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Snap Shots: by Harry Flashman
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On the track of a 62 mm Skylight 1A
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Have you ever heard of a ‘sacrificial’ lens filter? Actually, I made that term
up, but it is what I consider the first lens that the light has to go through to
produce a final image.
Despite CCD’s and CMOS receptors in place of film, the optical light path is
just the same, irrespective of whether the camera is film or digital. Now the
individual lenses that make up the final lens unit (and there can be quite a few
of them) are made to exacting tolerances, and are expensive, and that is why you
should protect the outermost one. This is done by virtue of my ‘sacrificial’
lens filter. In my case this was a Skylight 1A.
This lens had been on the front of the lens barrel for at least four years and
was 62 mm diameter. The diameter was no accident as I used what is called a
stepping ring to increase the diameter, so there are no unwanted vignetting
effects, especially with wide angle settings. My regular camera has a 55 mm
diameter lens, which I have then stepped up to 62 mm so it takes all my old
filters. This is really a good idea and also cuts down the number of filters you
will need to carry.
Looking carefully at the Skylight 1A recently I noticed the tell-tale streaks of
fungus coming across the glass, which would not polish off. Time for a new one,
but where?
Sometimes it is not an advantage living in Pattaya, as opposed to Bangkok. The
MBK center has a whole floor of photo shops, but the closest we have down here
is Tuk Com, which is mainly for electronic products, however, and not cameras,
but I was told Second Floor and dutifully I braved the sprawling chaos called
Tuk Com.
Now I know I am in a foreign country, but I may as well have been talking in
Hindustani to an Eskimo when asking for a Skylight 1A. The best I got was blank
looks. Not even a smile!
However, eventually I struck gold, or iron pyrites at least, in a place called
Best Camera, 2nd floor, Tuk Com, and ask for K. Ton 089 249 5827. He at least
knew what I was looking for, and although unable to provide a Skylight 1A, did
have a UV filter (which is basically the same). Thank you Khun Ton! By the way,
it was not altogether cheap at B. 400, but still a lot cheaper than the multiple
lenses used in the lens of the camera (a 35-410 zoom).
So what other screw on lens should you have? The next most important after the
sacrificial one is a polarizer. Quality polarizing filters are different from
most others in the fact that they are made up of two distinct elements. There is
an outer ring that rotates the outer “glass” relative to the inner element. This
increases or reduces the degree of polarization to allow the photographer an
endless range of polarized effects from one filter.
The principal behind these filters is to remove reflections, and funnily enough
it is reflections that take the color out of color photography. Look at the
surface of a swimming pool, for example - a shiny white, non-transparent
surface. Now look through a polarizing filter and you can see right down to the
tiles on the bottom of the pool.
One of the traps for young photographers is that because you know the grass is
green, you see it as green when you look through the camera viewfinder - even
though it is not truly well saturated green. Look again at the scene in the
viewfinder. The green grass is really a mixture of green and silvery
reflections, dark shadows and pale green shoots. Put the polarizing filter on
the lens and slowly rotate the outer ring. Suddenly the silvery reflections
disappear and become a deep, solid green color. The grass is now made up of
green, dark green and pale green. This green will really leap out at you and
smack you fair between the eyes!
So the message this week is stepping rings, sacrificial filters and polarizing
lenses.
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