Posted by Max Waugh on November 1, 2013 at 6:38 PM
I recently started playing with Nik's noise reduction brush, going back and treating a few older shots that suffered from excessive noise. The images I was working with were shot using my old Canon 7D, a body that's notoriously noisy in mid-range ISOs.
I took the "Strong Noise" brush in Nik Dfine 2 and worked the background over in this image, and thought it cleaned up pretty well. However, after reexamining the file I noticed what appears to be a very faint grid pattern overlaying the image. At first I wasn't sure if this was my imagination when staring at the web res. version, but sure enough it's there, even in the high-res PSD file I worked on.
When I remove the Dfine brush layer, the grid becomes much less apparent, so it's only obvious when the NR is applied. You can see this (hopefully) in the close-up detail I've provided in the second image above. It's still faint, but the widely-spaced lines are apparent.
I've never really noticed this grid in my images before, so I'm wondering if anyone knows if this is solely a byproduct of the "strong" noise reduction, or if the grid is actually from my (poor) camera sensor, and is being exacerbated by the NR effect.
Max, I'm a novice at noise reduction per se, but when the need arises I also use Dfine2. I really like the program. I wish the images were a bit larger here, but, I think this might be a bit of "banding" taking place. I very rarely will see that in images I've prepared for the web size. The full size images as PSD or TIFF are never an issue. So, it might be an item of compression at that point. Are the full size images showing the same "grid" look?
When I do see "banding" in my images for web usage it is almost always in the sky. To be quite honest the only fix for web size images I've ever found was to add noise back in, not much, but just enough to get the banding to not be so obvious.
Maybe some folks who use noise reduction more often might have better input.
Posted by Max Waugh on November 1, 2013 at 10:51 PM
Paul, I have seen banding before, especially with my much older bodies (10D - 40D) when I pushed the ISO. This is different though. There's definitely a grid pattern of evenly spaced, intersecting horizontal and vertical lines. Unlike any banding I've seen before, though I suppose it could be a similar phenomenon. Sorry if it's not too obvious in the posted example (the lines are most visible against some of the darker background tones), but to answer your question, yes, they appear in the high res PSD file too.
Max, I do understand. I'm now not sure if it also shows up in your hi res files too. Sounds like you could be on to something with the sensor maybe?
As I only shoot film it's easy for me to trace back on digital degradation of any sort in my images by merely looking at the slide on the light table. Obviously if there is no visible issues in the original slide and is then present in the digital file anywhere then it picked it up at some point in the scanning & post processing. At which point I can fall back and rescan from scratch.
If yours comes straight out of the camera with signs of digital degradation then I would think it is the camera, whether it be the sensor as the cause or any other formulation of capture & conversion from that point forward.
You got me swinging. I'm sure there are some others out there that can shed some more light on this subject too. Good luck.
Posted by Richard Ditch on November 2, 2013 at 12:46 AM
For those who are having trouble seeing the grid pattern I've pulled Max's example into Photoshop and used Adjustments > Equalize to maximize the contrast in each color channel. Note how the enlarged image appears to be composed of tiles. The pattern is very regular, and I'd suggest measuring the size/spacing of the grid. Perhaps that can be related back to the layout of the camera sensor?
Posted by Paul DeCesare on November 2, 2013 at 1:27 AM
Good NIGHT, there is a perfect grid there! Max, if you open the RAW and get it into Photoshop and do the Equalize adjustment, do you see a grid there? I hope it's not the sensor.
BTW, I never ever thought there would be a good reason to use Equalize, but you've educated me Richard.
Max, btw, this image is outstanding, I hope you get it sorted.
Ok, that's pretty interesting! I could not see it in the original image postings. But the postings by Richard really showed up fine! What happens when the image is "printed"? Grids or not?
That really brings the grids out. I saw horizontal lines in the original images which looked a bit like banding to me. But these clearly show tiles, actually larger in size then I kept looking for. I would think Paul De's suggestion working with the RAW as Richard did with the images & Equalize should reveal sensor issues possibly.
Posted by David Bostedo on November 3, 2013 at 11:22 AM
Max - This is really speculative, but it's possible that the grid is both caused by the sensor, but isn't a problem with the sensor. If you took a very high ISO and/or underexposed shot, this could be a noise characteristic of the sensor. All sensors have a certain amount of "fixed pattern" noise that is somewhat regular and can be brought out clearly in extreme circumstances (and possibly by lots of post processing). It would be odd for it to appear as a grid - usually what I've seen is some vertical banding, and it's not even across the whole frame.
