JPEG chroma subsampling

taob · Post by **taob** » Wed Mar 12, 2003 1:39 am

This issue came up (among other places) in the Canon SLR forum on www.dpreview.com:

http://forums.dpreview.com/forums/read. ... ge=4515688

It deals with the common practice of sampling chrominance information at a lower frequency than luminance when using JPEG compression. The default in many JPEG implementations is a 2x2 subsampling of the chroma channel (while leaving every pixel intact for the two luminance channels).

What does NeatImage use when saving to JPEG? More information here:

http://jpegclub.org/foveon/

Post by **NITeam** » Wed Mar 12, 2003 2:04 am

NI uses default: 4:1:1 subsampling (2x2)

taob · Post by **taob** » Wed Mar 12, 2003 2:13 am

May I request an enhancement for a future version to make 1:1:1 subsampling an option, or perhaps do what Photoshop does and automatically switch to 1:1:1 when you select a high enough quality setting?

My workaround right now is to save as TIFF and then use another program (like ImageMagick) to convert to JPEG... not the most convenient setup. I want maximum quality for the least amount of effort. Isn't that what NeatImage is all about?

Post by **NITeam** » Wed Mar 12, 2003 2:20 am

Neat Image is about noise reduction

but we will consider 1:1:1 subsampling (automatic or manual), thank you for the suggestion.

Vlad

searcher41 · Post by **searcher41** » Sat Mar 15, 2003 4:03 am

I also would like the Higest quality JPG saves available as an option. This is one great product and support forum.

Post by **NITeam** » Sat Mar 15, 2003 10:03 am

Say, 4:1:1 (standard) if quality level<85, 1:1:1 (no subsampling) if quality level>=85. Would it do?

Vlad

taob · Post by **taob** » Sat Mar 15, 2003 2:14 pm

That sounds like a good threshold... consistent with the way Photoshop does it.

searcher41 · Post by **searcher41** » Sat Mar 15, 2003 6:17 pm

<85 would be a good threshold. Thumbs Plus will allow selection of the output file compression when saving as a popup selection box. Would you consider having the file saves be selected for each file or batch operation?

Post by **NITeam** » Sat Mar 15, 2003 6:52 pm

How would it be different from the way it is now?

searcher41 · Post by **searcher41** » Sat Mar 15, 2003 7:28 pm

The JPG save menu box allows the saving as it was originally saved or an 8 different compression options with full preview and file size output. Quite the user interface and what all imaging programs would benefit from. I am not sure how you would like me to send the file to you so you could see the manner it is implemented but let me know and I will send it.

Post by **NITeam** » Sat Mar 15, 2003 9:00 pm

Now I've got your point. Thank you for the suggestion.