wharrison
TPF Noob!
Dave:
My apologies! So here's some further information and a story.
I am not certain that I can provide you will all of the "details" you might wish to know or need, but I will share more of what I've learned and experienced over the years.
1. My "old" Leitz Pradovit N-24 projector, which I purchased used and used my old Kodak Carousel 750H as a trade, had a lamp filament adjustment screw on the left side of the projector - as the projector was facing the screen.
As you may or may not know, Leitz was world renown - and still is - for the manufacture of superb microscopes - something that they did decades prior to Oskar Barnack's invention of the prototype Leica. (LEItz CAmera).
In viewing through a microscope and especially, when doing photomicroscopy, one of the things that needs to be done first is to "columnate" the light source. (I think I am using the correct term.) I will not describe the whole process, but basically one had to make certain the that light emerging from the bottom of the microscope was "centered" to provide even illuminatation all the way through the slide and thence to the optics of the miscroscope and also to the film.
FYI - I worked for some time as a Staff Photographer at the University of Illinois College of Medicine - Peoria (Illinois) campus and had the privilege of working with a $35,000 (decades ago prices) Zeiss Photomicroscope III. Not knowing anything about photomicroscopy, I obtained Kodak's publication "Photography through the Microscope" and spent hours - including many unpaid overtime - learning the art of photomicroscopy, developing B & W and Ektachrome films to eventually come to a high standard of producing consistent results.
In the process, I found out that the exposure metering system in this fine new Zeiss microscope was way off; the illumination diaphram at the bottom light source was defective; that the flash unit was disfunctional; that the microscope needed some other minor adjustments; and the poor service (not Zeiss) of the company in Chicago that sold the microscope to the School of Medicine in Peoria. But that's another interesting and long story.
At any rate, the Leitz Pradovit N-4, the Pradovit Color 150 and the Pradovit Color 250 - and I suspect newer models, all have an adjustment screw to make certain the the light source is centered to provide even illumination on the slide and through the optics.
All one had to do is to cut a nice 2 X 2 inch piece of cardboard and drill about a 1/4 inch hole in the absolute center. If you purchased your Leitz projector new, this centering slide came with the projector.
Then one just placed the centering slide in the slide tray, loaded it in the projector, and turned the projector on. Then one placed the (milky white - for want of a better description) dust cap over the lens and made certain that the projection lens was turned all the way back into the projector.
In this process, the centering slide produce a "double" image of the filament of the projection lamp on to the lens cap. In my old N-24 Leitz Pradovit - using a CYN lamp, the image would look something like this if it wasn't centered.
(Well, I tried providing a diagram, but it doesn't work, when I previewed it.)
One simply turned the lamp filament adjustment screw ever so slightly in either direction to make certain that the top and bottom images of the filaments were aligned - centered. A very short process that only needed to be repeated, if the lamp burned out and needed replacement.
I know that projectors made by Kodak, Sawyer's, Bell & Howell, Airquipt, Pentax, etc. never had a lamp filament centering device to insure even illumination of the slide. Perhaps, other European projectors - Kindermann or Rollei, for example - might have had them, but I've only seen these projectors and haven't used them.
2. At one time, Leitz made a "test" slide, which include a very nice "color wheel" in the center, a double (top and bottom) very long grey scale at the bottom center, and an array of other means by which to compare the image quality, sharpness, corner to corner luminosity of Leitz projectors.
This "test" slide - which is, unfortunately, no longer available - came in handy in other ways as well. For example, it provided a means to insure that your projector was exactly perpendicular to the screen on which you were showing your images. If the test slide projected a sharp image at the top of the screen, somewhat sharp in the center, and out of focus on the bottom, you quickly realized that the projector was not perpendicular to the screen and made the necessary adjustments. I still use my "test slide" - it's the first slide shown - when I show (somewhat rare these days - but that may change) slides
I obtained a Leitz Pradovit "test slide" for use when I was the Staff Photographer at the School of Medicine in Peoria. It came in very handy to insure proper exposure and developing times for B & W films and/or for color slides - at times we did a lot of duplicate slide shooting and processing for the medical staff/professors at the College of Medicine. It also came in handy when we made Cibachrome prints - on few occasions - for the "Pathology Boards" (4 X 8 foot masonite boards, painted blue, which held, prints, diagrams, words, etc. showing the progress of a disease) that the school's educational department did for the medical students.
3. If my memory serves me correctly, my old Pradovit N-24, the Pradovit Color 150 and the Pradovit Color 250 (all now older models) constructed the focusing or auto-focusing mechanism in such a manner that the slide chamber moves rather than the lens. Obviously, such engineering makes for more rapid (and perhaps, accurate) focusing and less eye strain on the viewers - over a long period of time - the projection of several hundred slides in an evening.
