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Author Topic: Can Stitching 1DsMk3 files = Med Format Quality?  (Read 34372 times)
eronald
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« Reply #160 on: June 18, 2008, 04:00:32 AM »
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You're welcome to publish these files - that's why I hand them out.

It's interesting that this demo clearly shows up the banding which made me declare that back as defective.

I think it would be worth applying the same technique to other images to see what one can learn.

As far as Sinar know, ISO is just a postprocessing setting in all the current backs including their own, which makes defining exactly what underexposed means a topic of debate.

Edmund

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In is nonsensical to talk about MFDBs sensors in general. Even the P25+ and P45+ from PhaseOne are different.

Related to the P45+: it is by far not so, that there were only 14 bits there. I created a demo about this; everyone can make his/her own conclusion about the usefulness of these or those bits.

The file is in TIFF format, layered, over 8MB; the layers contain screenshots of raw data displays: 16bit; 14bit; only the low order bit; only the low order two bits.

The P45+ file is from Edmund. I hope he does not mind that I use a small crop of that for this demo. (I guess he still does not believe, that the shot has been underexposed by almost four stops.)

Demo
[a href=\"index.php?act=findpost&pid=202173\"][{POST_SNAPBACK}][/a]
« Last Edit: June 18, 2008, 04:01:03 AM by eronald » Logged
drew
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« Reply #161 on: June 18, 2008, 04:01:27 AM »
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The questions you are all debating about dynamic range and shadow detail have been definitively resolved. All those technical treatises we have been pondering were a waste of time, it's all totally irrelevant.

Real photographers know DR does not matter...

http://www.kenrockwell.com/tech/dynamic-range.htm

 

Gotta love the guy!
[a href=\"index.php?act=findpost&pid=202200\"][{POST_SNAPBACK}][/a]

Ah yes, Ken Rockwell, doyen of technically minded photographers.
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Ray
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« Reply #162 on: June 18, 2008, 04:57:22 AM »
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The questions you are all debating about dynamic range and shadow detail have been definitively resolved. All those technical treatises we have been pondering were a waste of time, it's all totally irrelevant.

Real photographers know DR does not matter...

http://www.kenrockwell.com/tech/dynamic-range.htm

 

Gotta love the guy!
[a href=\"index.php?act=findpost&pid=202200\"][{POST_SNAPBACK}][/a]

I think this is one of the dumbest and least defensible opinion I've read from Ken Rockwell. But hey!,  we all make mistakes. I've been known myself to occasionally make a mistake, although I know that's difficult to believe   .
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« Reply #163 on: June 18, 2008, 04:30:38 PM »
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I put the RAW files in their own thread...
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Misirlou
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« Reply #164 on: June 18, 2008, 05:32:37 PM »
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I think this is one of the dumbest and least defensible opinion I've read from Ken Rockwell. But hey!,  we all make mistakes. I've been known myself to occasionally make a mistake, although I know that's difficult to believe   .
[a href=\"index.php?act=findpost&pid=202213\"][{POST_SNAPBACK}][/a]

Actually, to be fair, I think what Rockwell is saying is not that DR doesn't matter, but rather that a photgrapher should learn how to use the DR available from the camera to cover the scene, rather than obsess over how much DR is available in the first place. It's not an entirely unreasonable statement.

The distinction between those two concepts might have bearing on the main thrust of this thread. Or, it might not.
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Ray
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« Reply #165 on: June 18, 2008, 07:36:29 PM »
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Actually, to be fair, I think what Rockwell is saying is not that DR doesn't matter, but rather that a photgrapher should learn how to use the DR available from the camera to cover the scene, rather than obsess over how much DR is available in the first place. It's not an entirely unreasonable statement.

The distinction between those two concepts might have bearing on the main thrust of this thread. Or, it might not.
[a href=\"index.php?act=findpost&pid=202311\"][{POST_SNAPBACK}][/a]

Yes, his argument is not totally indefensible. If you are shooting in jpeg mode, reducing contrast can increase dynamic range somewhat; bringing in a truckload of lighting can improve the shadows; sticking a grey gel or plastic sheet over the windows can lower the contrast of the scene, and using a split ND filter for a landscape shot can allow one to use a single exposure which is suitable for both sky and land, provided the horizon is reasonably straight.

