Digital BW, The Print

There has been some discussion of this topic before herein but I guess
I failed to take real notice of it until the other day when I was
amazed to see a very rough edge to an angled black line on a print. 
This line appeared as a very smooth edge on my screen.  This effect
appeared on any high contrast edge that ISN'T parallel to or
perpendicular to the image edge – i.e. it slopes or is angled across
the image.  The line was actually the edge of some large text
(specifically the letter `A') that I'd added to an image in Photoshop.
 This was sufficiently bad to be visible in the print to the naked eye
– and once noticed, it was obvious.  It's not some micro effect that
only a loupe would reveal.  Once I'd noticed it in the letter A I
realised it was in all of the sloping parts of the text AND in the
image area wherever there was a black or very dark sloping edge
against a much lighter area.

I tried all sorts of things including checking the head alignment, and
eventually printing on two different printers.  I then realised it
must be an artefact of the conversion by the Epson Driver from the
image resolution (300ppi) to whatever resolution the printer uses. 
The thing that made me realise this was the fact that the exact same
problem was present when I made the same print from the same image
file sent to two different printers – a 2100 and a 4800.

For some images I've been using 300ppi as a standard for outputting
files to print.  But I remembered reading something about Epson
printers using multiples of 360ppi in the driver.  So I then tried the
same file resampled in Photoshop from 300ppi to 360ppi.  It totally
cured the rough jagged edge problem in the printed image.  I've since
confirmed by other tests that this was not simply as a result of the
resampling.  This problem seems to occur when you use some simple
fraction of 360ppi.  For example my 300ppi is 5/6 of the 360ppi, or
360ppi is 1/5 more than the 300ppi.  I haven't noticed this problem
when my image ppi is larger AND not a simple fraction of 360ppi.

I know that some people use 300ppi as it is often said that this is
the point at which pixels are no longer visible to the naked eye.  I
wonder whether your output to print is as sharp as it could be.  My
experience suggests that if you are printing from an image at 300ppi
using the Epson Driver, try resampling it to 360ppi in Photoshop for
printing existing images, and work at 360 ppi for future images.

I'm writing this up so that if there are others who've puzzled over
the cause of these jagged hard edges then at least there's a possible
explanation and cure available.  I somehow think that I can't be the
only printer who hasn't understood this and acted on it before!

I'm sure the maths used in resampling will explain this fully, but for
me avoiding it is what really matters.

Steve Gledhill
http://www.virtuallygrey.co.uk/

Actually if you ever get that problem again, just change the res to  
301ppi or 299 ppi and it will probably go away. I do not know the  
reason - but it works. BTW I have always done the 360 ppi thing and  
find it makes a difference on what size print you are making. A  
larger print can do with lower setting (288 ppi) with no difference  
in quality, and things RIP faster. Might depend on driver or RIP  
being used although.
Mark


On Sep 17, 2005, at 9:08 AM, Steve Gledhill wrote:

> There has been some discussion of this topic before herein but I guess
> I failed to take real notice of it until the other day when I was
> amazed to see a very rough edge to an angled black line on a print.
> This line appeared as a very smooth edge on my screen.  This effect
> appeared on any high contrast edge that ISN'T parallel to or
> perpendicular to the image edge � i.e. it slopes or is angled across
> the image.  The line was actually the edge of some large text
> (specifically the letter `A') that I'd added to an image in Photoshop.
> This was sufficiently bad to be visible in the print to the naked eye
> � and once noticed, it was obvious.  It's not some micro effect that
> only a loupe would reveal.  Once I'd noticed it in the letter A I
> realised it was in all of the sloping parts of the text AND in the
> image area wherever there was a black or very dark sloping edge
> against a much lighter area.
>
> I tried all sorts of things including checking the head alignment, and
> eventually printing on two different printers.  I then realised it
> must be an artefact of the conversion by the Epson Driver from the
> image resolution (300ppi) to whatever resolution the printer uses.
> The thing that made me realise this was the fact that the exact same
> problem was present when I made the same print from the same image
> file sent to two different printers � a 2100 and a 4800.
>
> For some images I've been using 300ppi as a standard for outputting
> files to print.  But I remembered reading something about Epson
> printers using multiples of 360ppi in the driver.  So I then tried the
> same file resampled in Photoshop from 300ppi to 360ppi.  It totally
> cured the rough jagged edge problem in the printed image.  I've since
> confirmed by other tests that this was not simply as a result of the
> resampling.  This problem seems to occur when you use some simple
> fraction of 360ppi.  For example my 300ppi is 5/6 of the 360ppi, or
> 360ppi is 1/5 more than the 300ppi.  I haven't noticed this problem
> when my image ppi is larger AND not a simple fraction of 360ppi.
>
> I know that some people use 300ppi as it is often said that this is
> the point at which pixels are no longer visible to the naked eye.  I
> wonder whether your output to print is as sharp as it could be.  My
> experience suggests that if you are printing from an image at 300ppi
> using the Epson Driver, try resampling it to 360ppi in Photoshop for
> printing existing images, and work at 360 ppi for future images.
>
> I'm writing this up so that if there are others who've puzzled over
> the cause of these jagged hard edges then at least there's a possible
> explanation and cure available.  I somehow think that I can't be the
> only printer who hasn't understood this and acted on it before!
>
> I'm sure the maths used in resampling will explain this fully, but for
> me avoiding it is what really matters.
>
> Steve Gledhill
> http://www.virtuallygrey.co.uk/
>
>
>
>
>
>
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[Non-text portions of this message have been removed]

