Which 90mm lens has the shortest rear element?

Discussion in 'Large Format Cameras and Accessories' started by Icescapes, Dec 22, 2008.

  1. Icescapes

    Icescapes Member

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    Hi, guys.

    Anybody know a decent 90mm that fits this bill?:

    --A rear element that's not much longer from the flange than that of the Symmar 110mm XL (i.e., stubby)
    --Coverage of 220mm or more.

    Thanks!

    Pete.
     
  2. Martin Aislabie

    Martin Aislabie Subscriber

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  3. Icescapes

    Icescapes Member

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    Thanks, Martin.
     
  4. Trevor Crone

    Trevor Crone Member

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    Pete, I don't know if you've considered the 80mm XL Super Symmar. Smaller image circle, 212mm. But it's a cracking little lens. Just measured the rear element and it protrudes just under 12mm. Being a wider lens then a 90 this has got me out of trouble a few times when I couldn't get back far enough with the 90
     
  5. Icescapes

    Icescapes Member

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    Hi, Trevor.

    Yes, definitely considered the 80mm...the focal length is a bit too short for me to focus at infinity with my setup. Though, I might be able to do some mods to get there.

    Much appreciated.

    Pete.
     
  6. Trevor Crone

    Trevor Crone Member

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    Pete, can your setup take a suitable recessed lens panel?
     
  7. Nick Zentena

    Nick Zentena Member

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    Can I ask why you're looking for a small rear element? I'm guessing you really should be asking about flange distance. For example the Nikon 90mm is I think a 98mm flange distance.
     
  8. Icescapes

    Icescapes Member

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    Yes, but it involves a digital application--I'll be careful here.

    So...I guess you could say that my film plane is further back from the rear-standard than would normally be the case, so it's causing me to focus wider lenses pretty snug with the rear-standard. I've been using a Fujinon 120mm f8.0 that has a rather long rear-element (nice hard to find lens with good coverage, up for sale soon). When focusing at infinity, the rear element actually enters the standard and bumps up against the sides when making lateral shifts.

    A recessed board doesn't help the situation, as it's not a question of how close I can bring the flange to the rear-standard, I'm good to go in that respect.

    I am going to make a few mods to shorten the distance from the back of the rear-standard to my film plane, in which case the 80mm XL might be an option as the flange (and hence, the rear element) won't have to be so close to the rear-standard then.

    Thanks,

    Pete.
     
    Last edited by a moderator: Dec 22, 2008
  9. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Lenses like the old 90mm/6.8 Angulon are very compact front and back, but may not be sharp enough for your application that dare not speak its name.
     
  10. Icescapes

    Icescapes Member

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    What kind of coverage are we talking on the older 90mm/6.8 Angulon?
     
  11. Mick Fagan

    Mick Fagan Subscriber

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    Mine covers 4x5 with a small amount of shift spare.

    With the rear lens cap off it sticks out about 5mm with the lens cap on about 7mm.

    I don't think you will get much a smaller rear intrusion than that.

    Mick.
     
  12. jnanian

    jnanian Advertiser Advertiser

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    a 3 1/2" wollensak exwa f12 has a large circle
    when stopped down it will cover a 5x7 sheet
    and it is tiny, like an angulon.
    a 90mm raptar (OPTAR) as well
    ( and i think one is for sale in the classyfieds ) ...
    i had both lenses and used them often.
    lots of coverage / image circle ...
     
  13. kirkfry

    kirkfry Member

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  14. 2F/2F

    2F/2F Member

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    Perhaps it would help if you told us what you are doing that is moving your plane of focus so far behind the ground glass, and that also requires 5x7 coverage. No one will shoot you for mentioning your plan, even if it involves digital. We just don't want to hear a bunch of effing questions and answers about the digital part of it.

    The 90mm Wolly in the classifieds is spoken for by me. I did not plan on it providing any movements even on 4x5, and am surprised to hear that it will cover 5x7 stopped down. Everything I have found about it mentions how soft it is and how it allows almost no movement. I am hoping that John's description is closer to the truth! :D
     
    Last edited by a moderator: Dec 23, 2008
  15. Icescapes

    Icescapes Member

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    Thanks guys.

