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02-26-2015, 09:48 AM   #16
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Great discussion, thank you!

You all have probably saved my bacon here, future wise. I kind of agree that it seems like an arbitrary setting of where middle grey "is" in the Z. I can adjust.

So, as a further question: since we should boost shadows---ETTL---has anyone found the acceptable (a moving target, I know...) highest iso if we ETTL, since "properly" exposed, well-lit areas in high iso images don't usually smack us over the head noise-wise.

02-26-2015, 11:48 AM   #17
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QuoteOriginally posted by itshimitis Quote
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.
Ok, that certainly helps... sort of. The kind of sky you show doesn't really happen in the part of the world I live in, so I can't replicate the effect. The tone is almost always even and it doesn't come close to having colors that deep/saturated, and definitely never cyan, although once I photographed a purple sky.

I do see skies like that when I'm on trips to the USA, so it might be a regional thing.

QuoteOriginally posted by texandrews Quote
So, as a further question: since we should boost shadows---ETTL---has anyone found the acceptable (a moving target, I know...) highest iso if we ETTL, since "properly" exposed, well-lit areas in high iso images don't usually smack us over the head noise-wise.
Hmm hard to say, but if we generally accept that a 5-stop shadow push at ISO100 is "usable", ISO3200 should be the effective ISO at that level. Considering that I find even ISO12,800 usable for average print sizes, ~3200 doesn't seem like an unreasonable value for critical viewing.

Last edited by Kolor-Pikker; 02-26-2015 at 12:15 PM.
02-26-2015, 12:29 PM   #18
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QuoteOriginally posted by itshimitis Quote
...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...

Exactly what I'm talking about. Thank you.

It's not just normal highlights burning to white. It's in the blue/cyan area near the highlight end. The camera creates a nasty band that looks like an aurora across the sky. It ruins nearly every crisp blue sky twilight evening frame. Under exposing doesn't help. It's a big pot hole in the colour gamut to try avoid, but our crisp clear evening skies in New Zealand hit it every time. Help!

Last edited by rob8888; 02-26-2015 at 03:18 PM.
02-26-2015, 01:47 PM   #19
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QuoteOriginally posted by rob8888 Quote
Exactly what I'm talking about. Thank you.

It's not just normal highlights burning to white. It's in the blue/cyan area near the highlight end. The camera creates a nasty band that looks like an aurora across the sky. It ruins nearly every crisp blue sky twilight evening frame. Under exposing doesn't help. It's a big pot hole in the colour gamut to try avoid, but our crisp clear evening skies in New Zealand hit it every time. Help!

I spent a few weeks in NZ last year, 11 days of which I was driving around taking photographs. Pure blue skies especially around places like Lake Tekapo are very deep and as the light drains away there will be a fair amount of cyan tones, so this issue will hit you hard. I've ben shooting in the twilight this evening, and have found the banding still present, but as am ETTL it's not such a big problem on this shoot, but the clearer the sky, the more noticeable it can be. Hopefully it is something that can be rectified in a firmware update. I have the additional issue that my remote cord isn't functioning as it should. It cost me 60 which is a ridiculous cost for a remote cord. I'm hoping it is the cord rather than the socket and I've ordered a third party release to check it. If it turns out to be the camera I'll be disappointed as the last repair to the 645D took over 3 months, and that was a paid for repair.

02-26-2015, 02:12 PM   #20
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QuoteOriginally posted by rob8888 Quote
Exactly what I'm talking about. Thank you.

It's not just normal highlights burning to white. It's in the blue/cyan area near the highlight end. The camera creates a nasty band that looks like an aurora across the sky. It ruins nearly every crisp blue sky twilight evening frame. Under exposing doesn't help. It's a big pot hole in the colour gamut to try avoid, but our crisp clear evening skies in New Zealand hit it every time. Help!
The only way I can think of replicating this is with a special LED lamp that I have at work which can generate any color of light there is. If I pick the right shade and bring the exposure level up, I might be able to find where this so-called pothole is; it's got me intrigued.
02-26-2015, 02:59 PM   #21
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Here's a typical nightmare scenario (with almost no post work done, taken at iso200):

I've had to completely re-engineer my workflow to try to minimise this problem. 16bit tiffs show it a little, but by the time it becomes a medium res jpeg for website use it looks very poorly and unprofessional.
Impacts nearly every evening/dawn shoot I do and is not satisfactory for a professional camera I'm starting to feel.
02-26-2015, 03:03 PM   #22
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QuoteOriginally posted by Kolor-Pikker Quote
The only way I can think of replicating this is with a special LED lamp that I have at work which can generate any color of light there is. If I pick the right shade and bring the exposure level up, I might be able to find where this so-called pothole is; it's got me intrigued.
Thanks, much appreciated.
02-26-2015, 03:24 PM   #23
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QuoteOriginally posted by Kolor-Pikker Quote
The only way I can think of replicating this is with a special LED lamp that I have at work which can generate any color of light there is. If I pick the right shade and bring the exposure level up, I might be able to find where this so-called pothole is; it's got me intrigued.
That would be interesting. To help I've pulled some rough RGB values you could look around: R 46 G 52 B 75 ; RGB 35 41 65 (taken from the island shot above) . It appears most noticeably in blue graduations.

02-26-2015, 04:17 PM   #24
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Do you have an example DNG you don't mind sharing so I can try to demosaic it in the Iridient Raw Converter?
02-26-2015, 04:36 PM   #25
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Banding & strange colour shifts in sky highlights?

If anybody wants to have a look at a file for me and see what you can see I'd be grateful. Here's one .DNG raw to download here (just happens to be right up against the highlight limit, but this doesn't always need to be so):
02-26-2015, 05:19 PM   #26
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Alright, to be honest I have some problems in this area which is related to a very mild red/green weakness.
Appended are screenshots in the following order:
1. v3 Detail+ fast
2. v3 Standard (slower)
3. v3 Ultimate (slowest)

Even with my colour weakness it is apparent in all versions, but it seems a bit better in version 3.
Not sure if it tells us anything else than further assurance that it is indeed a hardware (or to say firmware) problem.
What do you think, will they take it seriously if reported by just one person?
I just bought the cam...it seems like a major bug to me, as I am doing landscape 95%...

---------- Post added 02-27-15 at 01:20 AM ----------

Edit: Now on the white background they seem similarly bugged,
Attached Images
     
02-26-2015, 05:26 PM - 1 Like   #27
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Thank you very much for that.

I'm predominantly a landscape professional and it's got income implications for me. I'm starting to loathe it. I'm seeing it in prob 10-20% of my shooting now (that's % of shoots, not frames). The results are unusable without a complete sky rebuild which is impossible in most cases, and against my minimal retouching style anyway.

It's not just me seeing it, so I really hope it gets some attention, and I really hope it is a firmware issue only. How do we make Pentax aware of it?
02-26-2015, 06:10 PM   #28
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This is a truly frustrating find, but thanks alot for finding this issue in the first place! Weird it's taken so long to emerge, considering that this lighting situation is a preference for us landscape shooters.
This totally destroys the confidence I had in this camera. I will try to get hold of a contact address through the shop where I bought mine.

---------- Post added 02-27-15 at 02:16 AM ----------

Have you compared similar scenarios between DNG and PEF?
02-26-2015, 07:21 PM   #29
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Yeah right I can see that now.

As for the blinkies, yes I know that live view is correct but just saying that once you take the photo it will tell you it's blown out due to the JPEG treatment for the preview.
02-26-2015, 08:36 PM   #30
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Rob8888, I took a quick look at your sample DNG file. The magenta area in the sky is that way because both green channels in the raw data are completely clipped in that region -- zero data. Highlight recovery is attempting to pull back some detail, but there's only red and blue channel info to use; the result is magenta. So totally clipped green is the immediate cause.

Why the green channels are clipped is another question. Is it as simple as an overexposed frame? You say underexposing doesn't help -- underexposing by how much? How does the RGB histogram look at the time of capture? Admittedly the camera histo is only showing data from the JPEG thumbnail, but I'm curious how you see the G channel vs. R & B in-camera at the time of capture.
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