LenC

This is long – my questions start in the third big paragraph.



After spending a couple of years trying to learn how to improve my photos in AP, I think I see some light along the difficult path in the form of Dan Margulis’s Professional Photoshop (5th ed.) and his other books.* His approach to color correction involves understanding human perception, color spaces, image processing algorithms, and means of rendering images in print and on screen. It should translate well to other image processing programs such as AP. I find his approach so persuasive that if I had the time I would get PS to pursue it. Right now, I need some help applying some basics to AP.


Two fundamental tools that Margulis discusses at length are curves and channel mixing. He gives many examples of color correction with curves in RGB, CMYK, and LAB that are easy to learn from. A minor issue is that he displays curves with dark on the right, whereas AP only shows dark on the left. These can be compared by mentally or physically rotating the curves 180 degrees. PS has a one-click control to flip them.


Channel mixing does not translate so well. The fundamental Margulis maneuver in PS is to choose a channel in RGB (e.g., the most contrasty), use the Apply Image command to create a BW layer from that channel above the image layer, and then use Luminosity blend mode to increase the contrast. Creating this layer from existing channels seems to involve only a couple of steps. But this does not work in AP, which seems to be set up only to blend two layers, not create a separate one. Also I can select a source layer but I don’t understand how I select the destination (the pixel layer I created to receive the channel). This has got to be trivial but reading Apply Image help does not seem to help. “Apply” button grays and becomes active in a way I have not figured out. Also it appears that the equations operate in only one color space, while PS allows blending cyan with RGB. Can someone help me see if my task can be done in AP? It’s got to be simple.
And why are the Composite channels more functional (show, edit) than those of the other layers?


 
Although it goes beyond my immediate inquiry, it could be an important influence on the evolution of AP if, among those AP and PS users who are aware of Margulis’s work, there is enough interest to justify developing better user interface elements. (I already have a couple of ideas.) Many advanced retouchers are very enthusiastic about his writing (see reviews of his books on Amazon). Margulis and co-workers have also automated some of his more complex approaches using PS script actions, available through a freely distributed panel. This appears considerably more capable than the AP macros.


 
* Professional Photoshop: The Classic Guide to Color Correction (5th ed., 2006); Photoshop LAB Color The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace (2nd ed., 2015); Modern Photoshop Color Workflow: The Quartertone Quandary, the PPW, and Other Ideas for Speedy Image Enhancement (2013).  Somewhat pricey, but good value. I bought second-hand copies of the first book and the first edition of the second. One lacked the CD. I have not read the third, but there is plentiful information available online, including videos for most chapters.

This is long – my questions start in the third big paragraph.



After spending a couple of years trying to learn how to improve my photos in AP, I think I see some light along the difficult path in the form of Dan Margulis’s Professional Photoshop (5th ed.) and his other books.* His approach to color correction involves understanding human perception, color spaces, image processing algorithms, and means of rendering images in print and on screen. It should translate well to other image processing programs such as AP. I find his approach so persuasive that if I had the time I would get PS to pursue it. Right now, I need some help applying some basics to AP.


Two fundamental tools that Margulis discusses at length are curves and channel mixing. He gives many examples of color correction with curves in RGB, CMYK, and LAB that are easy to learn from. A minor issue is that he displays curves with dark on the right, whereas AP only shows dark on the left. These can be compared by mentally or physically rotating the curves 180 degrees. PS has a one-click control to flip them.


Channel mixing does not translate so well. The fundamental Margulis maneuver in PS is to choose a channel in RGB (e.g., the most contrasty), use the Apply Image command to create a BW layer from that channel above the image layer, and then use Luminosity blend mode to increase the contrast. Creating this layer from existing channels seems to involve only a couple of steps. But this does not work in AP, which seems to be set up only to blend two layers, not create a separate one. Also I can select a source layer but I don’t understand how I select the destination (the pixel layer I created to receive the channel). This has got to be trivial but reading Apply Image help does not seem to help. “Apply” button grays and becomes active in a way I have not figured out. Also it appears that the equations operate in only one color space, while PS allows blending cyan with RGB. Can someone help me see if my task can be done in AP? It’s got to be simple.
And why are the Composite channels more functional (show, edit) than those of the other layers?


