mamiya extension tubes

Discussion in 'Medium Format' started by chris_stevens|2, May 29, 2002.

  1. 1.Could anybody tell me what extension tube I need to get a 1:1 ratio
    with either a 127mm and a 65mm lens on my Mamiya RB67?
    2.Are there any cons with using a 65mm lens as a close up lens with
    the extension tubes?
    3. Are the extension tubes for a RB67 and RB67 pro SD different?
    4. Does anybody know where I may purchase some used extension tubes?
    Thanks
    Chris Stevens.
     
  2. Chris,

    I just went through this same dilema with my RB67 including experimenting with close up filters and other nonsense. I finally forked over $225 for a #2 extension tube (82mm) and am happy as hell. The B&W closeup diopter I purchased was a complete waste of time and resulted in far inferior results to the extension tube.

    Mamiya makes two tubes for the RB67; a #1 and a #2. The #2 is the longer one of the two and the one you want. With my 90mm I get down to about 1:1 with the #2 and it eats almost exactly one stop of light making exosure compensation easy to figure out. Your 65mm should be able to get much closer, but you'll find your working distances pretty small with that lens. The 127mm and the #2 sounds like a good combination to me.

    There are different versions of the RB extension tubes, but I believe they are all compatible with the RB series. New they cost close to $500, which is absurd considering they are just hollow tubes. Used (how I got mine) they run around $225, and are farily common. Just do a search on Google and you should find several camera shops that have them.

    Just remember that Macro work with MF doesn't provide as much depth of field as 35mm and you'll typically have to stop WAY down by default, but the resulting 6x7 chromes with the extension tube will blow your mind.
     
  3. Chris, with any lens, when the total extension (from infinity focus position) equals the focal length, you get a 1:1 magnification. Mamiya makes 45mm & 82mm tubes for the RB, and they can be stacked (but not more than one of each). The focusing mechanism provides another 45mm of extension, so with both tubes in place, you can get up to 172mm of extension. Also, a 1:1 ratio requires 2 steps of additional exposure. If you want to play with the exposure increase factors, eif = ((ed/fl)+1)^2, where ed = extension distance and fl = focal length. Steps of exposure increase = log(eif) / 0.301. For example, with your 127mm lens, an 82mm tube, and the focus racked all the way out (extension = 82 + 45, or 127), the first formula yields eif=4, meaning you need 4 times more light. The second formula will tell you to use 2 steps more exposure. Same thing-use whichever measurement you like.
    Shorter lenses yield higher magnification, but force closer working distances. This can cause problems in getting the lighting right without having the lens cast a shadow. Another factor is that perspective changes with distance.
    Frequently, I know the dimensions of my subject, so I find it useful to know which tubes I need to plug on to get the framing I want. So, I came up with the table below. My lenses are different from yours, but maybe you and others will also find it useful. It provides the range in millimeters of the image width (long dimension) visible in the viewfinder. The smaller number of each pair is what you see with the focus racked all the way out; the larger number is with the focus racked fully back.


    Tube​
    90mm​
    140mm
    -​
    inf. > 130​
    inf. > 212
    45​
    130 > 65​
    222 > 108
    82​
    73 > 46​
    116 > 73
    both​
    46 > 33​
    73 > 54​


    So far as I know, an RB tube will work with any camera/lens in the RB series. They are frequently available on eBay, as well as from sources such as Midwest Photo Exchange (www.mpex.com), Columbus Camera Group (www.columbuscameragroup.com) and many others. See http://people.smu.edu/rmonagha/mf/albro.html for a long list of dealers.
     
  4. [​IMG]My first tests with the #2 extension tube with 90mm / Provia 100F
    For example, with your 127mm lens, an 82mm tube, and the focus racked all the way out (extension = 82 + 45, or 127), the first formula yields eif=4, meaning you need 4 times more light.

    Mel's math seems convincing, but it doesn't pan out. He also seems to imply that different lenses with different focal lengths require different exposure factors when used with an extension tube, and that's also not true.
    To prove my point, I went outside about an hour ago, focused my RB on the side of my white garage, coupled my 82mm extension tube, and cranked my focus all the way out. I then took meter readings with a hand meter *AT* the film plane with the back off with my 180, 90 and 65mm Mamiya lenses. Results: Both my 180mm and 90mm gave *IDENTICAL* exposure readings while my typically flaky and retarded 65mm was 1/3 stop off.
    Doing the same test without the extension tube results in almost exactly one stop difference in light at the film plane. This means when I use the extension tube I compensate for 1-stop of light loss regardless of lens I use, which makes my life pretty easy in the field. If this isn't complicated enough for some people, I can't help you.
    Extension tubes have a bad rap for some reason and are usually met with long strings of formulas to calculate exposures and magnification ratios. This tends to chase people off to purchase front mounting close up filters which in my experience don't work as well as extension tubes with MF. Again, my 82mm #2 extension eats about 1-stop of light which I've confirmed with meter reading and half a dozen test rolls of Provia, and I'm a fanatic about slide exposure. I can also close focus on 2 1/4 inches on a tape measure with my 90mm and extension tube which means the 127mm will be just a bit less than 1:1.
     