    As to the digital application 2f/2f, I've modified a mount with an EOS bayonet in the center that I attach to the rear standard. This allows me to do up to 9 rows of 9 shots through rise and fall and shifting. I later stitch together in PS3.

    The problem that this setup has (other than not having grain) is that the Canon camera's sensor is recessed about 35mm or so into its body. Once you add another 10mm to clear the hand grip and some wasted space between that and the filmback mount surface, you've used up the focal length of a wide-angle lens for 4x5 coverage by positioning the film plane all those millimeters behind the rear standard.

    The mods that will help this are 1) sand about 2mm off the hand grip, 2) reduce the bayonet extension tube by about 7mm, and 3) use a thinner piece of aluminum by about 1mm for the filmback mount.

    These mods will allow me to barely focus a 75mm lens at infinity (currently can only focus at about 1 foot with it), but will allow me to focus a 90mm at infinity and have room for shift/fall/rise movements on the rear standard (provided that the rear element isn't long as mentioned through this thread).

    Pete.
     
  16. 2F/2F

    2F/2F Member

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    Hi, Pete.

    That is exactly what I assumed you were doing.

    If everything is aligned perfectly, you can get one heck of a file with this method. Drawback, of course, is still life work only, and the aforementioned hassle of making sure everything is perfectly square before shifting.

    How far can you shift the camera before the image is clipped by the shadow of the lens mount?

    My next question would be: Why do you want such a wide angle of view? Do you need it for still life work?

    Sounds like a custom camera is the key here. You need something that completely eliminates the rear carrier frame. Not hard to rig, actually. You just need to engineer a way to squarely mount the SLR to the rear standard (modified L bracket), and a way to seal the bellows to the EOS lens mount (AKA lots of gaffer tape).
     
    Last edited by a moderator: Dec 23, 2008
  17. Ole

    Ole Moderator Staff Member Moderator

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    ... depending on the age of the lens and your definition of "coverage". As my little test shows, later ones are sharper within the intended coverage but fall off more rapidly outside that radius. Older ones have a more gradual loss of definition beginning earlier, which leads to the curious result that the corners on 5x7" are actually sharper than with a newer lens - which however gives sharper corners on 4x5".
     
  18. Icescapes

    Icescapes Member

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    I actually did a custom fit to a Horseman LE, and it worked great...down to 120mm. I still use the groundglass for composition, then i put in the modified plate to hook up the EOS, so I still want the carrier (I've seen the SLR L-bracket mount before, and though a good solution that I've contemplated, I don't want to have to dismount the carrier, and mount the L-bracket everytime after composing). This time around, though, I'm confident that I can reduce enough wasted space between the mount and the standard to get to 90mm with comfortable movements. A little bit of work myself, and a little bit of machine shop work will get me there.

    As for why I want to work with wide-angle glass like 90mm, I like the field of view it gives for landscapes.

    Haven't had any shadow clipping caused by the lens mount, I can go to the edge of the image circle of both my 120mmm and 150mm Fujinons comfortably. What shows up on 4x5 groundglass is pretty close to the resulting stitched image.
     
  19. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    I wouldn't use a 90mm/6.8 Angulon for a format larger than 4x5", unless you want the soft edges as an effect. It illuminates a large circle, but definition drops off rather drastically.
     
  20. Ole

    Ole Moderator Staff Member Moderator

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    I agree David, but the degree of "drops off rather drastically" depends on the age of the lens. A pre-WWII one can be stretched to cover quite a lot, although you have to sacrifice overall sharpness by shooting at f:45!
     
  21. rshepard

    rshepard Member

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    I just purchased a Wollensak 3.5" (90mm) f/12.5 lens in a Raptar shutter. The rear of the lens is no further from the board than is the mounting ring. That is, essentially flat. I know the lens covers 4x5 film and read in another thread (on Wollensak lenses) that it will also cover 5x7 if stepped down.

    Rich