What's the best way of testing a used lens?

Discussion in 'Medium Format' started by ron_hughes, Jun 19, 1998.

  1. I recently bought a 50mm f2.8E lens and would like to know the best way of testing it. I realize this is a rather stupid question! Obviously, the thing to do is to use it. What I mean is, what if any, is the recommended procedure for testing a lens like this, given that it has a shutter built in? Apart from checking the smoothness of the focusing, should I test it at all shutter speeds? Anything else?
     
  2. The scientific method is best, but for me, I just get some plus-x, and take pictures of subjects with lots of detail in them from varying distances. Be sure to use a tripod! Then I put the negatives in the enlarger, put it up to 16x20 magnification and look at the negs with a grain focuser, then make some 8x10 prints at 16x20 magnification. You can see pretty easily whether the lens is sharp or not!

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    I have found a lot of older medium format lenses to be lousy... I had a Bronica 50mm for ETRS. I had the lab calling me on... they couldn't find a single sharp portion on the negative! I couldn't get a sharp 8x10 out of that thing! Traded it for Pentax 645 and got much better results. A friend of mine used an older RB system at school and my Nikon made a better-looking 8x10. (Of course, 35mm lenses tend to be sharper than mf lenses, but the difference was VERY pronounced in an 8x10 print!)

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    The newer Bronica and Mamaiya lenses are excellent. I think what made Hassy so successful early on is they were the only company with really sharp lenses across the board. If everyone else had lenses as good as theirs 30 years ago, they may not enjoy the position they have today!
     
  3. One of the simpliest checks for any lens is to simply hold it up to the light and see how many defects are in the glass. You can also check for lens fungus that way.

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    One thing that most photogs NEVER check with older lenses is the functionality of the apeture diaphram.
    By default lenses are wide open but you rarely see then when the apeture is closed to a certain F-stop. 9x out of ten photographers blame their shutters for bad exposures when in fact it's the diaphram sticking open.
    While holding the lens in your hand close the apeture down all the way and then manually work the diaphram open and closed. The motion should be smooth and not stick.

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    As an example, about 50% of all 35mm off brand lenses (Tokina, Tamron, Vivitar) that I've used has severe diaphram problems. MF can be just as bad because the components are larger.

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    //scott
     
  4. When I bought my Yashica Mat 124G last year I loaded it with E100SW, took it to a park, metered the scene, and shot a series of exposures with stepped shutter/aperture combinations: 1/60atf/22; 1/125 at f/16; 1/250 at f/11 etc. All exposures were identical. Not scientific, but it has been a very good camera. Another method would be to take the camera to a decent repair shop and have them test the shutter speeds. International Camera Technicians in Mountain View, CA did this for a friend of mine a couple of weeks ago and didn't even charge him.
     
  5. As far as inspecting the lens goes, someone mentioned holding the lens to the light, which is a start, but a *much* better test is to take a small flashlight and shine it through the lens. This will show ALL the lens's defects right away. In fact, after doing this the first time, you will probably find yourself going back to your other lenses and checking them out too because you will likely see a lot of crap that just doesn't show up any other way. If the lens has the slightest bit of cloudiness anywhere you will see it with the light. Of course real-world tests are also important. The light just helps with initial inspection.
     
  6. Many thanks for the feedback above, and to Bob Monaghan who referred me to www.smu.edu/~rmonagha/broncameratest.html for lens and camera testing ideas and resources.

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    He also mentioned:

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    Bronica 6x6 medium format
    www.smu.edu/~rmonagha/bronica.html

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    Medium format cameras
    www.smu/edu/~rmonagha/mf/index.html
     
  7. For critical testing, the only way to isolate the performance of the lens from camera shake and all of the things that contribute to it is to use an electronic flash in a totally dark room. You set up your target/lens chart, mount the camera on a sturdy support, darken the room, open the shutter and wait at least 10-20 seconds before firing the flash by hand. Go thorough all or a least most of the apretures, to determine the optimum apreture.

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    This type of test saved me from keeping a some what less than acceptabel used "blad" with focusing and shutter problems. I never determined how sharp the lens was, as f2.8, 4, and 5.6 were fuzzy! It also confirmed that I needed to purchase a heavier tripod for the p67 that I am now using!
     

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