Ad
Ad
Ad
Pages: « 1 ... 7 8 [9] 10 »   Bottom of Page
Print
Author Topic: Your Curves  (Read 148234 times)
Mark D Segal
Contributor
Sr. Member
*
Offline Offline

Posts: 6973


WWW
« Reply #160 on: August 02, 2007, 11:13:18 AM »
ReplyReply

Quote
The idea of an Adjustment layer being non destructive isn't correct. IF you flatten the image or print the document, the edit is stamped somewhere (even if the term stamped applies to data being sent to a printer). So I don't consider this non destructive. [a href=\"index.php?act=findpost&pid=131207\"][{POST_SNAPBACK}][/a]

Andrew, for clarity here, do you agree that an adjustment is non-destructive if you DO NOT flatten the image, because it is a layer of meta data on top of the image?

I guess the issue is what happens to the pixels as a result of the meta-data once you do certain things - for example: if I send a file having adjustment layers to the printer without flattening it (but obviously it does get temporarily flattened for printing purposes somewhere in the processing between Photoshop and the printer driver) those meta-data instructions are temporarily "carried-out" on the file. Is this destructive or non-destructive in the strict sense of creating rounding errors in the process?

Once the file is printed, but my adjustment layers are still there intact, have I created some "destruction" regardless, because of the print process I just described here?
Logged

Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #161 on: August 02, 2007, 11:20:39 AM »
ReplyReply

Quote
Andrew, for clarity here, do you agree that an adjustment is non-destructive if you DO NOT flatten the image, because it is a layer of meta data on top of the image?

Yes, as long as all you're doing is viewing the image.

Quote
if I send a file having adjustment layers to the printer without flattening it (but obviously it does get temporarily flattened for printing purposes somewhere in the processing between Photoshop and the printer driver) those meta-data instructions are temporarily "carried-out" on the file. Is this destructive or non-destructive in the strict sense of creating rounding errors in the process?

To print the file, the adjustments if visible HAVE to be applied to the pixels, so there's damage.

In my mind, the bottom line is this. IF you alter the pixels, to print or anything besides just looking at the document, there's some data loss, the edit isn't non destructive. If you don't touch the pixels, you haven't edited the document. This too isn't non destructive editing (cause its not editing). Saving a copy isn't changing the facts that you've altered the pixels and saved them into a new document while leaving the original untouched. Same with Undo.
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Ray
Sr. Member
****
Offline Offline

Posts: 8901


« Reply #162 on: August 02, 2007, 11:27:38 AM »
ReplyReply

Quote
The idea of an Adjustment layer being non destructive isn't correct. IF you flatten the image or print the document, the edit is stamped somewhere (even if the term stamped applies to data being sent to a printer). So I don't consider this non destructive. Nor do I find using metadata edits on existing rendered images in CR or LR non destructive. If anything, it might be more destructive (or less) depending on the edits. An existing rendered image in CR and LR still need to be converted to high bit, linear encoded ProPhoto RGB just to apply any tweak from the metadata instructions.
[a href=\"index.php?act=findpost&pid=131207\"][{POST_SNAPBACK}][/a]

As much as I respect your knowledge and experience, Andrew, this sort of reasoning needs some graphic examples.

Speaking for myself, I need to see some examples comparing non-destructive ACR editing with with 'destructive' 16 bit editing in PS, using the best procedures in each case to achieve the desired result.
Logged
Mark D Segal
Contributor
Sr. Member
*
Offline Offline

Posts: 6973


WWW
« Reply #163 on: August 02, 2007, 11:36:11 AM »
ReplyReply

Quote
As much as I respect your knowledge and experience, Andrew, this sort of reasoning needs some graphic examples.

Speaking for myself, I need to see some examples comparing non-destructive ACR editing with with 'destructive' 16 bit editing in PS, using the best procedures in each case to achieve the desired result.
[a href=\"index.php?act=findpost&pid=131216\"][{POST_SNAPBACK}][/a]

Ray while this sounds like a reasonable reequest, it may not be easy to fulfil. The errors may be small enough to go un-noticed or be hardly noticeable, except for really contrived stress conditions - and I've never fussed myself about what those may be.
Logged

Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #164 on: August 02, 2007, 11:36:21 AM »
ReplyReply

Quote
As much as I respect your knowledge and experience, Andrew, this sort of reasoning needs some graphic examples.