I understood good practice to be at least always use a clean factor of the
print resolution ie 2880/4=720, 2880/5=576, 2880/6=480, 2880/8=360,
2880/9=320, 2880/10=288.  The 300 simply came about as a result of the old
2x150lpi (as Bob Frost noted in an earlier post).

> From: Steve Gledhill <stephengledhill@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Sat, 17 Sep 2005 13:08:42 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] 300ppi vs 360ppi
> 
> There has been some discussion of this topic before herein but I guess
> I failed to take real notice of it until the other day when I was
> amazed to see a very rough edge to an angled black line on a print.
> This line appeared as a very smooth edge on my screen.  This effect
> appeared on any high contrast edge that ISN'T parallel to or
> perpendicular to the image edge ­ i.e. it slopes or is angled across
> the image.  The line was actually the edge of some large text
> (specifically the letter `A') that I'd added to an image in Photoshop.
>  This was sufficiently bad to be visible in the print to the naked eye
> ­ and once noticed, it was obvious.  It's not some micro effect that
> only a loupe would reveal.  Once I'd noticed it in the letter A I
> realised it was in all of the sloping parts of the text AND in the
> image area wherever there was a black or very dark sloping edge
> against a much lighter area.
> 
> I tried all sorts of things including checking the head alignment, and
> eventually printing on two different printers.  I then realised it
> must be an artefact of the conversion by the Epson Driver from the
> image resolution (300ppi) to whatever resolution the printer uses.
> The thing that made me realise this was the fact that the exact same
> problem was present when I made the same print from the same image
> file sent to two different printers ­ a 2100 and a 4800.
> 
> For some images I've been using 300ppi as a standard for outputting
> files to print.  But I remembered reading something about Epson
> printers using multiples of 360ppi in the driver.  So I then tried the
> same file resampled in Photoshop from 300ppi to 360ppi.  It totally
> cured the rough jagged edge problem in the printed image.  I've since
> confirmed by other tests that this was not simply as a result of the
> resampling.  This problem seems to occur when you use some simple
> fraction of 360ppi.  For example my 300ppi is 5/6 of the 360ppi, or
> 360ppi is 1/5 more than the 300ppi.  I haven't noticed this problem
> when my image ppi is larger AND not a simple fraction of 360ppi.
> 
> I know that some people use 300ppi as it is often said that this is
> the point at which pixels are no longer visible to the naked eye.  I
> wonder whether your output to print is as sharp as it could be.  My
> experience suggests that if you are printing from an image at 300ppi
> using the Epson Driver, try resampling it to 360ppi in Photoshop for
> printing existing images, and work at 360 ppi for future images.
> 
> I'm writing this up so that if there are others who've puzzled over
> the cause of these jagged hard edges then at least there's a possible
> explanation and cure available.  I somehow think that I can't be the
> only printer who hasn't understood this and acted on it before!
> 
> I'm sure the maths used in resampling will explain this fully, but for
> me avoiding it is what really matters.
> 
> Steve Gledhill
> http://www.virtuallygrey.co.uk/

Steve Kale wrote:

> I understood good practice to be at least always use a clean factor of the
> print resolution ie 2880/4=720, 2880/5=576, 2880/6=480, 2880/8=360,
> 2880/9=320, 2880/10=288.  The 300 simply came about as a result of the old
> 2x150lpi (as Bob Frost noted in an earlier post).
>
My understanding is that the two are not related.

