Digital BW, The Print

As noted by a couple of forum members, the image files that have had
partitioning workflows -- specifically the VM curves -- applied to them can
show "combing" in the histogram.

While I have never identified this as a source of trouble in my prints, I do
try to avoid this apparent reduction of grayscale steps as much as possible.

One member (whose name, I apologize, I forget) noted that changing the size
of the image could smooth it out.

I have just taken a look at this suggested approach to smooth-out image
files.  Changing the size/pixel-count of the image does appear to eliminate
the combing in the histogram.

Likewise, changing the size of the image file after the partitioning/VM
curves have been applied seems to eliminate/smooth-out the combing.

My thanks to the member who shared the knowledge with us.  (I apologize for
not remembering names.  Concepts I can handle -- names I can't.)

Based on this experience, my VM workflow relative to this includes: working
at the scanner's native resolution as long as possible, and not changing the
size of the image until after I have done all my editing, saved the image,
converted to RGB, and applied the VM partitioning curves.

The very last step I now take is to change the size of the image in
Photoshop from the scanner's native resolution to my print size at 360 dpi.

When I check the histogram there is no combing.

I have not analyzed prints to see if I can see any difference.

Paul
http://www.PaulRoark.com

On 3/19/02 2:01 PM, "Paul Roark" <paul.roark@...> wrote:

> The very last step I now take is to change the size of the image in
> Photoshop from the scanner's native resolution to my print size at 360 dpi.
> 
> When I check the histogram there is no combing.
> 
> I have not analyzed prints to see if I can see any difference.

It is obvious why this eliminates combing. When you resize, Photoshop
interpolates between the discrete values that represent the teeth of the
comb to arrive at the pixel values for the new image.

For example, let's say you have two neighboring pixels, one with value 150
and one with value 175, and the image displays combing between these two
values. Downsampling will probably produce a pixel in this region of the
photograph with an intermediate value of around 165. Thus you now have some
pixels with the intermediate value where previously there were none.

The absence of combing in the resized image is not a sign that it's
'better', it's a sign that information has been lost. You could also
eliminate combing by applying a 1 or 2 pixel radius gaussian blur before
printing, but I don't suppose anyone is doing that.

-- 
John Brownlow

http://www.pinkheadedbug.com

Paul,

I was the one who suggested the reizing option for reducing/removing 
combing seen in work flows that incorporate curves adjustment layers. 
I have found this to be true even in global RGB (as opposed to RGB 
partitioned) curves. Visually, I find this does not produce any 
discernible effect on the final printed image.

Additonally (off-topic), I am working on using the VM inks without 
any partitioned curves. Instead I use a global RGB curve to control 
density, and use of the the following to control tone (1) using the 
magenta slider, and (2) using color adjustment layer (magenta bias). 
Both of these are doable, with #2 providing a more tone controlled 
image. I use a 1280 printer, and am finding less posterization with 
my work flow (once perfected).

Best wishes.

Shilesh

--- In DigitalBlackandWhiteThePrint@y..., "Paul Roark" 
<paul.roark@v...> wrote:
> As noted by a couple of forum members, the image files that have had
> partitioning workflows -- specifically the VM curves -- applied to 
them can
> show "combing" in the histogram.
> 
> While I have never identified this as a source of trouble in my 
prints, I do
> try to avoid this apparent reduction of grayscale steps as much as 
possible.
> 
> One member (whose name, I apologize, I forget) noted that changing 
the size
> of the image could smooth it out.
> 
> I have just taken a look at this suggested approach to smooth-out 
image
> files.  Changing the size/pixel-count of the image does appear to 
eliminate
> the combing in the histogram.
> 
> Likewise, changing the size of the image file after the 
partitioning/VM
> curves have been applied seems to eliminate/smooth-out the combing.
> 
> My thanks to the member who shared the knowledge with us.  (I 
apologize for
> not remembering names.  Concepts I can handle -- names I can't.)
> 
> Based on this experience, my VM workflow relative to this includes: 
working
> at the scanner's native resolution as long as possible, and not 
changing the
> size of the image until after I have done all my editing, saved the 
image,
> converted to RGB, and applied the VM partitioning curves.
> 
> The very last step I now take is to change the size of the image in
> Photoshop from the scanner's native resolution to my print size at 
360 dpi.

> 
> When I check the histogram there is no combing.
> 
> I have not analyzed prints to see if I can see any difference.
> 
> Paul
> http://www.PaulRoark.com

John,

You wrote:

>...
>The absence of combing in the resized image is not a sign that it's
>'better', it's a sign that information has been lost. ...

True.  Downsizing clearly eliminates information.  I suspect the information
lost is beyond what can be seen.

So, the problem and cure -- that is, both the "combing" and the downsizing
(that I would do anyway) -- are probably irrelevant to the ultimate image
quality of the print.  I found it was not worth my time to print over 360
dpi anyway.

