Mixing colour spaces

[Jpjapers]

Hi Guys,

Im working with a client who is providing artwork as CMYK Vectors.
Obviously we render images to sRGB but they want the deliverables in Adobe RGB.

I cant figure out how to retain the proper colours of the artwork through to final render.
Any thoughts/ tips are much appreciated.

Thanks!

[sprayer]

From my experience you can't replicate color in render from photoshop, because color in 3d space will affect to light setup tonemapping etc, even if you place white light source, color will be different depend of intensity of light, but white color 6500 is actually a bit pink, you may notice this. For better understanding you may look at white paper in your room with different light bulb temperature, white paper will have different colors and brightness. So making the same color very hard especially in corona because it's not fake render engine like vray.

Knowing your scene may help. But i think only option is post processing with masks wire color.

Maybe other people know more tricks

[FrostKiwi]

As soon as the CMYK texture is read in it is interpreted as albedo. At this point no color space exists anymore. Just like taking a raw photo allows you to assign a color profile and change white balance after the image is taken. From here on out lighting takes over, as said by sprayer.

If your lights carry pure white color, then the color of the artwork under direct light will not change.
You can test this. point a light at the artwork in 3D. Disable Primary and secondary solver and export the image.
The hues (in degrees) from the original Artwork and from the 3d render should be a 1:1 pixel by pixel match. Although the intensity changed, if that spot in the artwork was 138° Green, then that spot in the artwork will have the same 138° green.
Obviously light bouncing will change color.
You can control how much the light bounces affect the artwork using rayswitcher material, if a certain physically fake look is needed. Or with an ID matte and photoshop for that matter.

As for exporting: According to the doc, Corona uses wideRGB internally, which should allow you to export in AdobeRGB. As for how to do the jump from VFB->AdobeRGB file->Photoshop, no idea.
Hope someone else can link an article or explain, I'm curious my self.
From this point on it's all a big mystery to me. After so much pain with photoshop I gave up trying to understand how to handle color. DeadClown's Quote related: ^^

That's an easy one of me...
I don't use photoshop. At all. Period. :D
I've given up trying to achieve anything in PS that requires accurate maths / workflow. I don't even have it installed anymore :) (6 months and counting - and happier than ever). Trying to do floating point stuff in PS is like defusing a bomb in an earthquake - it will eventually blow up into your face (rather sooner than later).

[Juraj]

Short answer ? You can't.

Just because (as SairesArt mentions above) Corona uses generic WideRGB spectrum for internal computation, doesn't matter. You need full Input/Output color management to manage correct pipeline from input color/texture to render output. And both those right no are sRGB regardless of what you do, so even if you after importing into Photoshop either:

A) Wrong "Assign AdobeRGB" profile. Yes the file doesn't have profile attached (because 3dsMax doesn't color manage) but it's sRGB. Assigning anything else than sRGB will convert values to incorrect colors.
B) Correct but useless "Assign sRGB" and then "Convert to AdobeRGB"

You will end up with file that is technically in AdobeRGB spectrum...but with the gamut of sRGB, because that was the input. It would be like re-saving jpeg as 32bit Tiff. The data would still be quality of original jpeg, just the container would change.

This is why need full color management, Autodesk Maya has it.... 3dsMax doesn't. Vray has it through framebuffer and texture node. What Corona devs could do, is integrate ColorOCIO (with ACES) into both framebuffer and CoronaColor and CoronaBitmap.
Then and only then, we can use wider gamut color pipeline.

So making the same color very hard especially in corona because it's not fake render engine like vray.

This is false. Corona and Vray treat light in the same way, regardless of what people believe. But Vray actually supports color management in partial way. Corona currently does not.

[FrostKiwi]

Awesome write-up!
Thanks, clears up a lot.

[James Vella]

I have clients that I deliver Adobe RGB to. I will just explain the Photoshop part as the 3D part is explained above.

Essentially create an empty Photoshop document in Adobe RGB 1998 Space > File > Place linked - your render into the new document. This document will be in the Adobe space and your render will be still as mentioned above just sRGB which is encompassed within Adobe space. Just be aware all color grading from this point will be in the adobe space so you have a bit more range on green/blue but it doesnt matter if its just for delivery.

If you just want to convert a document to Adobe space just go to Edit > Convert to Profile (never Edit > Assign Profile). But its better to convert from higher profiles to lower ones eg. Prophoto > Adobe > sRGB as you gain nothing from converting up. But the file will be in that color space regardless (as what Juarj explained).

