Date   

Re: Playing with color and shadows to remove 3D perception in living sculptures

Robert Wheeler
 

When we look at normal objects, there are transitions from the areas we can see in front to the areas on the sides/behind that are hidden from view. When the edges are curved, we normally see a gradual transition with subtle gradients in shading from light to dark. Changing that to a visually abrupt edge imitates what happens at the edge of a flat surface. A flat piece of paper or plywood looks flat in part due to the abrupt edge transition and in part due to the flat area appearing more uniform. Making curved edges appear abrupt by applying exaggerated contrast (or even a black outline effect to an edge area) could help make something appear two dimensional. It also echos what we see in selected styles of painting. So, with this second look, I suspect that this work on curved edges may be part of what she has in mind when talking about the intentional increase in contrast. Very interesting in any case.


Re: Playing with color and shadows to remove 3D perception in living sculptures

Kirk Thibault
 

Interesting.  The application of brushed color essentially fixes the lighting, and can result in visually confusing results as the viewer’s point of view changes relative to the scene.  Also, the patterns of strokes and areas of color disguise or confuse the actual form of the three-dimensional subjects, similar to the camouflage patterns applied to naval warships, for example:


Or animal forms painted on a subject’s hands:


Perhaps the reference to increase of contrast in the shadows and highlights is more referring to the contrast between the individual strokes that attempt to portray shading or highlight rather than the absolute difference between shadow and highlight that we would commonly refer to as “contrast” ratio or dynamic range in a photograph.

Kirk Thibault

On Sep 11, 2020, at 11:38 AM, jorgeparraphotography <jorgeparraphotography@...> wrote:

Gang, I may of course be wrong about the relevance of this link, but it really got my attention how this painter has been working with sets and people whom she paints with certain colors, mostly to either emulate or contrast with the background colors,
and the end result is a painted set with people posing inside the seats but the images look totally 2 dimensional. The Artis claims she has been working on this matter, remove tridimensionality to her work while working on 3D scenarios.

IMHO, there is an interesting interplay with colors so the standard "3D feel" of a normal studio set gets reduced to look like a painting or a photo before capture. In some of her work the process is just visually incredible.

So I wonder if the color experts may have a say as to what is really going on here, since it may have interesting application for some photo and video projects, and of course, creative retouching, where color will be king.

here is the link to the website and a comment in Wired News I read recently. 

https://www.wired.com/story/alexa-meade-art/

She claims that she is making the shadows stronger and the highlights brighter in order to flatten the image, and that got my curiosity instantly, since this is counter to "digital logic" in terms of retouching. or is it not?

Interestingly, her project has got the attention of Google and other tech parties who are now collaborating into expanding this color interplay to more digital applications into Augmented Reality and VR, and to me , it is all an interesting interplay of colors.

Here is her website

https://www.alexameade.com

Opinions ? 

Cheers!
Jorge Parra




Re: Playing with color and shadows to remove 3D perception in living sculptures

Robert Wheeler
 

Watching the works in progress in the video, I conclude that abbreviating the technique to "making the shadows stronger and the highlights brighter" omits many really important elements of what is going on perceptually. I see her adding paint to normally flat surfaces (forehead, wall) with multiple colors and imitations of texture that make it harder for us to read the area as "flat." On curved areas it become more difficult to follow the "real" curves. More is going on to counteract perspective clues, but I am less certain which parts are most important. I have the feeling that the blotches of colors and misleading edges have some relationship to the ideas used in designing camouflage, but they are not exactly the same. I think she is exactly right to categorize this as a reverse fool the eye technique "reverse Trompe L'Oeil." It just involves many other methods than exaggerating shadows and highlights. Thanks for posting the links.
Robert Wheeler


Playing with color and shadows to remove 3D perception in living sculptures

jorgeparraphotography
 

Gang, I may of course be wrong about the relevance of this link, but it really got my attention how this painter has been working with sets and people whom she paints with certain colors, mostly to either emulate or contrast with the background colors,
and the end result is a painted set with people posing inside the seats but the images look totally 2 dimensional. The Artis claims she has been working on this matter, remove tridimensionality to her work while working on 3D scenarios.

IMHO, there is an interesting interplay with colors so the standard "3D feel" of a normal studio set gets reduced to look like a painting or a photo before capture. In some of her work the process is just visually incredible.

