Why is this (noisy k plate)?


samarsh@...
 

--- In colortheory@y..., APR <amerphoto@i...> wrote:
Why is this?

I'm just expermenting.
APR, this is where most 'breakthroughs' are made. <g>

I take an old Tin Type photo.
Can you explain? Film or print? Colour or g/scale? An old tin type
photo means nothing to me.

I then adjusted in Lab for contrast.
Have you tried an adjustment layer set to luminosity, or a regular
curve with the fade to luminosity command,or duping the layer
curving then blending in luminosity mode or etc...

I then change to CMYK and
I deleted the Black channel
(since I see a lot of scratches and spots in Black channel)
Usually nose and jpeg artifact reduction/removal is attempted in
the AB channels of LAB, or in RGB/CMYK in a duped layer set to
color blend mode. I like to combine both methods, so the
luminosity of the original is not altered, only colour.

These changes then 'migrate' into the RGB or CMYK channels,
providing cleaner noise reduction than direct removal of noise.

...and all of a sudden 90 percent of scratches and spots are
gone.
It even looks sharper than the original without sharping it.
Also, I see more detail.
I would expect this to be the case for the B or Y channels - not the
K as such...but the CMY inks can really hide artifacts in the K
channel (with a light black GCR or UCR sep). This does not
excuse a messy plate - but the K is a bit different to others.

It would REALLY depend on the image and output.

How is the CMYK conversion performed? What type of built in
setting or profile is in use? What settings, such as BPC etc.


So, why is that?
Why are the scrathces and spots gone?
Why is it more sharper and has more detail.
What is it about removing the black channel that
causes this?
Can you post the original on the web, or email it off list to me?

I then go to Greyscale mode and back to LAB and CMYK curves
to bring back the contrast and blacks.
I personally would not do this in production, but I understand that
you are playing.

I just want to know, what is the Black channel all about?
Basically, CMY do not make a nice solid rich black, but a redish
muddy dark brown. The K black plate adds definition or Key.
There are many ways to produce black, being dependent on
output and image content. The K plate is you biggest enemy and
ally when it comes to four colour print.

Hope this helps,

Stephen Marsh.


Hector Davila
 

http://home.netcom.com/~amerphoto/TinType/
http://home.netcom.com/~amerphoto/TinType/tintype.html

The third photo I deleted the CMYK Black channel.
Tintype-3.JPG

samarsh@... wrote:


--- In colortheory@y..., APR <amerphoto@i...> wrote:
Why is this?

I'm just expermenting.
APR, this is where most 'breakthroughs' are made. <g>

I take an old Tin Type photo.
Can you explain? Film or print? Colour or g/scale? An old tin type
photo means nothing to me.

I then adjusted in Lab for contrast.
Have you tried an adjustment layer set to luminosity, or a regular
curve with the fade to luminosity command,or duping the layer
curving then blending in luminosity mode or etc...

I then change to CMYK and
I deleted the Black channel
(since I see a lot of scratches and spots in Black channel)
Usually nose and jpeg artifact reduction/removal is attempted in
the AB channels of LAB, or in RGB/CMYK in a duped layer set to
color blend mode. I like to combine both methods, so the
luminosity of the original is not altered, only colour.

These changes then 'migrate' into the RGB or CMYK channels,
providing cleaner noise reduction than direct removal of noise.

...and all of a sudden 90 percent of scratches and spots are
gone.
It even looks sharper than the original without sharping it.
Also, I see more detail.
I would expect this to be the case for the B or Y channels - not the
K as such...but the CMY inks can really hide artifacts in the K
channel (with a light black GCR or UCR sep). This does not
excuse a messy plate - but the K is a bit different to others.

It would REALLY depend on the image and output.

How is the CMYK conversion performed? What type of built in
setting or profile is in use? What settings, such as BPC etc.


So, why is that?
Why are the scrathces and spots gone?
Why is it more sharper and has more detail.
What is it about removing the black channel that
causes this?
Can you post the original on the web, or email it off list to me?

I then go to Greyscale mode and back to LAB and CMYK curves
to bring back the contrast and blacks.
I personally would not do this in production, but I understand that
you are playing.

I just want to know, what is the Black channel all about?
Basically, CMY do not make a nice solid rich black, but a redish
muddy dark brown. The K black plate adds definition or Key.
There are many ways to produce black, being dependent on
output and image content. The K plate is you biggest enemy and
ally when it comes to four colour print.

Hope this helps,

Stephen Marsh.


To unsubscribe from this group, send an email to:
colortheory-unsubscribe@...



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


samarsh@...
 

--- In colortheory@y..., APR <amerphoto@i...> wrote:
http://home.netcom.com/~amerphoto/TinType/
http://home.netcom.com/~amerphoto/TinType/tintype.html

The third photo I deleted the CMYK Black channel.
Tintype-3.JPG
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
image.

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
etc.

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

Sincerely,

Stephen Marsh.