Is anyone aware of a retro focus lens (longer back focal length vs. the lenses nominal fl) in the 120mm fl range?
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Is anyone aware of a retro focus lens (longer back focal length vs. the lenses nominal fl) in the 120mm fl range?
My first thought was a wide angle lens for a RB Graflex SLR, but I don't think any were ever made.
Were any retrofocus LF lenses made? I can't think of a single example.
Me, neither. As I recall the original point of the retrofocus design was to make room for a mirror box, and the only large-format reflex camera ever made (other than oddities like the Gowlandflex) that I can remember is the Graflex SLR. And those cameras predated Angenieux's 1949-1950 introduction of the retrofocus design.Quote:
Originally Posted by Jason Greenberg Motamedi
Seems like the largest SLRs made in enough quantities to drive lens design since that time were in the 6x7 format, and a 120mm lens wouldn't need to have a retrofocus design to fit in front of a 6x7 mirror box.
Rick "wondering what the application is" Denney
The Komura 75/6.3 & 90/6.3 are both retrofocus designs. The 75 measured up at 100mm from GG to the back of the shutter and the 90 was 135mm. The rear element of the 90mm is quite large (80mm in diameter) which is an issue with smaller cameras like a Speed Graphic or Gowland Pocket. You need to unscrew the rear element to mount the board and then if you use too much swing you hit the bellows. It is fine with a monorail. The 75mm on the other hand is smaller and works well on both a Speed Graphic (with the bed dropped) and the Gowland.
Really? Not that I have any substantive data to question your knowlege, but that just doesn't make sense to me. While I have never used either, I have seen both the 75mm and the 90mm f6.3 Komura lenses, and they both look like typical biogon-type eight-element "wasp-waist" lenses with similar sized (big) front and big rear elements. Retrofocus (or at least the traditional six-element variety), as best I understand, tend to have large front elements and smaller rear elements.Quote:
The Komura 75/6.3 & 90/6.3 are both retrofocus designs...
UPDATE: I did a few web searches and did indeed find a few references to a longer-than-FL flange distance for these lenses. That said, they still look like Biogon-type lenses to me, and according to the documents at camera eccentric, they are eight element lenses, which would suggest that they are Biogon-types.
I thought most of the modern wides are at least a little .
I'd assume the Nikon 120mm is but I can't remember the flange distance off the top of my head. The 90mm is 98mm IIRC. I want to say the 120 is close to 130.
On the question of why. A wide like this is easier on the camera. The 120 Nikon basically covers 8x10. The 90mm covers 5x7.
Jason, sorting through the literature for Schneider, Nikon, Fuji and Rodenstock wides, the flange focal distance usually comes in around 110% of the actual focal length. For the two Komuras it is 130% for the 75mm and 150% for the 90mm. They are physically large too, the 90mm is 120mm long compared to around 90mm for the other brands. They're a 6/4 f6.3 design that is larger and heavier (760g) than most of the 8/4 f4.5 or f5.6 designs.
Granted, they are nowhere near as retrofocus as a typical SLR wide angle lens, but given the loose definition of "apparent focal length longer than actual focal length" then I think they qualify. It is probably because they are mildly retrofocus compared to SLR lenses that they don't look much different to regular LF wides.
AFAIK the only other LF wide they made was the 47/6.3 for 6x9.
Guys, you have to understand two things - an optical retro-focus construction and a simple fact that the FFL of a lens is a little bit longer than its FL are two different things. The optical retro-focus construction is not done on LF lenses for many reasons. The fact that the FFL is a little bit longer than the nominal FL comes not from special retro-focus optics but from the mechanical construction. The FFL is measured from the back of the shutter assembly - the shutter can sometimes be moved a little bit here and there, the aperture placement is mechanically not so sacred in the lens, even if an optimum is clearly defined. After all, shutters have their standard dimensions that do not correspond exactly to the optically optimal aperture placement.
Once you know it you can make the distinction between an optical retro-focus lens and a mechanically slightly changed FFL of a lens.
Bill, what are you trying to accomplish?
What constrains you from using a lens of normal construction?