So I wonder if the color experts may have a say as to what is really going on here, since it may have interesting application for some photo and video projects, and of course, creative retouching, where color will be king.

here is the link to the website and a comment in Wired News I read recently. 

https://www.wired.com/story/alexa-meade-art/

She claims that she is making the shadows stronger and the highlights brighter in order to flatten the image, and that got my curiosity instantly, since this is counter to "digital logic" in terms of retouching. or is it not?

Interestingly, her project has got the attention of Google and other tech parties who are now collaborating into expanding this color interplay to more digital applications into Augmented Reality and VR, and to me , it is all an interesting interplay of colors.

Here is her website

https://www.alexameade.com

Opinions ? 

Cheers!
Jorge Parra






--
Jorge Parra 
www.jJorgeParraPhotography.com
Miami


Re: Cleaning up a photo of a newspaper photo

john c.
 

Considering what newsprint looks like that's not advisable. The texture and grime in the paper will be forced to black or white and really block up the contrast since the original dots aren't clean the way they'd be on a film. You'll need to retain some grayscale since the original isn't made of clean dots. 



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Rick Gordon <lists@...>
Date: 9/10/20 11:05 PM (GMT-05:00)
To: colortheory@groups.io
Subject: Re: [colortheory] Cleaning up a photo of a newspaper photo

The in addition, shouldn't it be saved and placed as a bitmap file, so that it's not being double-screened?

Rick Gordon

--------------------
On September 10, 2020 at 8:00:54 PM [-0700], Michael Jahn wrote in an email entitled "Re: [colortheory] Cleaning up a photo of a newspaper photo":
Hi Joe,

If you want to retain the halftone dots, you need the ability to scan at a MINIMUM of 900 ppi

higher is better !
Joe Marshall said:
My goal is to have the text and picture maintain a newspaper look. I do not wish to get rid of or minimize the halftone dots. Apologies for not including that in the question.

 ___________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________
WWW: http://www.shelterpub.com


Re: Cleaning up a photo of a newspaper photo

Rick Gordon
 

The in addition, shouldn't it be saved and placed as a bitmap file, so that it's not being double-screened?

Rick Gordon

--------------------
On September 10, 2020 at 8:00:54 PM [-0700], Michael Jahn wrote in an email entitled "Re: [colortheory] Cleaning up a photo of a newspaper photo":
Hi Joe,

If you want to retain the halftone dots, you need the ability to scan at a MINIMUM of 900 ppi

higher is better !
Joe Marshall said:
My goal is to have the text and picture maintain a newspaper look. I do not wish to get rid of or minimize the halftone dots. Apologies for not including that in the question.

 ___________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________
WWW: http://www.shelterpub.com


Re: Cleaning up a photo of a newspaper photo

Michael Jahn
 

Hi Joe,

If you want to retain the halftone dots, you need the ability to scan at a MINIMUM of 900 ppi

higher is better !


Respectfully,

Michael Jahn
2718 Cimmaron Ave
Simi Valley, CA 93065

805 416 6946



My goal is to have the text and picture maintain a newspaper look. I do not wish to get rid of or minimize the halftone dots. Apologies for not including that in the question.



Re: Cleaning up a photo of a newspaper photo

Joe Marshall
 

Thanks everyone for the suggestions. I will need some time to get the newspaper back from my friend and try the re scanning suggestions. I also need to spend time digesting (= understanding) your other ideas.

My goal is to have the text and picture maintain a newspaper look. I do not wish to get rid of or minimize the halftone dots. Apologies for not including that in the question.

Joe Marshall


Re: Retrieving impossible colour from Lab

Doug Schafer
 

"Here is an illustration showing the limits imposed by this integer encoding of Lab:"

3D view is nice.

I made a layered 2D .pdf view and posted to this group ... years ago.
check here:  https://groups.io/g/colortheory/files/2015%20and%20earlier/Doug.S%20LAB%20curves
And check out the Lab gamut diagram.pdf
Useful to check if a test sample (Lab #s) in Lab, is in gamut...look it up on the chart.
Also useful to note at various L levels, where the a and b values are limited/out of gamut.
If anyone wants individual layers, I can post them here too.