The output resolution, say 300 dpi, that you send the printer will be 
uprezed or downrezed by the driver to 360 dpi.

The print rez, say 1440, really controls how many ink dots the driver 
uses to create each pixel. And this is why the driver must resize your 
incoming 300 dpi data stream to 360 dpi - so that it can easily handle 
the math to represent the individual pixels, and the dither pattern it 
uses to "flow the tones" from one pixel to the next.

Most RIPs, being considerably larger and more sophisticated programs, 
don't need the resizing step. So I'm told.

I could be wrong though.
--
Bruce Watson

> From: Steve Kale
>
> I understood good practice to be at least always use a clean factor of the
> print resolution ie 2880/4=720, 2880/5=576, 2880/6=480, 2880/8=360,
> 2880/9=320, 2880/10=288.  The 300 simply came about as a result of the old
> 2x150lpi (as Bob Frost noted in an earlier post).

The stock Epson driver resamples everything to 720ppi for the desktop
models, 360ppi for the wide format models, and then dithers to the higher
dpi value. If you want complete control over the resampling, and don't want
to trust the Epson driver not to introduce aliasing, use an integral
subdivision of those numbers.

The old drivers used "nearest neighbor" for resampling, which was asking for
trouble. However, the most recent drivers include an edge smoothing option,
to eliminate aliasing when it upsamples. I haven't tested it to see how it
compares to other manual resampling techniques.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Steve,

I haven't printed at some of those resolutions, but I always understood that 
the numbers should be factors of 720ppi, the ppi that the printer uses for 
printing, not the dpi. So 360ppi is OK, as is 240 and 180, but not 480 or 
576. Easy to confirm by printing a set of black and white 1 pixel lines and 
looking for the aliasing patterns. Many give you a lovely 'tartan' like 
print (for those of you who know of Scotland).

Bob Frost.

----- Original Message ----- 
From: "Steve Kale" <stevekale@...>


I understood good practice to be at least always use a clean factor of the
print resolution ie 2880/4=720, 2880/5=576, 2880/6=480, 2880/8=360,
2880/9=320, 2880/10=288.  The 300 simply came about as a result of the old
2x150lpi (as Bob Frost noted in an earlier post).

What I don't get is, does this mean that you can really optimally
print only 4 or 5 different sized prints for a given file.  Say with a
given file you can print an 8x10 print at 720 ppi.  Then say you want
to crop it differently leaving the file smaller by 15%.  Does that
mean you can't print the file at the 8x10 size because it would no
longer print at 720 ppi (or 360 ppi)?  Or odes the printer dricer
automatically re-size file sent ot the printer to the optimal
resultion for the printer.  It would seem quite odd to me that a
proffessional quality printer would be so limited in effective print
sizes.  Or is the quality difference between printing at 360 ppi and
320 ppi in fact almost impossible to see?  I don't think I ever try to
print at 360 or 720 ppi.  I take the file as it comes and if I want an
8x10 or an 11x14 I print it to that size (using 1160 with CIS &
Piezotone inks).  I never really see any problems with the resolution,
detail, or quality of the print.

What shouls I be noticing in a print not printed at a multiple of 720
ppi that I am not seeing?


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Bob Frost"
<bob@f...> wrote:
> Steve,
> 
> I haven't printed at some of those resolutions, but I always
understood that 
> the numbers should be factors of 720ppi, the ppi that the printer
uses for 
> printing, not the dpi. So 360ppi is OK, as is 240 and 180, but not
480 or 
> 576. Easy to confirm by printing a set of black and white 1 pixel
lines and 
> looking for the aliasing patterns. Many give you a lovely 'tartan' like 
> print (for those of you who know of Scotland).
> 
> Bob Frost.
> 
> 
> ----- Original Message ----- 
> From: "Steve Kale" <stevekale@b...>
> 
> 
> I understood good practice to be at least always use a clean factor
of the
> print resolution ie 2880/4=720, 2880/5=576, 2880/6=480, 2880/8=360,
> 2880/9=320, 2880/10=288.  The 300 simply came about as a result of
the old
> 2x150lpi (as Bob Frost noted in an earlier post).

