Digital BW, The Print

Austin writes:

> What's your source for that claim?

It's human physiology.

The dimensions of the cone cells in the most densely-packed areas of the
retina are about 30 seconds of arc in size.  Resolution is thus limited to
30 seconds of arc under IDEAL conditions.  Typically working figures are 2-4
times lower (1-2 minutes of arc), given that conditions are so rarely ideal.

An 1:1.5 image held at a distance equal to the diagonal of the image
(standard viewing distance) subtends an area of about 6-8 million cones on
the retina (allowing for scanning operations of the eye).  Therefore that is
all that is needed to satisfy human visual acuity in an image at that
distance.

> What humans "need" for a "full-frame image" is entirely
> different than what is needed for photographic imaging.

Not if the photographs are intended for human viewing, which they almost
invariably are.

> Also, humans have variable resolution in their
> sight...

No, they do not.  The maximum resolution is set by physiology, as described
above.  Some people have less; but nobody has more.

> so how is that taken account with your claim?

It's not a claim, it's a very well established fact.  This being so, I
suggest that anyone who has a problem with it study the physiology in
question, and he'll be able to verify it for himself.  He need not (and
should not) believe me ... or you.

In case you haven't noticed, this is why the market always tends to converge
on whatever technology provides the requisite number of pixels as described
above.  Once 120 could do this, LF fell by the wayside; and once 35mm could
do it, 120 was no longer needed.  And now that digital can do it (barely),
35mm is gradually receding as well.  It's no coincidence.  People won't buy
a system that provides more resolution than they can see.