Transparency Blend Space is giving me trouble

[Roger Breton]

I created a new "Print" document using InDesign v19.0 on Win 11.

It automatically inherited current color settings which are RGB = sGRB and CMYK = GRACoL.

I drew three RGB circles on the page, partially overlapped them and used "Overlay" blend mode.

In Photoshop, I did the exact same thing and save as PSD with sRGB embedded ICC profile.

Placed the image in InDesign.

In "theory", the color apperance of these two groups of circles ought to closely look alike?

My question is why is there a visual difference between the two elements?
Activating Proof Setup does not solve the problem.

Here is a screen capture:

 Here is a link to the Packaged document:
https://1drv.ms/u/s!AkD78CVR1NBqm91SWA13tUYbjpH6zA?e=aL0UrC

Thank you in advance for your kind help and patience.

[Roger Breton]

For curiosity, using RGB Transparency Blend space, the result is flawless:

[Roger Breton]

I must be doing something "silly"?
I tried "flattening" the Photoshop file in Photoshop and import that back -- no difference.
I tried copying and pasting from Photoshop in InDesign -- no difference.

[rob day · Accepted solution]

Hi @Roger Breton , I think you asked the same here?

https://community.adobe.com/t5/indesign-discussions/expected-appearance-of-placed-photoshop-rgb-cont...

In Photoshop, I did the exact same thing and save as PSD with sRGB embedded ICC profile.

Photoshop files can only have a single color space, so there’s no need for a Transparency Blend Space choice—the sRGB document’s Blending Mode has to be RGB.

InDesign documents can have a mix of objects with different color modes—CMYK, RGB, or Lab—so when color gets flattened on export or output there needs to be a single output space selected, which is the Transparency Blend Space.

If I set InDesign’s Transparency Blend Space to Document RGB (sRGB in your case), both the placed sRGB Photoshop file (which by default has an sRGB blending space) and the native InDesign colors match:

They also match if I turn on Overprint/Separation Preview, which shows the conversion to Document CMYK:

Photoshop’s Proof Colors set to Working CMYK does the same. Here the Working CMYK space is GRACoL with the Intent set to Relative Colorimetric:

[Roger Breton]

Rob,

You're right. This is an old post I ended up revisiting.

You're right to point out "If I set InDesign’s Transparency Blend Space to Document RGB" everything matches.

Anyone can observe the same including yours truly.

BUT that is NOT the case, here, is it? 
It's a "Print" document and therefore "InDesign’s Transparency Blend Space is set to Document CMYK".
I wish you could help further.
At least, have you been able to replicate my results at your end? I'm going to submit this as a bug.

[rob day]

It's a "Print" document and therefore "InDesign’s Transparency Blend Space is set to Document CMYK".

I don’t think you will get anywhere with the bug report, there‘s nothing stopping you from setting a Print intent document’s Blend Space to RGB—the Intent simply sets up the intial colors and blend space, and they all can be changed once the doc is created.

Because the blend space is applied to the entire spread, you will have potential problems with built CMYK colors like CMYK Black only converting to 4-color when the blend space is RGB, but there are ways of getting around that problem with PDF/X-4 exports in AcrobatPro.

[Roger Breton]

Rob, I appreciate your help and i would appreciate you acknowledge the behavior I reported.

[rob day]

Yes I see the same, but I think it is expected.

I can replicate what you are seeing in InDesign over in Photoshop if I use Convert to Profile... and keep the transparency layers. The Screen blending mode produces a different color appearance when the mode is CMYK:

If I flatten the transparency there is no blending effect and the conversion is from the flattened RGB pixels to the chosen CMYK space:

[Roger Breton]

Thanks Rob, for ackowledging the "beahvior".
Before receiving your reply, I went through a series of RGB images.
My goal was  to test whether the RGB to CMYK conversion in "Print" mode was on par with Photoshop's and the answer is "Yes".
In Print Mode (CMYK Transparency Blend space), InDesign converts placed RGB images to CMYK the exact same way as Photoshop does -- sigh! Here's sample of that study:

I logged in a "Bug" report but they call it "A new idea" rather than a "Bug". 
Only "crashes" have the status of bugs?
So you were right, here, I'm wasting my time.
In conclusion, native RGB elements that use transparency (through blend modes) are not flattened the same as imported RGB elements that use transparency when document mode is CMYK / Transparency Blend space = CMYK. I'd like to understand the underlying logic. I used to speak to a certain Matt Philips, here, in the InDesign engineering team about color management when beta testing, a long time ago... I'll see if I can still reach him at his old address... Thanks for your time and help, Rob.

[rob day]

I logged in a "Bug" report but they call it "A new idea" rather than a "Bug".

I don’t think there is anything new about the way live transparency blending modes work in different spaces. I think it has worked the same as long as there have been layers and blending modes—blending modes are simply math calculations on the pixel values, so RGB and CMYK values will have different results.

With some blending modes the differences are more significant. Try your PS example with the layers set to Difference:

sRGB blending:

sRGB converted to Coated GRACoL 2013 with Flatten Image to Preserve Appearance unchecked:

[Roger Breton]

Rob,

You're absolutely 100% right when you state "there is anything new about the way live transparency blending modes work in different spaces". ABSOLUTELY: it's just NOT documented anywhere!!! InDesign's teams LONG figured out a way to handle native elements blending modes "flattening" differently from those of imported elements blending modes. Period. I'll simply warn my students of this conundrum.

[rob day]

InDesign's teams LONG figured out a way to handle native elements blending modes "flattening" differently from those of imported elements blending modes.

There’s no difference, if you want a match, work in the same blend space in both apps. If you prefer RGB blending effects, set your InDesign blend space to RGB—there’s nothing about print that requires the CMYK blend space, you just have export a default PDF/X-4 and handle the flattening in AcrobatPro.

[Roger Breton]

What do you mean "There's no difference"? You just said you "saw" the difference before?

It's not that "if I want a match", the match HAS to take place, irregardless of "Print" mode?
You don't agree? Again, you are eluding my "Magazine production" example: you think those people use a "Web" or "Mobile" document Mode? There is no excuse for this behavior. And I'll leave it that since you don't have a solution to offer. Case closed.

[rob day]

What do you mean "There's no difference"? You just said you "saw" the difference before?

You are misunderstanding my post. I see the difference in your example but that is because the Photoshop file has a different blend space than the InDesign file you are placing it in.

You can either work with a layered CMYK file in Photoshop and place that in an ID doc with a CMYK blend space, or place a layered RGB file and set the InDesign blend space to RGB and get a match. Either can be exported for print.

[rob day]

it's just NOT documented anywhere!!!

For anyone who’s interested, here’s the blend mode documentation, which describes the channel operations for each mode.

https://helpx.adobe.com/photoshop/using/blending-modes.html

Because most of the modes look at the color information in the individual channels, the 3 channel RGB mode produces a different result than the 4 channel CMYK mode, which you can see in these transparency blend space comparisons— ProPhoto RGB and Coated GRACoL 2006: