preparing Duotone images

Hello guys,

I want to create duotone (or tritone) images for offset printing. I am not going to use special inks for these. I will just create duotone image from the photoshop Duotone setting and choose Black for the first ink and Yellow for the second. My common sense suggests that this way I don't have to pay for the extra ink but still will be able to create duotone/tritone effect images. Of course I will tweak the percentage of each color. For example: 100% black with 30 % yellow (may be add 15% magenta if I want to go tritone).
But one thing I don't understand is that when I print this kind of image from my laser-jet printer, the colors don't look right. If I convert this image from duotone to CMYK, the color comes out right. But the channels go back to 4 color CMYK.

Again, how do I prepare duotone image for offset printing?
Thanks.

 

generalbatzorig
Your laser-printer needs to have a mixed pantone colour to get a true pms colour, this will then be as if it was printed on the press for proofing. Your getting a conversion throught the software and it is not colour calibrated, therefore you can get some real weird colours for pantone colours.
FSA