Does anyone have ANY information on the ILEX-Caltar 508mm f=7.0 (20 inch) lens? When was it made? Type of construction? Is it a process lens... good for close-ups?? Overall quality and characteristic of lens?
Does anyone have ANY information on the ILEX-Caltar 508mm f=7.0 (20 inch) lens? When was it made? Type of construction? Is it a process lens... good for close-ups?? Overall quality and characteristic of lens?
Lynn Jones, who was involved at the time these lens were made for and sold by Calumet, briefly mentions them in an article in the Jan/Feb 1996 View Camera magazine. It was designed to be an affordable lens for a 8x10 camera and so is presumedly designed for studio to far subjects rather than optimized for 1:1 like a process lens. The design is a triplet and L. Jones comments "The early offerings were variable in quality but by 1967 they were uniformly excellent, covering about 35 degrees."
Years ago, (late 1970's) I used the 20" Caltar a few times on 8X10. The example I used produced chromes that were not critically sharp. I'm not sure of the age of the lens, but I suspect it was made later than 1967 -- the studio I worked for bought all their Calumet gear in the early 70's.
Michael and Jerry, thank you very much for your informative answers. A few more related questions which I hope you or others can shed some light. While I now understand that the Caltar is not a process lens, how would the image be -- with an 8x10 camera -- at a 1:1 or slightly less magnified close-up? Where would the image suffer? Is it just a matter of the edges deteriorating or the overall sharpness and image quality? How would the same image compare with what a Rodenstock 480mm Ronar would produce? Is the "bokeh" (unfocused parts of the image) rendered differently with each lens? I suppose I'm really trying to get a sense of the characteristic image created by both the Caltar and the Ronar as well as the difference between the two. I know this is quite a bit to ask but I would be very grateful for your insight and opinions. Thank you.
At 1:1, a "process" type lens is expected to perform much better than a general-poupose lens at the same ratio. The main difference is in resolution and, of course, shows up more and more as the image is enlarged. It is not just the edges. At 1:1 you are using only a small portion of the lenses coverage, so the "edges" are way out beyond the film. Even the center of the image will be relatively poor as compared to a lens made for the purpose.
A symmetrical lens designed for use at 1:1 will ordinarily perform better at infinity than a general-purpose lens perform ar 1:1. This is entirely true of the Apo-Ronar which is a "dialyte" type consisting of four airspaced elements, a type well-known for being particularly tolerant of variations in subject/image ratio. The main disadvantage of such process lenses is their small aperture. They are harder to focus than faster lenses.
Ordinarily, a shorter lens would be chosen for 1:1 on 8" X 10". It takes two focal lengths extension to get to 1:1, so the 24" extension of a 12" lens is less awkward to deal with than the 40" required for a 20" lens.
I can't comment on what differences you might expect to see in out of focus areas. Maybe someone else will provide opinions on this.
Ernest, thank you for your thoughts. Very interesting. While I understand that a shorter lens at double extension would be used for 1:1 images, even the 360mm Ronar doesn't have an image circle large enough to cover 8x10. Of course, I don't have first hand experience here and this is why I defer to those who do. Do I really need double extension though to fill the ground glass with let's say for arguments sake, someone's face -- on an 8x10 with a 480mm Ronar? Or, could I do that with the 360mm or even the 300mm Ronar with still smaller image circle? I'm not concerned with the obvious foreshortening here.
... Oh yes, one more thing. As Ernest points out, at 1:1 I am only using a "small part of the lens" and not to the "edges". So, if I understand correctly, would that mean that the smaller image circle of the Ronar 300mm or 360mm be academic?
Also, when I asked about the extension required to fill the ground glass on an 8x10 with a face, I referred to the 480mm APO-Ronar. My question would also apply, of course, to the 508mm Caltar. Again, thank you for your time.
Why do you think the 360mm Apo-Ronar does not cover 8x10? The Rodenstock literature says that the 360mm Apo-Ronar actually covers 8x10 already at _infinity_, though with nearly no movements (the official image circle is 318mm at inf.). For 1:1 the image circle doubles (636mm), so it will cover 8x10" with lots of movements at that magnification.
You would have laughed if you could have seen me trying to figure out how high a face is. I finally decided that mine is somewhere near 10" high, so 1:1 would be about right to fill an 8" X 10".
As Arne points out, the circles of definition and of illumination double at 1:1. I think that in considering coverage it is well to visualize the lens as a nozzle, spraying light instead of paint. The further the distance from the wall, the greater the size of the circle the nozzle sprays. Whether the nozzle itself has narrow or wide coverage determines the size of the circle you start with, but it still increases in the same manner.
The shorter focal lengths would result in your camera being closer to the subject to fill 8" X 10" with a face, but coverage would be no problem. An even shorter lens would do if you didn't mind a great big nose. In macro work, very short lenses are used so as to avoid ultra-long extensions. As an example, a 6" Tessar type lens with a 56 degree angle of view doesn't begin to cover 8" X 10", but if you used it for 3X magnification it would be 24" from the film, so would be covering way more than the film size.
What a great group of people here! You're all very kind and helpful. And, as I still have one more question... I hope you're all patient too. So please bear with me...
Okay, all clear on the Image-Circle stuff. Now, here's what I'm wondering:
If, with my 4x5 camera I use a 240mm lens at "X" camera-to-subject distance in order get the image size I want on the ground glass -- with a 50% bellows extension (ie - 360mm) -- would I be correct to assume that a 480mm lens on an 8x10 camera, at the same camera-to-subject distance as with the 4x5, would result in proportionally the same image size on the ground glass.... with 50% bellows extension (ie -720mm) ?
Whew! Did ya get all that? (I'm still imagining Ernest trying to measure his head!)
I really want to be absolutely clear on this so that I can select the right lens without resorting to the trial and error approach. Thanks everyone.
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