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View Full Version : Noise double-wammy



John Chardine
12-09-2008, 09:40 PM
I had suspected this for some time- the more noise in an image the more jpeg compression you will need to get under a certain file size target. Proved it today with an image I was working on in Ps. Saved the jpeg and had to use a setting of 9 for the compression to come in under 200k. Ran a round of NR on the BG and could save at jpeg 10 and I came in well under 200k. So noise gives you a double-wammy effect- the noise itself, and then the higher level of jpeg compression you need when you have noise to begin with.

Robert O'Toole
12-09-2008, 09:47 PM
Yes, most people dont realize the relationship between that ISO/Noise and file sizes even when you are dealing with memory size when shooting.
Noise in images is the same.. NR smooths detail and texture so the file sized drops.
You really should Run NR first in your workflow not last.

Robert

Roger Clark
12-11-2008, 08:55 AM
Yes, most people dont realize the relationship between that ISO/Noise and file sizes even when you are dealing with memory size when shooting.
Noise in images is the same.. NR smooths detail and texture so the file sized drops.
You really should Run NR first in your workflow not last.

Robert

Robert,
I'm not sure what you mean by "Noise in images is the same.."

All sharpening and noise reduction (NR) algorithms have undesirable side effects. NR generally trades spatial resolution for noise. Sharpening enhances noise. NR first then sharpening could bring back the noise. I rarely do noise reduction, but when I do, it is the last step. I tend to do noise reduction on selected areas, such as the sky and leave complex areas, like feather detail, alone.

Roger

Roger Clark
12-11-2008, 08:58 AM
John,
The more spatial detail, the less compression too. From the compressor viewpoint, it can't tell detail from noise. Both jpeg and raw files (on Canon, it is a lossless raw compression in .CRW and .CR2 files) the more fine detail, the larger the file size. Same with noise: raw files will be larger too with more noise.

Roger

Robert O'Toole
12-11-2008, 09:15 AM
I rarely do noise reduction, but when I do, it is the last step.
Roger

Hi Roger,

NR software companies usually recommend running NR first before any changes to the image. In my experience I have to say I agree about running NR first in many cases, it will give you a much cleaner final image. Increasing contrast, sharpness, or lightening the image will make noise, if present, more visible.

Compare running NR on a dark underexposed high ISO image first then lightening, then do the same with NR as the final step.

BTW I also recommend running NR selectively.

Robert

Robert Amoruso
12-11-2008, 12:25 PM
Hi Roger,

NR software companies usually recommend running NR first before any changes to the image. In my experience I have to say I agree about running NR first in many cases, it will give you a much cleaner final image. Increasing contrast, sharpness, or lightening the image will make noise, if present, more visible.

Compare running NR on a dark underexposed high ISO image first then lightening, then do the same with NR as the final step.

BTW I also recommend running NR selectively.

Robert

I agree with Robert here. My practical experience here is that I run selective NR as the first part of my workflow. Generally on blue skies as I really notice it the most there. If I was using a high ISO and have it elsewhere, I will target those areas. I use PS but also Noiseware and it let's you target specific color areas, etc.