Hi Lotusm50:
I think you're making things much more complicated than they really are. 
Remember that Photoshop and any other competent image processing program can 
resize to any desired size and resolution (within the limits of available 
memory). I work in  Photoshop and I simply set the size to the dimensions I 
want and the resolution to the appropriate level (I had been using 300 with 
no problems but 360 seems to have some advantage) and let the program 
resample the image to match. In other words say I want 4.75 inches x 6.8 
inches final print size (which I did recently for replacing a faded "5x7"). 
I plug one of the dimensions (4.75) in to the Image/Image Size dialog box 
with 360 dpi as the resolution and check Constrain Proportions and Resample 
Image: bicubic and let it run.
There are lots of options, of course, but that's the basic drill.
Hope this helps...
Bert

katzung1@...
www.astronomy-images.com
www.visionlightgallery.com/katzung/

----- Original Message ----- 
From: "Lotusm50" <LotusM50@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, September 17, 2005 10:54 AM
Subject: Re: [Digital BW] 300ppi vs 360ppi


What I don't get is, does this mean that you can really optimally
print only 4 or 5 different sized prints for a given file.  Say with a
given file you can print an 8x10 print at 720 ppi.  Then say you want
to crop it differently leaving the file smaller by 15%.  Does that
mean you can't print the file at the 8x10 size because it would no
longer print at 720 ppi (or 360 ppi)?  Or odes the printer dricer
automatically re-size file sent ot the printer to the optimal
resultion for the printer.  It would seem quite odd to me that a
proffessional quality printer would be so limited in effective print
sizes.  Or is the quality difference between printing at 360 ppi and
320 ppi in fact almost impossible to see?  I don't think I ever try to
print at 360 or 720 ppi.  I take the file as it comes and if I want an
8x10 or an 11x14 I print it to that size (using 1160 with CIS &
Piezotone inks).  I never really see any problems with the resolution,
detail, or quality of the print.

What shouls I be noticing in a print not printed at a multiple of 720
ppi that I am not seeing?


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Bob Frost"
<bob@f...> wrote:
> Steve,
>
> I haven't printed at some of those resolutions, but I always
understood that
> the numbers should be factors of 720ppi, the ppi that the printer
uses for
> printing, not the dpi. So 360ppi is OK, as is 240 and 180, but not
480 or
> 576. Easy to confirm by printing a set of black and white 1 pixel
lines and

> looking for the aliasing patterns. Many give you a lovely 'tartan' like
> print (for those of you who know of Scotland).
>
> Bob Frost.
>
>

Lotusm50,
I think the problem that I described to start this thread is only
apparent when your chosen ppi is some simple fraction of 360ppi - as
is 300ppi.  When the ppi is some odd number like 327ppi or 941 ppi or
perhaps as suggested earlier in this thread 301ppi or 299ppi then the
maths involved in the driver resampling to the native printer
resolution (360 ppi / 720 ppi / ...) doesn't give rise to the 'jagged'
effects that I described.

So, I believe the answer to your question is "no".  You can print any
file at any ppi without the jaggies problem - as long as your file
isn't a simple fraction of 360ppi - like the 300ppi where I found my
problem.  You, like many people, may have never seen this problem, but
those who print 300ppi files should look carefully - you my find a
step improvement in your printing by the simple action of resampling
to 360ppi before printing.

Steve
http://www.virtuallygrey.co.uk/

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Lotusm50"
<LotusM50@s...> wrote:
> What I don't get is, does this mean that you can really optimally
> print only 4 or 5 different sized prints for a given file.  Say with a
> given file you can print an 8x10 print at 720 ppi.  Then say you want
> to crop it differently leaving the file smaller by 15%.  Does that
> mean you can't print the file at the 8x10 size because it would no
> longer print at 720 ppi (or 360 ppi)?  Or odes the printer dricer
> automatically re-size file sent ot the printer to the optimal
> resultion for the printer.  It would seem quite odd to me that a
> proffessional quality printer would be so limited in effective print
> sizes.  Or is the quality difference between printing at 360 ppi and
> 320 ppi in fact almost impossible to see?  I don't think I ever try to
> print at 360 or 720 ppi.  I take the file as it comes and if I want an
> 8x10 or an 11x14 I print it to that size (using 1160 with CIS &
> Piezotone inks).  I never really see any problems with the resolution,
> detail, or quality of the print.
> 
> What shouls I be noticing in a print not printed at a multiple of 720
> ppi that I am not seeing?
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Bob Frost"
> <bob@f...> wrote:
> > Steve,
> > 
> > I haven't printed at some of those resolutions, but I always
> understood that 
> > the numbers should be factors of 720ppi, the ppi that the printer
> uses for 
> > printing, not the dpi. So 360ppi is OK, as is 240 and 180, but not
> 480 or 
> > 576. Easy to confirm by printing a set of black and white 1 pixel
> lines and 
> > looking for the aliasing patterns. Many give you a lovely 'tartan'
like 

