On the track of a 62 mm Skylight 1A


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.