4. The slide chamber on Leitz projector is designed to keep the slide cooler than other projectors thus eliminating or greatly minimizing the "popping" in and out of focus that can happen when a 'cool' slide hits a warm or hot chamber. One of our customer's - a Professor of Art at Knox College in Galesburg, IL deliberately used Leitz projectors because (1) she could leave the same (art) slide in for very long periods of time and (2) the projector wouldn't damage her slides in anyway whatsoever.
5. Of course, there are other important factors as well - beginning with the optics of the condensors and Leica projection lenses - the most famous of which is the 90mm Colorplan. If you come across an old Leitz Pradovit N-24, you'll find out that it weighs a ton. Well, not literally, of course, but it is much heavier than the Kodak Carousel. My Pradovit Color 150 is a little lighter, but still manufacture with more than durable materials - beginning with the housing.
6. I hesitate to "advise" you on what Leitz Pradovit projector to seek for possible purchase, but I will offer the following.
Although the Pradovit N-24 is still an excellent purchase, I am not certain of the availability of CYN projection lamps. If interested, you should, of course, email Dave Elwell of the Leica Camera repair dept. and inquire if they still have the quartz halogen lamp conversion kit still available, which will allow you to use the FCS bulb. At one time, I found 18 FCS lamps and paid a mere $12.00 for the lot - so I have more than enough lamps to last me the rest of my life.
So if you're currently constrained by budget, I might opt for a used, but excellent condition, Leitz Pradovit N-24, but be certain to check with the Leitz repair department first for the conversion kit.
If you're moderately constrained by a budget, I'd seek out the Pradovit Color 250 - not because you intend to project images in a very large auditorium, but because you may wish to have a slightly brighter light. The Pradovit Color 150 produces a much brighter and whiter light on the screen and is very well suited for home use.
Both the N-24 and the Pradovit Color 150 and 250 projectors used the same type (diameter) lenses and are, therefore, interchangeable. In addition to the 90mm Colorplan, I would also opt for a 120mm Leitz Projection lens - I believe the name is Elmaron - it's been a long time since I've looked at mine. The 120mm lens will simply give you a little more distance between the projector and a 50 X 50 inch screen.
Sometime later and I don't know when, Leitz redesigned both its projectors and its lens - so I am not certain as to whether the lenses for 1500 and 2500 series projectors - also a nice buy these days - are compatible with the older projectors. You'll have to do your homework in this area. On the point, members of the Leica Historical Society and/or Leica Camera should be of great help.
Hope this additional information is useful.
Again, my apologies for the mis-interpretation.
Bill
My apologies! So here's some further information and a story.
I am not certain that I can provide you will all of the "details" you might wish to know or need, but I will share more of what I've learned and experienced over the years.
1. My "old" Leitz Pradovit N-24 projector, which I purchased used and used my old Kodak Carousel 750H as a trade, had a lamp filament adjustment screw on the left side of the projector - as the projector was facing the screen.
As you may or may not know, Leitz was world renown - and still is - for the manufacture of superb microscopes - something that they did decades prior to Oskar Barnack's invention of the prototype Leica. (LEItz CAmera).
In viewing through a microscope and especially, when doing photomicroscopy, one of the things that needs to be done first is to "columnate" the light source. (I think I am using the correct term.) I will not describe the whole process, but basically one had to make certain the that light emerging from the bottom of the microscope was "centered" to provide even illuminatation all the way through the slide and thence to the optics of the miscroscope and also to the film.
FYI - I worked for some time as a Staff Photographer at the University of Illinois College of Medicine - Peoria (Illinois) campus and had the privilege of working with a $35,000 (decades ago prices) Zeiss Photomicroscope III. Not knowing anything about photomicroscopy, I obtained Kodak's publication "Photography through the Microscope" and spent hours - including many unpaid overtime - learning the art of photomicroscopy, developing B & W and Ektachrome films to eventually come to a high standard of producing consistent results.
In the process, I found out that the exposure metering system in this fine new Zeiss microscope was way off; the illumination diaphram at the bottom light source was defective; that the flash unit was disfunctional; that the microscope needed some other minor adjustments; and the poor service (not Zeiss) of the company in Chicago that sold the microscope to the School of Medicine in Peoria. But that's another interesting and long story.
At any rate, the Leitz Pradovit N-4, the Pradovit Color 150 and the Pradovit Color 250 - and I suspect newer models, all have an adjustment screw to make certain the the light source is centered to provide even illumination on the slide and through the optics.
All one had to do is to cut a nice 2 X 2 inch piece of cardboard and drill about a 1/4 inch hole in the absolute center. If you purchased your Leitz projector new, this centering slide came with the projector.
Then one just placed the centering slide in the slide tray, loaded it in the projector, and turned the projector on. Then one placed the (milky white - for want of a better description) dust cap over the lens and made certain that the projection lens was turned all the way back into the projector.
