The trouble with all those Epson flatbeds, and I have owned or tested
three of them, so far, must at least in part be due to internal
reflections or stray light. The scans always look like those from my
See Flextight. The problem is with the way that they hold and scan
the negatives.
http://www.imacon.dk/sw323.asp
"The Flextight holder
What do we want to achieve with an original holder? We want to be able
to keep the original in perfect focus across the scan line. We want to
avoid Newton rings. We want to have as few surfaces in the light path as
possible to clean and to break the light waves. Finally we made it as
easy as possible to mount the original in the holder.
All this we have achieved in the Flextight original holder, which is
glass free, with a magnetic rubber overlay, which makes mounting a very
easy task. The perfect focus across the scan line is achieved by bending
the original around a virtual drum. When you bend a media in one
direction it becomes perfectly straight and stable in the other direction.
The holder concept makes it possible to take the holder from the
scanner, after preview, and place it on a light table for comparing and
adjusting the scanner preview. When finished the holder is easily put
into the scanner for final scanning. This feature is not available on
most of the competitive scanners.
Focal Length
Why is the scanner so high? It is because we want to have a long focal
length. By having a long focal length we only utilize the lens where it
is best, which means less distortion and therefore fewer corrections.
» Larger image
The glass free optical path
By building the scanner like we did we have actually achieved a glass
free optical path. This means that we do not have to correct for
unwanted effects like chromatic aberration or diffusion caused by glass
plates, prisms or mirrors. It also means that less mechanics are to be
adjusted and finally that less surfaces are to be kept clean.
CCD facing downwards
A simple but obvious thing is to place the CCD face down, as it is
unlikely that dust gathers on the light sensitive cells in this position.
The direct analogue to digital conversion
When the analogue signal produced in the CCD is to be converted to a
digital signal it has to move from the CCD to the AD converter. As the
analogue signal is a low tension electric current it is very sensitive
to electrical noise, which very likely is produced by other electrical
units in and around the scanner.
Imacon has therefore decided to place the AD converters directly on the
CCD board to keep the travelling distance as short as possible. And to
lower the risk of noise we have even decided to have one AD converter
for each color channel instead of sending the signals through a
multi-plexer, which has the potential risk of adding more noise.
Keeping heat out/down
Every time the temperature raises with 10° Celsius the electrical noise
in the sensor doubles. This means that it is very important to prevent
the sensor from heating up.
The most obvious source of heat is the power supply. By removing that
from the cabinet and placing it outside the scanner one big problem is
eliminated.
A second thing is the light tube. This light tube is a cold catode tube,
which produces very little infrared waves and therefore produces very
little heat.
The sensor itself is an electronic device that heats up when the clock
frequency is speeded up. This is usually done to make fast previews. The
sensor samples full information even at preview scans, so every cell has
to be emptied to produce even a low-resolution preview.
Imacon has found a way to add the information in the sensor together
directly, which means that we do not have to speed up the readout of the
sensor, therefore not producing the heat, which is common in this process.
At the top of the line scanner Imacon has even chosen to cool the sensor
actively, which means that an electronic device is placed directly on
the CCD to cool it down. This will increase signal to noise ration with
1 to 2 bits.
Stable metal construction
To keep the scanner stiff and stable all mechanic parts as well as the
cabinet are made out of metal. And due to the fact that the scanners are
high speed and have attachable batch feeder devices we expect that they
will make thousands of scans and are therefore build to last.
"