[pokoy]

As a former pre-press guy... this thread just hurts.

In general, in contrary to what's been said, do not convert to a profile. This means that your image pixel values will be changed.
You want your value output unchanged. That's what 'assign profile' is for. It doesn't change your values at all, it just *displays* colors within the specified profile gamut.

Conclusion - if you're unsure what to do, just assign AdobeRGB and let them do the conversion to CMYK. If they take their part seriously, the image will go through pre-press where people will take care of proper color reproduction for print, that's what pre-press is for.

The bigger problem here is the first conversion from CMYK to RGB, because CMYK has a smaller gamut for most color tones. But since this is what you get you can't really do much about it.

[Jpjapers]

As a former pre-press guy... this thread just hurts.

In general, in contrary to what's been said, do not convert to a profile. This means that your image pixel values will be changed.
You want your value output unchanged. That's what 'assign profile' is for. It doesn't change your values at all, it just *displays* colors within the specified profile gamut.

Conclusion - if you're unsure what to do, just assign AdobeRGB and let them do the conversion to CMYK. If they take their part seriously, the image will go through pre-press where people will take care of proper color reproduction for print, that's what pre-press is for.

The bigger problem here is the first conversion from CMYK to RGB, because CMYK has a smaller gamut for most color tones. But since this is what you get you can't really do much about it.

They are providing illustrator files. Is there anything i can do within illustrator to give myself better input data?
This thread has been very educational so far thanks to everyone thats contributed!

[James Vella]

Here is a good article on it if you are interested. At the bottom in the QA there is a good explanation of going from sRGB to Adobe. (As well as a video in the link below which goes into CMYK)

http://www.theartofretouching.com/blog/color-space-srgb-adobe_rgb-prophoto-cmyk#.XG0rSs5KiUm

[Juraj]

James has very good point that using wider gamut color space has still benefits for post-production (regardless of output, if the output is wide gamut, the benefits will stay visible, if the output will be in lower gamut, than there is "theoretical" benefit in higher fidelity of color transition, but in many practical tests done of this (not by me) this was almost never proved sufficiently which basically discards for example super high gamut ProPhoto as only being 'halo' space, perfect on paper definition but not leading to actual improvements even for severe color transitions post-production).

I didn't mention it since the OP's client's purpose was for having the wide gamut (CMYK>sRGB) on input texture maintained correctly from conception to print and that currently can't be done.

You want your value output unchanged. That's what 'assign profile' is for. It doesn't change your values at all, it just *displays* colors within the specified profile gamut.

You don't want this at all, I didn't make any mistake with "convert to AdobeRGB", it does convert values to closest resembling, the practical difference of converting to higher gamut space is minimal and we don't want those colors to visually change at all.
If you assign the space, you will interpret those color differently than they were stored at, which is currently sRGB from Corona or 3dsMax (3dsMax does all the saving from framebuffer, doesn't matter which).
You might be pre-press guy but you still got the point of this thread wrong so don't go accusing anyone that your head hurts from reading their post.

What James wrote is correct also.

If you just want to convert a document to Adobe space just go to Edit > Convert to Profile (never Edit > Assign Profile). But its better to convert from higher profiles to lower ones eg. Prophoto > Adobe > sRGB as you gain nothing from converting up. But the file will be in that color space regardless (as what Juarj explained)

And here is where your reading comprehension fails Pokoy.

The bigger problem here is the first conversion from CMYK to RGB, because CMYK has a smaller gamut for most color tones

CMYK doesn't fall neatly in extremities compared to RGB models (since it's substractive) but it better converts to AdobeRGB (which fully covers it) than sRGB, hence OP's client's request for pre-print files.
His client don't care about the gamut per se, they want exact representation of their original colors, which were selected in CMYK, to be represented correctly in final result. But this will be butchered in first step of input in 3dsMax as the bitmap loader.
So if OP could maintain his whole pipeline in AdobeRGB, everything would work. He could go and do so right now with Vray in Maya for this job. But not for Corona in 3dsMax.

This thread had literally nothing to do with pre-press preparation but maintenance of fully managed color pipeline, but you still had to come and claim to be the smartest. Every time Pokoy, I will ignore these color threads in future, there is no point.

[pokoy]

...
They are providing illustrator files. Is there anything i can do within illustrator to give myself better input data?
This thread has been very educational so far thanks to everyone thats contributed!

