Like many others on this message board, I also have the old 55 F3.5 lens. Reading other posts I see that since the 100mm filter is extremely rare. One recommendation is to use a 100mm to 105mm step-up ring and then use 105mm filters. I actually want to use a 105mm polarizer with this lens. Has anyone actually tried this combination? My local photo supplier warned me that this would likely cause vignetting... but he was trying to sell me a newer 55mm at the time as well. Has anyone that has tried this had vignetting problems? Is it only at a specific f-stop range?

-- Ivan Leith (ivan_leith@stockamp.com), March 31, 2002

Answers

Ivan, I couldn't tell from your description whether or not you already own a 105mm filter. If you do (or if any local camera shop stocked one), you could remove the prism (assuming you have one on the camera), and try to hold the filter where it would be assuming you had the step ring. I believe with the prism removed the viewing screen shows 100% of the image. This sounds like a "faky" way to do it, and partly it is, but it should answer the vignetting question - unless the step ring is unusually think. I have an old users guide to Exakta and also one for Miranda cameras; both cameras accepted waist-level finders. Both books describe something like the above, as a way to test if a filter adaptor, stacked filters, or certain series filter configurations would interfere with the recorded image on wider angle lenses. Also, and I dont know if anyone makes one in 100mm, but flexible wide-angle rubber shades are sometimes a decent way to estimate vignetting. When retracted almost all the way they often mirror the dimensions of a step ring with filter. But, if even the slightest touch of corner loss is important to you, you would want -as you requested- to to hear from someone using this exact setup.

-- Michael Tolan (mjtolan@kbjrmail.com), April 03, 2002.

Ivan: I have the older 55 f3.5 and I sold my filters a couple of years ago. For when I do need a filter I have a 100mm gelatin filter adapter made by Pentax for this lens. It holds 4" gelatin filters in place in front of the lens. The holder is a bayonet mount unit and gels are still available from Kodak, I believe. I saw one of these adapters on e-bay a couple of months ago. They alos made a gel adapter for the 67mm bayonet mount filters of some of the other lenses. FWIW

-- Mark J. (logical1@catholic.org), April 06, 2002.

Ivan,

To add to the previous answer, remove the pentaprism and then manually stop-down the lens to F16 or 22. If the edge darkens then you are vignetting. You may need to hold the camera close to an light bulb if you are trying this indoors to get enough light to see the viewfinder.

My guess is that you will be OK with any filter at 105 since they would have made the lens to work ok with 100mm polarisers. You only generally get problems with polarisers vignetting on ultra-wides. You will probably need to get the adapter (100-105) manufactured. I can recommend speed-graphic of the UK who can get brass adonised ones made from Heliopan (approx cost £40).

-- Tony Estcourt (tony.estcourt@talk21.com), April 14, 2002.

I have to admit I thought maybe this was an odd thread, the first time I read it. I wasn't sure why there was such interest in big, alterred or stock filters. My initial thought was, if you are to buy such a nice medium format camera, then why not just buy the filters. It obviously isnt that simple, not to mention all that cheap. In case anyone else is interested, an ebay auction ended tonight (#1345799573), with bidders paying -with shipping- nealry $110 for a 100mm Pentax skylight filter; yes, $100+ dollars for a used filter! God knows what a polarizer or infrared would sell for there. And I thought my local shop was bad at $69 each for 100mm...

-- David Stors (DSiii@cybernetcity.net), April 18, 2002.