 
Although it goes beyond my immediate inquiry, it could be an important influence on the evolution of AP if, among those AP and PS users who are aware of Margulis’s work, there is enough interest to justify developing better user interface elements. (I already have a couple of ideas.) Many advanced retouchers are very enthusiastic about his writing (see reviews of his books on Amazon). Margulis and co-workers have also automated some of his more complex approaches using PS script actions, available through a freely distributed panel. This appears considerably more capable than the AP macros.


 
* Professional Photoshop: The Classic Guide to Color Correction (5th ed., 2006); Photoshop LAB Color The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace (2nd ed., 2015); Modern Photoshop Color Workflow: The Quartertone Quandary, the PPW, and Other Ideas for Speedy Image Enhancement (2013).  Somewhat pricey, but good value. I bought second-hand copies of the first book and the first edition of the second. One lacked the CD. I have not read the third, but there is plentiful information available online, including videos for most chapters.

The /Users/Shared/ folder is a standard one automatically created on the boot volume during the install or first run of OS X. As discussed in this article (among many others), it is commonly used to share files among different user accounts on a Mac.
A few apps also use it as an alternative to (or sometimes in addition to) the more commonly used top level Library > Application Support folder for support & related files to make them accessible to all users of the Mac. However, the Affinity apps, iPhoto, Apple Photos, & most others are not among them. Regardless, you should not try to delete this folder because it could cause problems with your system. Likewise, don't delete any of the subfolders in it unless you are sure they are not used by any app installed on your Mac, or contain files you want to keep.
From the file path shown at the bottom of your screenshot for file IMG_0533.jpg, it came from your iPhoto Library.photolibrary > Thumbnails folder, which is organized by year (2009 for this file), & further by roll number (roll 181 for this file) or by month number or photo album in the photolibrary folder. Thumbnail files are used by apps like iPhoto & Apple Photos in some views, which is why that file is just 240x180 px.
How it (& any other iPhoto thumbnail files like it) got into your /Users/Shared/ folder is anybody's guess, but like @Jeremy Bohn said, since you no longer use iPhoto, you can safely delete those files from the /Users/Shared/ folder, & all subfolders that relate to iPhoto that might be in the /Users/Shared/ folder.

In System Preference, click on Spotlight. Click the Privacy tab. If your Time Machine hard drive is not in that list, add it.

For the benefit of the Serif AP beta development team, I will try to describe the strange trip on the way to a successful launch of AP 1.7.110 on my desktop Mac. A couple of days ago I downloaded a macro offered  by an advanced member that, it turned out, would not run in AP 1.6.7 because it had been created in a beta build. This .afmacros file when downloaded displayed the square beta logo rather than the triangular one before the file name. Shortly thereafter, practically all my existing  .afphoto files (created in production versions) changed to display the beta logo in Finder or in other windows (e.g., Open). (Cause and effect presumed, not proven.) Attempting to address what I presumed was a faulty icon look-up, I removed the old beta app (1.7.106), using AppCleaner to remove auxiliary files. After that, most though not all of the square logos were replaced by the appropriate triangular ones. I then installed 1.7.110, but it would not launch, with error window exactly as before.
I then decided to try to reinstall 1.6.7, though I did not remove it. At the Apple App Store, there was an icon suggesting to download from the cloud, but clicking it did not start a download. Then I clicked the square-in-circle icon that is usually a download progress indicator. This initiated an unfamiliar response from my Launchpad Dock icon that appeared to show downloading, though nothing appeared in my Downloads folder. When done, I clicked the beta icon in Launchpad, and the beta launched successfully.
I still have something of a mix of production and beta icons in my directories, though it appears that the betas are gradually (mostly!) being replaced.

I've created a couple of macros.
One for Dodging & one for Burning.
Basically they are identical, only the name giving differs.
 
 
Dodge & Burn.afmacros

Depends on settings, brush type, hardness, further he used the highlights tonal range. - Related to setting fill to 50% gray, there is also a keyboard shortcut entry in the preferences for this (Photo, under misc) where you can assign an own key combo for quicker access then when applied.

.