In this process, the centering slide produce a "double" image of the filament of the projection lamp on to the lens cap. In my old N-24 Leitz Pradovit - using a CYN lamp, the image would look something like this if it wasn't centered.
(Well, I tried providing a diagram, but it doesn't work, when I previewed it.)
One simply turned the lamp filament adjustment screw ever so slightly in either direction to make certain that the top and bottom images of the filaments were aligned - centered. A very short process that only needed to be repeated, if the lamp burned out and needed replacement.
I know that projectors made by Kodak, Sawyer's, Bell & Howell, Airquipt, Pentax, etc. never had a lamp filament centering device to insure even illumination of the slide. Perhaps, other European projectors - Kindermann or Rollei, for example - might have had them, but I've only seen these projectors and haven't used them.
2. At one time, Leitz made a "test" slide, which include a very nice "color wheel" in the center, a double (top and bottom) very long grey scale at the bottom center, and an array of other means by which to compare the image quality, sharpness, corner to corner luminosity of Leitz projectors.
This "test" slide - which is, unfortunately, no longer available - came in handy in other ways as well. For example, it provided a means to insure that your projector was exactly perpendicular to the screen on which you were showing your images. If the test slide projected a sharp image at the top of the screen, somewhat sharp in the center, and out of focus on the bottom, you quickly realized that the projector was not perpendicular to the screen and made the necessary adjustments. I still use my "test slide" - it's the first slide shown - when I show (somewhat rare these days - but that may change) slides
I obtained a Leitz Pradovit "test slide" for use when I was the Staff Photographer at the School of Medicine in Peoria. It came in very handy to insure proper exposure and developing times for B & W films and/or for color slides - at times we did a lot of duplicate slide shooting and processing for the medical staff/professors at the College of Medicine. It also came in handy when we made Cibachrome prints - on few occasions - for the "Pathology Boards" (4 X 8 foot masonite boards, painted blue, which held, prints, diagrams, words, etc. showing the progress of a disease) that the school's educational department did for the medical students.
3. If my memory serves me correctly, my old Pradovit N-24, the Pradovit Color 150 and the Pradovit Color 250 (all now older models) constructed the focusing or auto-focusing mechanism in such a manner that the slide chamber moves rather than the lens. Obviously, such engineering makes for more rapid (and perhaps, accurate) focusing and less eye strain on the viewers - over a long period of time - the projection of several hundred slides in an evening.
4. The slide chamber on Leitz projector is designed to keep the slide cooler than other projectors thus eliminating or greatly minimizing the "popping" in and out of focus that can happen when a 'cool' slide hits a warm or hot chamber. One of our customer's - a Professor of Art at Knox College in Galesburg, IL deliberately used Leitz projectors because (1) she could leave the same (art) slide in for very long periods of time and (2) the projector wouldn't damage her slides in anyway whatsoever.
5. Of course, there are other important factors as well - beginning with the optics of the condensors and Leica projection lenses - the most famous of which is the 90mm Colorplan. If you come across an old Leitz Pradovit N-24, you'll find out that it weighs a ton. Well, not literally, of course, but it is much heavier than the Kodak Carousel. My Pradovit Color 150 is a little lighter, but still manufacture with more than durable materials - beginning with the housing.
6. I hesitate to "advise" you on what Leitz Pradovit projector to seek for possible purchase, but I will offer the following.
Although the Pradovit N-24 is still an excellent purchase, I am not certain of the availability of CYN projection lamps. If interested, you should, of course, email Dave Elwell of the Leica Camera repair dept. and inquire if they still have the quartz halogen lamp conversion kit still available, which will allow you to use the FCS bulb. At one time, I found 18 FCS lamps and paid a mere $12.00 for the lot - so I have more than enough lamps to last me the rest of my life.
So if you're currently constrained by budget, I might opt for a used, but excellent condition, Leitz Pradovit N-24, but be certain to check with the Leitz repair department first for the conversion kit.
If you're moderately constrained by a budget, I'd seek out the Pradovit Color 250 - not because you intend to project images in a very large auditorium, but because you may wish to have a slightly brighter light. The Pradovit Color 150 produces a much brighter and whiter light on the screen and is very well suited for home use.
Both the N-24 and the Pradovit Color 150 and 250 projectors used the same type (diameter) lenses and are, therefore, interchangeable. In addition to the 90mm Colorplan, I would also opt for a 120mm Leitz Projection lens - I believe the name is Elmaron - it's been a long time since I've looked at mine. The 120mm lens will simply give you a little more distance between the projector and a 50 X 50 inch screen.
Sometime later and I don't know when, Leitz redesigned both its projectors and its lens - so I am not certain as to whether the lenses for 1500 and 2500 series projectors - also a nice buy these days - are compatible with the older projectors. You'll have to do your homework in this area. On the point, members of the Leica Historical Society and/or Leica Camera should be of great help.
Hope this additional information is useful.
Again, my apologies for the mis-interpretation.
Bill
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