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W.A. Lenses and Angle of View

Discussion in 'Large Format Cameras and Accessories' started by KenM, Jun 7, 2005.

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  1. Jun 7, 2005 #1
    KenM

    KenM Member

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    I'm currently looking at expanding my kit with an (extreme) wide angle lens. My widest lens is a 75mm, and at times I need something a bit wider, so I've been doing some research on the current crop of available W.A. lenses. And yes, my forthcoming trip into Escalante Canyon has *something* to do with this requirement :D

    It seems that Schneider and Rodenstock are the only major manufacturers of wide angle lenses at this time, so I've been looking at the specs for their 58/55mm and 47mm lenses (the Rodenstock 45mm will not cover 4x5). My 75mm Grandagon-N has a specified angle of view of 105 degrees. The specs for the 58/55 and 47mm lenses indicate that the angle of view is 110 degrees.

    Why are the angle of views so similar between the three lenses? I would expect that the 47 would have a much larger angle of view than the 75 - but the difference is only 5 degrees? Or, is angle of view something different than what I'm assuming?

    I'm planning on getting the 57mm lens, but I'm a bit concerned that the jump between 75mm and 57mm isn't enough to warrant the price tag. Then again, the extra few $100 for the 48mm may just cancel out the deal entirely.

    I also have a 110mm lens, so I can somewhat image how wide the 57mm would be, and it seems pretty darn wide; certainly much wider than my 75mm.

    Lastly, for those of you own one of these lenses and use them for B&W work, do you use a center filter? It's certainly a pricey addition to the lens, and one that I would like to avoid.

    Comments?
     
  2. Jun 7, 2005 #2
    jd callow

    jd callow Moderator Staff Member Moderator

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    Ken, I have a 75mm and bought the 58mm XL. There is a good amount of difference between it and the 75mm. I thought of getting the 47mm, but decided that I really want to get into panoramics, so I am going to eventually get a 6x12 RFH and the 38mm. Otherwise I think I would have gone for the 47mm.

    I don't have the center filter, but I do think it is needed. That will be my next purchase.


    jdc

    I believe that the angle of view has to do with coverage on the film plane so a 58mm will need a little larger angle of view than a 75mm to have similar coverage.
     
  3. Jun 7, 2005 #3
    Mongo

    Mongo Member

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    I believe that the angle of view specifications for the lenses takes into account the size of entire image circle. The Super Angulon 72mm has a circle of 226mm at f/22, whereas the 58mm only has a circle of 166mm. Thus, a similar angle of view even though the image that's actually on the film is much wider. (If you use the "divide by 3" method of comparing lenses with 35mm, the difference between the two Super Angulons is the difference between a 24mm lens and a 19mm lens. That's quite a difference.)
     
  4. Jun 8, 2005 #4
    MichaelBriggs

    MichaelBriggs Member

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    You are probably confusing angle of view with angle of coverage.

    The angle of view tells you how much of the scene will appear in the photo. Assuming that the lens is focused on infinity, isn't a fisheye, and that the lens produces an image that covers the format, the angle of view is solely a function of the focal length of the lens and the dimensions of the format. So the 47 mm will show much more of the scene than your 75 mm lens. Using 120 mm for the long dimension of 4x5, the angles of view are 77 degrees for 75 mm, 95 deg for 55 mm, and 104 deg for 47 mm.

    The angle of coverage tells you the full angle of the cone of quality image projected by the lens. The angle of coverage tends to be approx constant for lenses of the same design type, independent of focal length. The wide-angles lenses that you are looking at have, very approximately, the same design, and hence approximately the the same angle of coverage. That is the similarity that you noticed.

    Probably most photographers will find the diameter of the circle of coverage more useful. The diameter needs to be at least the diagonal of the format. The more that the diameter is larger than the diagonal of the format, the larger the possible movements.

    The diameter of the circle of coverage is from the intersection of the cone of coverage with the image plane. Two lenses of the same design may have exactly the same angle of coverage, but the one with a longer focal length will have a circle of coverage with a larger diameter because the apex of the cone is farther from the film.
     
  5. Jun 18, 2005 #5
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    KenM

    KenM Member

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    Well, I ordered and received the 58mm Super Angulon XL a few days ago. I was quite suprised how small it was. Kind of nice, considering that my kit already weight about 900 lbs :D

    It's a bit tricky to focus on my Master Technika, since you have to use the back to focus, which of course doesn't have geared focusing. Focusing should prove to be a challenge in dimmer light. The shutter has 1/3 stop click stops, my only lens to have that feature. I wish that all my other lenses has that feature - it's kind of nice!

    Now, if only the rain would bugger off so I can go photograph!
     
  6. Jun 18, 2005 #6
    Loose Gravel

    Loose Gravel Member

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    KenM

    Go with the 47. I love wide angle lenses, too. I have the 58xl. Turns out, it will almost cover my 5x7...just the corners are nicked off a bit. I'm sure it is not the sharpest out there, but I don't try to put things in the corners that require that much detail. So I crop about 5mm out of the corners all the way around and I'm shooting 4.5 x 6.5. I'm allowed to crop.

    If you get the 47 and you feel like you need a 58, then crop a little. But if you have the 58, you can't zoom out and you'll not be able to justify the 47 for a long time.

    Have fun in the canyons.
     
  7. Jun 18, 2005 #7
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    KenM

    KenM Member

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    Already bought the 58, so the 47 will have to wait for a while. I'm anxious to get out and use it, but there is just so much water on the ground, there's no point.
     
  8. Jun 18, 2005 #8
    Claire Senft

    Claire Senft Member

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    If I remember correctly the 47mm Super Angulon XL covers 120º not 110º. The 10º difference is acually quite a bit.
     
  9. Jun 19, 2005 #9
    JohnArs

    JohnArs Subscriber

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    Yes Claire is right the 47mmXL is 120° and thad for sure!
    I prefer it over my 55mm more and more!