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02-25-2015, 05:55 PM   #1
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Banding & strange colour shifts in sky highlights?

Hi All
I'm really struggling with banding in sky. Most evening shots especially with sky have really bad banding, and any adjustments just compound. I'm working of .DNG RAW, 16 bit processing in ProPhotoRGB profile. If i make any slight adjustments (say highlight recovery, or a grad over the sky, or dropping the exposure) I get bad banding and also strange colour shifts towards cyan/greens.

Havng worked with Canon .CR2 files for years I have never seen anything like this? Elasticity of the image is great at the shadow end, but seems very bad towards the highlight end? I've just tried comparison with the SlikyPix app on the OEM disc to see if it was LR specific,but similar outcomes. Almost feels like I'm processing a worse than 8bit jpeg from a very old sensor.

Any advice, similiar experiences? Is there anything obvious I'm missing? Thanks, Rob


02-25-2015, 06:06 PM   #2
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I've been getting some banding, but not to this extreme. Generally with deep blue skies when I try and brighten part of it. A few images I've had to change how i was processing the file, I don't process my files over aggressively, but most see this banding when using Viveca and it is usually on the border of blue and cyan toned areas that gets this.
02-25-2015, 06:19 PM   #3
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QuoteOriginally posted by itshimitis Quote
I've been getting some banding, but not to this extreme. Generally with deep blue skies when I try and brighten part of it. A few images I've had to change how i was processing the file, I don't process my files over aggressively, but most see this banding when using Viveca and it is usually on the border of blue and cyan toned areas that gets this.
Sounds similar. Almost makes my 645z camera useless professionally with the amount of extra work it can create to some shoots. Some images are unworkable and carry banding in native raw images.
02-25-2015, 06:34 PM   #4
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QuoteOriginally posted by rob8888 Quote
Hi All
I'm really struggling with banding in sky. Most evening shots especially with sky have really bad banding, and any adjustments just compound. I'm working of .DNG RAW, 16 bit processing in ProPhotoRGB profile. If i make any slight adjustments (say highlight recovery, or a grad over the sky, or dropping the exposure) I get bad banding and also strange colour shifts towards cyan/greens.

Havng worked with Canon .CR2 files for years I have never seen anything like this? Elasticity of the image is great at the shadow end, but seems very bad towards the highlight end? I've just tried comparison with the SlikyPix app on the OEM disc to see if it was LR specific,but similar outcomes. Almost feels like I'm processing a worse than 8bit jpeg from a very old sensor.

Any advice, similiar experiences? Is there anything obvious I'm missing? Thanks, Rob
Rob;
Go to Imaging Resource and download some of their 645Z samples. See if your processing of their DNG file gives you the same poor results you have with the one above. I tried with Imaging Resources files on ACR 8.7.1 using Prophoto as the space changing the exposure, highlights and adding grad and try as a I might I could not replicate anything like what you have above (no banding or color shifts all the way to blown highlights). Try these files YIMGp2759.DNG and YIMGP2849.DNG. You could check that you are using the Embedded profile rather than Adobe's and recheck your settings when your convert from PropPhoto to RGB before you create your JPeg (Destination Space sRGB IEC61966-2.1 using Adobe (ACE), Saturation or Perceptual and Black Point Compensation). What ISO are you shooting at?

02-25-2015, 06:41 PM   #5
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QuoteOriginally posted by rob8888 Quote
Almost makes my 645z camera useless professionally
You might want to consider using a Pentax 67II as a backup camera.

I saw something similar to your banding on flickr and I inquired and the shooter said he thought it was the use of a cheap polarizer. That could have been the case for his banding because a polarizer uses 2 optical flats. If they are not perfectly parallel, one could get banding of colors caused by optical interference.

