RE: filmscanners: Nikon film flatness (was Glass slide mounts)

["PAUL GRAHAM" <peegee@btinternet.com>]

Hi all,

My opinion on film flatness has been explained before, so this will be my
final word on the topic.
I've worked in very high end darkrooms for 20 years, typically making 4 foot
to 6 foot prints (110 to 180cm) every day, from 35mm and medium format negs.
That is an enlargement factor of 5000%.
I have the brightest enlarger heads for these formats - 1000W of halogen
lamps, BUT.. I still have problems with film flatness. Brighter light
sources make no difference - you simply have to use a glass film holder for
this type of high quality work to get edge to edge film flatness.. there is
no other way, and there has been no real alternative in 100 years of
darkroom technique/ equipment.
Now a regular home enthusiast with a small enlarger won't use a glass holder
because they don't look so closely at detail corner sharpness plus typically
they stop down too much (enlarger lenses are at their optimum 2 stops down,
any more degrades the resolution) to get the depth of field/ corner
sharpness, which masks any uneveness of film. Or perhaps their lenses are
not as wide in aperture to begin with.
My point is that the higher your demands get, the more you notice things
like film flatness becoming critical.
Cheap scanners, or low resolution scanners, like cheap enlargers, dont show
the best from the film, but neither do they show the faults in the
technique, such as absolutely flat film. it's a good compromise - a stopped
down aperture masks a lot of alignment issues  that look good up to a point
but ask for resolution beyond that point, and the problems begin.
I think this is what we are coming across with the new high end prosumer
scanners.
If you want the ultimate - a 4000 dpi scan, with edge to edge sharpness,
then you may have to accept that you need to use glass holders or take other
measures to ensure flat film.
My point has always been that it is wrong to expect ultimate resolution
corner to corner by just dropping a strip of film in a holder and pressing
'scan'. Nobody in the pro-scanning world of drum scanners does that or gets
that. Nobody in professional darkroom work does that or gets that. So lets
get realistic here...
Maybe, just maybe, Nikons approach has been to use a light source that
requires a wider lens aperture, gaining very high resolution (they come top
in most critical resolution tests) and long term colour stability. Polaroid
have taken a different path, used a different (brighter) light source, a
smaller aperture and gained depth of field, trading off against ultimate
resolution.
Nikon make and sell glass holders for their scanners, so...
You pay your money and you makes your choice...

paul