Open .pdf and, for example, you can see that at L=50, lower left teal colors (-a and -b) are limited, and upper greens/yellows/reds are limited to b<80

Doug Schafer


Re: Retrieving impossible colour from Lab

Michael Jahn
 

Hi John

( i copied you directly as I am not sure if the io form scrum technology allows html embedded image in the reply - that way you should get the image in this reply )

see;

http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html#SideNotes

Paragraph 3 should be of interest to you then..

The first entry in the table is the Lab Gamut. This is the set of Lab color coordinates for which there could possibly be a physical sample. These are the "real colors." Lab color coordinates that lie outside this gamut can never exist in nature, and therefore it is not important that these coordinates be represented in a working space definition. Further information about the Lab Gamut may be found here 

http://www.brucelindbloom.com/index.html?LabGamutDisplayHelp.html

and 3D images of it may be found 
here.  

http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html#SideNotes

i especially like this part

Integer Encoding of Lab

Many real world implementations of Lab encode the values as integers. Common examples include TIFF image files, ICC profiles and Adobe Photoshop images. Integers have limited ranges. Typically, the full L* range [0, 100] is encoded. However, the encoding range of the a* and b* components is usually restricted to cover the range [-128, 127]. Therefore, all possible Lab colors cannot be encoded using this scheme. Even when 16-bit values are used instead of 8-bit values, the extra bits are used to make finer divisions between values, and are not used to extend the range of values.

Here is an illustration showing the limits imposed by this integer encoding of Lab:

LabGamutIntegerAnnotated.jpg

The semi-transparent boxes show the portion of Lab color space that may be represented by integer encoding. You can see that some real colors are excluded (the lobes that bulge outside the box). You can also see that much of the available encoding space, about two-thirds in fact, is wasted because these Lab values can never occur.  

Hope this helps.

Respectfully,

Michael Jahn
2718 Cimmaron Ave
Simi Valley, CA 93065

805 416 6946


On Tue, Sep 8, 2020 at 5:05 AM John Phillips <paulsimonrichards@...> wrote:
Hi, I am curious about what happens to out of gamut colours during an Lab - to RGB conversion - where do they go and is there a way to keep this information? 

As I understand it, when a L*a*b image is converted to RGB, the colour values are clamped to fit into the 255 range, leaving legal representations of colours. 

I wondered if it is theoretically possible to conduct this conversion and store on file only the data which is out of gamut, without the proxy colours? 

Mr Margulis' work has inspired me for nearly 2 decades, I am an artist working on an experimental project and would like to produce files which are entirely out of gamut, with nothing visible to SRGB. Even if this means producing a blank image. 

Thank you


Re: Retrieving impossible colour from Lab

Rex Waygood
 

Agreed, he is the colour oracle in the maths/science arena :-)


Re: Retrieving impossible colour from Lab

Doug Schafer
 

I have always found interesting Lab info at this website...look around various pages and you might find your answer...
http://www.brucelindbloom.com/index.html?LabGamutDisplayHelp.html

Doug Schafer


Re: Retrieving impossible colour from Lab

Rex Waygood
 

I expected this to be under Dan's post. It isn't on my screen.


Re: Retrieving impossible colour from Lab

Rex Waygood
 

I couldn't get my head round this working as John wanted. It will do something but not quite what John described. I had thought of it as a possible solution.
When the conversion is made to sRGB the OoG colours will be put on the periphery of the sRGB gamut.
When the difference is taken the result will not be the sRGB gamut subtracted from the ProPhoto Image but the subtraction will be the sRGB image plus the OoG colours using RC Intent. If Perceptual were available that would cause more non-John results.  
The results might satisfy his artistic intent but I am not convinced it meets his stated intent.
Rex


Re: Retrieving impossible colour from Lab

Kirk Thibault
 

One approach that may be interesting and is more graphical and qualitative as opposed to quantitative, spreadsheet manipulation is the following….

Start with a full Lab image (for example, make a new document in PS in Lab color - fill the L channel with L50, fill the a channel with a left-to-right,  black-to-white linear gradient, zero smoothness, fill the b channel with a top-to-bottom, black-to-white gradient, zero smoothness.  Make a set of Lab images, say in L10 increments, by duplicating the above document and replacing the L channel fill with L0, L10, L20 … L100.

