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Author Topic: Better than ETTR ?  (Read 16015 times)
Eric Myrvaagnes
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« Reply #80 on: August 10, 2011, 08:42:46 AM »
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We could then leave Plato's cave where ACR prisoners live, jump the wall and look into the real world of RAW. Just for academic purposes of course.


Grin Terrific, Guillermo!
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-Eric Myrvaagnes

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francois
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« Reply #81 on: August 10, 2011, 09:23:50 AM »
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Grin Terrific, Guillermo!
I didn't know that JPEG, ACR, PS and other stuff was already used by the Greeks…
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Francois
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« Reply #82 on: August 10, 2011, 10:55:00 AM »
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Jeff probably an unfair question but as a user of a P65+ I would be interested to know if you prefer Capture  One or LR for you Phase RAW files. I use both and find sometimes one does better, sometimes the other. Thanks, Eleanor

Correct...I never said anything to imply that I was referring to ALL raw processors. In fact, the only other raw processors I've looked into is the camera company's offerings and in the case of my P-65+, Capture One (which handles ETTR pretty much the same way as ACR/LR).

The ONLY raw processor I claim to be an expert on is ACR/LR...I kinda have to be an expert to write a book on the subject. (and I DON'T claim to be an expert on C1...just an average user :~)
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Schewe
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« Reply #83 on: August 10, 2011, 12:11:34 PM »
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Jeff probably an unfair question but as a user of a P65+ I would be interested to know if you prefer Capture  One or LR for you Phase RAW files.

A bit OT but I'll answer...it depends on what I'm shooting. If I'm in the studio and shooting tethered, I use C1 so I can control the camera functions and shoot from the laptop. Then I'll usually go ahead and process files in C1 (but also import the raws into LR for organization). If I'm shooting a lot like on a multi-day shoot in the field, I'll use LR for the importing and processing. I'm really good at ACR/LR and competent in C1, so I can basically get equal results out of either. I do find C1's current local tools to be lacking though (I look forward to more functionality there) and I think ACR/LR's sharpening and noise reduction is prolly better–but I'm prolly biased :~).

I much prefer printing from Lightroom even over Photoshop and I think C1's printing isn't great yet...fine for contact sheets. I also think C1's asset management is primitive...it'll be interesting to see what Phase One does with asset management now that they have Expression Media. iView Media Pro was a really good early asset management app that MSFT let falter. I hope P1 can bring it back...
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Eric Myrvaagnes
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« Reply #84 on: August 10, 2011, 12:52:04 PM »
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I didn't know that JPEG, ACR, PS and other stuff was already used by the Greeks…
I think Plato was the first to urge photographing averything in RAW. He also insisted that only Philosophers should be allowed to use PhotoShop.
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Ray
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« Reply #85 on: August 10, 2011, 05:58:53 PM »
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If you don't want to analyse that RAW file perhaps you could upload it to some fileserver and I'd do it for you. We could then leave Plato's cave where ACR prisoners live, jump the wall and look into the real world of RAW. Just for academic purposes of course.



Guillermo,
I'd be interested in any quick method of resconstructing a blown sky, as in my example which is fairly typical of the problem of a shift from a natural blue in the darkest part of the sky to an unnatural cyan, then sometimes to a complete blow-out in the brightest part of the sky.

I believe this is due to a mismanagement of Extra Terrestrial Tyrannosaurus Rex.

I notice you have a Hotmail address. Is Hotmail still restricted to 10MB limits for attachments? The RAW file is 13.7MB.
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ErikKaffehr
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« Reply #86 on: August 10, 2011, 11:24:46 PM »
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Hi,

I posted some DNGs from Stouffer Wedges for download here: http://echophoto.dnsalias.net/ekr/images/StoufferWedge/

Preliminary finding I have done with LR indicates that both cameras tested have a latitude for ETTR of 1.5 step when exposure is adjusted so we are just short of blinking highlights on step 10 of total 41 steps.

http://echophoto.dnsalias.net/ekr/images/StoufferWedge/

Best regards
Erik
« Last Edit: August 11, 2011, 03:19:15 PM by ErikKaffehr » Logged

Guillermo Luijk
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« Reply #87 on: August 11, 2011, 01:55:38 AM »
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I notice you have a Hotmail address. Is Hotmail still restricted to 10MB limits for attachments? The RAW file is 13.7MB.

I think it is 25MB now, so it should work.


Primary finding I have done with LR indicates that both cameras tested have a latitude for ETTR of 1.5 step when exposure is adjusted so we are just short of blinking highlights on step 10 of total 41 steps.

