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Can I in principle use my Ziess Hasselblad lenses in my projector?

S Carl , Sep 27, 2012; 02:44 a.m.

Hello,
I have two medium-format projectors: a Rollie P11 and Rollei P66, both having Hiedosmat lenses. The resulting projected images are quite nice but out of interest I repositioned the slide so that my Ziess C lenses could image them onto my wall. As far a resolution is concerned all of the Ziess camera lenses outperformed the projection lenses - though this is not a surprise. In fact, the photographic detail that one can see by this method is extremely close to that observed when viewing the slide on a light table through a Luminar 25 mm lens - in other words you seem to closely approach the actual slide detail. Another interesting observation is that if I project I slide taken with the 30 mm Distagon "fish eye", when I project that slide back onto the wall using the fish eye lens, much of the original distortion is straightened out.
A lot of people who whant to project medium format slides have a medium format camera. But I don't see any medium format slide projectors that accomodate camera lenses. I realise that the light throughput is generally superior with projection lenses - but this is not such a big issue and, as far as I can make out, the projection beam does not cause too much warming of the lenses.
Can anyone think of potential problems in adapting my projectors to accomodate my camera lenses? After all one could then approach the image quality (or maybe equal it) of a hasselblad projector using a Rollei P11.

Many thanks

Responses


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Q.G. de Bakker , Sep 27, 2012; 03:35 a.m.

Heat, as you already mentioned. The camera lenses have shutters and diaphragms that need to work quickly and reliably. Who knows how they would stand up to excessive heat. I wouldn't like to try with my lenses.
The mount: how to fix a lens to a projector at the correct distance to the slide.
Nothing else, i guess.

You could try finding better projection lenses, even if that means switching to another projector. But that fish-eye trick will not work unless, of course, the same lens is used.

David Bebbington , Sep 27, 2012; 04:41 a.m.

Most projector lenses are Petzval type:
http://en.wikipedia.org/wiki/Petzval_lens
This features a air-spaced back group of 2 elements. Traditionally the advice has been not to use camera lenses for projection since there is the risk that heat may cause the balsam used to assemble the rear group to turn yellow. With the original Leica. the maker Leitz specifically mentioned that the taking lens (5 cm Elmar) could be used for enlarging - this advice was no longer given for later more complex lens designs with cemented rear groups.

S Carl , Sep 27, 2012; 08:36 a.m.

This was my first posted question on the forum and I have to say I'm impressed by the speed and quality of the responses already. So thank you for those.
To Mr. de Bakker: I do see that, indeed, over time on might cause loss of lubricanting oils due to increased vapor pressure of these with temperature, thus affecting shutter timing and focussing. Initially I estimated that this would not be a large effect , but I suppose one only requires few degrees above ambient over long periods to begin to see a difference.
By the way, I have found your information webpages on C-lenses to be very useful.
Mr. Bebbington: I'm not at all sure of the photochemical response of balsam to light, but you might have hit the nail on the head. I wonder though if there are reported lens problems associated with their use in bright sunlight - which might approach the intensity of a dim projector lens (on the basis that it is difficult to see a projected image on a white wall outside if sunny even if the proected image is a few inches on either side).
Thank you again for your responses. Forever the experimenter, I shall try to get hold of a (cheap, slightly) damaged Ziess lens to experiment on and report back later on the results. I suppose one advantage of occasionally sending projector light through a lens would be to prevent/remove fungus.

Robin Smith , Sep 27, 2012; 11:48 a.m.

I think you would be better off seeking to obtain superior projection lenses (which are optimized for the distances involved and with low distortion and fast aperture) than doing what you are doing: but do let us know how you get on.

Ray Butler , Sep 27, 2012; 01:10 p.m.

I would expect that your Rollei projectors can be used with the Schneider AV-Xenotar HFT projector lenses...those should be sharper performers than the Heidosmat lenses.

Richard Fateman , Sep 27, 2012; 02:04 p.m.

Rollei made an attachment for a TLR that made it into a slide projector:
(link)
While this uses a camera lens, it uses the wrong one, namely the viewfinder lens,
not the presumably much superior taking lens!

As is the case with some other rollei accessories, it looks more appealing to the collector of nicely engineered objects than to an actual photographer.

Q.G. de Bakker , Sep 27, 2012; 03:19 p.m.

I wouldn't dare suggest they are better than the Heidosmats, simply because i do not know that they are. But you could try, see if it makes a difference, and switch to another projector, the Hasselblad PCP 80, and use Zeiss projection lenses.

Rob F. , Sep 27, 2012; 10:42 p.m.

"Another interesting observation is that if I project I slide taken with the 30 mm Distagon "fish eye", when I project that slide back onto the wall using the fish eye lens, much of the original distortion is straightened out."

Lenses exhibit reciprocity; so whatever the lens does when light passes from front to back, they will do in reverse when light passes from back to front. Thus when an image is passed through a fisheye lens backwards, it becomes an "anti-fisheye" that undoes the fisheye effect. The Omnimax theaters use a fisheye projection lens, made by Leica (or by the Canadian plant that used to be E. Leitz Canada) to cancel some of the distortion inherent in their dome screens. Fascinating!

I thought of suggesting you use Zeiss lenses with bad shutters/diaphragms for projection, as you mentioned; but if the Schneider lenses Ray mentioned are available in MF format, I think that is a better place to start. I use some Schneider/ISCO lenses for 35mm projection, and they are very good. Of course, better still is to get a PCP80 with either the 75mm or the 150mm Zeiss projection lenses, depending on your screen size and projection distance. That's what I use.

Edward Ingold , Sep 28, 2012; 07:03 p.m.

If it's any indication, the half-million dollar Zeiss projector at the Chicago Planetarium uses Zeiss Planar lenses. The shutter and diaphram of Hasselblad lenses are wide open in the default (cocked) condition. If you can find a way to mount the lens on a projector and focus it, you should be good to go.


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