Set the working color space for PS to the color space that you want to compare to Lab (for example, sRGB).  Open one of the Lab images and simply change the mode from Lab to RGB - this will place the Lab colors into the current working color space.  As Dan pointed out, real images do not change appearance very much, but the smooth gradients of color will show some banding and discontinuity when you perform this operation.  The real interesting thing about this change of mode though, is the R, G and B channels in the RGB document, which are grayscale representations of the color.  This is where, regardless of the ability of your color display, you can see clipping that occurs in the change from Lab to RGB - clipped values in each channel go to black.  You can examine each channel and combine all of the channels’ grayscale images into a single grayscale image with BlendIf permitting you to threshold each of the three images (R, G and B channel representations) into a single image, against a white background layer, that shows you what it is gamut (white) and what has been clipped (black).  Repeat this operation for each level of L that you made in the original L series of images.  You can make an action that will automate the process after you open a L image:

1) Change the mode to RGB
2) Make a new layer above the background layer and fill with white
3) Make a new layer - Apply Image … Normal blend mode, Background layer, RED Channel
4) Make a new layer - Apply Image … Normal blend mode, Background layer, GREEN Channel
5) Make a new layer - Apply Image … Normal blend mode, Background layer, BLUE Channel
6 Select the BLUE layer and adjust the BlendIf by dragging the “This Layer” white slider down to a value like “5” or so - repeat for the GREEN and RED layers.
7) Stamp a copy of the resulting composite.

Now you have a binary image of the gamut for that slice of L.  Not surprisingly, it looks like the gamut volume for sRGB in Lab coordinates.  You can do this for any image, preferably by converting a raw digital camera image file directly into Lab (ACR will do this, as will some other raw converters).  You can also mess with the fall off and threshold of the BlendIf operation to get the effect that you are looking for, in terms of how the boundary of the gamut appears in each image.

What is interesting is the abstract image that can result from layering the resulting binary images and compositing them - you can do this with a Smart Object (load images to stack and make a Smart Object) and then play with the Smart Object stack mode - Entropy is interesting.  You might also get interesting effects if you combine different binary images into R, G and B channels of a new RGB document, producing a Harris Shutter kind of effect.

Or…

For a given pixel in your Lab document at a given X,Y image location, you could extract the L, a and b value of the pixel and perform a simple distance calculation (SQRT(a^2 + b^2)) at the pixel’s L plane and compare that distance to the distance of the sRGB gamut volume boundary on the specified L plane in the direction specified by the direction of the ab vector in Lab.  If the ab distance is greater than the corresponding point intersected on the sRGB gamut volume boundary, then the result is “0” (OOG), else the result is “1” (in gamut).

Kirk Thibault

On Sep 8, 2020, at 9:53 AM, John Phillips <paulsimonrichards@...> wrote:

Your last sentence is a doozy.
Respectfully, I don't understand this comment.

While I understand that I am coming in from the left field somewhat, but I hope that my question comes across as valid within this group.
I am trying to produce an animation which paradoxically contains a wealth of colour information, yet cannot be seen with standard screen technology.

I am working with software developers for a well known 3D render engine to allow for Lab output of animation frames to produce OoG images from the jump.
If this is not possible then I will render in RGB and then undertake exaggerated Lab colour modifications in Photoshop, pushing the chroma values OoG.
I would then like to undertake some kind of boolean operation to separate the data which remains legal and that which is OoG. Rex's suggestion to work with Color Think Pro seems like a good starting point.

With this data I then hope to compile the animated frames as a video, ideally in L*a*b keeping the OoG data, but for the sake of final presentation the file will have to be converted back to sRGB
at which point I would like the OoG information to be more or less invisible on screen.

This may all seem rather silly, but it's a work that is accompanied by a full description of process and I would like to be as truthful to my materials and the Lab colour space as I can be.

Thanks for your time




Re: Retrieving impossible colour from Lab

Henry Davis
 

That’s ok, I couldn’t understand what your project was about and frankly still don’t see the point of it.  But, this is a shortcoming on my part and I thank you for the additional information in this post.

The last sentence in the OP reads:

"Even if this means producing a blank image.”

That caused me to wonder what a blank image might accomplish for you as an artist.  I meant no disrespect with the word ‘doozy’.

I’ll see myself out now.

Henry Davis

On Sep 8, 2020, at 9:53 AM, John Phillips <paulsimonrichards@...> wrote:

Your last sentence is a doozy.
Respectfully, I don't understand this comment.