Paul

_______________________-

  -----Original Message-----
  From: John Brownlow [mailto:lists@...]
  Sent: Tuesday, March 19, 2002 11:13 AM
  To: DigitalBlackandWhiteThePrint@yahoogroups.com
  Subject: Re: [Digital BW] Combing cure -- change size after the curves
areapplied


  On 3/19/02 2:01 PM, "Paul Roark" <paul.roark@...> wrote:

  > The very last step I now take is to change the size of the image in
  > Photoshop from the scanner's native resolution to my print size at 360
dpi.
  >
  > When I check the histogram there is no combing.
  >
  > I have not analyzed prints to see if I can see any difference.

  It is obvious why this eliminates combing. When you resize, Photoshop
  interpolates between the discrete values that represent the teeth of the
  comb to arrive at the pixel values for the new image.

  For example, let's say you have two neighboring pixels, one with value 150
  and one with value 175, and the image displays combing between these two
  values. Downsampling will probably produce a pixel in this region of the
  photograph with an intermediate value of around 165. Thus you now have
some
  pixels with the intermediate value where previously there were none.

  The absence of combing in the resized image is not a sign that it's
  'better', it's a sign that information has been lost. You could also
  eliminate combing by applying a 1 or 2 pixel radius gaussian blur before
  printing, but I don't suppose anyone is doing that.

  --
  John Brownlow

  http://www.pinkheadedbug.com


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[Non-text portions of this message have been removed]

Paul, John,

While the resizing may smooth out the histogram I am concerned that it is a
case where the original image information was lost due to over manipulation
and you wind up replacing that lost information during resizing with
artificial information.

Resizing may be an improvement over not resizing but I would want to work
very hard at not losing the data to start with.

I realize that a certain amount of data lose in 8-bit mode may have no
effect on the final print. Pushed to some point it will give you problems
and at that point I think if is better to go back to square one and rethink
your adjustments doing as much as you can in 16-bit space. I had one touchy
image that I wound up adjusting as 8 separate 16-bit files, applying the RGB
separation curve to each file, converting to  8-bit and then combining all
of them with layer masks for the final file. A lot of work but it did the
trick.

Martin

----- Original Message -----
From: "Paul Roark" <paul.roark@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Tuesday, March 19, 2002 1:58 PM
Subject: RE: [Digital BW] Combing cure -- change size after the curves are
applied


> John,
>
> You wrote:
>
> >...
> >The absence of combing in the resized image is not a sign that it's
> >'better', it's a sign that information has been lost. ...
>
> True.  Downsizing clearly eliminates information.  I suspect the
information
> lost is beyond what can be seen.
>
> So, the problem and cure -- that is, both the "combing" and the downsizing
> (that I would do anyway) -- are probably irrelevant to the ultimate image
> quality of the print.  I found it was not worth my time to print over 360
> dpi anyway.
>
> Paul
>
> _______________________-
>   -----Original Message-----
>   From: John Brownlow [mailto:lists@...]
>   Sent: Tuesday, March 19, 2002 11:13 AM
>   To: DigitalBlackandWhiteThePrint@yahoogroups.com
>   Subject: Re: [Digital BW] Combing cure -- change size after the curves
> areapplied
>
>
>   On 3/19/02 2:01 PM, "Paul Roark" <paul.roark@...> wrote:
>
>   > The very last step I now take is to change the size of the image in
>   > Photoshop from the scanner's native resolution to my print size at 360
> dpi.
>   >
>   > When I check the histogram there is no combing.
>   >
>   > I have not analyzed prints to see if I can see any difference.
>
>   It is obvious why this eliminates combing. When you resize, Photoshop
>   interpolates between the discrete values that represent the teeth of the
>   comb to arrive at the pixel values for the new image.
>
>   For example, let's say you have two neighboring pixels, one with value
150
>   and one with value 175, and the image displays combing between these two
>   values. Downsampling will probably produce a pixel in this region of the
>   photograph with an intermediate value of around 165. Thus you now have
> some
>   pixels with the intermediate value where previously there were none.
>
>   The absence of combing in the resized image is not a sign that it's
>   'better', it's a sign that information has been lost. You could also
>   eliminate combing by applying a 1 or 2 pixel radius gaussian blur before
>   printing, but I don't suppose anyone is doing that.
>
>   --
>   John Brownlow
>
>   http://www.pinkheadedbug.com
>
>
>         Yahoo! Groups Sponsor
>               ADVERTISEMENT
>
>
>
>
>   Please visit the Group Homepage to check the Files, Bookmarks, Polls and
> other resources as they are often being updated. The page is at:
>
>   http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
>   Please follow these basic guidelines:
>   - Include your full name with your message.
>   - Include the address of your website, if you have one.
>   - As threads develop, trim off excess portions of earlier messages to
keep
> them short.
>   - As the topic of a thread changes remember to change the subject
header.
>   - Good manners are required at all time. No personal attacks or
"flames."
>   - Complete your Yahoo profile.
>   - Before posting a question, search the message archives and the various
> resources on the homepage.
>
>
>
>
>   Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> Please visit the Group Homepage to check the Files, Bookmarks, Polls and
other resources as they are often being updated. The page is at:
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> Please follow these basic guidelines:
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> - As threads develop, trim off excess portions of earlier messages to keep
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> - Good manners are required at all time. No personal attacks or "flames."
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> - Before posting a question, search the message archives and the various
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>
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>

