[rollei_list] Re: Lens coatings and veiling flare.
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Tue, 7 Jul 2009 12:27:28 -0700
----- Original Message -----
From: "Sanders McNew" <sanders@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Tuesday, July 07, 2009 4:52 AM
Subject: [rollei_list] Lens coatings and veiling flare.
I shoot a variety of older Rolleiflexes --
a 3.5E and a 2.8C getting most of the
work. Their weakness, in my use, has
always been veiling flare when shooting
a strongly backlit subject, or in other
conditions where the sun or a bright
reflection is in the frame.
Does anyone onlist know when F+H
or its lens suppliers upgraded the lens
coatings on the TLRs? Are later TLR
models more effective at suppressing
veiling flare in these conditions? Do
I need to ask Austin for his GX to tame
this beast?
Sanders
---
Check your lenses for internal haze. Shine a flashlight
through the lens with the shutter and iris open. A very
small amount of haze will destroy image contrast. The haze
can be cleaned off but usually requires opening the lens.
The difference between single layer coatings and later
multiple layer ones is mostly exhibited in color contrast.
The single layer is most effective at a single wavelength
and falls off in effectiveness above or below that. Usually
single layer coatings are peaked for either green or blue
light. The residual reflection from the lens will indicate
the peaked wavelength because it is its compliment. Lenses
peaked for green light have magenta reflections and those
peaked in the blue have amber reflections.
Multi-coating broadens out the band of wavelengths, or
colors, where the coating is effective. Double coatings were
the first but modern lenses may have several coatings. A
really good broadband coating should have nearly no
reflection and that with no residual color. I doubt very
much if any consumer lenses have this grade of coating but a
practical coating will come close.
The main visual effect of a multiple coated lens in
photographs is an improvement in color purity and saturation
although it will certainly improve monochrome contrast as
well. The main effect of flare is to lower _shadow_
contrast, in effect similar to a long toe film. Haze has a
similar effect but can be considerably greater than the
internal reflection flare from relatively simple lenses.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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