I am a beginner in LAB attempting to apply the writings of Dan Margulis, who uses only Photoshop, to Affinity Photo. The LAB underlying functionality is mostly OK, but I have found that the AP user interface could be improved in several places. More experienced users, please comment.


 
1)  In the Curves adjustment layer with LAB selected, the A channel curve is colored green and the B curve magenta. The appropriate colors are green left and magenta right for A; blue left and yellow right for B (with light or high luminosity on the right).
2)  Creating a check box on the A and B curve windows for Intersect Midpoint would make it easier to construct color-intensifying curves. This is probably the most important basic move in LAB, and even Photoshop does not have this feature.

3) The Input Minimum and Maximum default to 0 and 1. Though I have not found a use for these, shouldn’t they be -1 to 1 or -100 to 100 or -127 to 127?

4) The Curves/LAB window’s second drop-down menu offers Master, L, A, B, and alpha. Is there a known use for ‘Master’ as in RGB? Nothing I have read about LAB indicates that there is. For that matter, is there any use for Master in CMYK? And how about ‘All’ as an alternative to Master in RGB? Furthermore, the histogram curves displayed for the LAB components here are not positioned the same as when one transforms the document to LAB and displays its histograms. May relate to previous point (3).

5) Photoshop can display the graphs of the various color space curves with the light (high-luminosity) side on the right or left (one-click toggle). This option would be useful to people learning from Margulis’s books, which show dark on the right.

6) Other Affinity users have called for improvements in the Curves window in general, not just for LAB: more precision and ways of placing nodes, a larger or scalable window, saving curves.  Because of the sensitivity of the A and B curves to small movements, a fine control on node dragging would be handy, e.g., option-drag would reduce the motion by 1/5 or 1/10. Perhaps it already exists.

7)  A LAB curves user on this forum called for a keyboard shortcut to move among the channels. Why not? He needs efficiency in a much-used workflow application. In the same vein, having selected the color space, instead of a second drop-down, radio buttons for the three or four channels would slightly simplify choosing one.

8)  In the Channel Mixer adjustment layer, the LAB window A and B sliders need appropriate coloring like the RGB and CMYK. Just for consistency.

9)  The Levels adjustment layer makes sense in RGB, but I am not so sure about LAB and CMYK. Does this lead to a useful correction? (Please help me, advanced users.) If you push the existing RGB colors to the AB limits of +/-127 won’t you just create out-of-gamut colors that will have to be distorted back in RGB space? And is gamma defined for this color space? Also, in the LAB window, shouldn’t the correct labels for the sliders be, for the A channel, green and magenta, and for the B, blue and yellow. Similar questions for CMYK.

10) The Apply Image filter and Channel Mixer adjustment layer seem as if they should have similar functionality, but their capabilities and interfaces are rather different. My understanding of Apply Image in Photoshop from Margulis is to blend or replace channels one at a time, sometimes across color spaces, but to do that in AP one has to create a gray scale image of a channel in a layer and make that the source. The destination seems to be all channels of a selected layer, or does one have to separate out those channels as well? The Channel Mixer is designed to specify a single channel as destination, but it appears the source must be in the same color space. Shouldn’t these two processes allow individual choice of source and destination channels in all color spaces? Are equations (Apply Image) and sliders (Channel Mixer) of equal value in practical applications?


 
I don’t think this exhausts these issues, but this post has already exhausted me. My compliments if you have read this far. If you want to know more about Margulis, use a search engine or post here and I will try to summarize what I have earned from a large corpus of writing.

I am a beginner in LAB attempting to apply the writings of Dan Margulis, who uses only Photoshop, to Affinity Photo. The LAB underlying functionality is mostly OK, but I have found that the AP user interface could be improved in several places. More experienced users, please comment.


 
1)  In the Curves adjustment layer with LAB selected, the A channel curve is colored green and the B curve magenta. The appropriate colors are green left and magenta right for A; blue left and yellow right for B (with light or high luminosity on the right).
2)  Creating a check box on the A and B curve windows for Intersect Midpoint would make it easier to construct color-intensifying curves. This is probably the most important basic move in LAB, and even Photoshop does not have this feature.

3) The Input Minimum and Maximum default to 0 and 1. Though I have not found a use for these, shouldn’t they be -1 to 1 or -100 to 100 or -127 to 127?

