Luminosity blend mode not working as expected

[DanH]

Edit: appears to be an issue affecting CMYK documents. This isn’t happening, it seems, in RGB documents. Also, a screenshot of the issue is provided in another post below.

Luminosity blend mode doesn’t work as expected in the following scenario. Perhaps I am misunderstanding something.

Steps:

1. Place any image in a document. Edit: Must be Placed in a document, rather than opening an image directly. (No, my mistake, it has to do with being a CMYK document, nothing to do with placing vs opening directly.)

2. Convert it to black and white with black and white adustment layer. Rasterize. Set blend mode to Luminosity.

3. Create another layer, paint any color on it (not black and white).

4. Clip the black and white image inside the painted layer.

The image remains black and white whereas I expect it to become colorized by the painted layer it is clipped inside of.

What is expected to happen is this:

If you follow the above steps, but begin by “Placing” an image that is already black and white and omit the black and white adjustment layer step, then clipping the black and white image (while it is set to Luminosity blend) will cause it to become colorized by the painted layer it is clipped inside of. 

Edit: Following is a separate issue than described above, but still related to the Luminosity (or maybe just blend modes generally) acting out of sorts. Later, while testing more, in an RGB document, placing a couple images that were already black and white (so bypassed the Black and White conversion that seems to be causing the above issue in CMYK documents), and altough Placing images had previously worked as expected with Luminosity, this time they did not work, that is, they did not colorize, not initially, but then after doing something, not sure what, I think maybe hiding and unhiding the three different images that were clipped (each set to luminosity), then suddenly the colorization was occuring as expected. Happened once.

 

[NotMyFault]

It would help to reproduce the issue if you add the actual document, and provide screenshots.

You have posted similar issues where you are working with CMYK documents, while using adjustment layers which are well defined only for „additive“ color formats (RGB, LAB, GREY).

I don’t know why you are using blend mode luminosity in a CMYK document. It is slightly undefined / random what result you get. As explained in the other thread, CMYK behaves different to RGB and the separated K channel and subtractive nature lead to surprising results for adjustment, filter layers and blend modes. In CMYK, those functions do not produce the same result as doing everything in RGB and just exporting in converted to CMYK as last step.

If you want to use adjustments and blend modes beside normal better work in RGB. 
It would help if you describe „your artistic intention“, e.g.

• I want to use a B/W image as luminosity applied to a pixel layer with (solid) colored content to influence its luminosity. 

Again, luminosity is a RGB concept which does not really fit for CMYK documents. There you have paper (normally white) and tint, and adding tint reduces luminosity. But the dynamic range of CMYK is far lower than RGB.

[DanH]

Attached is a visual. Plus the original file.

If you follow the steps layed out above they should produce the results I described and are evident in the attached image, unless I made an error in writing those steps.

To test your statement that luminosity in CMYK would “not produce the same result as doing everything in RGB,” I copy and pasted the textured squares into a new RGB document (this image is not shown, only the CMYK document is shown below). Perhaps you are correct for certain situations, but for what I have done, the RGB version and the CMYK version look nearly identical, maybe a slight difference, with the exception that the texture in the righthand square became colorized in the RGB document instead of black and white. Alternatively, if the CMYK document is converted to RGB, the black and white texutre is then colorized.

Edit: when testing another color, a different one than the yellow in the example shown,  I see more pronounced difference. With that different color I switched between RGB and CMYK, and the texture portion changed more distinctively even while the untextured portion of the color remained about the same because it was within the CMYK gamut. But I am not clear on why I would want to work in RGB when I can work in CMYK so I know I am within gamut all along, and whatever the blend mode looks like that is what I work with. If the blend mode generates a color somewhat different than I’d like, I adjust it afterward to bend it to be what I want.

[Side note: You may be thinking of someone else, because I have not previously posted about working in CMYK documents while using adjustment layers.]

Luminosity blend mode example.afphoto

[NotMyFault]

6 hours ago, DanH said:

Edit: when testing another color, a different one than the yellow in the example shown,  I see more pronounced difference. With that different color I switched between RGB and CMYK, and the texture portion changed more distinctively even while the untextured portion of the color remained about the same because it was within the CMYK gamut. But I am not clear on why I would want to work in RGB when I can work in CMYK so I know I am within gamut all along, and whatever the blend mode looks like that is what I work with. If the blend mode generates a color somewhat different than I’d like, I adjust it afterward to bend it to be what I want

The difference is simple: The left side is CMY mixed to rich black (but K zero), the right side is K only black (and CMY zero).

To spot the difference, put one of the nested BW layers in solo/isolation mode, and then use channels panel to selectively activate one color channel only.

Both black variants can look similar, but behave totally different in specific situations like this case.

With help of channels mixer adjustment, you can convert both blacks if you want to rescue your workflow.

So the results you observe are perfectly explainable and „by design“ of CMYK color model.

[NotMyFault]

To check the different, just add a rectangular shape nested with blend mode luminosity.

then use the color panel in cmyk mode to play with colors of the rectangle. When you start with white and add black (K), the results is always grayish.

when use a mixture of (same values) CMY, you get some colorful results.

[DanH]

I at least partly succeeded with your suggestions, and even though I still don’t really know what is going on, I now see something is happening that may be expected—well, expected by anyone who knows what is going on. The rest of this post is just me talking out loud to try and synthesize what I just went through, and you might skip it unless you’re very curious about my failures to yet understand the “why” of what is happening. In the end, for me this has been an exercise in realizing the useful Lessons Learned given below.