Speaking for myself, I need to see some examples comparing non-destructive ACR editing with with 'destructive' 16 bit editing in PS, using the best procedures in each case to achieve the desired result.
[a href=\"index.php?act=findpost&pid=131216\"][{POST_SNAPBACK}][/a]

Well that's going to be somewhat difficult because in one case, you have Raw data you're going to turn into pixels, versus taking rendered data you want to edit in Photoshop and applying an edit there. The gamma encoding isn't the same (although one could adjust that), the processing probably isn't identical. This goes back to a question posed to Thomas Knoll about upszing in CR versus in Photoshop. He said the practical effects should be about the same but the math certainly isn't. So its apples to oranges yet the practical effects are, you can hardly see any difference even when you use the Apply Image technique to subtract the differences in the two processes.

The math is undeniable, if you alter the values of pixels in any bit depth Photoshop supports, there are going to be errors. Some call this destruction and if you go way over board, certainly with 8-bit files, eventually the result is banding (aliasing). But doing this work in high bit, using say 64000 levels instead of 256 makes the damage pretty moot. But do you think its fair to use the term non destructive?
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Ray
Sr. Member
****
Offline Offline

Posts: 8901


« Reply #165 on: August 02, 2007, 12:04:14 PM »
ReplyReply

Quote
But do you think its fair to use the term non destructive?
[a href=\"index.php?act=findpost&pid=131218\"][{POST_SNAPBACK}][/a]

Fair? Misleading? Confusing? It's all relative. I get back to my analogy of 16 bit editing versus 8 bit.

I recall some time ago we had a visiting young guru on this site demonstrating some photoshop techniques in an article on LL (rather than the forum).

He made the blunder of stating that, if an image was already in 8 bit, there was no need to to convert it to 16 bit for editing purposes. Jonathan Wienke proved him wrong.

I felt the visitor's embarrassment. But we need to substantiate our claims with examples. Theory has to be put into practice.

It sounds very reasonable that edits made in ACR before conversion are non-destructive, but seeing is believing, as one very famous photographer said - HCB of course.

Show us the difference.
Logged
digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #166 on: August 02, 2007, 12:21:56 PM »
ReplyReply

Quote
Fair? Misleading? Confusing? It's all relative. I get back to my analogy of 16 bit editing versus 8 bit.

I recall some time ago we had a visiting young guru on this site demonstrating some photoshop techniques in an article on LL (rather than the forum).

He made the blunder of stating that, if an image was already in 8 bit, there was no need to to convert it to 16 bit for editing purposes. Jonathan Wienke proved him wrong.

I'd like to see that because based on my work and conversations with Adobe engineers, the only thing going from 8bit to 16-bit brings to the party is the ability to now composite differing bit depth images.

Quote
It sounds very reasonable that edits made in ACR before conversion are non-destructive, but seeing is believing, as one very famous photographer said - HCB of course.

Show us the difference.
[a href=\"index.php?act=findpost&pid=131223\"][{POST_SNAPBACK}][/a]

The difference is, the Raw, the original data isn't touched. That's not what is happening when you edit a rendered image. The original pixels HAVE to undergo a numeric change otherwise, you don't produce any change and you're not editing the data.

Of course, we should discuss the kinds of editing. If I rotate an image 180 degrees, the numbers remain the same in each pixel, I've just changed the order so to speak. So to be clear, when I talk about editing, I'm referring to altering the numeric value of pixels.
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Guillermo Luijk
Sr. Member
****
Offline Offline

Posts: 1291



WWW
« Reply #167 on: August 02, 2007, 12:30:01 PM »
ReplyReply

Quote
It sounds very reasonable that edits made in ACR before conversion are non-destructive

But I still don't get the point. What do you mean by saying "edits made un ACR before conversion"? with "conversion" you mean to perform the whole RAW developing process and import the resulting 16-bit TIFF into PS?

What's the difference between playing with ACR's curves until you get the desired result, and playing with a mask layer in PS until you get the desired result? is the first non-destructive and the second destructive? If so I disagree with this.
If ACR shows you the effect of let's say a curve, is because has performed the whole RAW developing process at least on the area currently displayed. And that means Bayer interpolation, and pixel levels alteration. Otherwhise it simply couldn't be displayed.

ACR is not going to perform all its adjustments at a time over the RAW file. They look like that to the user, but internally what ACR does is a completely sequential process where, for speed and simlpicity reasons, adjustments are applied one after another. White balance and exposure control are first, demosaicing comes next, hightlight recovery (if activated) is next, then comes colour profile conversion, curve adjustments,...
Some of the elements can be applied in differente positions obtaining advantages in some cases, but finally the process is a sequence.