4) The Curves/LAB window’s second drop-down menu offers Master, L, A, B, and alpha. Is there a known use for ‘Master’ as in RGB? Nothing I have read about LAB indicates that there is. For that matter, is there any use for Master in CMYK? And how about ‘All’ as an alternative to Master in RGB? Furthermore, the histogram curves displayed for the LAB components here are not positioned the same as when one transforms the document to LAB and displays its histograms. May relate to previous point (3).

5) Photoshop can display the graphs of the various color space curves with the light (high-luminosity) side on the right or left (one-click toggle). This option would be useful to people learning from Margulis’s books, which show dark on the right.

6) Other Affinity users have called for improvements in the Curves window in general, not just for LAB: more precision and ways of placing nodes, a larger or scalable window, saving curves.  Because of the sensitivity of the A and B curves to small movements, a fine control on node dragging would be handy, e.g., option-drag would reduce the motion by 1/5 or 1/10. Perhaps it already exists.

7)  A LAB curves user on this forum called for a keyboard shortcut to move among the channels. Why not? He needs efficiency in a much-used workflow application. In the same vein, having selected the color space, instead of a second drop-down, radio buttons for the three or four channels would slightly simplify choosing one.

8)  In the Channel Mixer adjustment layer, the LAB window A and B sliders need appropriate coloring like the RGB and CMYK. Just for consistency.

9)  The Levels adjustment layer makes sense in RGB, but I am not so sure about LAB and CMYK. Does this lead to a useful correction? (Please help me, advanced users.) If you push the existing RGB colors to the AB limits of +/-127 won’t you just create out-of-gamut colors that will have to be distorted back in RGB space? And is gamma defined for this color space? Also, in the LAB window, shouldn’t the correct labels for the sliders be, for the A channel, green and magenta, and for the B, blue and yellow. Similar questions for CMYK.

10) The Apply Image filter and Channel Mixer adjustment layer seem as if they should have similar functionality, but their capabilities and interfaces are rather different. My understanding of Apply Image in Photoshop from Margulis is to blend or replace channels one at a time, sometimes across color spaces, but to do that in AP one has to create a gray scale image of a channel in a layer and make that the source. The destination seems to be all channels of a selected layer, or does one have to separate out those channels as well? The Channel Mixer is designed to specify a single channel as destination, but it appears the source must be in the same color space. Shouldn’t these two processes allow individual choice of source and destination channels in all color spaces? Are equations (Apply Image) and sliders (Channel Mixer) of equal value in practical applications?


 
I don’t think this exhausts these issues, but this post has already exhausted me. My compliments if you have read this far. If you want to know more about Margulis, use a search engine or post here and I will try to summarize what I have earned from a large corpus of writing.

I am a beginner in LAB attempting to apply the writings of Dan Margulis, who uses only Photoshop, to Affinity Photo. The LAB underlying functionality is mostly OK, but I have found that the AP user interface could be improved in several places. More experienced users, please comment.


 
1)  In the Curves adjustment layer with LAB selected, the A channel curve is colored green and the B curve magenta. The appropriate colors are green left and magenta right for A; blue left and yellow right for B (with light or high luminosity on the right).
2)  Creating a check box on the A and B curve windows for Intersect Midpoint would make it easier to construct color-intensifying curves. This is probably the most important basic move in LAB, and even Photoshop does not have this feature.

3) The Input Minimum and Maximum default to 0 and 1. Though I have not found a use for these, shouldn’t they be -1 to 1 or -100 to 100 or -127 to 127?

4) The Curves/LAB window’s second drop-down menu offers Master, L, A, B, and alpha. Is there a known use for ‘Master’ as in RGB? Nothing I have read about LAB indicates that there is. For that matter, is there any use for Master in CMYK? And how about ‘All’ as an alternative to Master in RGB? Furthermore, the histogram curves displayed for the LAB components here are not positioned the same as when one transforms the document to LAB and displays its histograms. May relate to previous point (3).

5) Photoshop can display the graphs of the various color space curves with the light (high-luminosity) side on the right or left (one-click toggle). This option would be useful to people learning from Margulis’s books, which show dark on the right.

