roodpe said:Michael,
The Zeiss 150mm f9 dagor would not cover 10x12 based on my experience with other focal lengths of this design. The 180mm covers 8x10 with movement and probably 10x12 based on the range of movements I get. I have a 75mm version that just makes 4x5 stopped down so I would assume the 150mm just covers 8x10. My 210mm covers 11x14. Maybe there is some variance between lenses and some cover more than others.
I do agree with you and Sandy that there is a market for this design. I would suggest that if you are serious about pursuing a manufacturer, then you're best bet would be Cooke Optics. I talked with their lens designer a little over a year ago and he said they were looking at the possibility of reintroducing modern designs of their wide angle series VIIb. He told me they used modern coatings and exotic glass (lanthanum) for the new triple covertible lens. I am sure they could surpass the performance of the f9 dagors with a modern re-design of the VIIb. I can't remember their designers name but I am sure this could be brought to Barbara Lowry's attention to see if they have any interest.
Peter
Michael Mutmansky said:Sandy,
The Zeiss WA dagors will cover more than the Computar, if the 150mm version is any indication. The computar will maybe hit the corners of 8x10, but the Zeiss will cover 10x12 with a little room. I can't say how the performance is for them because I haven't use them. Longer focal lenghts will probably vary in coverage.
The Computars suffer from field curvature terribly in the outer limits of coverage, but I suspect that a slight modification to the design could correct that nicely and make a great design for ULF shooters. It's possible to have good sharpness out towards the edges with these lenses, but not at the same time as the center.
roodpe said:Michael,
The Zeiss 150mm f9 dagor would not cover 10x12 based on my experience with other focal lengths of this design. The 180mm covers 8x10 with movement and probably 10x12 based on the range of movements I get. I have a 75mm version that just makes 4x5 stopped down so I would assume the 150mm just covers 8x10. My 210mm covers 11x14. Maybe there is some variance between lenses and some cover more than others.
<SNIP>
Peter
Harrigan said:I can have lenses designed for you but I doubt you can afford to pay for lens manufacturing. The cost to make such lenses is extreme and the market is tiny. If you are serious about wanting a lens designed and built contact me. I have very close connections to very well known optical lens designers. I've had some lenses made myself to my specs but I have to tell you the cost is pretty high and the market is minescule. You can get a decent price on manufacturing lenses but you have to order alot of glass. If you are serious I can help you design and have lenses made. The initial investment is significant but a group of people invensting could make it happen.
Harrigan said:The cost is related to many issues including paying the lens designer. The physical size of the glass is an issue and the quantity of production. Basically getting a design and having a prototype made would cost thousands. The lenses I had made weren't too bad but it was a simple stereoscope cemented achromat. Making photographic objective would be considerably more although a small lens like the computar wouldn't be so bad. The smaller the glass the less expensive it is to machine etc. Actually I may have a direct contact to the computar designer and could possibly get the design right from the man who did the original. I do have a connection to the computar enlarger lens designer and I think the same guy did the process lens. I do think that the market for such lenses is pretty small, isn't it?
Harrigan said:The cost is related to many issues including paying the lens designer. The physical size of the glass is an issue and the quantity of production. Basically getting a design and having a prototype made would cost thousands. The lenses I had made weren't too bad but it was a simple stereoscope cemented achromat. Making photographic objective would be considerably more although a small lens like the computar wouldn't be so bad. The smaller the glass the less expensive it is to machine etc. Actually I may have a direct contact to the computar designer and could possibly get the design right from the man who did the original. I do have a connection to the computar enlarger lens designer and I think the same guy did the process lens. I do think that the market for such lenses is pretty small, isn't it?
Michael Kadillak said:I agree with Sandy on his objectives but would add that a 12" lens in the coverage range of 12x20+ would be also very nice.
Comments? Let's do it!
Cheers
sanking said:For ULF work one could sacrifice a fair amount of performance in the center for maximum coverage and good performance on the far edges. The Computar design is nice, but would need to be tweaked to give a flatter field (it has lots of field curvature) and better resolution on the edges.
kthalmann said:Sandy,
Have you tried playing with the cell spacing of your Computar to get better edge performance? My 240mm Computar came without the spacer that goes between the rear cell and the shutter. I supect a lot of these spacers have gotten lost over the years. Supposedly, the purpose of these spacers was to improve edge performance at the expensive of absolute sharpest performance in the center of the field. I just picked up a 240mm Computar spacer from Dagor77 on eBay, but haven't had a chance to test performance with/without spacer, yet.
If getting better edge performance is as simple as chaging the cell spacing AND someone can get access to the opriginal f9 Computar design, perhaps no optical redesign would be necessary to get the improved edge performance ULF users desire.
Kerry
Michael,
I guess my rule is want more. I already have a 300mm Computar lens that covers 12X20 with at least two inches of movement, and sharp all over the field when stopped down. Just wanted to push the limits a bit to 270mm, which I think would be fairly conservative for the Computar design.
How about a line of 210, 300 and 450 Computar lnses, all with coverage of 110 degrees, and sized for format by aperture so that all three are of about the same weight and fit Copal 3. The 210mm would just barrely cover 12X20, the 300 would cover with a bunch of movement, and the 450 would cover 20X24 with a fair range of movements.
BTW, my Schneider 550mm f/11 XXL has arrived, and also the 210mm f/5.6 SSXL which was thrown in just to make me happy with the deal. I have tested both of them for perormance on the 12X20 format and there is no question but that both lenses are *vastly superior* on the far edges of the circle of illumination to any lenses of comparable focal lengths I have tested in the past.
What I have not checked is the maximum circle of illluminatin of the 550mm f/11 Dagor XXL (did not want to set up my 20X24 to do so). I am hoping that it is much greater than the 78 degrees of stated coverage. If so, and up to 90-95 degrees with good pefomance at the far edges, this might be a very good design for lenses in the 300mm-450mm range for ULF work. I think plain Dagor design has a lot to offer for ULF, provided we can get good performance on the edges of the circle of illumination, somthing I have not seen so far with any Dagor type lens.
Sandy
Sandy,
I'm planning on a 550XXL purchase soon. I wonder if Jeff at Badger will throw in a 210 f/5.6 SS/XL to make me happy? Anyway, last week when I spoke with him, he commented that he has sold an astonishing number of 550XXL's. Great news for ULFers.
I would like to put my name on any list that develops for additional ULF lens alternatives, particularly for 14X17 and 16X20 formats. I have several Apo-Ronars and a couple of long Apo Artars, but would be interested in some of these other ideas that are kicking around.
Just plainly curious - why did you prefer the 550XXL instead of the 600 Fuji C? A question of the additional coverage?
And forget the Chinese Zeiss version - Zeiss would never allow to ruin its fame with such a version... It's not just a matter of the lens design. It's the machinery, the toleration, the quality control with its special device demands etc. To produce the Zeiss quality you have to have the Zeiss quality factory!
Just plainly curious - why did you prefer the 550XXL instead of the 600 Fuji C? A question of the additional coverage?
And forget the Chinese Zeiss version - Zeiss would never allow to ruin its fame with such a version... It's not just a matter of the lens design. It's the machinery, the toleration, the quality control with its special device demands etc. To produce the Zeiss quality you have to have the Zeiss quality factory!
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