Digital BW, The Print

Hi Kevin,

> >> 1. Does anyone know what the resolving power of the Epson printers are
> >> (4 lp/mm 10lp/mm, 20 lp/mm)?
> >
> > Depends on the printer.  You can do the math...if it's a 720DPI
> > printer,
> > that's 360lp/inch, divide that by 25.4, or 14.7 lp/mm.
>
> Yes, I can do the arithmetic but that seems to be a theoretical
> maximum.  What if the line pairs are grey.  I thought that the 720DPI
> is 720 printer dots per inch and it takes several printer dots to make
> a grey.  Doesn't dithering reduce this number.

Yes.  Is it significant or not, it depends on the image.

> I have printed the 21step greayscale that someone provided (Paul
> Roark?) which has small line pair patterns on it.  At 3.6 lp/mm the
> contrast is high and the lines obvious, at 7.2 the contrast is very low
> the lines are not distinct at all.  Under a loupe the vertical lines
> are much worse than the horizontal.  In practical terms is seems to me
> that the resolving power is much less that 14.7.

Print it at black only and see what you get.  Also, make sure you are
printing in high resolution mode.  And...it is very VERY dependant on what
resolution you send to the printer.  I'm going to guess this image is
natively 720PPI when sent to the printer that is maintained?

> It also seems to me that the printers resolution is dwarfed by every
> other upstream component and I wonder whether you could even tell the
> difference between a good lens and an adequate lens in an inkjet print.

Absolutely.  It depends on the size of the "enlargement", obviously.

> Or whether, for a fixed print size, you could tell the difference
> between a 4000dpi scan and a 2000dpi scan?

Again, it depends on the size of the enlargement.

> >
> >> 4. Do papers have a significant impact on resolution/sharpness number
> >> of tones rendered and tonal transition
> >
> > Resolution/sharpness, yes.  Number of tones, probably minimally, and
> > tonal
> > transition...not sure what you mean.
>
> For the numerically inclined it would be interesting to construct
> MTF(like) charts for paper/printer/driver combinations.

Be my guest ;-)

Regards,

Austin