6) Other Affinity users have called for improvements in the Curves window in general, not just for LAB: more precision and ways of placing nodes, a larger or scalable window, saving curves.  Because of the sensitivity of the A and B curves to small movements, a fine control on node dragging would be handy, e.g., option-drag would reduce the motion by 1/5 or 1/10. Perhaps it already exists.

7)  A LAB curves user on this forum called for a keyboard shortcut to move among the channels. Why not? He needs efficiency in a much-used workflow application. In the same vein, having selected the color space, instead of a second drop-down, radio buttons for the three or four channels would slightly simplify choosing one.

8)  In the Channel Mixer adjustment layer, the LAB window A and B sliders need appropriate coloring like the RGB and CMYK. Just for consistency.

9)  The Levels adjustment layer makes sense in RGB, but I am not so sure about LAB and CMYK. Does this lead to a useful correction? (Please help me, advanced users.) If you push the existing RGB colors to the AB limits of +/-127 won’t you just create out-of-gamut colors that will have to be distorted back in RGB space? And is gamma defined for this color space? Also, in the LAB window, shouldn’t the correct labels for the sliders be, for the A channel, green and magenta, and for the B, blue and yellow. Similar questions for CMYK.

10) The Apply Image filter and Channel Mixer adjustment layer seem as if they should have similar functionality, but their capabilities and interfaces are rather different. My understanding of Apply Image in Photoshop from Margulis is to blend or replace channels one at a time, sometimes across color spaces, but to do that in AP one has to create a gray scale image of a channel in a layer and make that the source. The destination seems to be all channels of a selected layer, or does one have to separate out those channels as well? The Channel Mixer is designed to specify a single channel as destination, but it appears the source must be in the same color space. Shouldn’t these two processes allow individual choice of source and destination channels in all color spaces? Are equations (Apply Image) and sliders (Channel Mixer) of equal value in practical applications?


 
I don’t think this exhausts these issues, but this post has already exhausted me. My compliments if you have read this far. If you want to know more about Margulis, use a search engine or post here and I will try to summarize what I have earned from a large corpus of writing.

Buttons instead of drop-down menus has been requested before; I have encountered it browsing forum searches. Makes sense in curves and other places, and now we have the HSL example. Perhaps the development group thinks the austere drop-down is plainer and thus more elegant, but ease of use wins! I am also regularly posting suggestions for easy UI improvements and encourage people to do the same, and create images with visual suggestions if you are able.

I was able to get the beta to run on my MacBook Air and to discover what I was most curious about: the various deficiencies in Curves LAB mode are not being addressed in this release. (RGB histograms displayed when LAB or CMYK channels are requested; numerical range of A and B is 0-1 rather than -1 to 1 or a scaled version.) I have started to collect my suggestions on LAB in AP in the feature request forum and will add to that.  These issues have been known for a while and are said to have been passed on to developers, so I conclude, based on earlier posts, that Serif is not ready to devote resources to them. I had hoped to adapt the methods of Dan Margulis to Affinity and that AP's capabilities might grow as I learned more about his methods, but it may be easier to do that in PS. Would appreciate comments on Serif's plans if senior people can comment.

I was able to get the beta to run on my MacBook Air and to discover what I was most curious about: the various deficiencies in Curves LAB mode are not being addressed in this release. (RGB histograms displayed when LAB or CMYK channels are requested; numerical range of A and B is 0-1 rather than -1 to 1 or a scaled version.) I have started to collect my suggestions on LAB in AP in the feature request forum and will add to that.  These issues have been known for a while and are said to have been passed on to developers, so I conclude, based on earlier posts, that Serif is not ready to devote resources to them. I had hoped to adapt the methods of Dan Margulis to Affinity and that AP's capabilities might grow as I learned more about his methods, but it may be easier to do that in PS. Would appreciate comments on Serif's plans if senior people can comment.

I am a beginner in LAB attempting to apply the writings of Dan Margulis, who uses only Photoshop, to Affinity Photo. The LAB underlying functionality is mostly OK, but I have found that the AP user interface could be improved in several places. More experienced users, please comment.


