5D2 noise and banding worst in B+W

Question

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.
I only shoot in RAW (not sRAW or jpg) I mention this because firmware 1.0.7 was meant to address these issues but for when shooting in sRAW as I was shooting with the earlier version of the firmware on these files ( I have updated now but havent had time to check out the new firmware v.1.10). I have these probelms even though I shoot in RAW (not sRAW). It might be the camera, I realise that, however as it doesn't seem to be a recognised problem with that camera when shooting RAW, and as I haven't heard reports of it being the camera, I am looking for other solutions/causes.
As I open the RAW files in Prophoto in ACR I thought I'd ask your opinions here. I am quite prepared to accept that it's just me doing something dumb in Photoshop, so I'll give a brief rundown of my process: First I open through ACR and make global adjustments for exposure etc, then in Ps I process the colour version using adjustment layers to tweak levels and use masks to apply this to selective areas. Nothing dramatic. Then I flatten and add B+W adjustment layer and use masks to apply to selective areas. I don't crash the blue or cyan or magenta all the way to the bottom ( which I might expect to dramatically increase noise). In fact those only have very slight adjustments masked to the sky, on this image.
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?
thanks
example:
full pic:
556802641_LkNGo-S.jpg
100%crop of top RHS:
557888476_igLaZ-O.jpg
Forum profile refuses to update so I'll put info here: PsCS4 11.0.1. ACR 5.0.3, LR2.3, Mac G5 dual 2.3PPC 6GB RAM

Answer 1

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.
http://www.panopeeper.com/Canon/Canon5DMkII_ISimonius_Adobe_2012_Noise_Red.GIF
http://www.panopeeper.com/Canon/Canon5DMkII_CCC_ISO0100_Noise_Red-9.26EV.GIF
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
Gabor