  5. Howdy Chris!

    I found some of these for you..

    at:

    www.KEH.COM

    in their used section.
    The double cable release which i'd recommend so you can use the mirror lockup function and also so you don't induce vibration, is $47.00 in excellent condition.

    the #1 tube in excellent condition is $94.00

    the #2 tube in excellent condition is $172.00

    the #2 SD version in excellent condition is $199.00

    You can order it from the website or call Jeannie at 1 404 748-6041.
    I always use the same sales person and it seems to work good for me, thats why i gave you her direct number.

    miles
     
  6. hey Scotty,

    are you showin' off??????

    beautiful work!!!

    miles
     
  7. CHRIS......

    YOU BETTER READ THIS INFO FROM MAMIYAS WEB SITE!!!!!!!!!!!!!!!!!!!

    PRO SD #1 Extension tube on PRO S Body
    Drew Williams - 12:04am May 11, 2001 EST

    I have a Pro S Body and just bought a Pro SD #1 extension tube. My 90mm lens connects nicely to the extension tube, but I can't get the extension tube to connect to the body. I read here that Pro SD lenses will fit a Pro S Body so I thought I would be ok. When I look at the end that should connect to the body, it seems that the posts next to the green and red dots are reversed from my lens. Also, the ring that projects from the center of the tube is larger in diameter than the ring on my lens. I don't see a metal adapter in the tube, but I'm not sure what it would look like. I'm really puzzled. Can anyone help. Thanks.

    Drew Williams




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    Paul D'Ambrosio - 09:51am May 11, 2001 EST (1.)
    Mamiya America Corporation
    Dear Drew: The extension tube for a Pro-SD will not fit a Pro-s body. You would need to purchase an extension tube for the Pro-S body. Our catalog number for the #1 tube for the Pro-S is 214-450 and for the #2 tube is 214-451. A Pro-S extension tube will fit on a Pro-S or a Pro-SD (if an adapter ring is used), however a Pro-SD extension tube will only fit on a Pro-SD body.



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    Drew Williams - 10:21am May 11, 2001 EST (2.)

    Thanks Paul. I'll swap it out. I appreciate the quick respose.

    Drew



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    Drew Williams - 05:37pm May 11, 2001 EST (3.)

    I have one more question on the #1 extension tube. How much light will I be losing when I use it? Also, I have the standard waist level viewfinder. Is there a brighter one I can obtain, preferably with a cross hair focus and (in a perfect world) grid lines?

    Thanks Drew



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    Matt Hill - 05:44pm May 11, 2001 EST (4.)
    Mamiya America Corporation
    Drew: The amount of light lost depends on the lens used and the magnification. A good rule of thumb is the if you are at 1:2 magnification, compensate 1 stop. At 1:1 magnification, compensate 2 stops.

    The scale on the side of the bellows gives you compensation guidelines, and the instructions that come with the Auto Extension Tubes give the compensation values when the tubes are in use.

    Here's a link to more info about the magnifications from the Mamiya website:

    http://www.mamiya.com/products2.asp?id=1&id2=15&id3=40&id4=429&id5=431

    Mamiya only makes one set of focusing screens, and they are all the same brightness. Other manufacturers make brighter screens for the RB in a variety of options (grids, etc.) but we cannot guarantee that the focusing plane will be correct, or if you use a metered prism, you will have to compensate because of the extra light passing through the screen.



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    Drew Williams - 01:33pm May 12, 2001 EST (4.1)

    Thanks Matt, I'm using the 90mm lens which I think gives me 1:1 at full bellows extension and the #1 tube.

    Drew



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    (1 following message)
     
  8. are you showin' off??????
    On a scale of 1 to 10 I give this image about a 3 in terms of what I usually do. Spring is real late here in MI and there's still not a lot blooming, so I have yet to really give my new toy a real work-out. Give me a month and I'll have some knockout stuff.
    Further notes are than both my 90 and 180 Mamiya lenses handle the extension tube pretty good optically. The 180 starts to stress a little with just a bit of color fringing, but nothing serious. The 90mm is tight and clean all the way. The 127 Mamiya runs in the some caliber as the 90 in my experience.
     
  9. Mamiya makes 45mm & 82mm tubes for the RB, and they can be stacked (but not more than one of each).​
    Is it optically unviable to stack multiples of these tubes or just practically difficult to work it?
     

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