 
1)  In the Curves adjustment layer with LAB selected, the A channel curve is colored green and the B curve magenta. The appropriate colors are green left and magenta right for A; blue left and yellow right for B (with light or high luminosity on the right).
2)  Creating a check box on the A and B curve windows for Intersect Midpoint would make it easier to construct color-intensifying curves. This is probably the most important basic move in LAB, and even Photoshop does not have this feature.

3) The Input Minimum and Maximum default to 0 and 1. Though I have not found a use for these, shouldn’t they be -1 to 1 or -100 to 100 or -127 to 127?

4) The Curves/LAB window’s second drop-down menu offers Master, L, A, B, and alpha. Is there a known use for ‘Master’ as in RGB? Nothing I have read about LAB indicates that there is. For that matter, is there any use for Master in CMYK? And how about ‘All’ as an alternative to Master in RGB? Furthermore, the histogram curves displayed for the LAB components here are not positioned the same as when one transforms the document to LAB and displays its histograms. May relate to previous point (3).

5) Photoshop can display the graphs of the various color space curves with the light (high-luminosity) side on the right or left (one-click toggle). This option would be useful to people learning from Margulis’s books, which show dark on the right.

6) Other Affinity users have called for improvements in the Curves window in general, not just for LAB: more precision and ways of placing nodes, a larger or scalable window, saving curves.  Because of the sensitivity of the A and B curves to small movements, a fine control on node dragging would be handy, e.g., option-drag would reduce the motion by 1/5 or 1/10. Perhaps it already exists.

7)  A LAB curves user on this forum called for a keyboard shortcut to move among the channels. Why not? He needs efficiency in a much-used workflow application. In the same vein, having selected the color space, instead of a second drop-down, radio buttons for the three or four channels would slightly simplify choosing one.

8)  In the Channel Mixer adjustment layer, the LAB window A and B sliders need appropriate coloring like the RGB and CMYK. Just for consistency.

9)  The Levels adjustment layer makes sense in RGB, but I am not so sure about LAB and CMYK. Does this lead to a useful correction? (Please help me, advanced users.) If you push the existing RGB colors to the AB limits of +/-127 won’t you just create out-of-gamut colors that will have to be distorted back in RGB space? And is gamma defined for this color space? Also, in the LAB window, shouldn’t the correct labels for the sliders be, for the A channel, green and magenta, and for the B, blue and yellow. Similar questions for CMYK.

10) The Apply Image filter and Channel Mixer adjustment layer seem as if they should have similar functionality, but their capabilities and interfaces are rather different. My understanding of Apply Image in Photoshop from Margulis is to blend or replace channels one at a time, sometimes across color spaces, but to do that in AP one has to create a gray scale image of a channel in a layer and make that the source. The destination seems to be all channels of a selected layer, or does one have to separate out those channels as well? The Channel Mixer is designed to specify a single channel as destination, but it appears the source must be in the same color space. Shouldn’t these two processes allow individual choice of source and destination channels in all color spaces? Are equations (Apply Image) and sliders (Channel Mixer) of equal value in practical applications?


 
I don’t think this exhausts these issues, but this post has already exhausted me. My compliments if you have read this far. If you want to know more about Margulis, use a search engine or post here and I will try to summarize what I have earned from a large corpus of writing.

I am a beginner in LAB attempting to apply the writings of Dan Margulis, who uses only Photoshop, to Affinity Photo. The LAB underlying functionality is mostly OK, but I have found that the AP user interface could be improved in several places. More experienced users, please comment.


 
1)  In the Curves adjustment layer with LAB selected, the A channel curve is colored green and the B curve magenta. The appropriate colors are green left and magenta right for A; blue left and yellow right for B (with light or high luminosity on the right).
2)  Creating a check box on the A and B curve windows for Intersect Midpoint would make it easier to construct color-intensifying curves. This is probably the most important basic move in LAB, and even Photoshop does not have this feature.

3) The Input Minimum and Maximum default to 0 and 1. Though I have not found a use for these, shouldn’t they be -1 to 1 or -100 to 100 or -127 to 127?

