RGB Black to CMYK Black

[Colin30187875eszd]

Hello there

    First time user here so go easy on me. Right this is more than likely a question that's been asked many a time on here but I'm having trouble with the black tones when I'm converting from RGB to CMYK. Basically up until about eight months ago, I'd no idea there were two different ways to work so I'd always just used the RGB one on Medibang. However on finding out about CMYK and then converting the art pieces I'd already completed to it, I could see that there was somewhat of a drabness to the colour tones thereafter.

       Now on getting a local printer to try printing the converted art pieces, I must admit that I thought they looked really rather good. Okay the colours weren't quite as sharp as with the RGB images but still very good for all that. However, the black tones remained just a little too very, very dark gray; therefore I was wondering if it's possible, after the conversion to CMYK, to tweak the blacks at all to make them blacker still? Many thanks for reading this and I've got my fingers crossed someone out there might have the answer to my problems! 

      Colin

[Conrad C]

On screen, not all potential printing problems are easy to preview, even on a calibrated display. Some of the Photoshop features D Fosse mentioned help more easily identify and measure those problems, such as soft-proofing (visual print simulation), viewing Proof Color and Total Ink Limit in the Info panel, and (the much less useful) gamut warning.

[NB, colourmanagement net]

@Colin30187875eszd "So basically the quality of the image that Photoshop is showing me in the CMYK conversion will not necessarily by reflected in the quality of the image that a printer will ultimately print out? ( I think I've got that right!)"

NO the Photoshop soft proof [on a well calibrated screen] should give an accurate representation IF the output device is characterised accurately by the CMYK profile you're using

In soft proof also try checking "ink black" in softproof. CMYK printed black cant be as dark as on your screen.

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

[NB, colourmanagement net]

@Colin30187875eszd "Thanks for this! So if I'm reading this right, even the kind of paper you print stuff onto can have a bearing on the kind of black you end up with?"

yep absolutely.

think newsprint v a glossy magazine.

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

[NB, colourmanagement net]

@Colin30187875eszd "But every printer I've emailed concerning having prints made always insists on the pics being sent in CMYK; what should I do then?"

ask them what CMYK ICC profile to use. If they say just give us CMYK 300 dpi, then find a new printer.

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

[NB, colourmanagement net]

Colin, you can increase black density after conversion to CMYK using Photoshop tools but you have to be super careful not to violate the ink limits.

Black in offset print isn't just black ink it's made up of black and a mixture of the other inks. (i.e. CMY)

An ICC profile for a CMYK process includes information about the max ink a printing system can accept, we call that an inklimit, it might be 320 TAC (total area coverage) so converting to that from RGB is safe. Upping black density using, say, curve adjustments has its risks because you can push the ink ab mounts above the mac ink the machine can take, this can result in offset or even ink running. 

If you have black in your RGB file that's reading 0,0,0 and a good CMYK profile for thew conversion that's going to give as much black density as allowed. Unless, of course, your (offset) printer isn't running optimal curves when making the printing plates. 

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

[Colin30187875eszd]

Yeah the black that I originally put down when colouring my art piece was 0
0 0 which at the time I thought was fine but of course since then I've
found out that in the RGB to CMYK conversion, the resulting black looks
very much like an extremely dark gray instead. But having access to
Photoshop now I'd always just supposed that you could do something like
rewrite the ink code so the incorrect black could then become the correct
kind of black for printing, especially once the art piece had been
converted to CMYK. I find I can tweak the other colours manually post
conversion such as all the flesh tones and what not to a satisfying degree
but essentially resetting the hard blacks to the correct kind of CMYK
blacks for satisfying printing remains a problem

[D Fosse]

It's pretty simple really: RGB 0-0-0 converts to the deepest possible black in the target CMYK profile.

Don't try to tweak this afterwards! You'll exceed the maximum ink limit, the inks will smear and not dry properly.

And again, you absolutely must have the correct CMYK profile.

That's all there is to it.

[NB, colourmanagement net]

@Colin30187875eszd "RGB to CMYK conversion, the resulting black looks
very much like an extremely dark gray instead. But having access to
Photoshop now I'd always just supposed that you could do something like
rewrite the ink code so the incorrect black could then become the correct
kind of black for printing, especially once the art piece had been
converted to CMYK. I find I can tweak the other colours manually post
conversion such as all the flesh tones and what not to a satisfying degree
but essentially resetting the hard blacks to the correct kind of CMYK
blacks for satisfying printing remains a problem"

If a conversion of 0,0,0 RGB to CMYK gives a black that's less than what you want when printed I'm afraid you're pretty much stuck with it. That is IF (and it’s a big IF) the pointer is running the press in a way that’s truly reflected in the CMYK profile you used in the conversion.

If their plate curves aren't right and/or if the press densities are run too low (compared to the CMYK profile) then you need to find a more skilled print house which truly prints "to standard". 

When I convert my Adobe RGB testimage: https://www.colourmanagement.net/index.php/downloads_listing/ to ISOcoated_V2_eci.icc  and have it printed on a well maintained and accurately set sheetfed press the result is great, no shortcomings in the black appearance. 

The CMYK ICC profile characterises a printing press in a certain condition, it has to continue to be run just the same for the ICC profile to be able to accurately (same plate curves, same ink densities, same roller pressures etc) used in conversions and for soft-proofing. 

To assess such situations I use this 

Have you ever wondered how to KNOW whether your screen [or printer] is ACCURATE and not just 'pleasing'?
If so please check this out: http://www.colourmanagement.net/products/icc-profile-verification-kit

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management