I'm new to the forum and I would like to ask a question.
To print a postcard I have to submit my design using a CMYK template provided by the printer (Moo printing).
The design is a grayscale image made in Photoshop RGB mode. I tried some things:
1/ converting the image in Image Mode > Grayscale and then dragging & dropping in the CMYK template
2/ converting the image by Edit > Convert to profile > CMYK and dragging & dropping in the CMYK template.
In both cases the image CMKY template does not look perfectly grey. There's always a hint of red or blue/green.
I also don't find a way to objectively test this, what looks just a bit red on my screen may be perfect neutral grey on print. How do you know that there's not going to be any color on the print? Using the hue/saturation in CMYK also not takes the color out...
What is the best practice for these types of images?