> > print (for those of you who know of Scotland).
> > 
> > Bob Frost.
> > 
> > 
> > ----- Original Message ----- 
> > From: "Steve Kale" <stevekale@b...>
> > 
> > 
> > I understood good practice to be at least always use a clean factor
> of the
> > print resolution ie 2880/4=720, 2880/5=576, 2880/6=480, 2880/8=360,
> > 2880/9=320, 2880/10=288.  The 300 simply came about as a result of
> the old
> > 2x150lpi (as Bob Frost noted in an earlier post).

I think its very much like a moire pattern or aliasing.  All the Epson drivers
effectively resample the image to 360 or 720 ppi.  With a straight diagonal
line its likely you would see a jagged pattern of aliasing.  Exact multiples of 
360 or completely odd numbers would be probably be all right.  The 301
may be slightly jagged but won't have a pattern in it so your eye doesn't
object to it.

Roy

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Steve Gledhill" 
<stephengledhill@y...> wrote:

> Lotusm50,
> I think the problem that I described to start this thread is only
> apparent when your chosen ppi is some simple fraction of 360ppi - as
> is 300ppi.  When the ppi is some odd number like 327ppi or 941 ppi or
> perhaps as suggested earlier in this thread 301ppi or 299ppi then the
> maths involved in the driver resampling to the native printer
> resolution (360 ppi / 720 ppi / ...) doesn't give rise to the 'jagged'
> effects that I described.
> 
> So, I believe the answer to your question is "no".  You can print any
> file at any ppi without the jaggies problem - as long as your file
> isn't a simple fraction of 360ppi - like the 300ppi where I found my
> problem.  You, like many people, may have never seen this problem, but
> those who print 300ppi files should look carefully - you my find a
> step improvement in your printing by the simple action of resampling
> to 360ppi before printing.
> 
> Steve
> http://www.virtuallygrey.co.uk/
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Lotusm50"
> <LotusM50@s...> wrote:
> > What I don't get is, does this mean that you can really optimally
> > print only 4 or 5 different sized prints for a given file.  Say with a
> > given file you can print an 8x10 print at 720 ppi.  Then say you want
> > to crop it differently leaving the file smaller by 15%.  Does that
> > mean you can't print the file at the 8x10 size because it would no
> > longer print at 720 ppi (or 360 ppi)?  Or odes the printer dricer
> > automatically re-size file sent ot the printer to the optimal
> > resultion for the printer.  It would seem quite odd to me that a
> > proffessional quality printer would be so limited in effective print
> > sizes.  Or is the quality difference between printing at 360 ppi and
> > 320 ppi in fact almost impossible to see?  I don't think I ever try to
> > print at 360 or 720 ppi.  I take the file as it comes and if I want an
> > 8x10 or an 11x14 I print it to that size (using 1160 with CIS &
> > Piezotone inks).  I never really see any problems with the resolution,
> > detail, or quality of the print.
> > 
> > What shouls I be noticing in a print not printed at a multiple of 720
> > ppi that I am not seeing?
> > 
> > 
> > --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Bob Frost"
> > <bob@f...> wrote:
> > > Steve,
> > > 
> > > I haven't printed at some of those resolutions, but I always
> > understood that 
> > > the numbers should be factors of 720ppi, the ppi that the printer
> > uses for 
> > > printing, not the dpi. So 360ppi is OK, as is 240 and 180, but not
> > 480 or 
> > > 576. Easy to confirm by printing a set of black and white 1 pixel
> > lines and 
> > > looking for the aliasing patterns. Many give you a lovely 'tartan'
> like 
> > > print (for those of you who know of Scotland).
> > > 
> > > Bob Frost.
> > > 
> > > 
> > > ----- Original Message ----- 
> > > From: "Steve Kale" <stevekale@b...>
> > > 
> > > 
> > > I understood good practice to be at least always use a clean factor
> > of the
> > > print resolution ie 2880/4=720, 2880/5=576, 2880/6=480, 2880/8=360,
> > > 2880/9=320, 2880/10=288.  The 300 simply came about as a result of
> > the old
> > > 2x150lpi (as Bob Frost noted in an earlier post).