMP v 2.10. Surely this can’t be right for something that’s meant to be a rival to PS?

The reason I am asking is before I get a license for StarTools can GIMP do similar for free?

[Thalestris24]

Hi

Make sure you set the right bit depth under Image -> Precision

hth

Louise

[JohnSadlerAstro]

Hi,

You need to use Gimp 2.9--the 16-bit version. The standard release is only 8-bit, which ruins images. Believe me, I used 8-bit for almost a year and whatever people say, it ruins images.

It is available from here : https://www.partha.com/

P.S. In the box on the right hand side of the page, half way down, in the listings it should appear as 2.9.5 or something similar. hth  

John

[pipnina]

5 minutes ago, JohnSadlerAstro said:

Hi,

You need to use Gimp 2.9--the 16-bit version. The standard release is only 8-bit, which ruins images. Believe me, I used 8-bit for almost a year and whatever people say, it ruins images.

It is available from here : https://www.partha.com/

P.S. In the box on the right hand side of the page, half way down, in the listings it should appear as 2.9.5 or something similar. hth  

John

GIMP 2.10 has been released and can be installed from the official website now https://www.gimp.org/downloads/

It's the final (and now stable) release of 2.9. 6 years in the making. I think it also now comes with a dark theme.

[wimvb]

51 minutes ago, Dazzyt66 said:

The reason I am asking is before I get a license for StarTools can GIMP do similar for free?

In my, very personal opinion: no. StarTools, AstroPixelProcessor, PxiInsight are astro image processors, designed for astrophotography. Photoshop has added plugins and actions that are targeted to AP. As far as I know, GIMP has none of these. Consider your astrophotography software to be a central part of your setup, and prepare to invest in it, both time and money.

[JamesF]

Does sound as though you might have something configured non-optimally.

James

[Whistlin Bob]

Whilst I agree to a point with @wimvb- it's generally easier to achieve great results with specialist AP software, you can still get good results with GIMP if your starting data is of reasonable quality. I'd suggest you do a search on Astrobin to see what others have achieved.

[happy-kat]

For best results from StarTools use the autosaved FITS file from DSS.

[happy-kat]

There are a few GIMP astro plugins somewhere there is a post on how to set them up but whether they work on the new version just out I do not know.

[Dazzyt66]

13 hours ago, Whistlin Bob said:

Whilst I agree to a point with @wimvb- it's generally easier to achieve great results with specialist AP software, you can still get good results with GIMP if your starting data is of reasonable quality. I'd suggest you do a search on Astrobin to see what others have achieved.

I’m using someone else’s raw data which I know will give good results. I can get a great image when using StarTools following a guide I found, I just can’t seem to even get close to something similar in GIMP although I have seen others have. I’m rechecking all settings now to check it’s not user error... which it very well could be... lol

[Dazzyt66]

13 hours ago, happy-kat said:

For best results from StarTools use the autosaved FITS file from DSS.

Yep, have had a good result with both FITS and TIF in ST ?

[Dazzyt66]

15 hours ago, Thalestris24 said:

Hi

Make sure you set the right bit depth under Image -> Precision

hth

Louise

Oooooh, OK, so it leaves it at 8 bit initially, but what should I be setting it to? I’m using a TIF from DSS so 16 bit? And then it asks: integer or floating point and Perceptual gamma or linear light? #confused.com

[Thalestris24]

Hi

I think the DSS autosave tiff is 32-bit floating point.(rational). You can, of course, also do a 'save as' and that gives you various options.

Louise

[happy-kat]

Here's a blog talking about the astronomy plugin for GIMP (unsure if Linux only).

link

Though I read a more recent use of it on here then the date of that blog.

[happy-kat]

Though given you also have stacie I would go for StarTools are there are some great processing capabilities to remove chromatic aberration, I just tweaked one recently and had good success with it.

[Dazzyt66]

35 minutes ago, Thalestris24 said:

Hi

I think the DSS autosave tiff is 32-bit floating point.(rational). You can, of course, also do a 'save as' and that gives you various options.

Louise

Thanks Louise. Have tried all combinations now with GIMP and it either:

Keeps the image at 8 bit initially, although you can convert it, the quality is still shocking, or

If I edit import preferences to promote to floating point, it will open most TIF versions, keeps them at 32 bit but quality looks similar to 8 bit...

So, I think StarTools is the winner come next months spending money...

[Dazzyt66]

43 minutes ago, happy-kat said:

Here's a blog talking about the astronomy plugin for GIMP (unsure if Linux only).

link

Though I read a more recent use of it on here then the date of that blog.

 

25 minutes ago, happy-kat said:

Though given you also have stacey I would go for StarTools are there are some great processing capabilities to remove chromatic aberration, I just tweaked one recently and had good success with it.

Thanks for these. I have indeed (for now) given up on GIMP. My future spend goes on StarTools. Although I might get BYE first...

I’ve indeed had some promising widefield practice shots with Stacey and she defo has potential... I’m gonna do a Mak comparison against M101 and see how they stack up (no pun intended) lol... ok, maybe there was... ?

I just need two clear nights....

[happy-kat]

I shared revised workflow that worked for me on how I fine tuned my CA removal. It might seem fiddly but it was not too bad and was quick to do and the beauty of the startools log is you can see what you did and repeat it or repeat and tweak.

link here

[dph1nm]

32 minutes ago, Dazzyt66 said:

Thanks Louise. Have tried all combinations now with GIMP and it either:

Keeps the image at 8 bit initially, although you can convert it, the quality is still shocking, or

If I edit import preferences to promote to floating point, it will open most TIF versions, keeps them at 32 bit but quality looks similar to 8 bit...

I use GIMP for all my post processing after DSS stacking - even the old 8-bit version - and I have no problem with it whatsoever. The new (well, 2.9 in my case at  the moment) version is noticably better and opens DSS output with the correct bit depth - you shouldn't need to fiddle with the precision. It should not be saying 8-bit for the DSS tiffs, they should be 16 or 32 bit depending on how you told DSS to save them. Make sure you do not apply the settings in DSS - the resulting GIMP image should be mostly black, you then need to apply curves as required.

NigelM

[ChrisEll]

Very odd, not seen your problems in GIMP ever, even when I was using the 8-bit 2.8 version. Perhaps a complete uninstall and re-install may help.

[Dazzyt66]

24 minutes ago, ChrisEll said:

Very odd, not seen your problems in GIMP ever, even when I was using the 8-bit 2.8 version. Perhaps a complete uninstall and re-install may help.

You know what, I did, and it now works fine! Well, on initial look it works better than before and it keeps the TIF at the level it was saved!

More experimenting for me now then... although I do think I’ll get StarTools too! ?

[happy-kat]

You'll still use GIMP for say resizing and save as png for uploading here etc.