Digital BW, The Print

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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