From       : Bobs31@aol.com
Subject    : Re: B+w or Tiffen filters?
Datum      : Tue 27.06.95



This is becoming endless.

There are two common methods of making filters today. American filter
manufacturers (Tiffen and Harrison and Harrison) make their filters by
gluing 2 pieces of glass together with colored glue. This results in 4
glass surfaces. Virtually all of their filters are uncoated and are in
aluminum rims.

Most other major manufacturers, Heliopan, B+W, Hoya use dyed in the mass
glass which are then ground and polished. This means that there are only 2
glass surfaces and these filters are normally coated or multi-coated.
Heliopan and B+W use brass mounts and Hoya usually uses plastic mounts.

Filters can only affect the resolution of long lenses unless the filter is
grossly defective. The further from being absolutely flat the more likely
a filter will affect sharpness with long lenses. Normal, short teles and
wide angles should not be effected by a filter (except for possible
mechanical problems like vignetting).

How filters will affect a resolution test will depend upon:
1: focal length of lens
2: optimization of lens (most lenses are not desigbed to photograph 2
   dimensional objects at close range
3: quality of filter
4: film used
5: lighting
6: processing
7: quality of loupe used to evaluate negative or slide, critical judgement
can not be made from prints as these will introduce other variables.

Instead of continuously worrying about what happens the best advice is to
buy good filters and stop worrying.
Bob Salomon, HP Marketing Corp., Giottos, Gepe, Heliopan, Kaiser
Fototechnik, Linhof, Minox, Rimowa, Rodenstock, Rollei, Silvestri

If you have any question, remark, comment, want to share some philosophy or just want to express your opinion about these pages, feel free to send email to: w.j.markerink @ a1.nl