The same happens in PS when many mask layers are used. I find it difficult to believe that PS summarizes all of them before applying them to the image, avoiding error propagation for rounding. Layer adjustments are applied one after another; but still 16 bit (actually 15) is still good enough to keep a high level of quality in the results.
« Last Edit: August 02, 2007, 12:33:47 PM by GLuijk » Logged

digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #168 on: August 02, 2007, 12:35:39 PM »
ReplyReply

Quote
What's the difference between playing with ACR's curves until you get the desired result, and playing with a mask layer in PS until you get the desired result? is the first non-destructive and the second destructive? If so I disagree with this.

One takes the Raw data, a set of instructions and builds new, virgin pixels. The other takes existing rendered pixels and alters their numbers.

One works in linear high bit color space, the other may work in high bit, but almost always in a gamma corrected space.

Quote
ACR is not going to perform all its adjustments at a time over the RAW file.

The Raw remains untouched and is only used to build a set of colored pixels that didn't exist. Not the case with the original and existing pixels.
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Guillermo Luijk
Sr. Member
****
Offline Offline

Posts: 1291



WWW
« Reply #169 on: August 02, 2007, 12:50:35 PM »
ReplyReply

Quote
One takes the Raw data, a set of instructions and builds new, virgin pixels. The other takes existing rendered pixels and alters their numbers.

One works in linear high bit color space, the other may work in high bit, but almost always in a gamma corrected space.
The Raw remains untouched and is only used to build a set of colored pixels that didn't exist. Not the case with the original and existing pixels.
[a href=\"index.php?act=findpost&pid=131232\"][{POST_SNAPBACK}][/a]

With "high bit" you mean 16 bits or more? integers or floating point numbers?

At the moment in which ACR curves (for instance) are plotted versus a gamma corrected histogram (the one that appears on the background in ACR), one has the feeling they are already working over a gamma corrected space. In fact it has to be so as in a linear image, information is so deeply concentrated in the low end of the histogram that curve edition is an almost impossible task.
Or you think that ACR converts the curve set by the user into what it would be in a non gamma corrected image to apply it in linear mode? I found this a really weird movement. It's nonsense to translate a curve designed to be applied on a gamma corrected image, to linear mode, to be then applied in linear mode.

Some adjustments are easier and more precisely to be performed in linear mode (WB, exposure control), some others are better performed once gamma has been corrected as they are directly related to human eye non linear response (curves, black and white points, Hue and Saturation adjust,...)
« Last Edit: August 02, 2007, 12:53:23 PM by GLuijk » Logged

digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #170 on: August 02, 2007, 12:54:32 PM »
ReplyReply

Quote
With "high bit" you mean 16 bits or more? integers or floating point numbers?

More than 8-bits.

Quote
At the moment in which ACR curves (for instance) are plotted versus a gamma corrected histogram (the one that appears on the background), one has the feeling they are already working over a gamma corrected space.

Nope, all processing is done in a linear encoded space. Even if you import or open an existing rendered image into CR or LR, its converted to a linear encoded space (ProPhoto primaries) for all editing.
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Guillermo Luijk
Sr. Member
****
Offline Offline

Posts: 1291



WWW
« Reply #171 on: August 02, 2007, 01:02:11 PM »
ReplyReply

Quote
Nope, all processing is done in a linear encoded space. Even if you import or open an existing rendered image into CR or LR, its converted to a linear encoded space (ProPhoto primaries) for all editing.
[a href=\"index.php?act=findpost&pid=131236\"][{POST_SNAPBACK}][/a]

well if so that is good news. But I find strange then that all user parameter adjustments in ACR (most of them conceptually and visually "gamma corrected") are translated into a linear version of themselves prior to being applied.
I am talking about the Curves, the black point, the Bright, Contrast and Saturation controls,...