All this is true. However, there are much more convenient ways of improving DR, such as using a camera in the first instance which has a high DR, shooting in RAW mode instead of the jpeg format which Rockwell seems to always recommend, and bracketing exposure for digital blending or merging to HDR where the subject is stationary.

Also some statements in his article, such as the following, appear to be completely wrong.

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It is trivial to design a digital camera with far more dynamic range than any other camera. All a designer does is lower the contrast.

Here, Ken could have written an article recommending the eschewing of those complicated and cumbersome procedures (sticking gel on the windows etc), and his article would still have been in character, like his article suggesting tripods are no longer needed because digital cameras have high ISO capability and image-stabilised lenses which enable shutter speeds which are generally adequate for most hand-held shots.
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Panopeeper
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« Reply #166 on: June 18, 2008, 09:15:41 PM »
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It's interesting that this demo clearly shows up the banding which made me declare that back as defective
I am not convinced, that  it is really defective, and I am not convinced, that you should not use it with higher ISO (your dealer does not know the camera).

If you are interested on it, the post (yousendit) pls following shots (raw files, of course):

1. whatever, with the lowest ISO, metered for that ISO,

2. shots for all other ISOs with the very same exposure, i.e. successively overexposing,

3. one shot with the banding, the raw file and a crop showing the banding in the converted TIFF or high quality JPEG.

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As far as Sinar know, ISO is just a postprocessing setting in all the current backs including their own, which makes defining exactly what underexposed means a topic of debate
Well, I could say "underexposure" means, that you have to adjust the intensity in raw processing so much, that the banding becomes visible.

However, I used the term differently. I admit it is not correct, and I don't want to redefine "underexposure", but there is no short term for this: the distance in EV measured from the very right.

In other words, my "underexposed by almost four stops" means, that the exposure could have been increased by almost four stops without causing relevant pixel clipping on raw level.
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Gabor
eronald
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« Reply #167 on: June 18, 2008, 09:39:44 PM »
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Gabor - I don't have that back anymore. It had centerfold issues and banding issues and got sent back. No idea what the software solution for those is. As for underexposed by 4 stops, I have no idea what that means these days, since I have found out that the back is always run at ISO 100...


Edmund

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I am not convinced, that  it is really defective, and I am not convinced, that you should not use it with higher ISO (your dealer does not know the camera).
In other words, my "underexposed by almost four stops" means, that the exposure could have been increased by almost four stops without causing relevant pixel clipping on raw level.
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Panopeeper
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« Reply #168 on: June 18, 2008, 10:21:30 PM »
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As for underexposed by 4 stops, I have no idea what that means these days, since I have found out that the back is always run at ISO 100...
No, the P45+ is not. Axel's shots showed, that there is a gain between 400 and 800. However, the P25+, the P45 (not plus) and the P30 (not plus) appears to capture everything in a single ISO shot; though I don't have enough shots sufficiently proving this.

I became convinced, that theis is the way to go: capture everything possible (i.e. expose as high as you can under the given circumstances), convert everything at the highest reasonable ISO and write everything in the raw file. Let the raw processor think about what to do with it.

This requires huge storage and massive in-camera processing capacity, but I would happily sacrify the 6.5 frames per second of my camera if the DR became two stops higher in exchange.

What camera do you have now?
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Gabor
eronald
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« Reply #169 on: June 18, 2008, 10:40:37 PM »
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No, the P45+ is not. Axel's shots showed, that there is a gain between 400 and 800. However, the P25+, the P45 (not plus) and the P30 (not plus) appears to capture everything in a single ISO shot; though I don't have enough shots sufficiently proving this.

I became convinced, that theis is the way to go: capture everything possible (i.e. expose as high as you can under the given circumstances), convert everything at the highest reasonable ISO and write everything in the raw file. Let the raw processor think about what to do with it.

This requires huge storage and massive in-camera processing capacity, but I would happily sacrify the 6.5 frames per second of my camera if the DR became two stops higher in exchange.

What camera do you have now?
[a href=\"index.php?act=findpost&pid=202347\"][{POST_SNAPBACK}][/a]

I have another sample of the P45+
Edmund
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TechTalk
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« Reply #170 on: June 19, 2008, 02:25:13 AM »
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It has been written many times that those last two bits (between 14 and 16) do not hold any image data which directly translates to an increase in dynamic range.
I believe that MF has better D.R., but it is said that this improvement in D.R. comes from data which is contained within the first 14 bits...
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Probably less than 14 bits are recorded. The advantage of a 16-bit analog to digital conversion is the additional number of levels that are available in all of the exposure zones recorded. Within each exposure zone, subtle and smooth tonal gradations rely on having an adequate number of levels to represent the source subject. This is especially important in the highlight and mid-tone regions where the eye is better able to differentiate small tonal variations.

