Physics 101
My first enlarger was a Durst F60 (way back in 1977). Shortly after getting it, I read somewhere that it would be useful to have a head-absorbing glass...it didn't appear to be anything more than an unusually thick piece of glass - about 3/16" thick. It may have had some unusual spectral absorption characteristic, but that certainly was not apparent to this observer. Instead, it seemed to me that the shear bulk of the glass was the factor that made it heat absorbing.
So that leads me to wonder if all that is really required is thick glass.
Yes they all do seem to be rather thickish...
I think that they actually are compounded differently, however.
This does bring up an interesting question regarding how filters work,
particularily about what role their thickness and reppitition might play in their behavior.
For simplicity, all examples here assume 100% transmission for all other wavelengths:
1.
If filter "007" (which is 1 mm thick)
reduces the amount of wavelength "Agent X" by 50%
How much would the same filter reduce that wavelength by
if the filter were twice (ie 2 mm) as thick ?
And if that same filter was 2 meters thick?
2.
If the 1mm thick filter above reduces a certain wavelength by 50%
does this mean that a second filter (of the same type & thickness)
placed in the same light pathway will remove an
additonial 50%?
thereby outputting only 25% of the orignial wavelength?
3.
Same question as #2, but now the filters are different in composition:
Assume you have two different filters, "007" and "86".
Both reduce the transmission of wavelength "X" by 50 %
Can you reduce the amount of wavelength "X" by 50%
twice
(once for each filter) to get a final of 25% ?
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This may be very basic for some of you,
but I think how filters add and subtract (?) can be confusing for many people.
Many People
