Why is there conflict in CMYK and RGB?


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germ_boi

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#1
Consumers monitors are usually in RGB mode. Even our cameras shoot in RGB.

So why is the output CMYK? Even if you guys say that your screen is calibrated, there will still be variations because of the difference in color spaces.

What I want to know is why printers cannot print in RGB, and how you guys ensure that your workflow is smooth? ;p Because on my LCD screens, laptop or monitor, CMYK colors look pretty bland but when it comes out in print, it looks vibrant!

Therefore, it's a really hard gauge for me, any tips? ;)
 

photo_kbc

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#2
Let me start with what i have know.

1) Photo printing lab's machine, Konica, Fuji, Noritsu are using Window as their OS. Manufacture make it easy for the printers(the man behind the machine, 85% are non photographers) and made the system to be able to read ONLY RGB files. So if u convert the files into CMYK, the printer either tells u, the system cannot read your file or curse and swear that they have to convert the file to RGB for u...

2) LFP, Solvent , books printing uses CMYK because they speak 1 language on the system and also "traditional" CMYK is for HARD COPY and RGB is for viewing...

Summary, if u are using prints that go thru chemical, advice is to use RGB files. If u are printing by Ink, use CMYK. ;)
 

photo_kbc

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#3
Calibrated printers and monitors are usually for your PERSONAL home or office use. therefore, even if u have calibrated your system for your personal use, when the files goes to other printer and monitor, the colour may not be even 100% same as what u have, it will be about 10%-20% off on the true colour u are expecting.

A good workflow is to have Calibrated printers and monitors and your own printout before u send to the printers for enlargement (if u are planning to do so)

if u have regular printer that allows u to send them your ICC profile, good for u, if not, no way they will entertain you.

As for chemical machine, don't expect ICC profile from them because, different paper have different profile and chemical's temperature will cause the ICC profile to be different. therefore, lab's machine have different ICC profile EVERYDAY!!! If u are their regular, they may give you the daily profile, if not, they may not even want to entertain this point...
 

germ_boi

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#4
Oh interesting, so printing at Fujifilm outlets using their Frontier machines are known as chemical print?

Whereas those large format hp printers(plotters?) are known as solvent prints?

So thats why for the former(fuji) even though they process in cmyk we still pass them our photographs in RGB? actually, for these i find the color conversion quite accurate.

then for the latter, hmmm, my printer actually asks me to pass to them the file in EPS, CMYK and to uncheck the ICC profile box. The color output is on a hit or miss basis. Usually it's a hit, my printer is nice enough to slightly adjust my file before printing. however, that said, I still do not like looking at cmyk colors in my laptop. (can i work in rgb then at the last step convert to cmyk instead?)
 

grantyale

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#5
Oh interesting, so printing at Fujifilm outlets using their Frontier machines are known as chemical print?

Whereas those large format hp printers(plotters?) are known as solvent prints?

So thats why for the former(fuji) even though they process in cmyk we still pass them our photographs in RGB? actually, for these i find the color conversion quite accurate.

then for the latter, hmmm, my printer actually asks me to pass to them the file in EPS, CMYK and to uncheck the ICC profile box. The color output is on a hit or miss basis. Usually it's a hit, my printer is nice enough to slightly adjust my file before printing. however, that said, I still do not like looking at cmyk colors in my laptop. (can i work in rgb then at the last step convert to cmyk instead?)
You printer :thumbsd: ... CMYK also has variations depending on the paper and ink used.
 

sulhan

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#6
Hiee...

Just to share some basics...

The RGB and CMY and two types of colors (laymans term).

RGB - Being the Additive Color
CMY(K-where K is black alone) - Being the Subtractive

Okay lets get to the physics of it......
Lets talk about Additive. Imagine that there is no light ...just a black wall. And you Want to
make White. You would shine Red light - which means you are adding Red onto the balck wall/surface. Then you Shine Green Light. Then you shine Blue light. You see here that you are adding lights(colored lights) to form the white light. The overlapped areas of between two of those colors forms another range of colors.