On 3/19/02 paul.roark@... wrote:

>>The absence of combing in the resized image is not a sign that it's
>>'better', it's a sign that information has been lost. ...
>
>True.  Downsizing clearly eliminates information.  I suspect the information
>lost is beyond what can be seen.
>
>So, the problem and cure -- that is, both the "combing" and the downsizing
>(that I would do anyway) -- are probably irrelevant to the ultimate image
>quality of the print.  I found it was not worth my time to print over 360
>dpi anyway.

I think you are probably right on all counts. It depends what driver you
are printing through but my point is that the extra step to downsample to
360 dpi is at best unnecessary. 

However it probably doesn't have any impact on image quality either way.
Re dpi, in tests I *thought* I could see some marginal improvements in
image quality through the piezo drivers beyond 360 dpi but frankly I
wouldn't be remotely confident about picking the higher rez images blindfold.

-- 
John Brownlow

http://www.pinkheadedbug.com

I can't tell neither who nor where, but I remember someone stating that
sending files with a dpi number over 360 (or some other threshold) to the
printer is a waste of time, since the printer's driver (at least Epson own
driver, don't know about Piezo) is going to discard anyway the
extra-information (i.e., it's downsampling the file). Therefore, apart from
efficiency issues (sending smaller files), it's better to downsample in
Photoshop, that has a better algorithm.
Can someone confirm this, or is it yet another digital legend?
 
Alessandro Pardi

-----Original Message-----
From: John Brownlow [mailto:lists@...]
Sent: mercoledì 20 marzo 2002 04.27
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: RE: [Digital BW] Combing cure -- change size after the curves are
applied


On 3/19/02 paul.roark@... wrote:

>>The absence of combing in the resized image is not a sign that it's
>>'better', it's a sign that information has been lost. ...
>
>True.  Downsizing clearly eliminates information.  I suspect the
information
>lost is beyond what can be seen.
>
>So, the problem and cure -- that is, both the "combing" and the downsizing
>(that I would do anyway) -- are probably irrelevant to the ultimate image
>quality of the print.  I found it was not worth my time to print over 360
>dpi anyway.

I think you are probably right on all counts. It depends what driver you
are printing through but my point is that the extra step to downsample to
360 dpi is at best unnecessary. 

However it probably doesn't have any impact on image quality either way.
Re dpi, in tests I *thought* I could see some marginal improvements in
image quality through the piezo drivers beyond 360 dpi but frankly I
wouldn't be remotely confident about picking the higher rez images
blindfold.

-- 
John Brownlow

http://www.pinkheadedbug.com <http://www.pinkheadedbug.com> 



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<http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint> 

Please follow these basic guidelines:
- Include your full name with your message.
- Include the address of your website, if you have one.
- As threads develop, trim off excess portions of earlier messages to keep
them short.
- As the topic of a thread changes remember to change the subject header.
- Good manners are required at all time. No personal attacks or "flames."
- Complete your Yahoo profile.
- Before posting a question, search the message archives and the various
resources on the homepage. 




Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service
<http://docs.yahoo.com/info/terms/> . 




[Non-text portions of this message have been removed]

I'd agree that a large file size is probably a waste of time, but I'm not so 
sure that Photoshop has better algorithms than the Epson drivers.

Remember that a number of different things are going on at the same time when 
you send a file to the printer. As well as downsizing or upsizing to fit the 
image to the desired reproduction size, it is also doing the internal CMYK 
conversion and dithering to match the dot patterns and ink colours in use.

My gut feeling is that doing just one of those actions in isolation is going 
to be less efficient than giving the driver the opportunity to optimise every 
factor at once.

This gut feeling is backed up by the fact that I get perfectly satisfactory 
results IMO by just trusting to the Epson drivers. 

I never print from Photoshop, but nstead use Paint Shop Pro as I am fairly 
sure that it does no resizing of its own, just passing the expected 
magnification factor to the drivers along with the image data.

