Digital BW, The Print

Austin writes:

> What is the source of the claim?

As I've explained, it's not a claim, it's a fact.  I don't need a source.
Anyone can research this for himself; he doesn't have to believe me.
Eventually he'll find a source reliable enough to satisfy him that will
confirm what I am saying.  Just as most people don't need a source to
believe that the sun rises in the east, since that fact is so widely known,
it is not necessary for me to provide a source for this information, as
anyone familiar with the field already knows all of this, even if you do
not.

> It's physiology that the human eye has
> variable resolution, with the highest
> area being in the very center ...

That's what I mean by the "scanning action of the eye."  These figures
correspond to the region of greatest acuity in the retina, the fovea
centralis; this zone is scanned over an image by the eye in order to provide
detailed vision over a larger area.

The resolution outside the fovea is so low that it makes virtually no
contribution to the type of eyesight required to view photographs.

The figure of 6-8 megapixels, then, is the figure obtained by the scanning
of the fovea over the entire print or image.  If one stares at one point on
the image without scanning, the required resolution on the print is orders
of magnitude lower.  But nobody ever does that, so it is a moot point.

> ... so you can't extrapolate the real
> "resolution" of the human field of view as you have.

Yes, I can, and I have, and I'm not the first or only person to do so.  This
is how depth-of-field markings were calculated on camera lenses decades
before my birth.  The circles of confusion used to calculate DOF are in the
region of 30 micrometres on the film surface, which corresponds to an image
of only two megapixels.  The figure of 6-8 megapixels for optimal viewing is
thus very conservative in comparison to the assumptions for visual acuity
made for DOF calculations.

> It's a physical fact that your eye has higher
> resolution in the center, and decreased resolution
> around the periphery.

I'm aware of this, and the figures I give are for the fovea.  Since the
fovea is scanned over the entire image, its resolution applies to the entire
image.  Even so, the total figure is 6-8 megapixels.  That's all you need.

> Then, of course, you can point me to an established
> resource that supports your claim?

No, you must do your own research, and your posts will be much more cogent
if you undertake this before preparing any further replies to my posts.

> The number of pixels for a camera is ENTIRELY
> UNRELATED to what the resolution of the human
> eye is.  It depends on what size the resultant
> image is!

Images are typically viewed from distances that fall within a fairly narrow
range in proportion to the print.  That's why everyone does not insist on
shooting Tech Pan in 8x10 sheets, and it's also why virtually nobody is
happy with prints made from aging digicams with 320x200-pixel sensors.