Okay now we talk about Subtractive. Now you have a paper which is white. White ...but can have different color temperature based on where you view the "white" paper(white balance). Lets say we just have a particlar white paper. So now we want to get Black. So now go and Add first Cyan, to get Cyan, i.e subtracting from the white. Then we put megenta, and then yellow. All we do is we are "subtracting" from the white and hence get the black (composite color - as we call it in printing industry).

So as you can see from the above, LCD is basically an Additive type of color system based on RGB. Formed in generally by light going through some dyed RGB filter array - each pixel formed by three colored light. Variations in the RGB intensity mixing of each pixel will result in color shift. Each color response may be of a certain range but not a "golden value". Hence the slight variation between displays to displays. Sharp recently introduce RGBCMY LCD displays...utilising both Subtractive and Additive light (backlight and sunlight when used in outdoor)...

Whereas for prints, the variation in the mix of CMY(K) will again result in different color shifts in say black. This mixing of a composite black have advanced to some printers having shades of grey as another set of ink to be added on to the original CMYK only system to enhance the black to get the true black. The mixing of ink and the absorption levels on paper(media type) plays a very important role in ensuring color repeatability.

So When one talks of calibration, though it may be possible - many people I know have done that...with helps of the ICC profiles etc..... There may be some that encounter problems matching their monitor and printer. This is just because of the two different Subtractive and Additive colors where variations and mismatch between Monitor & Printers from different brands may occur.

So to answer the question - Why Printer cannot print RGB....its because of the Subtractive and the Additive thingy that i have mentioned above. Hope it helps.
 

Witness

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#7
yes i tink tt's the most important point...one is additive colours and one is subtractive colours... :D
 

#8
Consumers monitors are usually in RGB mode. Even our cameras shoot in RGB.

So why is the output CMYK? Even if you guys say that your screen is calibrated, there will still be variations because of the difference in color spaces.

What I want to know is why printers cannot print in RGB, and how you guys ensure that your workflow is smooth? ;p Because on my LCD screens, laptop or monitor, CMYK colors look pretty bland but when it comes out in print, it looks vibrant!

Therefore, it's a really hard gauge for me, any tips? ;)
If you put a magnifying glass on an offset printed copy or an inkjet copy you'll see minute dots of cyan, magenta, yellow and black. That's how printing has been done for decades. For offet printing the black is added to extend density range especially in shadow areas.

CMCK is never going to be vibrant as RGB mode because of the limitation of ink pigmention on papers. That why some printers introduce second cyan and second magenta to enhance and extent the colour gaumet. Cetain colours are difficult to reproduce in CMYK e.g. orange, purple and pink.

Coming from printing background I still read my RGB files in CMYK breakups. I calibrate my monitor to a CMYK output print.
 

singscott

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#9
If you put a magnifying glass on an offset printed copy or an inkjet copy you'll see minute dots of cyan, magenta, yellow and black. That's how printing has been done for decades. For offet printing the black is added to extend density range especially in shadow areas.

CMCK is never going to be vibrant as RGB mode because of the limitation of ink pigmention on papers. That why some printers introduce second cyan and second magenta to enhance and extent the colour gaumet. Cetain colours are difficult to reproduce in CMYK e.g. orange, purple and pink.

Coming from printing background I still read my RGB files in CMYK breakups. I calibrate my monitor to a CMYK output print.
Right on. Because both colour spacing have different gamut. This will result in the different shade or vibrant of the same colour been presented in the print.
 

photo_kbc

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#10
Oh interesting, so printing at Fujifilm outlets using their Frontier machines are known as chemical print?

Whereas those large format hp printers(plotters?) are known as solvent prints?

