Panasonic Lumix G 20mm F1.7 II (H-H020A) - Banding

Started Aug 6, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: It is in my world

tsi wrote:

texinwien wrote:

Anders W wrote:

texinwien wrote:

Anders W wrote:

texinwien wrote:

Sosua wrote:

Not in my experience - shooting tea pots at F4 and ISO 6400 then boosting exposure by a stop and cranking contrast to max in lightroom does not happen that often for me.

Shooting my 20mm F1.7 and EM5 in low light however does and i've never seen any banding.

ISO 800, F1.7 and 1/10th of a second sucks in some pretty low light, certainly enough for me.

One of many of my low-light images ruined by the Panny 20mm + the E-M5:

It's a real shame Panasonic doesn't seem to have addressed this issue in the new version of this lens. Hard for me to understand how they could go to the trouble of releasing an updated design without taking care of this problem.

Tex! Since that's a very nice image worth "rescuing", have you tried giving it additional NR specifically on the sky? One technique I have been playing with for night shots like this is to mark the sky area by means of the LR brush. There's an auto-mask option for the brush that allows you to follow contours (in this case the mountain ridge) quite precisely without too much work (although it still requires some time). Of course, you'd first try to brush the sky in a rough and approximate way and then check whether additional NR might help. Not worth taking the trouble to match the mountain contour precisely if it doesn't.

Hi Anders, thanks for the suggestions!

The high frequency luminance banding in the sky cleans up a little if I use a brush with 100NR, except toward the very top of the image. So I switched to a 2:3 crop, removing pixels from the top.

Partly addressing the higher-frequency banding leaves some lower-frequency banding with a magenta color-shift: I haven't been able to figure out how to get rid of this lower-frequency banding, yet. I've tried desaturating and adjusting hue/luminance settings on the purple and magenta channels with little luck.

FWIW, I have used the technique I describe with some success (to my own mind at least) for night scenes, where the objective was not to reduce banding but simply to get the sky as noise-free as possible, without applying additional NR to the rest of the scene (where I prefer to keep the detail rather than have it washed out by NR). Here's an example. This is at a camera ISO 1600, like yours, but far from ETTR when it comes to exposure. The image I post has a horizontal resolution of about 2000 so isn't full size. I don't really think it holds up at 1:1 but at this display size, I think it works reasonably well. A very nice result, indeed! I'd be quite happy to get the skies in my sample photo that clean.

Hi Tex. Don't know quite what, if anything, to do about the magenta shifts that remain. A few comments nevertheless.

First, you might already have seen (or be aware for other reasons) that the banding is likely to cause color shifts for reasons discussed by tsi and me in the subthread beginning with this post earlier in the present thread:

http://www.dpreview.com/forums/post/51977740

A concomitant reason might be that at least one channel (in your case, I'd primarily suspect red) is so close to the black point that the read noise (vayring due to the interference that creates the banding) gets partly clipped by the black level offset. There is a special tint (magenta-green) slider in the camera calibration section of the LR develop panel, which is specifically for dealing with the problems caused by read-noise clipping combined with channel imbalance (green stronger than blue and/or red) as you approach the black point. You might try to play with that although I doubt it will help.

Thank you, Anders. I was not aware of the calibration section as well.

Another option for adjusting the channel imbalance may be to tune the tone curves of the rgb channels individually. For example if an images is taken with candle light, white balance seems to increase the gain of the blue channel, which causes the distribution of black levels of the blue channel to become wider than those of the other channels in the histogram. This can be countered by reducing the gain of the blue channel in the shadows and following an almost linear curve in mid tones and high lights. However, I am not sure if this will help with color shift banding.

Thanks for that suggestion. It seems to help a little, and gives me something else to work with.

When I first tried to apply the LR brush to the sky in night scenes of the kind I exemplified, I tried to play a bit with other sliders apart from NR, to see how far I could reduce the sky noise. Among those worth looking at for this purpose are contrast, sharpness and clarity (moved toward the negative rather than positive end). In the end, I didn't use any of them, but they are at least worth a look.

I had worked with most of these settings without a lot of luck, but I'll give it another go.

Another technique that I did use was to reduce "exposure" of the sky specifically, and this might indeed help a bit in your case too (unless you find the sky becomes too dark for your taste). The moon-lit scene I posted looked pretty much like it was caught in the afternoon sun when I first opened it in LR. To make it look like the night scene it actually is, I pulled back exposure generally a little bit (about 2/3 EV) and the sky (via the brush) another bit (another 2/3 EV).

Another good tool in the toolbox. The shadows tint slider is the one thing I hadn't worked with yet, and it seems promising. I'll give it another go a mix of techniques and see what I can come up with. Thanks again for the tips!

I have tried Topaz DeNoise trial version and applied it to your image. Before the banding correction, distortion was changed to -11 in Lightroom. Here is the side to side comparison before after banding correction. Both images show a crop of the sky with the aspect ratio changed. The correction works very well.

left: original , right: after banding correction

One thing I forgot to ask: Have you tried any other software than Topaz for this purpose? If so, what would you say about their relative advantages/disadvantages? In general, I would be interested in anything you have found out in your search for a "Band Aid", whether by means of your own trials or on the basis of whatever other sources you have consulted.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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