Something to consider about this is that a digital camera measures light as a mix of all wavelengths I guess, but then it produces RAW files with 3 channels, each of them weighted towards some part of the spectrum. So to define highlight headroom some considerations are to be made:
  • Which is the colour of the subject we are shooting at
  • Which is the colour of the light impacting that subject, since reflected light will be affected both by the subject and incident light colours
  • Finally what we consider blown highlights: it is when a single RAW channel clips? it is when certain RAW developer displays blinking highlights? and what if using the recovery slider of the software, those areas stop blinking? what if ACR/LR blinks but C1 doesn't because it uses a different criteria?


My conclusion is that the only reliable source to define highlight headroom is the pure RAW data, but unfortunately no absolut headroom can be defined for all situations since light is very different from one scene to another. Finally each user should learn how his RAW development software behaves if one or two RAW channels clipped (if no RAW channel is clipped there is no problem, if the 3 channels were blown surely all will produce pure white, no matter what WB setting was used).
« Last Edit: August 11, 2011, 02:28:28 AM by Guillermo Luijk » Logged

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« Reply #88 on: August 11, 2011, 04:08:15 AM »
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Guillermo,
I'd be interested in any quick method of resconstructing a blown sky, as in my example which is fairly typical of the problem of a shift from a natural blue in the darkest part of the sky to an unnatural cyan, then sometimes to a complete blow-out in the brightest part of the sky


I considered a gentle cyan hue in these contra light scenes as a sort of natural (deliberately) part of the sky transitions under such conditions. Leaving aside the big topic what the human eye and the camera see and crucially how both sides see it in many respects and also in these conditions, I just tried suppressing some cyan tones in the sky with strong highlights with what happened to be my last edit. I think I will involve these adjustments more in the future as I like the results of more uniformed sky in this sense.
I just looked at the referred image and while I see it’s a different case, the exchange brought me an interesting impulse, thanks.

Best,

Hynek
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Ray
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« Reply #89 on: August 11, 2011, 08:58:23 AM »
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I considered a gentle cyan hue in these contra light scenes as a sort of natural (deliberately) part of the sky transitions under such conditions. Leaving aside the big topic what the human eye and the camera see and crucially how both sides see it in many respects and also in these conditions, I just tried suppressing some cyan tones in the sky with strong highlights with what happened to be my last edit. I think I will involve these adjustments more in the future as I like the results of more uniformed sky in this sense.
I just looked at the referred image and while I see it’s a different case, the exchange brought me an interesting impulse, thanks.

Best,

Hynek


On reflection, and after a bit of experimentation, I get the impression that the degree of transition from blue to cyan in a partially blown sky has been reduced in CS5. Or perhaps it's the case that the number of controls in ACR, to enable such reduction, has been increased.
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eleanorbrown
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« Reply #90 on: August 11, 2011, 09:04:41 AM »
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Thanks Jeff. A bit OT too but printing through LR is second to none. I gave up using Imageprint for LR print module . Eleanor



I much prefer printing from Lightroom even over Photoshop and I think C1's printing isn't great yet...fine for contact sheets. I also think C1's asset management is primitive...it'll be interesting to see what Phase One does with asset management now that they have Expression Media. iView Media Pro was a really good early asset management app that MSFT let falter. I hope P1 can bring it back...
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bjanes
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« Reply #91 on: August 11, 2011, 09:04:55 AM »
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I've read Emil's treatise, and have great respect for his work. And, I also understand the theory.

But, in practice, I am confident that I see smoother tonal gradations on ETTR "normalized" shadow areas rather than native ones when I need to strongly open up such tonalities.

So, who do I believe? As the old joke has it, "The experts, or my lying eyes"?

Michael

Ps: Bumble bees can indeed fly, and prove it to themselves every day.


Michael,

Are you seeing better tonal gradations in the shadows because of increased SNR with ETTR or because of reduced posterization due to an increased number of levels? As mentioned elsewhere in this thread, noise dithers an insufficient number of levels in nearly all cases with current cameras, preventing posterization. What do you see that indicates that an increased number of levels is giving you better results rather than improved SNR?

That bumble bees can not fly was based on faulty theory. Where are Emil and Guillermo wrong?

Regards,

Bill
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Guillermo Luijk
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« Reply #92 on: August 11, 2011, 01:38:06 PM »
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I notice you have a Hotmail address. Is Hotmail still restricted to 10MB limits for attachments? The RAW file is 13.7MB.

Here the areas where a RAW channel was clipped (note that the R channel was the only one intact across the entire scene):


Looking at the gray bands in the sky (each gray tone in the colourscale represents 1EV), exposing 1 stop less would have been enough to avoid any clipping.

My belief that one clipped channel automatically means B&W output was wrong (although I have seen that clearly in other RAW files with a lot more texture). Also there are big differences in the HL strategies among the two RAW developers, the cyan colour produced by ACR was replaced by some kind of magenta cast in DCRAW. This cyan/magenta effect seems to extend in a region of influence outside the clipped zones:


Funily a mix of both skies (70% to DCRAW, 30% to ACR) produces a more pleasant image to my like.

