Friday, February 08, 2008

Raymond Maxwell Interview On Luminous Landscape

I've already commented on the interview with Jay Maisel, but another interview on issue # 17 of the Luminous Landscape Video Journal is with Raymond Maxwell, a colour expert. He nicely explains the difference between perceptual and relative colorometric rendering. Perceptual compacts the whole colour gamut to fit within the colour space of your output device (printer) while relatice colorometric simply flattens the colour range beyond the maximum gamut of your output device to the limit of the device.

He further talked about colour spaces and addressed whether one should be using Profoto Colour Space or Adobe RGB 98, the previous standard. He points out that the vast majority of images don't get near the limits of even Adobe RGB 98, especially landscapes and that if you use a much wider colour space, you have to divide that space up into the same number of chunks as you would divide the smaller space into, and thus images using the bigger space have bigger chunks, more distance between steps and coarser gradation of colour, which can on occasion be a problem.

He suggested that if you have a purely 16 bit workflow, then it might not be a problem, though as currently all Epson printers use 8 bit, perhaps this means we should be thinking about going back. Problem is, for that occasion when Adobe RGB isn't as wide as the colour we have and the ability of the printer to make it, we're screwed. It sounded like hadn't convinced Michael to switch back.

I'm still using my Canon 5000 with the 16 bit driver, so perhaps I can continue to work in ignorant bliss. Perhaps this is more theory than practice and not to be noticed by us mere mortals. Time will tell. I suggest you watch the video.

1 comment:

Alan Rew said...

George,

You say

"He suggested that if you have a purely 16 bit workflow, then it might not be a problem, though as currently all Epson printers use 8 bit, perhaps this means we should be thinking about going back."

It depends how you do the conversion. If you convert from 16-bit per channel ProPhoto RGB to a 16-bit per channel printer profile (i.e. printer RGB colour space) in 16-bit mode, and _then_ convert to 8-bit mode before sending the data to the printer driver, you're OK; if OTOH you convert from 16-bit ProPhoto to 8-bit ProPhoto before converting to 8-bit printer space then you can be in trouble. The posterisation can occur in the first step. It's just a case of being careful to retain the level of precision (= number of bits) that is needed for the _current_ colour space.

To stay in control of this process, I think it's better to use Adobe Photoshop (for example) to do all the conversions, and don't allow the colour engine in the operating system to do it (when invoked by the driver).

FWIW, on Windows Vista there is a new colour system that in principle allows you to have printer drivers with 32 (or more) bits per channel. All we need is for the printer vendors to actually write their drivers using this new technology :-)

Regards,

Alan