The concept that noise floors should be the defining factor in how much bit-depth in a/d conversion is advantageous only makes sense if one disregards the tonality of the levels above the noise floor. In other words, yes--you only need a number of bits equal to the useful dynamic range that the sensor can output if all you want to do is record the minimum number of levels that represent that tonal range. However, you eye needs more than a handful of levels to perceive a smooth tonal gradation even in deep shadow areas. To record more levels than the minimum--you need more bit-depth. To record an adequate number of digital levels to properly represent the analog sensor output, you need some headroom in the analog to digital conversion.

Additional bit-depth (more levels in each zone) is also desirable when making post conversion tonal adjustments as has been noted. It is also useful to have more levels as the linear RAW files are converted into the nonlinear and higher gamma color space required for producing a useable image. As RAW levels are redistributed into the desired color space highlight levels will be compressed while shadow levels are expanded.

[attachment=7094:attachment]
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eronald
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« Reply #171 on: June 19, 2008, 05:34:37 AM »
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Probably less than 14 bits are recorded. The advantage of a 16-bit analog to digital conversion is the additional number of levels that are available in all of the exposure zones recorded. Within each exposure zone, subtle and smooth tonal gradations rely on having an adequate number of levels to represent the source subject. This is especially important in the highlight and mid-tone regions where the eye is better able to differentiate small tonal variations.

The concept that noise floors should be the defining factor in how much bit-depth in a/d conversion is advantageous only makes sense if one disregards the tonality of the levels above the noise floor. In other words, yes--you only need a number of bits equal to the useful dynamic range that the sensor can output if all you want to do is record the minimum number of levels that represent that tonal range. However, you eye needs more than a handful of levels to perceive a smooth tonal gradation even in deep shadow areas. To record more levels than the minimum--you need more bit-depth. To record an adequate number of digital levels to properly represent the analog sensor output, you need some headroom in the analog to digital conversion.

Additional bit-depth (more levels in each zone) is also desirable when making post conversion tonal adjustments as has been noted. It is also useful to have more levels as the linear RAW files are converted into the nonlinear and higher gamma color space required for producing a useable image. As RAW levels are redistributed into the desired color space highlight levels will be compressed while shadow levels are expanded.

[attachment=7094:attachment]
[a href=\"index.php?act=findpost&pid=202368\"][{POST_SNAPBACK}][/a]

Techtalk,

 It's the morning for me, my brain is not up to speed. But my BS detector has just been set off:
- How can you have more levels available in the zones if you are not recording them ?
- Why does having non-recorded but present low-end bits affect the Raw conversion ?
- To summarize, aren't you conflating the data captured by the camera with the data post conversion ?
Edmund
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ejmartin
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« Reply #172 on: June 19, 2008, 09:43:37 AM »
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Techtalk,

 It's the morning for me, my brain is not up to speed. But my BS detector has just been set off:
- How can you have more levels available in the zones if you are not recording them ?
- Why does having non-recorded but present low-end bits affect the Raw conversion ?
- To summarize, aren't you conflating the data captured by the camera with the data post conversion ?
Edmund
[a href=\"index.php?act=findpost&pid=202384\"][{POST_SNAPBACK}][/a]

It should have been set off.   The number of effective levels in any exposure zone is the S/N ratio in that zone; one cannot distinguish two tonalities as being different unless their difference is greater than the ambient noise (otherwise the difference looks like the same tonality in the presence of noise fluctuations).  Having more bits just divides the noise into a finer set of levels, with little or no effect on image quality.

The absolute number of levels in any zone is largely irrelevant; the true figure of merit is the S/N ratio.   And it matters quite little what one does in terms of levels/curves/gamma corrections, since the noise spectrum gets pushed around in the same way that the signal does; for instance, stretching the levels makes gaps in the histogram, but the noise gets stretched too and dithers the tonal gaps.

Complaints about a lack of levels not providing enough detail or sufficiently smooth tonal transitions are really a complaint that there is not sufficiently high S/N in the image.
« Last Edit: June 19, 2008, 09:51:00 AM by ejmartin » Logged

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