Hi Graeme, I'm stuck with this problem since days, I hope I have now collected enough info to provide you with. I'm still making experiments profiling plain paper which, I know, sucks (in every sense ;) - but as I told, I don't feel to proceed expending efforts and time in profiling quality papers until I'm sure that everything is working just fine (from my side also, if that's the case). Any way I proceed, I'm more or less getting bluish bumps in the deep blacks. And xicclu seems to confirm some serious problem in that area, when looking with it at the kplot. I included details, using a ofps 1300 target as reference. targen -v -d4 -e4 -s21 -g21 -f1300 -l310 ofps I measured it with my i1 pro, making sure that everything went fine. I then generated a profile: colprof -v -D"Argyll ofps kx qm" -y -qm -kx -ssRGB.icm here is the command output: http://www.elenadomain.it/pub/argyll/Colprof_OFPS_kx.txt and here is the profile, if you want: http://www.elenadomain.it/pub/argyll/ofps1.icm here are some SRGB to CMYK test converions made with photoshop from a test picture with color gradients, using the above generated profile. So you can visually see the problem in the blacks. TIF files are original CMYK conversions, JPGs are the same converted to RGB for quick watching: Relative colorimetric: http://www.elenadomain.it/pub/argyll/rgb2cmyk_ofps_rc.tif http://www.elenadomain.it/pub/argyll/rgb2cmyk_ofps_rc_preview.jpg Perceptual: http://www.elenadomain.it/pub/argyll/rgb2cmyk_ofps_perc.tif http://www.elenadomain.it/pub/argyll/rgb2cmyk_ofps_perc_preview.jpg Here are xicclu plots from the above profile (see the options inside the titles): http://www.elenadomain.it/pub/argyll/kplot_ofps_g_fb_ir.png http://www.elenadomain.it/pub/argyll/kplot_ofps_g_fb_ip.png As you see, the generated Rel intent does show this abrupt ramping down of K - and I honestly don't see why, since I have specified kx! Colprof shoudln't do that in any case, it should obey my black choices and adapt c,m,y correspondingly, NOT turning the black down! Afterall, this behaviour is well visible in the resulting pictures above. What I don't explain, instead, is why the -fb -ip kplot doesn't show such a K behaviour, while the perceptual conversion still visually shows the bluish bump! Here are kplots of the same profile exploring table inversion with -fif, and of course -l300 -L100 http://www.elenadomain.it/pub/argyll/kplot_ofps_g_fif_ir_kx.png http://www.elenadomain.it/pub/argyll/kplot_ofps_g_fif_ir_kcust.png this one with -kp 0 0 1 1 .5 The K ramping down is always predicted. I can't now flood you with data. It sufficies to say that I made dozens other tests with profiles generated with custom K, different targets (cubic grid centered space and also regular grid, -m6). I also made a test, converting with a custom written utility a testchart generated with Profile Maker to .ti1 as target, with matching grey generation options. I also tried iterating one step, i.e from the original OFPS target I made a profile, I then made a second OFPS target passing it as pre-conditioning profile. No improvement. In every case I get pretty the same results: bluish bumps in the dark blacks. Sometime more, sometime less, sometime it's more visible with the RC intent than with the Perc intent, sometimes else it's the opposite, but always there. I don't think that about 1300 patches aren't enough to generate a preliminary but overall correct profile for plain paper. Or just they aren't ?? Colors are right and pretty good after all, test photos printed are ok, except the bluish bump in the darks. I know that plain paper is bad and can't reach a decent dmax, but how is that I can't profile it ? Why colprof insists making the K ramping down ?? Is it my fault ? Where ?? Thanks for you support, /&