On Thursday 21 Mar 2002 9:17 am, Alessandro Pardi wrote:
> I can't tell neither who nor where, but I remember someone stating that
> sending files with a dpi number over 360 (or some other threshold) to the
> printer is a waste of time, since the printer's driver (at least Epson own
> driver, don't know about Piezo) is going to discard anyway the
> extra-information (i.e., it's downsampling the file). Therefore, apart from
> efficiency issues (sending smaller files), it's better to downsample in
> Photoshop, that has a better algorithm.
> Can someone confirm this, or is it yet another digital legend?
>
> Alessandro Pardi
>
> -----Original Message-----
> From: John Brownlow [mailto:lists@...]
> Sent: mercoled\ufffd 20 marzo 2002 04.27
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: RE: [Digital BW] Combing cure -- change size after the curves are
> applied
>
> On 3/19/02 paul.roark@... wrote:
> >>The absence of combing in the resized image is not a sign that it's
> >>'better', it's a sign that information has been lost. ...
> >
> >True.  Downsizing clearly eliminates information.  I suspect the
>
> information
>
> >lost is beyond what can be seen.
> >
> >So, the problem and cure -- that is, both the "combing" and the downsizing
> >(that I would do anyway) -- are probably irrelevant to the ultimate image
> >quality of the print.  I found it was not worth my time to print over 360
> >dpi anyway.
>
> I think you are probably right on all counts. It depends what driver you
> are printing through but my point is that the extra step to downsample to
> 360 dpi is at best unnecessary.
>
> However it probably doesn't have any impact on image quality either way.
> Re dpi, in tests I *thought* I could see some marginal improvements in
> image quality through the piezo drivers beyond 360 dpi but frankly I
> wouldn't be remotely confident about picking the higher rez images
> blindfold.

> I can't tell neither who nor where, but I remember someone stating that
> sending files with a dpi number over 360 (or some other threshold) to the
> printer is a waste of time, since the printer's driver (at least Epson own
> driver, don't know about Piezo) is going to discard anyway the
> extra-information (i.e., it's downsampling the file). Therefore,
> apart from
> efficiency issues (sending smaller files), it's better to downsample in
> Photoshop, that has a better algorithm.
> Can someone confirm this, or is it yet another digital legend?
>
> Alessandro Pardi

Hi Alessandro,

The Piezo driver does not throw the data away, and I do believe you are
correct, that the Epson driver does not benefit from it...what it does with
it, I can't tell you.  I would suggest that even if the Epson driver throws
it away, that it is better, as far as image quality goes, to send it to the
printer anyway.  Every time you re-size an image, you interpolate or
decimate the data, which degrades it.

I would suggest you do a few test images and see for your self.

Regards,

Austin

Interesting. Are you using the magenta slider in the printer dialog? 
If possible, could you outline the steps you take? 

Chris Hargens

--- In DigitalBlackandWhiteThePrint@y..., "janishilesh" 
<shilesh.jani@s...> wrote:
> Additonally (off-topic), I am working on using the VM inks without 
> any partitioned curves. Instead I use a global RGB curve to control 
> density, and use of the the following to control tone (1) using the 
> magenta slider, and (2) using color adjustment layer (magenta 
bias). 
> Both of these are doable, with #2 providing a more tone controlled 
> image. I use a 1280 printer, and am finding less posterization with 
> my work flow (once perfected).
> 
> Best wishes.
> 
> Shilesh
> 
> --- In DigitalBlackandWhiteThePrint@y..., "Paul Roark" 
> <paul.roark@v...> wrote:
> > As noted by a couple of forum members, the image files that have 
had
> > partitioning workflows -- specifically the VM curves -- applied 
to 
> them can
> > show "combing" in the histogram.
> > 
> > While I have never identified this as a source of trouble in my 
> prints, I do
> > try to avoid this apparent reduction of grayscale steps as much 
as 
> possible.
> > 
> > One member (whose name, I apologize, I forget) noted that 
changing 
> the size
> > of the image could smooth it out.
> > 
> > I have just taken a look at this suggested approach to smooth-out 
> image
> > files.  Changing the size/pixel-count of the image does appear to 
> eliminate
> > the combing in the histogram.
> > 
> > Likewise, changing the size of the image file after the 
> partitioning/VM
> > curves have been applied seems to eliminate/smooth-out the 
combing.
> > 
> > My thanks to the member who shared the knowledge with us.  (I 
> apologize for
> > not remembering names.  Concepts I can handle -- names I can't.)
> > 
> > Based on this experience, my VM workflow relative to this 
includes: 
> working
> > at the scanner's native resolution as long as possible, and not 
> changing the
> > size of the image until after I have done all my editing, saved 
the 
> image,
> > converted to RGB, and applied the VM partitioning curves.
> > 
> > The very last step I now take is to change the size of the image 
in
> > Photoshop from the scanner's native resolution to my print size 
at 

> 360 dpi.
> > 
> > When I check the histogram there is no combing.
> > 
> > I have not analyzed prints to see if I can see any difference.
> > 
> > Paul
> > http://www.PaulRoark.com