RGB —> CMYK: 16 BIT BETTER?

[Philippe]

Yes, the title is a bit hazy but the question might be as well, and I do not know if this is the right place for this topic...
A few days ago, I had a discussion with a graphic designer on the advantages of 16 bit on 8 bit color depth.
A 'chromiste' (*) told me that in order to convert RGB images in to CMYK for off-set printing, 16 bit is preferred  because there is more color information so the lost of color information is a little better compensated resulting in richer colors in the published results.
This graphic designer told me that 16 depth was useless and making the files unnecessary large.
Can somebody enlighten me on this matter?

P.S. Sorry for my bad English !
 
(*) The one who is responsible for the color management and related things in the printing, the step just before the CTP (Computer to plate).

[hjulenissen]

When you do most color-matrixing operations, the output will need more bits than the input to be represented without loss.

-h

[Mark D Segal]

For editing the photographs, 16-bit depth is definitely preferred because the huge number of additional levels of luminosity it provides protects against risks of banding and posterization. There is a huge amount of literature about this all over the internet. It's best to preserve a 16-bit environment up to the last stage this is possible, and then convert to 8-bit when necessary.

[digitaldog]

This primer may help: http://www.digitalphotopro.com/gear/imaging-tech/the-bit-depth-decision.html

[Philippe]

Thanks, this is was my argumentation too. But, I had to do my homework over and deliver all my pictures in 8 bit, imagine...
Now, the publisher told me that he was a little 'disillusioned' about the rendering of the colors, compared to my previous results, then the discussion started again...

This is, after shooting for 42 books in 20 years, the first time I see that a publisher tending to follow the judgement of the graphic designer on photographic  technicalities instead of the photographer!
Since the digital tsunami, every body thinks he knows all about photography

After 25 years of freelancing, I know for sure I do know notting!

[mediumcool]

I think if you have well-exposed and colour-balanced images which are going to be printed on conventional CMYK offset, 8-bit will suffice.

But, if you have images which need a lot of work, and/or are being printed in 6-colour, whether on offset or digital, higher bit depths are good to have.



Note in the diagram that the guitar pick-shaped CMYK gamut (blue outline) is much smaller than RGB’s (yellow outline). Six-colour process can push the gamut out a bit with green and orange inks, but it never quite covers the full RGB. The main thing is to avoid posterisation, as already discussed.

BTW, I have been a working photographer for 35 years and converting from RGB > CMYK for 20 years in my other work as a retoucher and designer.

[tived]

first off - being a photographer makes you no expert at Digital imaging - it makes you a guy/gal with a box that collects lights and records it - each have their on take on how that process evolves, but just because you shoot with a digital camera vs a pin-hole makes you no digital-guru. Just like a graphics designer isn't color expert either. Exceptions do exist ;-)

We would have to assume that when you get to the point where you are going to convert your files to CMYK that all post processing to this point has been completed.

Good exposure or not, we are at a point where we are as happy with how the file looks like in its RGB state. The next question is how are we going to convert this so that it will look good when it comes out of a CMYK press.

In my mind here there is a bit of reverse engineering that has to happen here, mainly because my experience tells me that just by going by the numbers doesn't always give you want you want in particular if the medium you are going to print on is less forgiving.

but to answer you question, I would keep my RGB file in 16-bit or greater for as long as possible, at the final step convert to CMYK and 8-bit and save the file as a TIFF, now there is a bit of magic happening in this step too at least i know I have to pull a rabbit or two out when doing this as I also need to take into account for any compensation in the printing process, one thing is to keep the colors in check that as many of them stay within gamut, but also that the end-points are going to end up where I have intented them to go.

Otherwise you will either have a very heavy with no details in the blacks image if the image has a lot of dark tones in it, or alternatively you will get a really flat image with no blacks, though the later is less likely to happen.

Now there  are times where you have absolutely no problems because just happen to be so lucky that your images will be printed on a top quality press with great paper, where the blacks are black and the whites are white, and all the subleties inbetween will come up just as on your screen.

However many book new editors love these new organic looking papers, such as woodfree etc.... which if not tamed will eat black well into the high midtones ;-) and through you a color-shift in your face too and not always in the same direction!

I am not sure if you can keep your CMYK file in 16-bit all the way but it would be great if it could, it really depends on the quality of the book/printer/paper/press/staff/money .....ohh and image ;-)

have fun

Henrik