Thank you for your patient help.

My results of your suggestions:

1.  Playing with the channels panel continued to show that the rightside texture indeed does not show any color while the leftside does. If I knew more, I’d probably see how this means something. 

2. After trying to “add a rectangular shape nested with blend mode luminosity” and fiddling with it’s CMYK values, I only succeeding in creating different shades of yellow-brown, the results of how the yellow square (parent) was blending with the clipped rectangle (child) that I was using to adjust its color via the CMYK sliders. So, I may be misunderstanding, but I didn’t get it to yield “colorful results”, unless this is what you mean, that I would get shades of yellow-brown instead of only shades of gray.

3. Added a Channel Mixer adjustment layer to the rightside texture, the one that would not colorize. I was then able to adjust the black values for each color channel to get varying brighnesses of yellow. Adjusting any of the CMY values, in any of the color channels, did nothing. Guessing you will say this is as expected, but it isn’t something I understand. When I put the Channel Mixer adjustment on the leftside texture, it was adjusting the CMY values that yielded changes, while the Black value did not change the color. These behaviors seem to match your statement: “The left side is CMY mixed to rich black (but K zero), the right side is K only black (and CMY zero).” There’s some bit of information that I just don’t quite grasp for any of this to really make sense to me.

Lessons learned:

1. Don’t make an image black and white with a black and white adjustment layer (when in a CMYK document) if I want to colorize it using Luminosity, because the channel mixer option to make it able to be colorized is far from ideal to me. Instead, make the texture black and white, export it as a jpg, and place it again. Then it will blend in a way that I expect it should. Or don’t make it black and white at all when this is not necessary for any other reason, since it colorizes just the same (using Luminosity) whether it has hue or not.

2. The channel mixer can be handy to tweak the occasional texture which isn’t quite the color I want it to be. But not very often because it drives me crazy randomly changing percentages for all the color channels to see what they will do. Also, the channel mixer controls are designed to make users frustrated. Probably not, but kinda feels like it.

3. Always post a visual, and workable file in the first post so others will faster understand me, since writing a step by step process may not be followed and therefore what I am trying to say is not understood. We’d have gotten to the point a bit sooner if I had.

[NotMyFault]

Thank you for your patience with my sometimes harsh comments and willingness do adjust your workflow and learn.

CMYK is a tricky beast as it behaves unexpected in many ways if you are coming from RGB.

 

[NotMyFault]

Below the recipe for the channels mixer adjustment which converts K only to CMY only:

• C - set input C to 0, K to 100
• M - set input M to 0, K to 100
• Y - set input Y to 0, K to 100
• K - set K to 0

When you nest it to the B/W image, it will act identical to a placed image and you can save those steps.

 

[DanH]

Oh thank you. Will test these different approaches further and see which I like to use.

Following is a another approach that is promising, but concerned that it doesn’t seem to be a documented feature, so wonder if it will disappear and thus ruin what I have created with it:

After placing an image, with it selected, the color panel sliders, as well as swatch selections, will recolor the selected image. I love this. So much.

Any knowledge of documentation about this functionality?

Also, does it make sense that when doing this, if all CMYK sliders are at O%, then moving Cyan (or Y or M) to 1% makes it just as saturated as if it were at 100%? (Works this way if the document is CMYK, but not when the document is RGB.)

[NotMyFault]

34 minutes ago, DanH said:

Oh thank you. Will test these different approaches further and see which I like to use.

Following is a another approach that is promising, but concerned that it doesn’t seem to be a documented feature, so wonder if it will disappear and thus ruin what I have created with it:

After placing an image, with it selected, the color panel sliders, as well as swatch selections, will recolor the selected image. I love this. So much.

Any knowledge of documentation about this functionality?

Also, does it make sense that when doing this, if all CMYK sliders are at O%, then moving Cyan (or Y or M) to 1% makes it just as saturated as if it were at 100%? (Works this way if the document is CMYK, but not when the document is RGB.)

The functionality to apply a fill color to a placed image is documented and will stay.

It will use only hue and saturation from the color panel, but the luminosity is taken from the layer pixels. 
When you move a cmy slider from 0 to 1 %, you effectively create a fully saturated color. The function to colorize placed images is best used with the hsl color wheel. Again, the CMYK model may create surprising results, as some implicit color format conversion is done.

 

[DanH]

I’ve searched help and online, with various search terms, and can not find any information on applying a fill color to a placed image in this manner, so your confirmation of it being a documented feature is assuring.  Where can we find information about it? 

Quote

When you move a cmy slider from 0 to 1 %, you effectively create a fully saturated color.

Seems strange to me, though, since that is not how it works when using the CMYK sliders when using the paint brush.

[NotMyFault]

Not every function is documented in help files. 
 

53 minutes ago, DanH said:

Seems strange to me, though, since that is not how it works when using the CMYK sliders when using the paint brush.

Did you read my older post, which explained that applying a color is something completely different vs brush strokes?
 

A brush uses the selected color (all HSL parameters, derived from RGB), whereas a color applied to an placed file ignores the L parameter and uses the layer content instead, and if you have only one color slider > zero the you always get 100% saturation.