RGB to CMYK when printing to a local printer

[bill@plunkettphoto.com]

When Photoshop is set to “Photoshop Manages Color”, does Photoshop do the conversion to CMYK or does the printer driver do it?

[digitaldog]

Depends on the printer driver. Some can't accept CMYK and get RGB converted to end up with CcMmYK or any number of colors based upon the ink set. If the profile is RGB, it converts to RGB and the driver then takes over. Quickdraw print drivers don't understand having CMYK sent.

[bill@plunkettphoto.com]

Thanks for reply.   I’m currently using the Epson P900 but really want to get back to a 24” printer.  I’ve used both Epson and Canon prints and have been very happy with both.

[digitaldog]

Thanks for reply.   I’m currently using the Epson P900 but really want to get back to a 24” printer.  I’ve used both Epson and Canon prints and have been very happy with both.

You send them RGB.

[langier]

The Epson printers seem to like and prefer RGB files and do their magic somewhere in the printer, especially if you have good printer profiles and the canned for the Epson are adequate for many users. I think I read somewhere that if you do send a CMYK image to the printer, it will convert the file to RGB before printing it using the CMYK+ ink sets.

Occasionally, I've got to print CMYK and simply let the printer do its thing for conversion making sure I have the proper paper profile selected for output.

[digitaldog]

Yes, if you send CMYK to a Quickdraw print driver (or driver that doesn't understand CMYK), it's converted to RGB (poorly) for output. Don't do that.
IF you want to print CMYK, you need a print driver that accepts CMYK. Some call them RIPs (although that's not always the case).
The only reason to do so would be for proofing (make my Epson simulate a proofing device for CMYK output).

[MfAlab]

Except some commercial solvent or UV printers, Epson driver runs under RGB data. The driver will take over the rest of works. You can only sent CMYK, actually C-lc-M-lm-Y-K-lk-llk-O-G..., directly to the printer via RIPs.

Proofing is not the only reason to do that, detailed and fully control of each inks is. An example, I could push the gamut to 94% Pantone coverage on Epson 9880 by fine turning every ink limit, while Epson claimed 85%. Moreover, using proper GCR settings and black ink amount, density could be increased by over 0.2 on the same paper.

[digitaldog]

Except some commercial solvent or UV printers, the Epson driver runs under RGB data.

They all do (that's what you “feed” them). At least all QD/GDI drivers.
Send RGB data.
What Epson claims for color gamut and what anyone's custom profile report can differ.
But the answer to the actual question is it depends. And then: send RGB.

[MfAlab]

They all do (that's what you “feed” them). At least all QD/GDI drivers.
Send RGB data.
What Epson claims for color gamut and what anyone's custom profile report can differ.
But the answer to the actual question is it depends. And then: send RGB.

Yes, send RGB data while using Epson fine art printer driver. Generally speaking, large commercial printers did not have an OEM driver. They need a RIP driver.

Sending CMYK signals and controlling every channel separately is not for proofing "only". Just want to make sure nobody was misled.

The only reason to do so would be for proofing (make my Epson simulate a proofing device for CMYK output).

I won't argue about the gamut. Here is the result, on the same printer (SP-9880) and the same paper (old Innova Warm Gloss Cotton) for sure.

[digitaldog]

I won't argue about the gamut. Here is the result, on the same printer (SP-9880) and the same paper (old Innova Warm Gloss Cotton) for sure.

Tells me virtually nothing. What's the gamut volume of each?

[MfAlab]

Tells me virtually nothing. What's the gamut volume of each?

There are obvious differences. I actually marked both of them on the image.

• Solid: Epson driver
• Wire: Caldera RIP

Here are numbers if you still need them.

gamut volume
driver: 847,116
RIP: 1,050,140

maximum density
driver: 2.27
RIP: 2.58

[digitaldog]

2D gamut plots are never obvious.
The gamut volume is; thank you. I don't need them but they provide some useful data the first doesn't.