[filmscanners] Re: Of Newton Rings and other things

["Arthur Entlich" <artistic-1@shaw.ca>]

Anthony Atkielski wrote:


>
>>You just need something that creates enough
>>of a space between the glass and the film
>>surfaces to remove the Newton ring interference
>>patterns.
>>
>
> But doesn't that leave more space for the film to flex, thereby negating the
> utility of the glass to keep it flat in the first place?
>

Well, I don't know how critical the DOF issue is.  It's worth a try, I
imagine.  If the glass is pressing hard on the film you are almost
guaranteed Newton Rings.  If you give the film a bit of breathing room,
you may be able to avoid it, its a simple cheap experiment.  If the
spacer does enough to keep the glass from coming in direct contact with
the glass, that should help.


>
>>Canned "air" creates dampness especially
>>when used in large volumes as it condenses
>>moisture out of the air and creates ice crystals
>>due to the change of state it goes through,
>>which is an endothermic action.
>>
>
> I don't know what gas specifically is used in Dust-Off, but it isn't cold
> when it leaves the can.  I tried some other stuff from Hama and it was
> scary--sometimes it comes out as a liquid, which is frightening when it is
> aimed at a $125 UV filter!
>


OK, Dust off might be better, I haven't used "canned air" since 1978.
The old stuff used to be CFC, and was non-flammable. (It just destroyed
the ozone layer ;-0

Some of the newer stuff is flammable and explosive and probably a

petroleum based volatile.


I have a "recent" can (three years or so old) of "Kensington Dust
Blaster" here, which was given to me as a sample but I have never used,
which has Tetrafluoriethane as the main propellant. It claims to be
"non-ozone depleting", but I do not believe that is fully accurate ...
it is just slower in its destruction and the chlorine is better bonded
to the other atoms so it is less damaging.  It does say "warning, may
cause frostbite", however, so it is a highly volatile liquid which cools
down considerably.


>>A cheaper and maybe better alternative is just a
>>rubber ball syring

>
> I'd have to suck air into it, and the air would almost certainly contain
> dust.
>
>


I suppose one could put a filter on it when it was filling it and remove
it with each blast, but I found it worked pretty well just by creating
air movement even if there was some dust in it.

Better yet, you could probably pay for a vibrator compressor and auto
pressure switch with a nozzle gun tip for about 10-15 canisters of
Dustoff.  It would be safer, and ultimately cheaper.


Art



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