Semi transparent black changed to to semi transparent grey

[Martin]

When Geocart re-projects a map with a feathered black edge on a transparent background in it - i.e. a tone gradation from black to transparent that does not pass through any grey mid-tones - Geocart introduces grey mid-tones (though the transparency levels remain fine). The same happens when I re-projected a semi-transparent dark blue - it came out as a semi transparent lighter blue.
Simple cases of this (such as a layer containing only semi transparent blacks) can be remedied easily enough in photoshop "curves", but more complex map layers with lots of different colours in them are more tricky.

[daan]

Hello Martin.

What is the format of the source file? Are you creating a “raster reprojection database” or using a whole-world image on plate carrée directly?

Regards,
— daan

[Martin]

Hi daan,

Thanks for replying.

This has occurred when using a whole world platte carree image input as a PSD, and the output either as TIF or PSB. However, I just found out that if I input TIF then it comes out fine in both TIF and PSB !
Its also occured when mounting PSB image onto a "general reprojection database", and I also just found out that that too works fine with TIF input.
Cant believe I hadn't spotted that before. Looks like Ill be using TIF all the way from now on. Thanks.

Martin

[daan]

Thanks, Martin. That’s a little concerning, given that TIFF won’t accommodate the very large files that PSD handles and therefore can’t always be a work-around.

I’ll poke around to see why the PSD converter might be introducing this sort of trouble. Is the color space in your image RGB or CMYK? And does it come with color management?

Thanks!
— daan

[Martin]

No problem, Im using Photoshop CS3, and I the colour space is RGB and under colour management policies it says: Preserve Embedded Profiles.
Best of luck!