RGB/CYMK

[Warren Beard]

first main difference is that there is no black, so anything black is made up of RGB and therefor will not be that sharp. Also a wider spectrum of colours can be created from CMYK apposed to RGB giving you much more contrast, highlights and lowlights.

It depends a lot on what you are printing weather to use CMYK or RGB

cheers

Warren

[keri baslow]

Wrong- RGB colour space is additive colour theory and primary colours emitted by light RGB added together produces white, absence of RGB produces black, used only on monitors, projectors etc

CYMK is a reflective subtractive secondary colour theory for print. CYM added together produces black, but not a rich black hence the K separate black cart.

RGB colour space has a far wider gamut, that why CYMK struggles to reproduce RGB colour gamut, a wider spectrum is produced with RGB and your rip often says ‘out of gamut’

You should be printing in CYMK, not RGB

[Warren Beard]

I was refering to Litho of Flexo printing and not digital printing, don’t know much about digital printing 😕

[Fred McLean]

Thanks Keri/Warren

Looks like i’ll be converting all to cymk before printing.

F

[John Harding]

quote :

Replies in laymans terms please

quote :

Wrong- RGB colour space is additive colour theory and primary colours emitted by light RGB added together produces white, absence of RGB produces black, used only on monitors, projectors etc

CYMK is a reflective subtractive secondary colour theory for print. CYM added together produces black, but not a rich black hence the K separate black cart.

RGB colour space has a far wider gamut, that why CYMK struggles to reproduce RGB colour gamut, a wider spectrum is produced with RGB and your rip often says ‘out of gamut’

You should be printing in CYMK, not RGB

maybe its just me, and a say hello wouldnt go amiss either 😕

john

[Andrew Boyle]

😕

[Andrew Boyle]

I’ll never understand loads of things.. 😉

[Russell Huffer]

Do not know much about the technicalities involved, however what I have found is on the few occasions I have been sent artwork in RGB format, I have a choice to convert using Illistrator or RIP however both these options change the colours noticeably, sending an RGB direct to the printer produces much better results with colours very close to original.

Regards

Russell.

[Alan Drury]

RGB/CMYK is the same litho or digital it depends on how RIPS or print drivers handle it. Normally a Postscript RIP will take the cmyk and use it as is, a non postscript print driver may want to do its own conversion so colour models may swap. Programmes which have colour management will try to alter the screen rendition to match what will come off the press or printer – RGB can display more colours (wider gamut) that is why, say in Corel when you change from RGB to CMYK you may see colours becoming slightly less vibrant.
Alan D

[David Rowland]

Easy way to remember it

White paper (need to print colour mixed with cyan, magenta and yellow (and a touch of black helps but not necessary))

Black screen (needs to print colour mixed with red, green and blue)

In file terms, CMYK is safe, it normally passes the values direct to the RIP as they are, some adjustments might happen.

RGB is converted to the RIP’s colour range (gamut range), this could be setup correctly or poorly but results are good.

RGB and Corel Draw, if corel mixes some shapes,bitmaps, shadows incorrectly, then you will get strange results.

Did I mention Profiles?

Stick to CMYK (you loose a little colour) but who cares.

[Phill Fenton]

Good question and thanks for the informative replies.

I usually create files in RGB format so that I can email them to my clients (as jpg) and they can see them on screen. I am under the illusion that a jpg file created in cmyk format is not visible on screen (am I right?). Consequently, once approved I print from the same file (jpg in RGB format). From what I have learned here, I should be printing in cmyk instead of RGB. Any advice?

[Fred McLean]

:headbang2:

[Russell Huffer]

My understanding is my printer is CMYK so best to stick to CMYK as much as possible as it is impossible to print RGB on my printer, it needs to be converted by RIP or other software to CMYK first, possably changing colours.

Regards

Russell.

[Phill Fenton]

I just did a test to check my understanding. I saved the same file twice – one as RGB the other CMYK. Then tried looking at each with windows explorer – to find I can view them both (I didn’t think I would see the CMYK file). So bang goes my understanding. 😳

Can someone explain why some jpg files won’t show on screen?

[Alan Drury]

Sorry Phil no I can’t unless they are jpg2. I view most of my jpg in Corel and sometimes it’s easy to pick the wrong filter.
Alan D

[Peter Normington]

just a question on the same theme, why when I print black from a cymk file, on my jv3 it is either not black, or has uneven stripes of dark and lighter shades, but if I designate the black as rgb it prints truer black?

cymk I know just prints the "black" ink, or should do.
but I never get a good print from just "k"
perhaps its my set up?
I use signlab and its rip

Peter

[Phill Fenton]

Dunno Pete 😕

[Chris Wool]

Dunni either but if you add to your cmyk mix extra 30% cyan and mag it will print nicer making black – 100 k 30 m 30 c
a cure if not a proper fix

chris

[James Martin]

Even my epson all in one can print a proper black, whether it is a cmyk or an rgb file.

converted to pdf things look ok as well.

converted to jpeg and printed it starts to look fuzzy.

[Andy Gorman]

I was told that just last week by my stationery printer. They say to add 40% cyan to any large areas of black to get a more consistent cover, so it’s obviously a common thing to do.

[Alan Drury]

If you look closely a black as in 100% K you will see that actually it is not jet black, adding a percentage of cyan is common printing practice and will produce a ‘darker’ black.
Alan D

[Peter Normington]

Thanks chaps, I will try that

Peter

[Warren Beard]

You guys are absolutely correct, there is a sort of standard for printing large solid black areas which has all 4 colours in it, I have a flexographic printing background and only worked in cmyk and this is how we always did solid blacks.

Although there is a standard simply adding about 30% CMY will strengthen the black, digital printing should be fine (I think) but if this was printing flexo or lithographic sometimes the order of the colours you print are very important or you will end up with a black with a green or blue tint to it.

just my 2p worth (if it’s worth that :lol1: )

cheers

Warren