Are colour conversions really that "complex"?
They're just converting colour coordinates in one colour-space to those in 
another, using some straightforward formulae that are hidden under the hood.
(The choice of formula, and what to do if a colour is 'out of gamut', depends 
on the 'rendering intent', of which we usually have a choice of four).
The conversions will give 'round-tripping' errors if they're out of gamut.
This is why better Adobe software (Illustrator, Photoshop, InDesign) maps RGB 
and CMYK via a device-independent ("LaB") representation, rather than straight 
from one to the other.
The problem with FrameMaker is that the conversion algorithms it uses are crude 
rubbish. This is why they frequently give such awful results, not because it's 

>From previous threads on the Adobe Forums, it seems that the conversion 
>formula Frame uses is:

C = max(R, G, B) - R
M = max(R, G, B) - G
Y = max(R, G, B) - B
K = 100 - max(R, G, B)

R = min(100 - K - C, 0)
G = min(100 - K - M, 0)
B = min(100 - K - Y, 0)

...which gives rubbish results.



From: Jacob Sch?ffer (Grafikhuset) <>
To: <>,      "'Craig Ede'" <>
Cc: 'framers' <>
Subject: RE: CMYK vs RGB RE: PDF query
Message-ID: <00a601cfec93$39b38e10$ad1aaa30$>
Content-Type: text/plain; charset="utf-8"

It?s definitely NOT easy to explain this. Color conversions are COMPLEX. 
Anyway, RGB -> CMYK conversion is lossy, and CMYK -> RGB is also lossy.

What is the point of the RGB switch afterall? Why not just pass through what?s 
input and remove this switch?

*** Confidentiality Notice: This e-mail, including any associated or attached 
files, is intended solely for the individual or entity to which it is 
addressed. This e-mail is confidential and may well also be legally privileged. 
If you have received it in error, you are on notice of its status. Please 
notify the sender immediately by reply e-mail and then delete this message from 
your system. Please do not copy it or use it for any purposes, or disclose its 
contents to any other person. This email comes from a division of the Invensys 
Group, owned by Invensys Limited, which is a company registered in England and 
Wales with its registered office at 3rd Floor, 40 Grosvenor Place, London, SW1X 
7AW (Registered number 166023). For a list of European legal entities within 
the Invensys Group, please select the Legal Entities link at 
Invensys Limited is owned by the Schneider-Electric Group.

You may contact Invensys Limited on +44 (0)20 3155 1200 or e-mail This e-mail and any attachments thereto may be subject 
to the terms of any agreements between Invensys (and/or its subsidiaries and 
affiliates) and the recipient (and/or its subsidiaries and affiliates).

You are currently subscribed to framers as

Send list messages to

To unsubscribe send a blank email to
or visit

Send administrative questions to Visit for more resources and info.

Reply via email to