While I understand that I am coming in from the left field somewhat, but I hope that my question comes across as valid within this group.
I am trying to produce an animation which paradoxically contains a wealth of colour information, yet cannot be seen with standard screen technology.

I am working with software developers for a well known 3D render engine to allow for Lab output of animation frames to produce OoG images from the jump.
If this is not possible then I will render in RGB and then undertake exaggerated Lab colour modifications in Photoshop, pushing the chroma values OoG.
I would then like to undertake some kind of boolean operation to separate the data which remains legal and that which is OoG. Rex's suggestion to work with Color Think Pro seems like a good starting point.

With this data I then hope to compile the animated frames as a video, ideally in L*a*b keeping the OoG data, but for the sake of final presentation the file will have to be converted back to sRGB
at which point I would like the OoG information to be more or less invisible on screen.

This may all seem rather silly, but it's a work that is accompanied by a full description of process and I would like to be as truthful to my materials and the Lab colour space as I can be.

Thanks for your time


Re: Retrieving impossible colour from Lab

Dan Margulis
 



On Sep 8, 2020, at 9:53 AM, John Phillips <paulsimonrichards@...> wrote:

I am trying to produce an animation which paradoxically contains a wealth of colour information, yet cannot be seen with standard screen technology.

I’m not sure there’s a basis for that statement. The file may be in LAB and it may contain “colors” that are outside the gamut of (say) sRGB but the monitor that displays the LAB file is an RGB device, so the LAB file, with rare exceptions, closely resembles what you’ll get upon conversion to sRGB.

The usual cause for concern is that somebody is trying to use LAB to force more color into a file destined for some other colorspace, not realizing that the LAB file already specifies something OOG for that space. Do this, and all that happens is that detail starts to go away.

So if you recover the parts of the file that are OOG chances are they will display differences in detail. The differences in color would be difficult to evaluate except by artificial instrument.

If you must see a close approximation of the difference, here is the procedure; for the sake of argument I assume you are concerned about an LAB>sRGB conversion.

Starting with the LAB file believed to contain OOG colors,

1) Make one copy and convert it to sRGB. Chances are you won’t see a difference.

2) Make a second copy of the LAB file and convert it to ProPhoto RGB, which technically speaking contains almost all the LAB gamut and almost certainly won’t show a visible difference.

3) Convert the sRGB version to ProPhoto RGB.

4) Put one of your two files that are now ProPhoto RGB as a layer on top of the other.

5) Change layer mode from Normal to Difference. Chances are, it will look black.

6) Duplicate this file, flattening it. Still looks black.

7) Auto Tone. This will display the differences that were previously hidden by black, showing the differences between the LAB>ProPhoto and the LAB>sRGB>ProPhoto files, which are basically those colors outside of the sRGB gamut.

That should be close enough, but for more accuracy you should turn off the automatic dithering in the conversion as that will produce some fine noise that really isn’t OOG. Also, rather than Auto Tone, it’s slower but more accurate to apply a straight-line curve to the Difference file, moving the highlight point inward until detail starts to appear out of the blackness.

Dan Margulis


Re: Retrieving impossible colour from Lab

Rex Waygood
 

If you are working with video then there is some serious processing to do due to frame rate and the final sample size. Wow what fun:-)
The reconstruction of the OoG image will then really be hard.

With video the best gamut isn't that much bigger than sRGB.
You can drop P3 and sRGB into CTP and discover your working space.

This is stopping me doing things that should be done! :-)


Re: Retrieving impossible colour from Lab

Rex Waygood
 

Strangely it is the kind of thing I love doing, so ask away.
You will notice there are lots of resources, a colorwiki and a forum, I guess others will be interested in your idea and be able to offer help.
Remember I have not done this so you may end up with an insuperable problem and be unable to achieve your objective.

When I set out to do my paper in knew little and worse didn't really know where I was going :-)
When I finished I knew a bit more and knew I had arrived :-)
An example of my naivety, I mathematically converted Lab coordinates to LCH and then found CTP had that option. :-) 

Rex


Re: Cleaning up a photo of a newspaper photo

Penny Gentieu
 

Joe -- did you try ironing the newspaper article before you scanned it? Iron it on low in between two sheets of plain paper or newsprint if you have it. (heat only, no steam!) That will make it at least a little easier to clean up it necessary. I've ironed older newspaper articles than that.

Penny Gentieu

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