Convex vs Concave Gamut Shape

Hi there,

just a simple (it seemed) question on gamut shapes… :confused:

I have been looking at the 3D gamut plots for canon i9900 (dye) and different pigment printers (Canon, HP, Epson). What really caught my eye is different gamut coverage in ORANGE areas. The dye based ink set shows nice convex (outward) shape, whereas all pigment ink sets show straight line or concave (inward) shapes. Its not only the ORANGE area, but its most visible there. All the tested printers have an extra Red ink, essential upgrade for an extended gamut volume.

Anybody can explain this phenomenon, please? Steve, any comment?

Why some mixing gives convex shape and other gives concave one???


Veronika L

Hey Veronika, I see what you are saying - the gamut edge line from yellow to red bulges uniquely for the i9900. I’m not seeing the same bulge on any other type of printer (I have a massive collection of profiles) including other dye based inkjet printers. Every inkset has it’s own characteristics, advantages and disadvantages. I’m tempted to simply conclude that the excellent oranges are a positive aspect of that generation of Canon inks and printers.

Scott Martin

At 6:29 AM -0800 1/10/07, funator wrote:

This can be caused by a number of different factors depending somewhat on where in the color space it occurs…

Could you send me two example profiles directly? Then I can give some better feedback…

send to steve (at)



o Steve Upton CHROMiX
o (hueman) 866.CHROMiX

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At 6:29 AM -0800 1/10/07, funator wrote:

thanks for sending the profiles, it helps to see the gamuts myself.

First, the gamut protruding out into orange as the i9900’s does is a bit unusual.

But more to the basis of your question. I think the biggest difference between the two gamut behaviors is probably due to the transparency of the inks. Pigmented inks tend to be more opaque and so will blend differently than the more transparent dye-based inks.

Other than that I’m not sure… hope that helps…



o Steve Upton CHROMiX
o (hueman) 866.CHROMiX

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Good point Steve but I’m not seeing that orange behavior on any other dye based printer. Are you?

Thanks, Steve! I thought it would have something to do with ink penetration into the substrate’s surface and forming a cake in case of pigmented inks. I am going to look at this issue more closely.

Scott, are you looking at different dye-based printers that have special RED inks such i9900? The red has very strong influence on how the ORANGES are produced.

No, most of the printers I can think of that have red ink are pigment or pigment/dye hybrids. Can you think of any other dye printers with red ink?