retro focus lens in ~120mm fl range

[bglick]

Is anyone aware of a retro focus lens (longer back focal length vs. the lenses nominal fl) in the 120mm fl range?

[ic-racer]

My first thought was a wide angle lens for a RB Graflex SLR, but I don't think any were ever made.

[Jason Greenberg Motamedi]

Were any retrofocus LF lenses made? I can't think of a single example.

[rdenney]

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.

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

[Paul Ewins]

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.

[Jason Greenberg Motamedi]

The Komura 75/6.3 & 90/6.3 are both retrofocus designs...

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.

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.

[Nick_3536]

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.

[Paul Ewins]

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.

[GPS]

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.

[Dan Fromm]

Bill, what are you trying to accomplish?

What constrains you from using a lens of normal construction?

[Bruce Watson]

Is anyone aware of a retro focus lens (longer back focal length vs. the lenses nominal fl) in the 120mm fl range?

I personally would love to see a line of retrofocus LF lenses for 5x4 and perhaps other formats. In particular I'd love to see new designs that would let me use short focal lengths (60mm - 100mm) with flange-film plane distances of 100+ mm.

Sadly I don't know of any that have ever been offered commercially. In any focal length.

[Dan Fromm]

Bruce, I think making a short 4x5 camera would cost you less than a set of lenses for 4x5 with short flange-to-film distances. Imagine a camera with bag bellows and standards large enough to make putting the lens on a deeply recessed board practical.

Cheers,

Dan

[Bruce Watson]

Bruce, I think making a short 4x5 camera would cost you less than a set of lenses for 4x5 with short flange-to-film distances. Imagine a camera with bag bellows and standards large enough to make putting the lens on a deeply recessed board practical.

Cheers,

Dan

And yet short focal length retrofocus lenses are what I want. What I don't want is a bigger heavier camera, or one specialized for short focal lengths. I don't want a bag bellows that I have to carry around and change in the field. I've got enough stuff (bulk and weight) on my back already.

No, what I want is another lens in the lens case. That I can't get it just means that I don't use super-wides. My shortest lens is an 80mm SS-XL. I don't feel like I'm missing a lot by not having a 60mm lens capability. But if I could find a 60mm retrofocus lens, I'd sure look at it. And no, I'm not holding my breath.

[Steve Goldstein]

Do any of the recent crop of "digital" LF lenses do what you need?

I'm not a lens designer, nor do I play one on TV, but I thought one of the issues they attempt to deal with is the angle at which the light hits the sensor. Seems to me that one way to make it more perpendicular is to move the lens further away from the "film" plane.

Of course, I could be completely wrong, and it wouldn't be the first time.