Digital BW, The Print

After posting here a couple of days ago (see "Very newbee question" 
thread), I have performed a couple of simple tests with an Epson 
Photo 750 printing in black only.  The 750 is a 6 color plus black 
720x1440 printer.

The image I used as my test image was from a 5 Mpixel digital camera 
that gives a resolution of about 350 dpi at a print size of 5x7.  I 
could have gotten a higher resolution image by scanning a negative 
of course, but I am an amateur trying to get back into BW by 
avoiding the darkroom and simplifying the process as much as 
possible.  The original image was color, but was converted to 
greyscale in Photoshop.  I printed the image at 5x7 on a Kodak matte 
paper (not a photo paper but with a bright white) on both the Epson 
750 and on a newer Epson printer (a C80) that is a 1440 x 1450 dpi, 
3 color and black printer (using BO on both).  I think Clayton's 
description of BO printing on this ilk of printer as "digital TriX" 
is a good description of the resulting print.  

The minimun dot size on the print is fixed so the smaller the print, 
the more pronounced the dots appear since there are fewer dots 
making up a particular element of the print.  For small prints of 
faces, the result is (in my opinion) very unsatisfactory.  The 
analogy with TriX breaks down in the print because you get better 
resolution printing a TriX image smaller since it is the grain size 
in the negative that drives the resolution and not the grain size in 
the paper.  When inkjet printing, you have two resolutions to deal 
with, the resolution of the printer and the resolution of the 
image.  In BO printing of a reasonably high resolution image, the 
grain/dot size of the printer can be the process-limiting issue 
instead of the grain/pixel resolution of the image.  For inkjet BO 
prints, printing larger final image sizes minimizes the effect of 
the print dot size, which is sort of backward from how 35mm 
photographers have tended to think when printing from film onto 
paper with silver-based systems.  Printing larger images decreases 
the effect of ink dot size in the prints but increases the effect of 
pixel resolution in the image.

The results of the test indicated that for this image, a 5x7 on the 
750 and the C80 printed black-only were pretty much 
indistinquishable.  The apparent "graininess/dot patterning" was 
about what I'd expect from a slightly larger enlargement from TriX 
from a 35mm negative, maybe after the film had been pushed a stop or 
so. Imagine an 8x10 from 35mm TriX pushed one stop and that is about 
what you get printing this test image at a size of 5x7.  For the 
reasons above, printing the image smaller does not improve, but 
actually decreases the print quality.

What all this implies to me is that there is an optimum BO print 
size for an image of a fixed pixel resolution where the combination 
of dot size and image pixel resolution give the "best" print.  This 
will be somewhat subjective but for images from my digital camera, 
is probably around a 5x7 or 8x10 (it is a 5M pixel camera) for most 
viewers.  

I will probably give quadtone printing a shot in the future with 
this printer, but I think in the end, the pixel resolution of my 
current digital camera and not the printer will be the process-
limiting factor because I prefer medium-sized prints (8x10s and 
11x14s).  I think with an 8x10 or possibly a 5x7, the "digital 35mm 
TriX" look is pretty good if you accept it for what it is.  One of 
my favorite photographs is an 8x10 from 35mm TriX pushed one stop.

With scans of negatives or a higher resolution camera, I'd probably 
want to make 11x14s and I'd need another printer, but given that I 
want to simplify the process, I think sticking with smaller prints 
and my current printer and "prosumer" digital camera is pretty sweet 
and makes it possible for me to get back into making some of my own 
images again.  I matted my first photograph in over 15 years last 
night.

This is a long message, but it summarizes the current state of the 
technology for this time-contrained amateur.  The optimum for pros 
and very advanced amateurs requires more effort and money than I 
want to commit.

Thanks for the help.