inkjet and large format printing - help

#1

I did a test print of my rendering on a HP DesignJet T630 plotter. The results are quite disappointing.
I think one of the problems is that the plotter is not able to reproduce all the shades of colors. By going heavy with the contrast mask in PS something has improved.
Furthermore, the plotter as well as large format printing cannot print a 100% black also due to the printing support.

So I thought that maybe I should reduce the number of shades in Keyshot rendering. Is it possible?
If Keyshot renders 32/64 shades of color perhaps the printed result in this case improves. What do you think?

#2

You can render 16 or even 32 bit images to have more space for post processing. Also you can use curve adjustment in image post processing settings in ‘photographic’ mode to tune blacks and shadows. I prefer to post process in PS, but it’s up to your workflow. Also you can use photoshop or other image editing software to preview simulation of printed output if you have right color profiles for the combination of printer+paper and calibrated monitor. It’s not perfect, but can give you some warning without spending a lot of ink.

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#3

It shouldn’t really be a problem I think but it’s a good idea to do the RGB > CMYK conversion yourself so you are more in control.

Depending on the image black is build up with all 4 colours most of the time. And with a lot of full colour images the actual black used is quite little. It gets different if you have a near black background you want to print. Than also the paper and total amount of ink the paper can hold will play a part.

I would do as Oleksii advises but also do the CMYK separation yourself. In the past Photoshop was not really good at it and we used more specialized software which came with our Linotype Hell scanners but that’s like 30 years ago :wink: Not sure how Photoshop does these days. It used to really overuse black ink while black ink only needs to be used in really dark areas like shadows or actual blacks. Not just on top of every other colour :wink:

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#4

agreed with all of the above-

  1. do the CMYK Seps yourself if you can. Its pretty dang simple these days.
  2. A render from keyshot should never be considered final, in my opinion. While I do appreciate thetone mapping and color controls they are building into KS, its no replacement for a proper color grade in Photoshop or something else with evaluative histograms and the tools to fine tune. Render outputs from KS can and do look absolutely amazing, but theres almost always that little push that it needs. And that’s totally ok, it says nothing about the artist, its just another tool to get the proper output.
  3. This is one of the reasons we have a huge wide format inkjet printer standing dusty in the corner of our office and is destined for ebay. People that work with this stuff every day are the ones that know the details and intricacies of print, ink, medium, all that black magic stuff. They are usually pale and skinny since the only light they see is the light over their eval table, and they never eat lunch because management never wants that super expensive print machines to sit idle. We use a lot of green in our print imagry, and that’s the hardest color to recreate in CMYK, and they have it nailed down. its not perfect, it still looks dingy compared to RGB but its the best I’ve seen and WAAAAY better than we could do in house.
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#5

Yes, change the image to the correct cmyk profile is already done.
Before this step I work with a proper unsharp mask
total area coverage will be recalculated by the press center rip software.
yes the green (and also blue) cmyk gamut limit is a problem (mainly to explain it to those who do not know the four-color separation)

thx Matt and Oscar

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#6

CMYK conversion make sense only when you prepare for offset printing. Conversion to some abstract CMYK profile will reduce colour range to safe, but can kill some nice colours which could be printed with modern inkjets as well. Almost all drivers of inkjet and laser colour printers made to work with RGB input.
Instead of conversion to CMYK, Photoshop have ‘Proof Setup’, ‘Proof colours’ and ‘Gamut warning’ under ‘View’ menu. Using them you can preview the look of printed output and find problem areas and colours. But, again, you need a valid printer/paper profile for this.
P.S. @oscar.rottink yeah, we also used LinoColor in 90s, it was damn advanced tech )

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#7

Nice to see more people here doing also print work. I only help out some ex-colleagues these days. I always assure they are the ones that check the colour stuff since my setup is not that calibrated and all things I did past years were more for screen use.

@oleksii.rybakov I remember a crane used to get the Linotype Hell drum scanner into the building at the second floor. For the price of that drum scanner you could buy a very decent house in the Netherlands :smiley: And I can still remember the sound it made when I forgot to tape the bottom of the slides to the drum and hit ‘scan’ :grimacing: but well, middle in the night and focus got worse :wink:

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#8

[quote=“oscar.rottink, post:7, topic:10883”]
Nice to see more people here doing also print work
[/quote] - me not, haha! Spent over 20 years in this, but once found I have enough )) Now just randomly editing images on request of old friends.

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