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Re: filmscanners: Figuring out size & resolution




--- RogerMillerPhoto@aol.com wrote:
> There's another value that has to do
> with how many dpi the 
> printer actually prints on paper, such as 1440 dpi. 
> But that value is 
> printer specific.

Good to point that out.

> My Epson 2000P doesn't even let
> me set that value.  It 
> gives me a choice of printing at "photo quality"
> speed or "high speed" and 
> adjusts the number of "dots" on the paper
> accordingly. 

We probably don't have the same driver. Anyway, with
my driver in the 'main' field of the print dialog I
can chose between 'automatic' and 'custom'. Automatic
only lets me chose between 'quality' and 'fast'. When
I chose 'custom' and configure the settings I can
specify the dpi incl. other settings.

> My recommendation is 
> that you tell your printer to print on paper at the
> highest number of dots 
> per inch your printer is capable of (1440?) so as to
> get the best "photo 
> quality" and that you send the image to the printer
> at 300 dpi.

That's exactly what I do. But the highest resolution
might not always be the best setting depending on the
paper used. On some (cheaper) paper I seem to get
worse result with the max setting.

> Most printers are happy if they are fed data at a
> "density" of 300 dpi.  With 
> less than that the print quality suffers.  With more
> dpi than that, it's just 
> a waste of good pixels and the print quality isn't
> any better than if 300 dpi 
> were used.  I've read on this list that some of the
> cheaper printers don't 
> improve past about 240 dpi and there are some that
> don't stop improving until 
> you pass 360 dpi.  But a good rule of thumb is to
> use something close to 300 
> dpi.
>

 
> But, suppose you want
> to an 8x12 print.  Divide 
> 4000 by 8 (or 6000 by 12) and you find that you'll
> be sending 500 dpi to the 
> printer.  That's more dpi than you really need, but
> it won't hurt anything.  

I am not sure about that. If you send more dpi the
printer (software?) has to downsample it. You might
get better results if you let photoshop doing that.
One reason for my thinking is that PS has better
algorithms. But more important the sharpening should
be done on the final resolution. So if you have too
many dpi you first do sharpening and then downsampling
instead of downsampling and then sharpening. I have to
admit though that I never made any tests but always
first downsample to 300dpi.

One other reason why to keep the size of the printed
data down is to reduce the amount of data that has to
be processed and sent to the printer.

> (I've heard on this list that using more dpi than
> necessary uses more ink, 
> but I don't think that's true.  Maybe someone on the
> list can enlighten me.)  

Well, not sure about that but there might be some
truth in that statement. When you set the printer to
higher dpi it will print more pixels per inch. On one
hand this will increase quality because now the
printer can use more micro pixels to generate one
pixel (the printer uses CMYK to produce 1 pixel. Some
printers add another two colors which does increase
accurecy further. Imagine you have a color that is
between C and M. If you have an additional color that
represents the value between C and M you need only one
single micro-pixel. If you don't have it you need a C
and M micro-pixel.). On the other hand printing more
micro-pixels will use up more ink IF the droplet size
is kept the same. Maybe the printer actually does
decrease the droplet size for higher dpi but I have
the impression this does not happen in a linear (or
x^2) ratio. One indication might be that on regular
paper the paper gets more 'currly' with higher dpi
because it seems to get more wet (more ink).


Robert

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