4) The Curves/LAB window’s second drop-down menu offers Master, L, A, B, and alpha. Is there a known use for ‘Master’ as in RGB? Nothing I have read about LAB indicates that there is. For that matter, is there any use for Master in CMYK? And how about ‘All’ as an alternative to Master in RGB? Furthermore, the histogram curves displayed for the LAB components here are not positioned the same as when one transforms the document to LAB and displays its histograms. May relate to previous point (3).

5) Photoshop can display the graphs of the various color space curves with the light (high-luminosity) side on the right or left (one-click toggle). This option would be useful to people learning from Margulis’s books, which show dark on the right.

6) Other Affinity users have called for improvements in the Curves window in general, not just for LAB: more precision and ways of placing nodes, a larger or scalable window, saving curves.  Because of the sensitivity of the A and B curves to small movements, a fine control on node dragging would be handy, e.g., option-drag would reduce the motion by 1/5 or 1/10. Perhaps it already exists.

7)  A LAB curves user on this forum called for a keyboard shortcut to move among the channels. Why not? He needs efficiency in a much-used workflow application. In the same vein, having selected the color space, instead of a second drop-down, radio buttons for the three or four channels would slightly simplify choosing one.

8)  In the Channel Mixer adjustment layer, the LAB window A and B sliders need appropriate coloring like the RGB and CMYK. Just for consistency.

9)  The Levels adjustment layer makes sense in RGB, but I am not so sure about LAB and CMYK. Does this lead to a useful correction? (Please help me, advanced users.) If you push the existing RGB colors to the AB limits of +/-127 won’t you just create out-of-gamut colors that will have to be distorted back in RGB space? And is gamma defined for this color space? Also, in the LAB window, shouldn’t the correct labels for the sliders be, for the A channel, green and magenta, and for the B, blue and yellow. Similar questions for CMYK.

10) The Apply Image filter and Channel Mixer adjustment layer seem as if they should have similar functionality, but their capabilities and interfaces are rather different. My understanding of Apply Image in Photoshop from Margulis is to blend or replace channels one at a time, sometimes across color spaces, but to do that in AP one has to create a gray scale image of a channel in a layer and make that the source. The destination seems to be all channels of a selected layer, or does one have to separate out those channels as well? The Channel Mixer is designed to specify a single channel as destination, but it appears the source must be in the same color space. Shouldn’t these two processes allow individual choice of source and destination channels in all color spaces? Are equations (Apply Image) and sliders (Channel Mixer) of equal value in practical applications?


 
I don’t think this exhausts these issues, but this post has already exhausted me. My compliments if you have read this far. If you want to know more about Margulis, use a search engine or post here and I will try to summarize what I have earned from a large corpus of writing.

@mikerofoto, can't say much without seeing, but I once fixed an issue by cropping one image before stitching.

I would be nice to have lab colours in the colour chooser as per attached.

Kind Regards

This is long – my questions start in the third big paragraph.



After spending a couple of years trying to learn how to improve my photos in AP, I think I see some light along the difficult path in the form of Dan Margulis’s Professional Photoshop (5th ed.) and his other books.* His approach to color correction involves understanding human perception, color spaces, image processing algorithms, and means of rendering images in print and on screen. It should translate well to other image processing programs such as AP. I find his approach so persuasive that if I had the time I would get PS to pursue it. Right now, I need some help applying some basics to AP.


Two fundamental tools that Margulis discusses at length are curves and channel mixing. He gives many examples of color correction with curves in RGB, CMYK, and LAB that are easy to learn from. A minor issue is that he displays curves with dark on the right, whereas AP only shows dark on the left. These can be compared by mentally or physically rotating the curves 180 degrees. PS has a one-click control to flip them.


Channel mixing does not translate so well. The fundamental Margulis maneuver in PS is to choose a channel in RGB (e.g., the most contrasty), use the Apply Image command to create a BW layer from that channel above the image layer, and then use Luminosity blend mode to increase the contrast. Creating this layer from existing channels seems to involve only a couple of steps. But this does not work in AP, which seems to be set up only to blend two layers, not create a separate one. Also I can select a source layer but I don’t understand how I select the destination (the pixel layer I created to receive the channel). This has got to be trivial but reading Apply Image help does not seem to help. “Apply” button grays and becomes active in a way I have not figured out. Also it appears that the equations operate in only one color space, while PS allows blending cyan with RGB. Can someone help me see if my task can be done in AP? It’s got to be simple.
And why are the Composite channels more functional (show, edit) than those of the other layers?


