Can you please post an example .CR2 raw file (e.g., to YouSendIt.com or
I have a problem where there is very noticeable banding (+ noise?) in black
and white conversions of my CR2 files from my Canon 5Dmk2.
I assume I am using the correct terminology here; I might not be; by 'banding'
I mean lines on the image, most noticeably vertical but sometimes also
horizontal, giving a chequered pattern.
This image was exposed for highlights (sky) so I realise that the offending area will be the least exposed part of the image (i.e. effectively underexposed) but all the same should I be getting such artifacts?
Uh, the image was underexposed alright and what you are seeing is typical of what happens to shadow noise when trying to bring up tone and texture of under exposed shadows. You are seeing a fixed pattern noise (plus some random stuff as well) from the simple fact that you didn't capture enough photons of light to make a quality capture in the shadows. Ever hear of "Expose To The Right"? What you did was just the opposite. You underexposed the highlights at the expense of the shadows. When you do that you get noise...the worst you do it, the worse the noise becomes.
You might be able to fix some of the worst noise by using a 3rd party noise reduction filter like NoiseWare but the fact remains that you captured noisy shots that are essentially sub par exposures so anything you do at this stage will only be an attempt at mitigation.
Also note that waiting to convert to B&W until you are in Photoshop means you aren't seeing the banding as badly in Camera Raw...depending on what you are doing to make the color to B&W conversion, you could also be adding to the basic under exposure problem. Can't really comment on that because you haven't indicated exactly how you are doing the B&W conversion.
Th e thing you need to understand is that digital is linear and by under exposing you are severely reducing the potential quality of your capture. You need to understand that there is a lot more detail in digital highlights that you may realize. The camera may indicate clipping but the odds are there is usable detail way up into the highlights. By under exposing to keep the highlights you prolly already have you are compromising the quality of the shadows.
If I have done this right you should be able to access the RAW file here:
thanks for your help
Sorry that didnt work - trying again..
maybe this is the way to do it...
OK I think that works?
Unfortunately that link didn't work for me. I get an error saying it's no
longer available. Can you try again?
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1. The pattern noise (lines, cross-hatch) is characteristic to Canon DSLRs. The 5D2 exhibits this characteristic unfortunately very strongly (the 1Dxxx cameras are better in this regard). This pattern occurs with all ISOs.
2. The following capture shows the red raw channel on a noisy area (the red is the lowest here). This is past the tenth stop of the dynamic range (the displayed number, -9.18 EV is from pixel saturation). The next capture shows the appearance of the noise at this intensity with ISO 100 on a smooth uniform patch. That noise can be removed, but your shot is more difficult: the noisy area contains fine structures, which would get eliminated by aggressive noise reduction.
3. Higher exposure helps. Your shot was slightly underexposed; the exposure could have been increased by 2/3 EV without causing clipping of the pixels (in the camera). See the raw histogram: http://www.panopeeper.com/Canon/Canon5DMkII_ISimonius_Adobe_2012_Hist.GIF
However, exposure with this accuracy requires either tightly bracketed shots, or a neutral setup resulting in histograms and clipping indication in the camera reflecting the raw data.
4. One possibility to increase the dynamic range of the camera: by a color correction filter, in this case by a magenta filter. As the histograms show, the green channel is half stop ahead of the blue one, even more ahead of the red channel. The magenta filter would reduce the greens more than the reds and blues, thus a 1/3-1/2 EV exposure gain can be attained (a WB shot with the filter on is required!). Unfortunately, there are no high quality color correction filters available.
5. Another possibility: give less weight to the red channel (and somewhat less to the blue as well), so that the green becomes more dominant. However, I don't know how this would affect the resolution. Play with it.
I Hope it helps
I have a problem where there is very noticeable banding (+ noise?) in black and white conversions of my CR2 files from my Canon 5Dmk2.
Sorry bud...I downloaded your raw and it's seriously under exposed. The fact that you could get a fairly nice looking image out of this is pretty remarkable considering the state of the starting raw image. The only real way of doing what you are trying to do here is to capture multiple exposures and to an HDR blend. The exposure for the clouds/sky was ok but the exposure for the country side should have + 2-4 stops (or more) to get a reasonable noise signature from the countryside.
I seriously doubt that using a heavy-duty 3rd party noise reduction like NoiseWare is gonna be able to fix the noise in your final B&W conversion. The final image looks "ok" small and that's what you are gonna have to deal with cause the noise that is exposed by the over-amplification of the shadow details is just a fact of life (or psychics). There just simply ain't enough bits in your image...
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You would be better off simply darkening down the hills on the right side that is showing the real bad pattern noise. Panoholic is correct that it's an issue although I would argue pattern noise is an issue for ALL digital sensors particularly when the photosites are so under filled with photons. With a normal exposure (ei one that needs no exposure increase) you would never see the pattern noise. The fact you are so strongly lightening the tonal curve is what is making it so glaringly obvious. Actually darkening the hills (and running a 3rd party noise reduction to kill as much of the noise as you can) will actually help the image. You'll note that the foreground that has a lot of high frequency image detail hides the pattern noise a lot better than the flat areas of the hills...so you can afford to light the foreground and still darken down the distant hills and thus keep the noise to a minimum...
you should be able to see it now ok?
Thank you all very much for your considered comments I really appreciate it
I had been trying to emulate this photographer
However it looks like I'll have to lug that ol' tripod around with me after all