Soft proofing - Are all bets off?

[Lorna Wiles]

So, our workflow goes something like this:

1) Edit client's file in RGB workspace in Photoshop with soft proofing on and set to simulate output device.

2) Convert a copy of the edited file to output device's profile, selecting the rendering intent that gives best conversion.

3) Import the saved copy of the file now in output devices colour space into the RIP.

4) With the same profile selected for output in the RIP, the RIP processes the file and sends it to the output device.

So to confirm; in the RIP the input profile = output profile, no conversion should take place, numbers in = numbers out and therefore rendering intents will have no effect. However .......

This does not happen. Selecting a different intent in the RIP dose produce a different output.

For clarity, the output device is a 4 channel CMYK printer, not spot channels or light inks.

When I enquired of the RIP manufacture as to why this was happening I received the below answer, which I think I understand but does not seem to answer the question.


'Hi ………

At the first glance it seems like you are right with your opinion that using the same profile as an input and as an output profile the rendering intend should have no effect. As it seems to be in Photoshop. Please take into account in Photoshop you can see a big difference between "assign a profile" and "convert into a profile"

In our software you have different parts where color management happens. And to handle colors independent from any device L-a-b is used as transformation color space. The way is always CMYK or RGB -> Lab -> CMYK+n. Even if you use the same profile on both ends. One defined Lab value can be realized with different CMYK combinations. And that is why the rendering intend can have impact to the numbers of CMYK.

One exception are device link profiles or look up tables. ................'


Could anyone shed some light on this please. What is it that I am missing. Do i need to completely rethink our work flow?

And, what is the point of soft proofing anything if the RIP can change the output in this way?

All advice much appreciated.

 

[gordo]

Just a question. Which flavour of RGB are you using?

 

[deaner]

In my experience, if the target color space is CMYK, you'll get the most predictable results converting upfront to CMYK before RIPping, and just turn off color management on the RIP. Then you can be assured that what you see in your upfront apps (PS, AI, ID, etc.) is what you're going to get on output.

 

[Lorna Wiles]

Thanks for the replies.
Gordo:
Most of the artwork we receive these days is in sRGB. It used to be Adobe 98 but I think that was only because of the default PS workspace. If there are no embedded profiles then first guess is to assign sRGB and then try Adobe 98. So to answer your question, we would work in either sRGB or Adobe 98.
Deaner:
Yes, I guess turning off the colour managment in the rip would do the same thing! I must admit I had not actually throught of doing that. Presuabily for the output profile in the RIP you would simply select 'none'? I take it you would leave the linerisation in the RIP - and the Total Ink?
Thanks

 

[deaner]

Not sure what you mean by "linearization in the RIP" and "total ink". I'm guessing you're talking about tone curves and GCR? In my shop, I allow the RIP to apply a tone-curve for the press, but that's it. Any UCR/GCR is handled upfront in Adobe Photoshop.

I know some people might view my CMYK workflow as not "modern", but I think RGB workflows aren't worth the effort when your output devices are plain old CMYK anyway. Now it's a different story if you have, for instance, both CMYK and CMYKOGV devices inhouse, and you need your art files to be portable so they can print in either color space at a moment's notice. Then RGB support and color management become important, of course.

 

[Lorna Wiles]

I use i1 Profiler for creating profiles. In i1 Profiler printer linerisation (individual ink channel curves & individual ink channel limits) can be set in the profile along with the TIC. My understanding is that it is not recomended to set these limits in both places, ie in the RIP & in the profile. I curently I set these in the RIP. GCR is set in the profile as part of the profile creation process.

 

[Magnus]

What RIP software are you using and what settings are there? I would also suggest that you turn off color management for CMYK objects in the RIP. That setting might be called ’ignore embedded CMYK profiles’ or similar.

 

[Lorna Wiles]

Thanks Magnus for you reply.
The RIP is Ergosoft and the quoted reply was from their tech support. Surely you would not want to 'ignore embedded CMYK profiles' in the RIP. I can understand turning off the RIP output profile setting (output profile = None) and I suppose then logicaly any embedded profile would be ignored as there is nothing to convert it to.

 

[Magnus]

Ignoring the input CMYK profile should result in the same result as in setting the output profile to "none", since your wanted behavior is "do not convert CMYK images in RIP". Well I hope you got a solution that works for you now.

 

[Lorna Wiles]

Thanks Magnus. I think I have got it!
Changing one's work flow is quite a big step!! To confirm my understanding is correct could you confirm the following 3 Rip settings would all turn off the colour managment.?

1) Ignore incoming profiles = No colour managment
2) Set outgoing profile to none = No colour maagment
3) Ignore incoming profiles and set outgoing profile to none = No colour managment.

Thnak you this has been a great help. It is much appreciated!

 

[Correct Color]

Lorna,

Y'know...

So to confirm; in the RIP the input profile = output profile, no conversion should take place, numbers in = numbers out and therefore rendering intents will have no effect. However .......

This does not happen. Selecting a different intent in the RIP dose produce a different output.

Well, yeah... That's to be expected. A different rendering intent will create different color values. That's its job.

1) Ignore incoming profiles = No colour managment
2) Set outgoing profile to none = No colour maagment
3) Ignore incoming profiles and set outgoing profile to none = No colour managment.

Man...

I can tell you I've been setting up color workflows around the world for over fifteen years and I would never -- and have never -- set up a workflow like that.

From what you initially posted, you seem to have a pretty good grasp of a lot of color management functions, but a little problem fitting them all together.

Where I see you falling down is converting from your working space to your printer profile in Photoshop.

No. Soft proof with your printer profile, work your file exactly as you want it, then save it in your working color space, and let the RIP convert it to the printer color space at print time.

As long as that's the color space you print to, and you use the same rendering intent as you soft proof to, and your profiles are correct representations of how your printer actually prints, you'll get the results you expect.


Mike Adams
Correct Color