Re: Why is this (noisy k plate)?


--- In colortheory@y..., APR <amerphoto@i...> wrote:

The third photo I deleted the CMYK Black channel.
APR - Now that I know what an 'old tin type' photo looks like, I
know why the noise etc found it's way into the K plate.

This image is RGB greyscale.

Any move to CMYK will put some of the detail in CMY - and some
in the K channel. Since all tones are neutral, the separation
method is critical in deciding the type of black plate and how
heavy it is.

Say for example you separated with GCR Max K separation type -
if you deleted the K channel 99% of your image would be gone!

The recent thread on UCR and GCR briefly explains all this.
Dans book goes deeper.

Since your image is _totally_ made from neutral RGB values,
how heavy the black plate is will depend on your separation
settings, which I originally asked about - which you did not reply
on. The image you refer to as CMYK is actually RGB, so I still
have no idea of your separation method.

But this probably does not matter.

If you can find a use for separation tricks which help your
retouching or restoration, then use them. I personally would not
convert a g/scale RGB file to an unknown CMYK variant and then
delete the K channel, in the attempt to restore an old damaged

The K plate when specially separated may provide the start for a
good selection mask for retouching in the original RGB...

Dans recent description on using lighten/darken blend modes
and blurring might be good as well, with or without masks. Other
noise filtering might be used as well, such as despeckle,
dustnscratch and median. Smart noise might be added to add
some life after retouching.

The layer options blend if sliders can also mask based on
luminosity - which is really great for quickly blending corrections
into underlying tones, without manual masks. Luminosity layer
blending/masking is very powerful.

Even some of Dans books descreening tricks would help, as in
scanning hires and resampling down, blend modes and filtering

Good luck in the restoration. Greyscale has less Photoshop
correction options than a damaged full colour original.


Stephen Marsh.

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