I don't think this is the case. Otherwise you would have seen this
phenomenon from enlargements made from transparencies long ago. Consider
this, the human eye can resolve about 1 minute of 1 degree of arc (1/60 of a
degree) in the horizontal plane (most sensitive - less in the vertical) So
take a 35mm slide (which is about 1" tall) and enlarge it full frame to
8x10" that's an enlargement factor of about 8. So a 4000dpi scan of a 35mm
slide is about the same as a 500dpi scan of an 8x10.
So plugging 1/500th of an inch into the formula X = TanTheta Y where X is
the lines/inch and Y is the eye's distance from the 8x10 enlargement, we get
.002 = Tan(1/60deg) Y or Y (max eye resolution) = .002/.000291 = 6.875".
IOW, anyone who has looked at a full frame 8x10 enlargement of a 35mm image,
closer than 7" is in essence 'scanning' the 35mm slide at greater than
4000dpi. And since we don't have reports of folks seeing this sort of
difference in enlargements at this level (remmember folks use grain
focussers to get even higher resolution during focussing of an
enlargement) - I don't think there is any 'real information' there.
----- Original Message -----
From: "Arthur Entlich" <artistic@ampsc.com>
To: <filmscanners@halftone.co.uk>
Sent: Friday, May 11, 2001 4:51 PM
Subject: Re: filmscanners: What causes this and is there any easy solution ?
> Hi Steve,
>
> I just took a look at your mottled sky within photoshop. I enlarged it,
> I sharpened it, I sent it through a spectral analysis, I looked for
> encrypted messages or codes, I ... ;-)
>
> And, you are absolutely right, it is the dullest picture I've ever seen
> on this list. ;-)
>
> OK, enough attempt at humor.
>
> I am beginning to develop a theory about these anomalies that appear in
> scanned images. Is it possible that the CCDs are recording information
> outside of the realm of human vision? What I mean is could we be seeing
> artifacts of either IR or UV (or other spectrums) information which are
> being translated into the visible spectrum?
>
> When people speak about these oddities, it is often a whole roll
> exhibiting the "defect" where another roll of the same film type
> doesn't. Could differences in manufacturing, processing or other
> chemical or structural differences in the film (say even variations in
> the thickness of some otherwise "invisible" film layers (remnants of the
> color filters within the film, gelatin layers, even film base) which for
> all normal viewing purposes would make no difference at all in the image
> quality, even at high magnification, be "captured" via the CCD sensor
> process, and then translated to visible artifacts?
>
> I imagine these things may never be tested for in the manufacturing or
> developing processes of the film. Does anyone know if CCDs are tested
> for sensitivity outside of the range of the human perceptible spectrum?
>
> I mean, bees see in UV, and their view of the world is vastly different
> from our own. Flowers with pollen and nectar send beacons to bees which
> get lost for us in the mix of brilliant colors and fancy shapes... then
> again, flowers aren't much interested in having me be attracted to their
> nectar or pollen.
>
> Phil Lippencott: does any of your equipment allow for testing CCD
> sensitivity for the IR or UV spectrum (or even higher or lower than
that?)?
>
> So, Steve, that's my "dumb" answer to your exceedingly "dumb"
> question... ;-)
>
> I think we might all be missing something here, simply because it is
> outside of our normally responsive reality.
>
> Comments, criticisms, supporting or other views?
>
> Art
>
>
>
> Steve Greenbank wrote:
>
> > Today I'm going for the dual prize of most boring picture (see
attachment)
> > and most dumb question ever on the list.
> >
> > Mark asked me about a problem in the background of some pictures
> >
> >
> > The problem is that my sample (a bit of sky) from a slide projects with
> > perfect continuous tones at any size even 40 inch by 60 inch and it
still
> > looks reasonably sharp (within reason) but yet when I scan it at
4000dpi I
> > get a grainy effect that will show up in an A3 print and a soft image in
> > general. The problem often gets worse with sharpening . I have found
that a
> > unsharp mask threshold 9+ usually avoids sharpening the graininess.
> > Alternatively a gaussian blur removes it but if you do this to the whole
> > image you end up with an even more soft image but on the plus side you
can
> > sharpen it more aggressively and use a threshold of 3-4 which means much
> > more gets sharpened.
> >
> > Obviously carefully selecting the sky/problem area and blurring that
> > separately is probably the best option but it takes ages to do this
> > accurately and you still may get noise problems elsewhere.
> >
> > Am I right to assume the noise is grain, CCD noise and chemical faults
on
> > the film ?
> >
> > Does every see this noise ?
> >
> > Should I see less with SS4000/A4000 scanner (is mine and Mark's a bit
duff)
> > ?
> >
> > And what do you do about it ?
> >
> > Steve
> >
> >
>