Regards
« Last Edit: August 11, 2011, 04:51:45 PM by Guillermo Luijk » Logged

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« Reply #93 on: August 11, 2011, 03:28:48 PM »
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That is exactly the phenomenon that I have seen repeatedly, and I don't like it. The risk of getting this cyan highlight in the sky has made me far less willing to use EttR unless I am absolutely certain that I have a very compressed histogram--rainy or foggy days in particular. 

I don't agree that avoiding this clipping is just a matter of always ensuring you haven't overexposed a highlight in one channel.  As you move the exposure to the right, you are doing more than simply moving the same shape of graph to the right.  As you move right, you are changing the magnitude and slopes of each channel.  As a result what is happening outside of the histogram area as you approach the highlight line on the right, may be a mystery to you. 

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« Reply #94 on: August 11, 2011, 03:32:53 PM »
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I don't agree that avoiding this clipping is just a matter of always ensuring you haven't overexposed a highlight in one channel. 

Why not? I’d suspect the color effects here are the creation of the data from the other channels. IOW, don’t clip. Anything.
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Andrew Rodney
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fike
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« Reply #95 on: August 11, 2011, 03:44:48 PM »
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Because I don't believe that on the back of the camera you have enough information to know that you haven't lost data off the right side of the histogram. 

Yesterday I was sitting in the woods, experimenting with my camera while considering this discussion.  Something that surprised me was that as I increased the exposure to move to the right the shape of the histogram changes--the slope and magnitude of each peak changed.  This suggests that the histogram isn't representing a linear transformation of the exposure data as you move to the right.  What I am inferring is that it is possible (even likely) that as you move the histogram to the right (as close to the edge as you can) there may be activity that would be shown outside the graph if it were to extend beyond the edge.  This activity may be a result of the change in the magnitude and slope of that I described above. 

I guess the response to that idea is I should watch the blinking highlight alert, but we have all seen that those are not particularly accurate and that many raw converters can bring back some of that data.  So what you end up doing is playing a game of chicken with the right edge.  What we never know is how far off that edge we have gone in any particular channel and whether or not the histogram would show that discrete information if we decreased the exposure enough.

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Fike, Trailpixie, or Marc Shaffer
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Guillermo Luijk
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« Reply #96 on: August 11, 2011, 04:31:59 PM »
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Because I don't believe that on the back of the camera you have enough information to know that you haven't lost data off the right side of the histogram.
(...)
as I increased the exposure to move to the right the shape of the histogram changes--the slope and magnitude of each peak changed.  This suggests that the histogram isn't representing a linear transformation of the exposure data as you move to the right.

Fike, I totally agree with what you say, but we must be clear: the reason is not the principle of ETTR (which is conceptually correct), nor the way sensors work (they are very linear devices). The one and only reason for this uncertainty is camera makers are making machines oriented to the JPEG shooter, not allowing the RAW shooter know about exposure accurately. Camera makers are making us RAW shooters prisoners in Plato's cave, trying to decipher what the shadows in the wall mean.

These are RAW histograms obtained from a series of shots equally spaced 1 stop apart over a white wall with uniform lighting, and represented in log scale. They move at totally regular 1EV intervals (as expected), and they don't change their shape (as expected; only the B channel spreaded slightly once all its surrounding R and G photocaptors reached saturation):

« Last Edit: August 11, 2011, 04:46:19 PM by Guillermo Luijk » Logged

Alan Goldhammer
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« Reply #97 on: August 11, 2011, 06:01:50 PM »
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Which is why camera makers should provide the option to give us RAW histograms on the LCD screen.
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« Reply #98 on: August 12, 2011, 02:26:59 AM »
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On reflection, and after a bit of experimentation, I get the impression that the degree of transition from blue to cyan in a partially blown sky has been reduced in CS5. Or perhaps it's the case that the number of controls in ACR, to enable such reduction, has been increased.


Without doubt it’s evolving and opening up better and better possibilities of editing through its tools and the engine, another factor that makes it a backbone of the digital photography darkroom.

Best,

Hynek
« Last Edit: August 12, 2011, 02:29:36 AM by HSway » Logged

Ray
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« Reply #99 on: August 12, 2011, 07:19:29 AM »
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Here the areas where a RAW channel was clipped (note that the R channel was the only one intact across the entire scene):


Interesting! An excellent demonstration of the situation, Guillermo. Thanks. It makes sense that the red channel would be the last to be clipped in a blue sky, unless it were a sunrise or sunset.

I guess someone at Adobe has decided that a reconstruction of a blown sky that leans towards cyan is more acceptable than one which leans towards magenta.

Regards
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