Last edited by desertscape; 02-26-2015 at 12:34 PM.
02-25-2015, 06:45 PM   #6
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QuoteOriginally posted by Fauxton Quote
Rob;
Go to Imaging Resource and download some of their 645Z samples. See if your processing of their DNG file gives you the same poor results you have with the one above. I tried with Imaging Resources files on ACR 8.7.1 using Prophoto as the space changing the exposure, highlights and adding grad and try as a I might I could not replicate anything like what you have above (no banding or color shifts all the way to blown highlights). Try these files YIMGp2759.DNG and YIMGP2849.DNG. You could check that you are using the Embedded profile rather than Adobe's and recheck your settings when your convert from PropPhoto to RGB before you create your JPeg (Destination Space sRGB IEC61966-2.1 using Adobe (ACE), Saturation or Perceptual and Black Point Compensation). What ISO are you shooting at?
Good suggestion. There's not really a file there that I'd expect, from experience, to encounter it with, but will try now. I don't really work in jpegs, I'm finding it even in my 16bit tiff files (viewed on a adobe 1998 monitor (not sRGB)) in both ProphotoRGB and after conversion to adobe1998 profile. These are shot at 100 or 200 ISO.

---------- Post added 02-26-15 at 02:05 AM ----------

Tried outputing as 16bit tiff from LR with all adjustments zeroed out - still visible. Slight exposure reduction to make it more visible. No filters on lens. Issue seems to always be with the cyan/blue area as Itishimitis mentions.

Last edited by rob8888; 02-25-2015 at 06:54 PM.
02-25-2015, 07:12 PM   #7
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QuoteOriginally posted by rob8888 Quote
Good suggestion. There's not really a file there that I'd expect, from experience, to encounter it with, but will try now. I don't really work in jpegs, I'm finding it even in my 16bit tiff files (viewed on a adobe 1998 monitor (not sRGB)) in both ProphotoRGB and after conversion to adobe1998 profile. These are shot at 100 or 200 ISO.

---------- Post added 02-26-15 at 02:05 AM ----------

Tried outputing as 16bit tiff from LR with all adjustments zeroed out - still visible. Slight exposure reduction to make it more visible. No filters on lens. Issue seems to always be with the cyan/blue area as Itishimitis mentions.
I've emailed my contact at Pentax Ricoh in the UK (he is the Service representative that coordinates between Pentax Ricoh and their agents). I'll let you know what I get back. I've sent him a couple of photos showing the issue. They are photos I gave up with where the blue sky meets the dying light of the sun.
02-25-2015, 07:22 PM   #8
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QuoteOriginally posted by itshimitis Quote
I've emailed my contact at Pentax Ricoh in the UK (he is the Service representative that coordinates between Pentax Ricoh and their agents). I'll let you know what I get back. I've sent him a couple of photos showing the issue. They are photos I gave up with where the blue sky meets the dying light of the sun.
I'd be REALLY interested in what they say. I shoot a lot of sky like this and also have images that I give up on. They're valuable frames too, and it's a headache.

02-25-2015, 07:36 PM   #9
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I have had this on my 645d when aggressively using highlight recovery or exposure brush in LR and also when making Hue/saturation adjustments in the HSL section.

Never have I had this on my Z.

I will go and try some shots and get back to you.
02-25-2015, 11:17 PM   #10
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Like 2351HD, I've never seen this on my Z, but then again I try to never over-expose my images. Yes, Canon files do have an impressive amount of headroom, back when I used Capture One 7 I could pull 2 stops of highlights easily just by setting the input curve to linear and adding 50 highlight recovery. The difference is that while the Canon files lacked shadow recoverability almost entirely (banding, discoloration, et.al), the Pentax 645Z it's completely backwards, you have barely any highlight headroom (-10 highlights is my limit in Lr) and an easy 5+ stops of shadows.

The problem is in the difference of where Pentax chose to place the middle gray point, if they had configured the sensor to report a darker exposure as the "correct" one and offset the metering system and preview to compensate, then perhaps we could have had more like 2 stops on the highlights and 3 stops on the shadows.