So thats why for the former(fuji) even though they process in cmyk we still pass them our photographs in RGB? actually, for these i find the color conversion quite accurate.

then for the latter, hmmm, my printer actually asks me to pass to them the file in EPS, CMYK and to uncheck the ICC profile box. The color output is on a hit or miss basis. Usually it's a hit, my printer is nice enough to slightly adjust my file before printing. however, that said, I still do not like looking at cmyk colors in my laptop. (can i work in rgb then at the last step convert to cmyk instead?)
U don't smell the chemical doesn't means its not chemical, the machine is BIG and bulky and everything is hidden inside, same goes to the paper... the paper can our be expose to "safe light"

Plotters are not only solvent, but inkjet as well...

Different printer have different work flow, but more or less are the same. stick to one of them will be a good choice
 

photo_kbc

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#11
can i work in rgb then at the last step convert to cmyk instead?
in order to get the colour that u think is correct, it will be a better choice to use CMYK for the particular file to work from the start.

For example, if u have been using RGB and your final work is RGB and before u sent to printer request for CMYK, u still have to convert and the colour will be off and u start the work again.. ;)
 

Pablo

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#12
One puts out colour (display)

One reflects colour (photo)

One transmitts the other absorbs and reflects.

:dunno: :dunno: :dunno:
 

ortega

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#14
you should calibrate your workflow to the output device

you don't want to see a nice nice image on your screen
and then find out that your output looks really bad

paper, ink, line screen, halftone shape also plays a part to your final output

take for example a really nice looking picture on your screen
if you used that file to place an ad in the newspapers and a flyer
it will look really different
 

ortega

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#15
the main difference as mentioned above is

screen is light, the more you ad the whiter it gets
print is ink, the more you ad the darker it gets

there is hexachrome
but there is the cost factor to consider
 

germ_boi

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#16
then why in the early days of inkjet printers there were RGB and RGY ink catridges? So RGB can also be used in ink form? then why aint it used commercially?
 

#19
then why in the early days of inkjet printers there were RGB and RGY ink catridges? So RGB can also be used in ink form? then why aint it used commercially?
Would like to share this...

From what I understand when I attended one of the seminar by Adobe...A time will come when most of the print shop will be using the sRGB color mode because Adobe is proposing an Adobe PDF print work flow in which all or in most cases we wouldn't be needing plates or CMYK but I think that this would still take some time for the industry to accept it...

And why SRGB??? Simply because it produce the most colors on your screen and more than what CMYK color mode can generate. This of course applies to the print industry (magazines, nespaper, books. etc.) :sweatsm:
 

Prismatic

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#20
then why in the early days of inkjet printers there were RGB and RGY ink catridges? So RGB can also be used in ink form? then why aint it used commercially?
I don't think inkjet printers ever had RGB inks. Essentially, when you put something down on a surface like paper, colours are reproduced by a subtractive process. Eg: Light falls on the paper and the ink, certain colours (or wavelengths of light) are absorbed by the inks and the colour you see, are the wavelengths of light that are reflected and not absorbed.

The fact is the colours that the human eye can see are a lot more than the colours available in RGB, and RGB is substantiately bigger than CYMK. So what printer manufacturers have been trying to do all along is get CYMK to match RGB. This they try to do by adding new inks to the original 4 colour inks C,Y,M,K. Printers will know of Hexachrome as Ortega mentioned, which adds orange and green. Inkjets will have others like blue, another yellow etc etc. They called it names like Extended CYMK for example. What they are trying to do is to match up to the RGB colour space, however it's still strictly a CYMK process simply because it's a substractive colour process.

EDIT: I know there are printers out there that calls their inks CYMK+RGB, do not be confused. The RGB inks in these printers are meant to be used on their own. Meaning, mixing them up like the way you do in CYMK will not get you the other colours of the spectrum. This is in contrast to RGB lights, if you add them together, you will be able to get the other colours of the spectrum. Mixing Red, Green and Blue inks will probably get you a muddy colour.
 

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