You could try taking a very underexposed high ISO shot and playing with it in PS to see if this pattern can be reproduced. If you could get the pattern, but only with noise reduction, it could be the noise reduction program, or some interaction between the two. If you can see the pattern without heavy noise reduction, it would be the sensor.
Use PS's NR not Nik's, maybe that will do the trick.
Posted by Max Waugh on November 3, 2013 at 1:16 PM
Thanks for the feedback, everyone.
After performing some more tests, including examining the original RAW file, equalizing and comparing PS noise reduction to Nik's, I do believe the grid comes from the camera sensor... but that Nik's NR brush has a way of making it much more apparent than any other adjustments. It's barely noticeable when I open and equalize the original file, or even when I apply strong NR using PhotoShop. There's something about Nik's filter that enhances it.
The 7D was never known for having a great sensor, so I don't believe this is necessarily a defect. It may be the nature of the beast (and I'm glad it's no longer my primary body). Obviously, I'll have to be pretty careful using Nik in the future though. Moderation is a good thing.
Max
Posted by Max Waugh on November 3, 2013 at 3:06 PM
Incidentally, someone else just mentioned to me that they've seen the grid appear when using Nik's Silver Efex functions as well. So it doesn't appear to be solely confined to their noise reduction tool.
Max
Posted by Jim Zipp on November 23, 2013 at 11:56 AM
I've heard discussion about this when using Canon's software for converting. If that happens to be the case then updating the software to the latest seems to fix that issue. Worth a try.
Discussion
12 repliesI took the "Strong Noise" brush in Nik Dfine 2 and worked the background over in this image, and thought it cleaned up pretty well. However, after reexamining the file I noticed what appears to be a very faint grid pattern overlaying the image. At first I wasn't sure if this was my imagination when staring at the web res. version, but sure enough it's there, even in the high-res PSD file I worked on.
When I remove the Dfine brush layer, the grid becomes much less apparent, so it's only obvious when the NR is applied. You can see this (hopefully) in the close-up detail I've provided in the second image above. It's still faint, but the widely-spaced lines are apparent.
I've never really noticed this grid in my images before, so I'm wondering if anyone knows if this is solely a byproduct of the "strong" noise reduction, or if the grid is actually from my (poor) camera sensor, and is being exacerbated by the NR effect.
Max
When I do see "banding" in my images for web usage it is almost always in the sky. To be quite honest the only fix for web size images I've ever found was to add noise back in, not much, but just enough to get the banding to not be so obvious.
Maybe some folks who use noise reduction more often might have better input.
Max
As I only shoot film it's easy for me to trace back on digital degradation of any sort in my images by merely looking at the slide on the light table. Obviously if there is no visible issues in the original slide and is then present in the digital file anywhere then it picked it up at some point in the scanning & post processing. At which point I can fall back and rescan from scratch.
If yours comes straight out of the camera with signs of digital degradation then I would think it is the camera, whether it be the sensor as the cause or any other formulation of capture & conversion from that point forward.
You got me swinging. I'm sure there are some others out there that can shed some more light on this subject too. Good luck.
BTW, I never ever thought there would be a good reason to use Equalize, but you've educated me Richard.
Max, btw, this image is outstanding, I hope you get it sorted.
You could try taking a very underexposed high ISO shot and playing with it in PS to see if this pattern can be reproduced. If you could get the pattern, but only with noise reduction, it could be the noise reduction program, or some interaction between the two. If you can see the pattern without heavy noise reduction, it would be the sensor.
After performing some more tests, including examining the original RAW file, equalizing and comparing PS noise reduction to Nik's, I do believe the grid comes from the camera sensor... but that Nik's NR brush has a way of making it much more apparent than any other adjustments. It's barely noticeable when I open and equalize the original file, or even when I apply strong NR using PhotoShop. There's something about Nik's filter that enhances it.
The 7D was never known for having a great sensor, so I don't believe this is necessarily a defect. It may be the nature of the beast (and I'm glad it's no longer my primary body). Obviously, I'll have to be pretty careful using Nik in the future though. Moderation is a good thing.
Max
Max