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
>
>
