Jump to content

30sec_exposures_2021.jpg.48851b1871a4bf9500ebd53c3e790d81.jpg

 

 

The "No EQ" DSO Challenge!


JGM1971
 Share

Recommended Posts

And it would appear the TIFF does not preview on these forums. I honestly cannot decide which format looks better between the JPG (TOP) and the PNG (bottom)
What are your thoughts everyone?

Link to comment
Share on other sites

4 hours ago, Stefan87 said:

One point of discussion I wish to raise is export formats.

JPEG is only 8-bit and of course is highly compressed. TIFF can be in 8-bit or 16-bit. To be honest, don't know much about PNG.

You should always work with the highest bit-depth uncompressed, linear data you can. It is customary to use the 32-bit FITS format with astro files (they are large files :wink2:). So, import RAW files into DSS, export the output of DSS as a FITS, and import the FITS into StarTools. It is only when you come to export the output from StarTools that you can decide what file format to use, it will depend on what you want to do with it. Personally, I export as a 16-bit TIFF, because I can always create a JPEG from that later if I want. Don't forget, data is lost during compression to form a JPEG, and that is lost data that can never be recovered.

For StarTools, there is specific guidance on what settings of DSS you should use to provide the optimum input. https://www.startools.org/links--tutorials/starting-with-a-good-dataset/deep-sky-stacker-settings

Hope that helps.

Ian

Edited by The Admiral
  • Like 1
Link to comment
Share on other sites

For sharing I just use jpeg as it's for discussion web use. If better web quality is needed I'll do png. I don't share tiffs as files are big and even when using jpeg don't find for web use the compression is a problem. 

  • Like 3
Link to comment
Share on other sites

I agree with happy-kat, JPEG is perfectly adequate for web use. If you are ever wanting to produce a large format print of your results, then 16-bit TIFF would be my choice. If you ever want to present an image for others to process, then use FITS or 16-bit uncompressed TIFF as a file for others to download. Given the sizes, you might need to use a link to a cloud service (I use Microsoft's OneDrive as I have an Outlook account). Mind you, having said that, I see that this sites upload file size is 1GB!

Ian

  • Like 2
Link to comment
Share on other sites

Just to add precision, but PNG is the open spec/rights successor to GIF. JPEG is still perfectly adequate and valid as a lossy compression.

BTW like other comments, use JPEG for web publication, since it will display by a browser and on 8-bit displays mostly.

PNG has 8- and 16- bits variants, all with lossless compression, but 16-bits isn't much used. PNG produces (much) bigger image files than JPEG at about any given size, and is much slower to compress (at save time). And again for display / publication to others it's limited to 8-bit, so process your work files correctly and publish as Jpeg at the end. Adjust the JPEG compression in relation to your resulting image quality : no need to use q=95%, for most images between 65 and 80% is perfect and will produce as much lightweight files as is possible.

  • Like 2
Link to comment
Share on other sites

That clears up alot. And thanks for the link Ian! I glossed over that one previously but never applied the settings as at the time I was between StarTools and Gimp. I will reprocess some data using those settings and see what kind of difference it makes.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.