CHROMiX

Converting to CMYK profile

I’m confused by a conversion I’m trying to do from RGB to CMYK.

We have a press profile that we commonly convert our work to. If we open the profile in ColorThink and do a 3D compare to US WebCoated SWOPv2 it exceeds the SWOP profile in every direction. Thus I perceive that our profile has a greater color gamut than SWOP.

I then bring in an image into the 3D view, in this case the ducky.tif image from the Photoshop samples folder. I can see that most of the image is within our profiles’ color gamut but there is alot of pixels that lie outside the SWOP gamut. From seeing this, I can assume that when I convert the image from RGB to our profile that there will be little change in the color. When I convert from RGB to SWOP I should see a greater shift in colors.

So I go to Photoshop. I convert the image to SWOP and there is very little change. I convert the image to our profile and there is a much greater change.

If I’m seeing that our profile has a greater gamut, especially in the color area of this picture, why is it not converting as well?

I’ve tried restarting with the profile’s measurement data and recreating a new profile using different ink density/GCR setups and they make very little difference.

Any help that anyone could give me would be greatly appreciated.

I am not an expert on this, but seeing that no had replied to post, I thought I would commiserate with you a bit.

I’ve experienced the same phenomena, and this is what I’ve concluded. The 3D rendering of your custom profile is larger than SWOP, but you don’t want it to be. SWOPv2 was designed to accommodate a variety of different devices and conditions so it has a larger colorspace so that someone can get something relatively ok no matter what they print it on. You on the other hand probably have some fantastic machine that you want to make fantastic prints with, and so you need to make a custom profile specific to that machine and media type. So your colorspace should be, by comparison to SWOP smaller, because you are not trying to include all of those machines that you don’t use to print.

So why does your colorspace extend outside of SWOP? And how does that effect your soft proof preview? Those seem to be questions of process. I suspect that something went wrong in the printing of the chart, or the measurement. Also, I highly recommend measuring the same chart four times and then averaging those measurements, and making the profile from that. We would have to get into detail, and even then I’m sure that my workflow and devices are far different than yours. But I hope I offered some insight.

You didn’t mention which rendering intent you chose for your conversion. If you are using perceptual you will see a change - even to colors that are within gamut.

Keep in mind your monitor’s capabilities also. If you are judging things by how big a change you see on your monitor, you should also be checking to see whether your monitor’s gamut is going to show you all the colors in the image.

Are you viewing this on ColorThink 2 or Pro? Pro allows you to specify which rendering intent you are graphing.