 
Although it goes beyond my immediate inquiry, it could be an important influence on the evolution of AP if, among those AP and PS users who are aware of Margulis’s work, there is enough interest to justify developing better user interface elements. (I already have a couple of ideas.) Many advanced retouchers are very enthusiastic about his writing (see reviews of his books on Amazon). Margulis and co-workers have also automated some of his more complex approaches using PS script actions, available through a freely distributed panel. This appears considerably more capable than the AP macros.


 
* Professional Photoshop: The Classic Guide to Color Correction (5th ed., 2006); Photoshop LAB Color The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace (2nd ed., 2015); Modern Photoshop Color Workflow: The Quartertone Quandary, the PPW, and Other Ideas for Speedy Image Enhancement (2013).  Somewhat pricey, but good value. I bought second-hand copies of the first book and the first edition of the second. One lacked the CD. I have not read the third, but there is plentiful information available online, including videos for most chapters.

This is long – my questions start in the third big paragraph.



After spending a couple of years trying to learn how to improve my photos in AP, I think I see some light along the difficult path in the form of Dan Margulis’s Professional Photoshop (5th ed.) and his other books.* His approach to color correction involves understanding human perception, color spaces, image processing algorithms, and means of rendering images in print and on screen. It should translate well to other image processing programs such as AP. I find his approach so persuasive that if I had the time I would get PS to pursue it. Right now, I need some help applying some basics to AP.


Two fundamental tools that Margulis discusses at length are curves and channel mixing. He gives many examples of color correction with curves in RGB, CMYK, and LAB that are easy to learn from. A minor issue is that he displays curves with dark on the right, whereas AP only shows dark on the left. These can be compared by mentally or physically rotating the curves 180 degrees. PS has a one-click control to flip them.


Channel mixing does not translate so well. The fundamental Margulis maneuver in PS is to choose a channel in RGB (e.g., the most contrasty), use the Apply Image command to create a BW layer from that channel above the image layer, and then use Luminosity blend mode to increase the contrast. Creating this layer from existing channels seems to involve only a couple of steps. But this does not work in AP, which seems to be set up only to blend two layers, not create a separate one. Also I can select a source layer but I don’t understand how I select the destination (the pixel layer I created to receive the channel). This has got to be trivial but reading Apply Image help does not seem to help. “Apply” button grays and becomes active in a way I have not figured out. Also it appears that the equations operate in only one color space, while PS allows blending cyan with RGB. Can someone help me see if my task can be done in AP? It’s got to be simple.
And why are the Composite channels more functional (show, edit) than those of the other layers?


 
Although it goes beyond my immediate inquiry, it could be an important influence on the evolution of AP if, among those AP and PS users who are aware of Margulis’s work, there is enough interest to justify developing better user interface elements. (I already have a couple of ideas.) Many advanced retouchers are very enthusiastic about his writing (see reviews of his books on Amazon). Margulis and co-workers have also automated some of his more complex approaches using PS script actions, available through a freely distributed panel. This appears considerably more capable than the AP macros.


 
* Professional Photoshop: The Classic Guide to Color Correction (5th ed., 2006); Photoshop LAB Color The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace (2nd ed., 2015); Modern Photoshop Color Workflow: The Quartertone Quandary, the PPW, and Other Ideas for Speedy Image Enhancement (2013).  Somewhat pricey, but good value. I bought second-hand copies of the first book and the first edition of the second. One lacked the CD. I have not read the third, but there is plentiful information available online, including videos for most chapters.

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I'm pretty sure I've seen the topic mentioned here somewhere before, but still… I'd vote to have the workbooks available as e-books also. I don't mind paying the €32.99 for the book, but the €17.99 for shipping (to Estonia) is what makes me think twice right now. Would be greate to have the book open in iPad and follow along on the computer.

Can panorama stitching be extended to tiling? I sometimes would like to merge two photos vertically for a tree or building. Another posting in this forum mentioned regular use of Brenizer portrait stitching, which according to Wikipedia involves tiling plus other effects. Microscopists, I believe, use such software to assemble mosaic pictures.