Split image focusing screens?

[richard_oleson]

Sorry for the double post, but I asked this question on the Medium

Format forum and was wondering if the response here would be similar:

 

I have been thinking about the possibility of buying commercially

made, blank Fresnel focusing screens with split image centers and

cutting them to fit older cameras that didn't have the split image or

for which this type of screen is hard to find.... cameras that came

to mind included most older TLRs, praktisix, 35mm exakta,

praktina.... if it worked out as planned, i think i would be able to

sell a finished screen for about $30 ready to install.

 

The consensus at the MF forum was that this market is already well

served, and that they would rather spend the money for a high end

brightscreen than get a cheaper one. These would not be superbright

screens like beattie etc, but they would be comparable to an OEM type

plastic screen with integral Fresnel field lens to brighten the

edges. Would a lower cost screen of this type be more attractive

among the Classic Camera users, or is this just not a good idea?

 

rick :)=

[david_richert]

I need a screen once in awhile but more often I need a new mirror.

[miles_s.]

Rick,

 

I would buy a screen for older SLRs and TLRs for $20 --$40 (but not much more). There are some cameras where the option of a screen upgrade would make them useable.

 

While I think Beattie screens are great for TLRs, a lowercost option would be appreciated by me.

 

miles

[james_lai]

I went the other way, I replaced the split screens in my SLRs with plain screens (with grid, Nikon E and Olympus 1-10).

 

If you make them for TLRs though, I could be tempted as I always have a hard time focussing my Yashicamat 124. I use that camera rarely and can't see myself spending the $$ on the high end brightscreens.

[richard_oleson]

Thanks very much guys. There are uncut blanks being sold on eBay very cheap, and I've tried one of these - cutting one of these to fit isn't something that I think everybody would want to do (or be able to without risk of breakage or a bad fit), based on my experience with it, but I think I can make a tool to let me cut them reliably so that I could sell them custom fitted and still keep the cost down in that $20-40 range. I don't need to make a big capital investment to do it, but it helps if there's someone besides me who might be interested in one.

[joseph_wei]

I would be very interested in such a screen for my Minolta Autocord. The standard screen is usable, but not bright enough for any indoor situations - and I can't afford the high cost of a Intenscreen or a Maxwell screen. The split image would help quite a bit in focusing as well.

[joseph_wei]

Sorry - "not bright enough for MANY indoor situations" (I've used the camera with excellent results indoors, of course - but it's a pain to focus.)

[berk_sirman2]

Hi Rick,

 

At the time I joined the spotmatic group on yahoo there was a discussing about fitting split image screens on spotmatics. Many members stated that it was very hard because Pentax never made one that would fit the spotmatics. Maybe there is a market for you there.

 

I like focusing screens more without split image so the spotmatic screen is good enough for me. What I would want to improve on my spotmatics is the meter. I'd like a meter that is usuable down to EV1 or EV0 and that reacts fast. I am wondering from time to time whether that is possible by changing the CdS sensors to silicon sensors and modifying the circuit accordingly. But that's for another thread...

 

Berk

[richard_oleson]

Hi Berk!

 

Sorry, I don't have a fix for the meter.....

 

:)=

[donnie_strickland]

Hi Rick --

I'd be interested in one for my Yashica-Mat and my Yashica 44 (it needs one even more).

[jonathan_james]

Tlr's are definitely the market. I would be interested in one for my Kalloflex. If I were keeping my weltaflex I'd probably want one for it too.

[richard_oleson]

Thanks everyone!

 

I'm going to go ahead with this. It will be a while (maybe a month or two) before I have the tools made and the blanks in stock. Anyone interested, please keep an eye on my website for it .... I don't want to turn this forum into an advertising venue.

 

I'll be using my own cameras for experimentation - for cameras that I don't have (like, say, the Kalloflex), I may have to ask you to send me the camera (or at least its screen) for measurements....

 

Thanks again!

 

:)=

[warren_colligan]

Richard, Make a tool? Are you aware that a company named Inland makes a glass cutting band saw that I believe sells for less than $200.00? I inherited one of their saws about 5 years ago, and it works fine for cutting screens so long as you make some kind of a fence for it since it is primarily designed for free-hand stained glass cutting. Regards, Warren

[mskovacs]

Rick, what about for the Contax/Pentacon SLRs? You know I have that Contax D w/ Biotar coming ;)

[richard_oleson]

Thanks Warren, I already have my design figured out and I think it will work well.

 

Mike, the Contax/Pentacon (through the E series) are unique in that there is no focusing screen per se. The bottom of the pentraprism itself is frosted to create the screen. In addition, the prism can't be replaced with a prism from another camera because the focusing surface is not horizontal: it tilts down slightly at the front. This combination explains the extremely low prism of the Contax/Pentacon compared to most other SLRs. The F series introduced a different arrangement with a screen and a brightening field lens, and managed to fit it into the same space - but my F's are in too good shape for me to have torn them apart just to see how they did it.....

 

:)=

[mskovacs]

I'll be darned! Will have to start having a detailed read over your tech notes to get ready for this mirror cord repair. In an arcane sense, I'm hoping to redo the curtains too, just so I can learn how!

[titrisol]

Your ingenuity never ceases to amaze me!

 

Count me in, Ricohflex, Fujicas, etc.

[grahams]

Rick - if you are still watching this thread, just a word of caution regarding split image in old Practicas, Zenits, Exaktas etc. Some of these old SLRs do not have sufficient transmission to allow the split image prisims to work - one side blacks out. I always put this down to too slow a lens, but I have come across an instance on a Praktica where the cause seems have been either too small a mirror, or poor reflection from the mirror, even when using a f2.0 lens. With the same lens mounted on a Pentax LX (with adaptor) split image worked. Some split image screens don't wotk with lenses greater than a certain focal length, depending on the included angle of the prisims, but I'm sure that you know this anyway.

[michael_p6]

I bought a "Pentacon 6" focus screen with microprism colar & split prisms on BEEPbay a few weeks ago. I wanted to replace the one in my Bronica S2A. These screens are *very* cheap!

It was uncut, so I dremelled it to size (it's easy, it's plastic !) and installed it witnout problems. But I didn't like it, it was indeed brighter than the original, but less precise to my eye.

So I reinstalled the old glass.

[profhlynnjones]

Hi Richard,

 

My experience has been that the rangefinder screens are not terribly accurate. I had to do quite a bit of sharpness testing and found that the ground glass was significantly more accurate than the RF prisms.

 

Lynn