Originally posted by GeneV
How can one tell if the problem is with NR or the jpeg engine or both?
Well, no way of telling for us for sure -
but since the image with no noise reduction does not show red problems (
K-x ISO1600 shot with Noise Reduction Off) - I would guess that it's probably not the JPG compression, but the way Pentax are doing the noise reduction?
However in practical terms there is obviously a problem if one sees or are concerned with it.
Let's use two simple examples
1) say one shoots and processes in RAW with very little noise reduction - so on the screen in the RAW editor the reds are fine.
Then because the pic is needed to be posted on the web with limited space - a fairly high compression JPG is used -
then the resultant image probably will have problems in Red - as shown above.
2) start with a normal default JPG from either the K-x or K7 at ISO1600 - do all the necessary processing - but because we're concerned with the quality in Red save to a very high quality (low compression) JPG - however since the image had problems in Red to begin with, a high quality JPG cannot restore Red details - so again the image has red problems.
In either case a viewer is not going to know the difference - if they noticed it at all. However as we know the end result is that there is some problem in Red.
Case (1) shows that even if one shoots and processes inn RAW if the JPG engine saving the file is weak in Red all that extra hard work would be for nothing. eg: if I shot and processed RAW with little or no noise reduction but finished in my normal editor PhotoImpact and saved using its JPG engine even if I used a fairly good quality - the resultant Red would have some problems. My alternative would be to use PhotoShop Elements 7 which seems to do better with Red
(however in mitigation for PhotoImpact 8 check the file sizes PSE=10 is 16Kb, PSE=4 is 4Kb - but PI=75% is 4.2K - no wonder the reds are "better" in PSE!)
Here's a the same crop comparison between PSE=10, PI=100%, and PSE=4


The PhotoImpact image is 19Kb and it is definitely better than the PSE=4 image and looks as good as the PSE=10 image -
so perhaps the PhotoImpact 8 JPG engine is not so bad afterall - it's just that its JPG Quality rating in % terms is not very informative and one has to use a much higher indicated quality
(** note: previously I had posted crops from PSE direct - but these contained metadata which made the files larger I used JPG Cleaner and stripped the metadata out and the files are now smaller PSE=10 is 15Kb and PSE=4 is 4kB)
Originally posted by GeneV
The beauty of the K-x to me is that at 1600, shots are amazingly clean right off the sensor. It is too bad if the jpeg engine mucks it up.
I'd agree with you - but other than shooting RAW - one can quite simply turn the noise reduction Off and get an image ready to use without additional processing - and its file size will be some 3 to 5 times smaller - less space on the hard drive, and less to backup......less processing.
Last edited by UnknownVT; 02-19-2010 at 11:50 AM.
Reason: typos, stripped metadata in PSE JPGs