The way I understand it is that all printer hardware requires a
certain native resolution and that their drivers will resize the
image, automatically and unseen, to that resolution before sending to
the printer. It is separate from any adjustments in Photoshop. Low
resolution, and the driver upsizes and high resolution it downsizes.
If you are going to let the printer driver do this then the best
results are obtained if it receives an image with a resolution that
is an even factor of the native. For instance with an Epson printer
which is supposed to have a 360dpi native resolution what you should
give it is that or 180 dpi or 120 or 90, with the image dimensions
specified in the printer dialogue, for the driver to do its best job
preparing the file for the printer hardware.
That said, a driver is a little program thrown in for free. Resizing
to its native resolution is best done in something more capable like
Photoshop before you print. All this stuff is a little like casting
runes though.
Winsor
Long Beach, California, USA
On Jul 22, 2005, at 4:50 AM, Andrew Dacey wrote:
>
> On 7/21/05, Chuck Norcutt <chucknorcutt@xxxxxxxxxxx> wrote:
>
>
>> I sure don't understand "prefers images to be at 400 dpi".
>>
>
> I did some looking as I had a suspicion that someone may have been
> confusing the printer's print resolution (dpi) with how many pixels
> you need for the size image you want (ppi).
>
> If anyone's not clear on the distinction then check my article on the
> difference between dpi and ppi:
>
> http://www.tildefrugal.net/photo/dpi.php
>
> So, I checked Agfa's site and saw that the specs do indeed state that
> the printer prints at "400ppi". Note that they've messed up their
> terminology and this should be dpi but in this case we're dealing with
> continuous tone so you can at least get 1 pixel for every dot.
>
> I suspect somewhere along the lines this spec has been mis-translated
> to be that the printer prefers the images to be at 400ppi or that the
> best results are achieved at 400ppi.
>
> I've done tabloid size (11x17) posters at as low as 150ppi and didn't
> notice issues (although this was on a colour laser and the quality
> wasn't great for other reasons so I may not have been able to
> adequately evaluate the print).
>
> Now depending on the printer and it's software, certain lower ppi
> settings may look better than others. I'd probably start with 200ppi
> since that's an even fraction of the printer's resolution.
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