BTW, do you know if ACR's noise reduction (both colour and luminance) algorithm is applied, before or after the demosaicing process?
« Last Edit: August 02, 2007, 01:02:43 PM by GLuijk » Logged

digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #172 on: August 02, 2007, 01:09:51 PM »
ReplyReply

Quote
well if so that is good news. But I find strange then that all user parameter adjustments in ACR (most of them conceptually and visually "gamma corrected") are translated into a linear version of themselves prior to being applied.
I am talking about the Curves, the black point, the Bright, Contrast and Saturation controls,...

http://www.ppmag.com/reviews/200701_rodneycm.pdf

Also this podcast (first half) is worth listening to:

http://photoshopnews.com/2006/07/07/lightr...isode-8-posted/
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Guillermo Luijk
Sr. Member
****
Offline Offline

Posts: 1291



WWW
« Reply #173 on: August 02, 2007, 01:23:24 PM »
ReplyReply

Quote
http://www.ppmag.com/reviews/200701_rodneycm.pdf

Also this podcast (first half) is worth listening to:

http://photoshopnews.com/2006/07/07/lightr...isode-8-posted/
[a href=\"index.php?act=findpost&pid=131242\"][{POST_SNAPBACK}][/a]

Interesting, specially when PS is such a gamma corrected oriented application. I would have always expected Adobe to try to leave behind the linear state of the RAW file as soon as possible in ACR/LR. Glad to see it is not like that.

Trying to edit linear images in PS is a pain, simply impossible. Just exposure control can be correctly applied.
Logged

Mark D Segal
Contributor
Sr. Member
*
Offline Offline

Posts: 6973


WWW
« Reply #174 on: August 02, 2007, 02:57:07 PM »
ReplyReply

Quote
http://www.ppmag.com/reviews/200701_rodneycm.pdf

Also this podcast (first half) is worth listening to:

http://photoshopnews.com/2006/07/07/lightr...isode-8-posted/
[a href=\"index.php?act=findpost&pid=131242\"][{POST_SNAPBACK}][/a]

Andrew, is there a way to access the MP3 said to be on George's iDisk. I went there and it is empty. iTunes won't cut it for me.
Logged

Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #175 on: August 02, 2007, 03:03:24 PM »
ReplyReply

Quote
Andrew, is there a way to access the MP3 said to be on George's iDisk. I went there and it is empty. iTunes won't cut it for me.
[a href=\"index.php?act=findpost&pid=131261\"][{POST_SNAPBACK}][/a]

What do you mean iTunes won't cut it? What else is there? <G>

I see MP3's and MP4's on his iDisk.
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Mark D Segal
Contributor
Sr. Member
*
Offline Offline

Posts: 6973


WWW
« Reply #176 on: August 02, 2007, 03:12:32 PM »
ReplyReply

ITunes won't cut it because I don't have an iPod. My wife does, but I can't start learning this now - no time.

I think as for the MP3, MP4 once again some fundamental issues between iDisk technology and Windows Internet Explorer - but when I open the link on Jeff's page to George's iDisk it is completely blank. Do you or anyone reading this thread know about this problem and how to cut through it?
Logged

Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
digitaldog
Sr. Member
****
Offline Offline

Posts: 9189



WWW
« Reply #177 on: August 02, 2007, 03:23:58 PM »
ReplyReply

Quote
ITunes won't cut it because I don't have an iPod. My wife does, but I can't start learning this now - no time.

You can still use it on your computer to store and listen to the podcast (or anything else). You have speakers on that computer? Load and listen.
Logged

Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
Mark D Segal
Contributor
Sr. Member
*
Offline Offline

Posts: 6973


WWW
« Reply #178 on: August 02, 2007, 03:35:25 PM »
ReplyReply

OK, but I tried loading and it stalled. Perhaps server overload somewhere. I'll try later.
Logged

Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
PeterLange
Guest
« Reply #179 on: August 02, 2007, 03:53:51 PM »
ReplyReply

Quote
He made the blunder of stating that, if an image was already in 8 bit, there was no need to to convert it to 16 bit for editing purposes. Jonathan Wienke proved him wrong.
[a href=\"index.php?act=findpost&pid=131223\"][{POST_SNAPBACK}][/a]
And Jonathan was right.
The secret may lie in the sequence:

After changing an 8 bit file to 16 bit, next step should be to apply some mild noise reduction depending on needs.  Even if it’s just at the threshold of visibility, this does not only smoothen and wipe out inherent posterization (not yet visible without further editing). Noise reduction as a technique of averaging fills the reservoir of real 16 bit data which don’t have an integer 8 bit equivalent anymore. Resulting files can tolerate further editing much better before showing distinguishable steps with smooth gradients.  That’s not rocket science.

Engineers might wish to reconsider this, before throwing 8 bit JPG’s in a linear gamma ProPhoto space.

Peter

--
Logged
Pages: « 1 ... 7 8 [9] 10 »   Top of Page
Print
Jump to:  

Ad
Ad
Ad