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  1. #1

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    Medium Format Lens Sizes

    Hi, I just recently bought a Mamiya RB67 and am new to the Medium Format and I have a question.

    Question: How do the lens sizes compare to 35mm format sizes. For instance I know that on my 35mm camera about how much the view angle is on a 18mm, 35mm, 100mm and what I can expect to get in the frame. What I don't know is how the view angles are on Medium Format compared to 35mm format. My RB67 came with a 90mm lens which is apparently equal to about somwhere around 40-50mm. Is there some formula to deterime how the lens compare so that when I buy another lens I know what to look for? For instance what would be the equivalant 35mm format lens to the RB67 50mm?

    Hope some of this makes sense.

    Thanks

    Ron

  2. #2
    AZLF's Avatar
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    I think the 55mm would best compare to your 35mm. A 45mm would be closer to the 28mm and a 30mm in mf is a fisheye.
    http://www.apug.org/gallery/showgallery.php?cat=500&ppuser=10716
    http://home.comcast.net/~rem700a/westviews.html

  3. #3
    MattKing's Avatar
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    The Mamiya website has information about all the current lenses:

    http://www.mamiya.com/home.asp

    The Mamiya site doesn't like Firefox - you need to use User Agent Switcher for IE.

    Check under products, and the Mamiya RB67 Pro SD camera - then on to the right of the page for lenses.

    Hope this helps.

    Matt

  4. #4
    DBP
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    The diagonal of a 6x7 frame is roughly twice that of a 35mm frame, so multiply by two for a rule of thumb. The aspect ratios are considerably different, however, so a 90mm (6x7) lens will not cover the same width as a 45mm would in 35mm, but will cover more height (assuming landscape format).

  5. #5

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    Just compare angle of view rather than focal length. Then you will be able to find equivalent lenses in different formats.

  6. #6
    Steve Smith's Avatar
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    Quote Originally Posted by wentro View Post
    Hi, I just recently bought a Mamiya RB67 and am new to the Medium Format and I have a question.

    Question: How do the lens sizes compare to 35mm format sizes.

    Hello.

    I have just bought an RB67 too and I agree with DBP that you should more or less double the 35mm size to get an equivalent for the 6x7 format.

    My most used lens on the RB67 is the 50mm and this is similar to a 24mm lens on 35mm.

    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  7. #7
    wclavey's Avatar
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    This link has a chart of lenses and, based on format, the relative equivalence to 35mm. I have used it for selecting LF lenses, but it also covers MF.

    http://www.viewcamera.com/images/focalchart.gif

    You need to view it full size if your browser automatically scales it down to fit the page...

  8. #8

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    This little "rule of thumb" was tought to me many years ago.
    It's an approximation, but a remarkably good one.

    First you memorise this lineup of lenses:

    18, 28, 50, 85, 135, 200

    For 6x4.5 and 6x6 move one step down.
    i.e. a 50mm lens on 6x4.5 is ~28mm lens on 35mm.

    For 6x7 double the 35mm focal length.

    for 6x9 take two steps down.

    For APS-sized image-capturing media you move one step up.

    It doesn't give you the exact equivalenses, but it gives you the ballpark numbers.

    -- MW
    Men, said the Devil, are good to their brothers: they don’t want to mend their own ways, but each others.
    -- Piet Hein

  9. #9

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    Thanks everyone for the help, that is the exact information that I was hoping for. That link to focalchart was perfect.

    Thanks again

  10. #10

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    Quote Originally Posted by wentro View Post
    Is there some formula to deterime how
    the lens compare ...?
    Thanks Ron
    The equation is x = 2 times y. RB focal length is x and
    y is 35mm focal length. To solve for y; y = x/2.
    Two, 2, is the ratio of edge lengths of the two formats.
    At least very nearly. Dan

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