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Digital enlarger DeVere 504 DS

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Old January 23rd 04, 06:21 AM
KHB Photografix
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Default Digital enlarger DeVere 504 DS

The DeVere 504DS is a unique application, but piezo movement technology is
being used in digital camera backs to allow a relatively small CCD to create
a large high resolution image file. If you do a Google search on "digital
camera piezo movement" you'll find quite a lot of information.

"Jorge Omar" wrote in message
Well, here we have something unusual.


Old January 23rd 04, 11:10 PM
Nicholas O. Lindan
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Default Digital enlarger DeVere 504 DS

"David Strip" wrote

You appear to be assuming that as the LCD is shifted, the image is constant, and
that the resulting printed image is just a blurred image of the LCD.

No, I wasn't, though I may have given that impression with references to 'etched
glass' and 'vibrating enlargers' producing much the same effect. I was referring
to elimination of the jaggies caused by imaging sharply defined pixels at 300 DPI.

To achieve a smooth gradation between pixels you would, of course, have to print
at intermediate pixel intensities at intermediate positions to achieve a smooth
gradation between pixels. DeVere clearly states that this is what they are doing:
Lots of discrete exposures at different display intensities with a filter and
each exposure really being three exposures, one through each of the positions
on the filter wheel.

The same effect, though, can be achieved by with a motion that varies velocity
with position, much the same as burning a print: the burning hole spends a lot
of time in the middle and less and less time as it is moved farther from the

While I have no idea what DeVere is doing, other systems have been built
around this concept in which the LCD is stepped to discrete positions and
a different image is projected in each position. Since LCD's often have a
fill factor of ~25%, you can image 4 distinct pixels/dots by moving the
LCD to four distinct positions.

Agreed, if an LCD has less than a 100% fill factor then a step and repeat
puts down a higher resolution image with more information. The net effect
is to create virtual pixels. Think of it as 100% fill.

The resolution is not increased "apparently", it's increased for real,
assuming the imaging optics aren't the limiting factor.

I wouldn't say it is increased. The pixel size is the same, and so the
minimum feature size is the same. It is just that without motion 3/4 of
the pixels are missing.

So, lets theorize a system with pixels with a 100% fill factor, as that
is what has been accomplished by DeVere.

Now we are now where we have started ... 300 sharply defined spots/inch on
the paper.

And the problem is how to blend the boundaries between the spots/dots/pix
to make the whole pleasing to the eye.

To do this one can move the screen in a smoothly in a 2-D Gaussian manner
(shudder), approximate same with discrete exposures, or approximate the same
by utilizing an optical system that produces a Gaussian blur of just the right

My guess was they already had the step and repeat action just to achieve
pixel fill. And frosted glass or a coke-bottle lens just didn't cut it,
so the solution was extra exposures at intermediate pixel positions.

Now, back to this idea that moving (packed) pixels around will create
resolution that is greater than achieved by stationary pixels.

I propose the following experiment:

Use a 1 pixel system in one dimension as the machine/printer/enlarger/
latest-term-thought-up-by-marketing. And further simplify the system
by constraining the pixel to horizontal moves - sort of like moving to
"Lineland" from "Flatland". If it works for one pixel and one dimension
it should be generalizable to many pixels in 2 dimensions.

This one pixel can print any shade from white to grey in an additive
manner: 2 white exposures = white, 1 white + 1 grey = grey, 2 grey
exposures = black ...

It is, obviously, possible to make a black one pix spot next to a white one
pix spot. A repeating pattern of white/black pixels is your basic MTF input,
though really one should use a sinus density profile a square wave profile
works about as well.

Now, with multiple exposures, is it possible to make a periodic image that is of a
higher frequency than that above? I.E.: one where the distance from the center
of one black area to the center of the next black area is less than two pixels.

If we allow the pixel to print with opaque ink then black and white then it is
easy to see that zebra patterns of any frequency can be made can be made.
But only at integer multiples of the base frequency. One leading cycle,
starting from a blank stretch, can be made at any frequency, but the pixels
will make a mess of the image to the right (assuming the pixel moves left to right)
so that an arbitrary frequency can not be repeated smoothly. The ability to image
frequency multiples is the same effect as size of the lens's bokeh (the size
of the pixel) causing apparent lens resolution in an MTF test to suddenly
spring to life again after having dissolved into pure grey.

The ability to image at discrete frequencies is called an artifact. Rather
than producing more detail it produces moire patterns in the output.

The moving pixel problem is a variation on 'box car averaging' filtering, a well known
technique in digital signal processing. It produces a low-pass filter with
a comb-like pass band after the first filter zero. The mathematical literature
for box car functions is hundreds of years old.

Just search for 'box car filter' with google.

In summation the effect of moving pixels around is a blur, no increase in
information transfer is possible.

Sorry, no free lunch.

And again, there is nothing new under the Sun but that thinking makes it so.

Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Old January 23rd 04, 11:22 PM
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Default Digital enlarger DeVere 504 DS

The proof is in the printing.
Be nice and share.
I look forward to receiving my complimentary DeVere 504DS.
When's it arriving?

Old January 23rd 04, 11:38 PM
Nicholas O. Lindan
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Default Digital enlarger DeVere 504 DS

"Claudio Bonavolta"

I've seen this enlarger [DeVere 504DS]...

The basic technology is from MuellerSOHN, DeVere is incorporating
it into its own product, as are several firms in the
photolab business.


Looks like the digital LCD mini-lab printer is on its way to
a drug-store near you.

And the name of the game here is _speed_. Resolution
only has to be consumer grade.

On another front, Intel has developed high resolution
LCOS (Liquid Crystal On Silicon), slated initially for
projection TV, but going who knows where.... a minilab
near you, maybe.


Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.

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