[alt-photo] Re: New Platinum Prints

Loris Medici mail at loris.medici.name
Tue Apr 13 08:39:18 GMT 2010


Further clarification:

Errr, 2000 ppi!? That's too much I think; 18 lines per mm (l/mm) is roughly
equivalent to (only) 460 ppi. (Which is very very good in fact!)

In case of halftone printing, you'll need 460 (screen) x 16 = 7360 dpi
hardware resolution (for being able to print all 256 tones), and a file
resolution of *920 ppi* (because you need a file with 2x resolution of the
screen, for optimum results in conversion from grayscale to bitmap), to be
able to hit the resolution limit of the process/paper combination mentioned
above.

For other output methods, you'll be all right with a hardware that is able
to print at *460 ppi*... (IIRC, some Lambda printers can achieve 400 ppi.)

OTOH, as I previously wrote in my reply to Christina, that much print
resolution is pretty unnecessary, since even someone with perfect 20/20 eye
sight / visual acuity won't be able to resolve something more than 13-14
l/mm at 10" (minimum comfortable) viewing distance, w/o the aid of a loupe.
Plus, practical viewing conditions are almost always farther away than 10",
therefore something significantly lower than 13-14 l/mm still does the job.
E.g. real life experience with inkjet prints / digital negatives; ~ 7-8 l/mm
in my case. (I don't even mention lighting conditions BTW; I just assume
perfect / ideal lighting instead - which is a whole other issue...)

Regards,
Loris.


-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org On Behalf Of
etienne garbaux
Sent: Tuesday, April 13, 2010 6:55 AM
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: New Platinum Prints

...

Using silver-based test negatives, I can resolve about 18 
lpmm with Pt on hot-pressed paper, and over 20 on baryta-coated 
paper.  Both will show the dither pattern on any inkjet negatives 
I've seen (as well as the raster pattern from imagesetter 
negatives).  I estimate that we need file and printer hardware 
resolutions of 2000 ppi or so to eliminate it (80 Mp for a 4x5" print).




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