As it is, make absolutely sure that the highlights in your scene do not clip, you can check this in Live View (but not preview, which is based on a jpeg) by looking for the red blinkies, it's the only indication the camera gives you that the area is 100% blown out and unrecoverable. Even if your shot looks under-exposed in-camera, the Z will take any amount of shadow push you can throw at it in post, so the only inconvenience is being unable to get a good sense of the exposure in the field as most of your shots will seem dark.
02-26-2015, 12:30 AM   #11
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I find the red blinkies on the Z to be somewhat inaccurate and usually have to underexpose by 1/3 stop as the jpg preview will be clipped.

That's not to say that if you follow the blinkies that the raw won't be spot on as it most likely will. The jpg preview will clip the highlights off and the raw will have the headroom. As you said, the blinkies are coming from the raw data and will most times be spot on.

I would rather keep the highlights and boost the shadows personally.
02-26-2015, 02:33 AM   #12
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Good discussion you lot.

That's exactly what I think I'm seeing - major resilience in the shadows but we've given something up in the highlights. Though it doesn't quite seem that simple as there's some weird stuff happening in the cyan area. It's like it does a weird Hue sidestep into cyan and back (if that makes sense?) right near the highlight limit of blue. Is there any post processing going on in camera that could be to blame (I'm assuming this doesn't affect a RAW output though?)?.
02-26-2015, 03:10 AM   #13
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I deliberately expose (slightly) to the left because of the way the camera behaves with highlights and shadows. Personally I prefer this way to the Canon way which made me switch to Nikon on the 35mm FF side. My concern is that Blues and clans are too fragile no matter how you expose.

---------- Post added 02-26-15 at 03:12 AM ----------

QuoteOriginally posted by 2351HD Quote
I find the red blinkies on the Z to be somewhat inaccurate and usually have to underexpose by 1/3 stop as the jpg preview will be clipped.

That's not to say that if you follow the blinkies that the raw won't be spot on as it most likely will. The jpg preview will clip the highlights off and the raw will have the headroom. As you said, the blinkies are coming from the raw data and will most times be spot on.

I would rather keep the highlights and boost the shadows personally.
Are you looking at the blinkies in live view or the post capture preview? Live view is based on what the sensor sees, the preview is a jpg image which won't be 100% accurate.
02-26-2015, 04:10 AM   #14
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QuoteOriginally posted by rob8888 Quote
Good discussion you lot.

That's exactly what I think I'm seeing - major resilience in the shadows but we've given something up in the highlights. Though it doesn't quite seem that simple as there's some weird stuff happening in the cyan area. It's like it does a weird Hue sidestep into cyan and back (if that makes sense?) right near the highlight limit of blue. Is there any post processing going on in camera that could be to blame (I'm assuming this doesn't affect a RAW output though?)?.
I really haven't seen anything like it yet. To give an idea of how I expose my images, the before/after in the following image should help - nothing was close to over-exposing except for the specular highlights, but the scene as I saw it was very bright and silvery so I adjusted the image to suit. Dialing in negative highlight recovery is only applicable when I raise the exposure level to prevent certain highlights from blowing out.


Also the finished photoshop variant.

Last edited by Kolor-Pikker; 02-26-2015 at 05:52 AM.
02-26-2015, 08:28 AM   #15
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QuoteOriginally posted by Kolor-Pikker Quote
I really haven't seen anything like it yet. To give an idea of how I expose my images, the before/after in the following image should help - nothing was close to over-exposing except for the specular highlights, but the scene as I saw it was very bright and silvery so I adjusted the image to suit. Dialing in negative highlight recovery is only applicable when I raise the exposure level to prevent certain highlights from blowing out.


Also the finished photoshop variant.
To be fair, I wouldn't expect to see it in a shot like this as there is even tone. What we are talking about is shots at twilight/sunrise where blue/cyan tones meet the emerging/disappearing sun. It's at the extremes of the dynamic range on the highlight side - though not necessarily when highlights are clipping or close to clipping. This banding still appears in other shots especially if you aren't careful in processing.

Here is an example - this is SOOC, just converted to jpg for web use with no adjustments at all. Fairly long exposure (60 secs) about 30 mins after sunset on a clear day.



this is with some adjustments, increasing overall exposure and some shadow recovery



There is flare there as I had a Lee Filter - A soft GND and a 0.9 ND on there.
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