Which lens design is shown in this diagram? f/4.5, 10 elements, 8 groups, 78°

[genotypewriter]

Left: Object end
Right: Image/film end

Max aperture: f/4.5
Construction: 10 elements in 8 groups
Angle of good coverage at ∞: 78° from f/4.5
Optimised focal distance: ∞ and thereabouts
Fwiw, it's also multi-coated.

Is there a close match or is it comparable to something that you've seen? I find the flatter front surface interesting/different.

Thanks in advance!

G

[Jac@stafford.net]

It looks like a Fujinon 55mm EBC for MF.

[Taija71A]

It looks like a Fujinon 55mm EBC for MF.

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WOW!!!
Great 'Eye' Jac!


http://www.gf670.com/downloads/GF670W_Brochure.pdf

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[genotypewriter]

Thanks but I was hoping if anyone knew if it's similar to any classic designs like biogon, etc. The lens looks similar to a reversed Voigtlander Ultron 28/2 but some +/- surfaces are -/+ so I don't think they came from the same place.

Being a non-retro focus rather modest 78-degree wide-angle, I find it interesting how it has 10 elements when even a 105-degree f/4.5 Super Symmar XL has only 6 elements. Any thoughts?

[Bob Salomon]

Thanks but I was hoping if anyone knew if it's similar to any classic designs like biogon, etc. The lens looks similar to a reversed Voigtlander Ultron 28/2 but some +/- surfaces are -/+ so I don't think they came from the same place.

Being a non-retro focus rather modest 78-degree wide-angle, I find it interesting how it has 10 elements when even a 105-degree f/4.5 Super Symmar XL has only 6 elements. Any thoughts?

Some Rodenstock wide angles for digital have up to 15 elements. Several have 10.

[EdSawyer]

Sometimes elements are used for things like field flattening, as opposed to correction. Also, modern lenses don't have the same choice of glasses for construction as they did pre-2002 or so, so optical formulas have a smaller choice of glass types and thus other compromises to a design may need to be made.

[EdSawyer]

Sometimes lens patents can be illuminating also , as to why certain design choices are made. Fuji obviously spent some money on this lens. It would be interesting to see how it stacks up against say the 50 and 65 from Mamiya for the mamiya 7.

[Jac@stafford.net]

Thanks but I was hoping if anyone knew if it's similar to any classic designs like biogon, etc. angle,

With respect, it does not matter how the lens is described. If you wish to know how it renders you have to use it yourself. ...and it is obviously not a Biogon type.

[genotypewriter]

Thanks for the inputs everyone. I didnt have a look at the Digitar and Digaron era designs. Didn't think they would be any more relevant than SLR designs because they're made to have a long back focus. This GF670W or Bessa 667/IIIW lens is only for film afterall and the lens isnt sitting suspiciously further away (or too close) going by the focal length. But I want to get to the bottom of this so I will have a closer look at digital stuff too.

Jac@stafford: oh I got a brand new one last week and love the images im getting with it. It's like a Leica for people who appreciate formats larger than 35mm I only asked this question to understand the lens design. I find this lens interesting because of the large number of elements used while having a fairly conservative f number and an angle of view, being optimised for low magnification and made only for film. So I was wondering if anything like this is there in LF too.

Would like to hear more thoughts from people... especially about the flat front element and the bulging rear element. What reasons are there to possibly use a lens in the reversed position if it's to be used for low magnifications?

Thanks again.

[Len Middleton]

Actually have an old Nikkor-UD wide angle 20mm f3.5 lens that will do you one element more (11), but that is an early pre-AI retro-focus design that followed their old 21mm design that required mirror lock up.