The most reasonable thing to do - since all the steps like going from CMYK>RGB, rendering with a certain light temperature etc. will probably end up changing the intended look of the CMYK - is to match your render output as closely as is possible to the CMYK illustrator files. Open you render in PS, assign AdobeRGB profile, open the CMYK illustrator file in PS, convert to AdobeRGB (here you need to convert because you are changing color models). Now try to match your rendered colors to what you see in the CMYK file.

The problematic thing is how CMYK gets converted to RGB. In pre-press, profiles are good to have (there are many different profiles for different papers), but print guys have to look at CMYK values in order to make sure it looks good in print. For example, orange color in RGB converted to CMYK may look fine on my display but it'll most certainly have a bit of Cyan. In print you'd want to avoid this because a vivid orange needs Magenta and Yellow, Cyan will only add a 'dirtier' tone to it. So even if colors may looks fine on my display, in pre-press I'd make sure I go into specific color channels and make sure they get 'clean', vivid colors.

Hence my suggestion to only match the colors on your display as far as you can (without making the colors look flat or too saturated) and hand this out to your client. It's then the job of their pre-press to ensure that the output matches what they want to see in print. There's no clean process, there are only some rules to make sure you don't mess up the colors completely.

The *most* valuable asset in any color critical environment is a wide gamut display with a good calibration. On a display like this, you'll see quite a big difference when going from AdobeRGB to sRGB, on a cheaper display colors will change only slightly. If these kind of jobs are regular for you, this will help you most, and some knowledge of what profiles really do and how to use them in PS. Most of the things you read online - such as "avoid sRGB" - make sense only if your display is able to display colors outside of it. Otherwise you can just stick to sRGB, that way you know your colors are within the range you can actually see and judge.

[pokoy]

This thread had literally nothing to do with pre-press preparation but maintenance of fully managed color pipeline, but you still had to come and claim to be the smartest. Every time Pokoy, I will ignore these color threads in future, there is no point.

Sorry... for not stepping on your toes? Was I getting personal? I'm not here to school you or anyone else, just some advice based on what I've learned in almost 10 years in a color managed environment.

Yes, converting to a profile will keep the *displayed* colors. But by doing so you are changing pixel values, which 'assign profile' won't do. But be careful giving out this advice, it may work in one direction but not the other (going from a bigger to a smaller gamut). People who don't know this might end up cropping their color range.

[sprayer]

Can't image how vray and maya can handle this task, you also forgetting what it has shader, glossiness etc, in illustrator we do not know where it will be print on fabrics banner, on gloss magazine, or other material, and with PBR workflow you need to set max reflection so it will not represent any cmyk color from illustrator. 3d CG can't match colors with graphics software. The task is impossible from the start

[James Vella]

They are providing illustrator files. Is there anything i can do within illustrator to give myself better input data?

If you are going to render with Corona this is what I suggest for your import (other renderers can manage this as Juraj explained):

Export the CMYK document to sRGB space. this way when you load it into Corona as a bitmap its reading it close to its intended space. (you will lose some colors which is explained in the last attached image)

Original CMYK document (download the file you can open it in photoshop its color mode is CMYK): attached cmyk.jpg

If you load this into corona bitmap the colors will become saturated: attached import_cymk_render.jpg

CYMK document exported as sRGB (if you download the file and open its in sRGB space): attached cmyk_export_to_srgb.jpg

Now when you render this file it will appear the closest to CMYK: attached render_from_converted_cmyk.jpg

You can also test this yourself by using the Proof modes available in Photoshop to further check your work for the intended color space/conversion.

As mentioned earlier, its easier to start your post production file in Adobe 1998 as it encompasses CMYK which is easier to convert for press printing (not your digital print shops but I wont go into this...). The attached image shows why its beneficial to go from Adobe to CMYK: attached color_space.JPG. Working now from your Adobe 1998 post file you can overlay the CMYK Proof profile and adjust colors for this space (if they require the output in CMYK of course, otherwise use the Proof profile for their requirements - in your case you can leave it off as you are just providing the final as Adobe 1998 space which you are already working in by this stage).

[Jpjapers]

Thanks everyone thats replied.

So my best option currently (due to software limitation) is to just convert the profile of the illustrator file to rgb and use that in the corona bitmap loader?
Now im starting to understand how all the stuff dubcat and Juraj have talked about with colour management in other threads, links into each other. Its something I really want to get a good understanding of.

So for the final output image I should then convert that image to adobe rgb NOT assign the profile.

In terms of lighting and tonemapping as its been mentioned, for this image a white environment is all i need. Ive set default tonemapping and have ran the bitmap through tonemap control disabling the LUT and tonemapping boxes.