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09-13-2009, 04:52 AM   #1
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Interesting thread reg. K-7's dynamic range

Or rather how it is being spoiled by poor raw development:
K-7 raw headroom - this can't be right [Page 1]: Pentax SLR Talk Forum: Digital Photography Review

09-13-2009, 07:15 PM   #2
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What I found interesting....

Was to see the progress of the thread to where the shot was rendered almost perfectly via some nice processing. I suspect that there is a learning or adjustment curve to the metering on the K7, as there is on almost every model I have owned. I don't have the K7, but find the metering very much to my agreement on the K20D. Processing is as key as any other part of 'getting it right".
Having said all that, I have never believed in ETTR...it almost always fails because you are right on the edge and just a little too far and the highlights are blown forever. I know some swear by it, but it has never worked consistently for me. If the K7 does this "automatically" I doubt I would get along with it very well. I will have to see more on this before I am ready to go K7.
Regards!
09-13-2009, 09:25 PM   #3
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QuoteOriginally posted by gaddigad Quote
Or rather how it is being spoiled by poor raw development:
Using GordonBGood's words:
QuoteQuote:

The K-7 does a brilliant job of raw exposure in very high contrast situations such as this one; one just needs the right tools and/or techniques in order to deal with the images properly.
Quick summary: The K-7 nailed the (RAW) exposure of a difficult scene but many RAW converters will make the highlights clip before the user can apply exposure compensation in post processing (and hence will make look some highlights to appear blown). Proper conversion won't introduce artificial clipping and will hence let you use the dynamic range the K-7 provides (through sensor and metering) to the fullest extent possible.
09-13-2009, 09:27 PM   #4
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what I find is the best is using spot on what you want to be white, and knowing how many +EV to make that spot just below clipping:

Quick, Accurate High Contrast Exposures for Digital Cameras

Unfortunately I want a split focus screen and it won't work

09-14-2009, 02:30 AM   #5
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How about PPL?

QuoteOriginally posted by Class A Quote
Using GordonBGood's words:

Quick summary: The K-7 nailed the (RAW) exposure of a difficult scene but many RAW converters will make the highlights clip before the user can apply exposure compensation in post processing (and hence will make look some highlights to appear blown). Proper conversion won't introduce artificial clipping and will hence let you use the dynamic range the K-7 provides (through sensor and metering) to the fullest extent possible.
Spot on. I find it interesting that PPL also seems to have failed to recover those highlights judging by the published jpeg in the thread, at least the workflow performed by the thread participant having the K-7 compatible version (which btw is not available publically yet). This raises the question whether the K-7's internal jpeg engine handles it correctly.
09-14-2009, 02:38 AM   #6
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QuoteOriginally posted by Rupert Quote
...
Having said all that, I have never believed in ETTR...it almost always fails because you are right on the edge and just a little too far and the highlights are blown forever. I know some swear by it, but it has never worked consistently for me. If the K7 does this "automatically" I doubt I would get along with it very well. I will have to see more on this before I am ready to go K7.
Regards!
I also much prefer exposing to the middle or even to the left half to two halves of the histogram most of the time. Highlights are better preserved and tonality is more to my taste. it's very easy to push it a bit to the right in PP and recover the dynamic range.
09-14-2009, 03:42 AM   #7
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I tested the CW meter on my K10D against the metering systems of a Pentax LX and Pentax 645 and a Pentax digital spotmeter as a control and I found it was quite accurate with only 1/3rd of a stop aberrant over/under exposure in certain situations.

I don't like intelligent metering systems.Because more often than not they do something stupid. so far I'm impressed with the K-7's metering system, I haven't run it through my testing yet; but from what I have seen so far it doesn't seem to be as easily fooled as it's predecessors. The cmos sensor in the K-7 responds well to exposing to the right, I don't think CCD's handle it well...I suspect it has something to do with the pixel architecture.
09-14-2009, 03:47 AM   #8
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QuoteOriginally posted by Eruditass Quote
what I find is the best is using spot on what you want to be white, and knowing how many +EV to make that spot just below clipping:

Quick, Accurate High Contrast Exposures for Digital Cameras
this one explains how to go about in pretty simple way
The Online Photographer: On Testing a New (Digital) Camera, Steps A and B

You should do this yourself since the various raw converters are a bit different on how they data at or just below clipping. I managed to squeeze out 3.5EV steps before clipping on the K-7, but I usually only go 3 steps to leave just a little margin. I use LightRoom 2.4

Just to mention it, this has really nothing to do with dynamic range. The highlight margin is more or less fixed, and is related to how ISO is defined. If a camera from a different brand is different (my Canon 5D was only 3EV steps), it is only because that manufacturer has a different understanding of how the metering is translated to actual exposure. If you're interested in the dynamic range, you need to go into the shadows as well.

09-14-2009, 05:02 AM   #9
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I thank GBGood for teaching me about an important difference between RawTherapee and others (no good) and ACR/Lightroom (good) when it comes to negative exposure compensation in post processing.
QuoteOriginally posted by gaddigad Quote
This raises the question whether the K-7's internal jpeg engine handles it correctly.
Not actually ...
Because you would never apply negative exposure compensation to the RAW data in camera the camera-internal JPG engine wouldn't be able to be affected by this "bug".

The camera does always apply negative exposure compensation to the shot itself, not its delivered data, i.e., even before data is produced.

However, it would make a difference for the manual RAW conversion which is possible in camera as well. But only few of us have ever used this feature, I guess
09-14-2009, 09:43 PM   #10
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Rather than taking GBG's word for it, why not check out RawTherapee's internal processing workflow for yourself:

http://www.rawtherapee.com/data/RT-Internal-Workflow_2.4.pdf

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09-14-2009, 10:14 PM   #11
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QuoteOriginally posted by jbinpg Quote
Rather than taking GBG's word for it, why not check out RawTherapee's internal processing workflow for yourself:
Do you question Gordon's statement?
How come negative exposure compensation just moves the already clipped area in RawTherapee?

It is quite likely that the clipping already occurs at the initial RAW decoding stage where RawTherapee (like many other programs) uses dcraw. The latter needs a fix (or needs to be used with the right parameters, IIRC) in order not to cause the clipping.

BTW, I have emailed the author of RawTherapee and there is a thread in the RawTherapee bugs forum. We'll see how the author responds.
09-15-2009, 08:09 PM   #12
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I believe that there are raw conversion programs that allow conversion to a linear file. I would think this would be as good as it gets for protecting highlights. But it may be a lot more work to get from the linear file to a final image that you like. I believe dcraw has this as an option as well as some others. Maybe Capture One, not sure. Might be worth playing with for a particular file image that is a problem.
09-16-2009, 05:01 AM   #13
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From my quick tests, it seems UFRaw does the right thing and actually allows the recovery of "blown" highlights.
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