Taming the Plasticca (and other meniscus lenses)

[Steven Tribe]

In a recent contribution, I mentioned that I seen a set of "tea strainers" (Rodenstock Imagon type) sold with a Plasticca a few years ago. I have thought about this for some time and checked when the Imagon was first introduced (1931). It seems obvious to me that this genius of an idea, reducing F values and controlling the reduction in aberrations/softness with the outer small holes, would have been taken up by other makers - if it had not been patent protected and if the market for soft lenses was falling at the same time. But private owners could still make their own experiments - hence the Plasticca set illustrated.

Now the Plasticca is the best suited candidate for "treatment" as effects are violent and it is born without an iris - but the same principles apply to all meniscus lenses. For landscape meniscus lenses, though, it would be a case of keeping some of the wild effects when using small apertures. It would be fun to see some Waterhouse stops with the Imagon pattern!

The illustration shows clip-on type "imagon" discs. I don't like the idea of a metal against metal fitment so I will make an modified leather lens hood with an open section in front with room for both ordinary "washer stops" and own production Imagon stops.

Further postings may be of GG images as I am suffering from the 3/4 completed darkroom syndrome.

[eddie]

i think "regular" stops "tame" the meniscus lenses just fine.

i love my plasticca as is.....

[Steven Tribe]

I mean, of course, taming the Plasticca - whilst retaining it's special character!
I have tried with ordinary front stops (as you can see) and the "special effect" seems to be still there. But I was afraid that it would become a very ordinary lens - just like the Graf variable and Landscape meniscus at small apertures.

Getting the F value down is pretty important for me in connection with use of a sinar/copal shutter set-up outside.

[eddie]

Getting the F value down is pretty important for me in connection with use of a sinar/copal shutter set-up outside.

use slow film and under develop...this is what i do and i have no shutter at all.....

[Mark Sawyer]

Steven ~ it looks like the Plasticca has filter threads. Have you considered buying a few cheap filters and mounting the stops in their housings? Just a thought...

Having used an Imagon with the h/stops, I found the echoes of the soup-strainer shape around the highlights objectionable, and started using the conventional iris in the compound shutter. This alters the effect a bit, I'm told, as the Imagon was designed to have a little light from the outer edges combine with the light from the center in graduated amounts. I think a better solution might be a reverse of the center filters designed for extreme wide angle lenses, so one doesn't get those odd little flares all over the image.

These are the Waterhouse-style diffusion stops for the Verito. They were meant for enlarging, but would also work using the lens on a camera.

[Steven Tribe]

Thanks Mark. I am certainly worried about the famous "bugs" as I think these apparitions are called and have an open mind about how to let some light through outside the traditional stop.

It does have a perfect undamaged filter thread (more a thread used in mounting the lens) but as this is around 122mm I think the cap/stop idea is more practical/economic!

Apart from trying different sorts of "holes", I will be experimenting with ND outside the clear central stop hole. Calculating the F value would be a lot easier with area sections of ND rather than, for example "36 holes with radius 10mm plus 72 holes with radius 4mm gives a grand total of xyz sq.mm and etc."

[tenderobject]

hey there, just curious.. is it ok to put f stop in front of the lens? thanks!

[Steven Tribe]

Frontal mounting of washer/disc front stops was standard for single meniscus lenses both in the 19th and 20th Century. Even some of the first Petzvals designs had facilities for front stops. An earlier discussion this year had contributions where we compared distances of the front stops from the front lens surface in relation to the effective focal length of the lens.

[tenderobject]

Frontal mounting of washer/disc front stops was standard for single meniscus lenses both in the 19th and 20th Century. Even some of the first Petzvals designs had facilities for front stops. An earlier discussion this year had contributions where we compared distances of the front stops from the front lens surface in relation to the effective focal length of the lens.

thanks steven. will check on that thread.. actually im thinking of putting it in front of a petzval lens.. i think putting nd filter infront or at the rear is best for me right now but still hassle when shooting especially putting a filter in the rear.