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

Discussion in 'Medium Format' started by s_carl, Sep 26, 2012.

  1. 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
     
  2. 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.
     
  3. 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.
     
  4. 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.
     
  5. 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.
     
  6. 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.
     
  7. Rollei made an attachment for a TLR that made it into a slide projector:
    http://www.ebay.com/itm/Rollei-TLR-Slide-Projector-Attachment-EXTREMELY-RARE-/150909328512
    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.
     
  8. 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.
     
  9. "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.
     
  10. 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.
     
  11. I'm glad to hear that the Chicago Planetarium got the new Zeiss projector. There is also one here at the McDonnell Planetarium here in St. Louis; and I saw a show using one in the Hayden Planetarium in NYC. Those new digital projectors do a fine job! However, I do miss the looks of the older Zeiss machine--the double-ended ones with the open grid structure. We had one in St. Louis, made by Goto, that looked like the Zeiss. And the Denver Planetarium had one made by, as I recall, Minolta. They all had a mystical, other-worldly look that seemed just right for a planetarium. I did see a show a few years ago in Chicago, when they still had their earlier Zeiss projector. The presenter was complaining that it was too old, and the motors were too old and noisy. In a way I'm sorry to see them go; and yet glad that my favorite planetariums have gotten the latest equipment that they wanted.
     
  12. Planar lenses come in different 'flavours', and the planetarium projector using Planars is not enough reason to assume the Hasselblad/Zeiss Planar (any of them) would be a good projector lens also. Could be, but you can't judge by that.
    The Zeiss P-Distagon, P-Planar and P-Sonnar lenses available for the PCP80 are made for projecting slides, so we can safely assume they are optimized for the task.
     
  13. The planetarium projector uses metal plates for its star charts, and the dome is more than 15x the distance of lens to "slide". The dome is roughly spherical, so either the star charts are sections of spheres, or the lens formula allows for the curviture. In a slide projector, both the source and screen are flat and the screen is relatively distant, so I see no major optical problems.
     
  14. Edward,

    Well, for instance, 'flat-to-flat' imaging is why they make Makro-Planars/S-Planars as well as 'regular' Planars. 'Flat-to-dome' is another thing and could indeed (i don't know how the planetarium thing works) require a lens that allows for the curvature.
    You get the best performance out of lenses that are made for the particular task. Whether that means a 'regular' camera Planar would be visibly less good than a P-Planar i don't know. But given that there are P-Planars available, already in a mount that fits a projector that itself doesn't need any further modification...?
     
  15. All rectilinear lenses are nominally "flat to flat", which is what you would want in a slide projector. The exact design of the planetarium lenses is off topic.
     
  16. If the design of the planetarium projection lenses is off topic, Edward, why did you mention them?
    If "all rectilinear lenses are nominallt flat to flat", why do they make special lenses that are particularly good at doing flat to flat?
    Or lenses that are good at projecting?
    Questions, questions... ;-)
     
  17. "If it's any indication, the half-million dollar Zeiss projector at the Chicago Planetarium uses Zeiss Planar lenses."
    It's an indication that Zeiss Planar lenses made for the Zeiss Planetarium Projector belong on the Zeiss Planetarium Projector. But I don't think it's an indication that Zeiss camera lenses necessarily belong on projectors. I do feel that Zeiss projection lenses belong on Zeiss 6 x 6 projectors (my Hasselblad PCP-80 projectors were actually made by Zeiss, according to the plaque underneath them). When people see my transparencies shot in my 500C/M and SWC/M CF, projected on my 8-foot wide screen, they say, "It's just like being there."
     
  18. I mentioned the planetarium to illustrate that Planar lenses are used in projectors, including one which requires exceptional resolution. The only question is that of field curvature. Since the "slides" in that projector are pierced metal, it would be far simpler to form those slides in a spherical section compatible with the spherical screen, than to redesign a lens with such a limited market.
    That's precisely how a Schmidt telescope works - the field is curved, and the film is held in a vacuum platen, conforming it to the matching curvature.
    The optical design of a Hasselblad camera lens is suitable for slide projection, because the slide is flat as is the screen. The distance from slide to the lens and lens to the screen is comparable to the use of that lens in photography, but with light traveling in the opposite direction. As long as the screen is more than 5' away, it's not even a macro situation. It's not exactly a new idea, either. There was an attachment for my Speed Graphic that allowed the camera to be used as an enlarger, which is nothing more than a projector.
    The remaining question is how the lens would be mounted and focused. Most projection lenses I've seen don't have a focusing system. It's part of the projector, or the lens is threaded on the outside. That doesn't mean it couldn't work.
    That doesn't mean it's a practical solution, however. If you can buy a MF projector, why would you want to build one? For that matter, why use a projector at all? A HD TV screen has more resolution than any projector I've seen, and Omnimax is only 4K (twice HD resolution). Of course if you've never had a projector, you can believe what you wish.
     
  19. "The remaining question is how the lens would be [...]"

    No, Edward. The question whether camera lenses make better or as good as projection lenses as lenses made for projection hasn't gone away. The answer is along the lines of "don't count on it" or "probably not".
     

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