If this video doea not address it nothing will! For EPSON

Started Mar 26, 2013 | Discussions thread
Hugowolf
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Re: Relative colorimetric vs perceptual
In reply to SoCal Dave, Mar 28, 2013

SoCal Dave wrote:

Hugowolf wrote:

The most common problems lie in the saturated greens and oranges. (A reason why Epson UltraChrome HDR inks include those two colors.) Fall foliage, with lots of yellow-reds, where you want differentiation between different yellow-reds (oranges), instead of a wash of the same color, is a fair example. Any landscape image with lots of greens that are different when seen next to one another, but would be difficult to tell apart when seen separately, would be another good candidate for look to perceptual, if you have those greens out of gamut.

Brian A

Can I ask you to clarify this statement specific to the Epson 4900 that has the green and orange inks you reference?  Specifically, using the Ultrachrome HDR inks, are you saying that you believe fall foliage would best be served by perceptual or by relative colorimetric?  Which?

It isn't specific to the Ultrachrom HDR inks. It doesn't matter what inkset you are using. You can have out of gamut blues, greens, reds, yellows, anything.

If you have no out of gamut areas, then relative colorimetric will give you the most accurate print. Perceptual will also work, and you might find the results more pleasing, but they will not be as accurate. Using perceptual when there are no out of gamut colors is a bit like applying a mild effects filter – you could call it the 'compress gamut filter'.

If you have out of gamut areas within the same color range, but of slightly different hues or tonality, then when using relative colorimetric, there is a strong chance of these being mapped to the same output value, and therefore indistinguishable from one another. It bears repeating, this will only happen to out of gamut colors. If this is the case, then that is a good time to look at using perceptual. If you don't have out of gamut colors, then using perceptual could cause those similar colors to be crushed closer together.

You determine this by softproofing with the profile for the paper/ink/printer you are using. Firstly turning on the out-of-gamut warning, then by looking closely at the out of gamut areas to see if the colors in those areas are being mapped/clipped to the same color, and if they are, and you don't find that meets your visual requirements, then you can try doing the same thing with the perceptual intent and see if that works better.

Having orange and green inks extends the output gamut for those colors. It reduces the chance of orange foliage (or orange anything for that matter), being out of gamut, but doesn't always prevent it.

The orange and green inks don't extend the gamut that much. CMYK does remarkably well, and has done for decades. Each additional ink extends the gamut a little. And if you print a normal range of subjects, you will find that the O and G inks are used very little.

There are other reasons why you may want to use one intent over the other, given different circumstances. But this is a long enough post already.

Brian A

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