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My Zuiko's and how they perform

  1. Jim Baker
    My Zuiko's: 24mm f2.8, 28mm f3.5, 35mm f2.8, 50mm f1.8, 50mm f2 MACRO, 85mm f2, 135mm f3.5, 200mm f4, 300mm f4.5. Over the years I've gradually assessed them in a sort of systematic way. I shoot the same target which has a label in the middle and at the edge. The lettering on the label is 0.1mm high on the negative. This enables me to assess lens sharpness. Next to each label is a hurricane lamp. They are shiny so I can assess chromatic aberration (CA) or the tendency of highlights to have red and/or blue edging. Finally I assess bokeh by looking at things in the background. My benchmark is my 50mm f1.8 at f8. When I test a lens I shoot at all aperetures (noting the shutter speeds) but I also make one benchmark shot. The target is outside and the preferred conditions are bright but overcast. Some comments:
    1. All the lenses are good! I now say to myself, stop thinking about lens performance and just use them! The only lens with poor performance I've tested is a 50mm f2 Ultron (state of the art, they say, in the 1950's) fitted to a Voigtlander Vitessa. It served to show me just how good all the Zuiko's were as a set. I also tested a 50mm f2.8 Color Skopar (a simple Tessar design) fitted to a Voigtlander Vito BR. It performed quite well. Quite useable, in fact.
    2. The 50mm f2 MACRO is best, no doubt.
    3. The 50mm f1.8 is almost as good. The main thing I noticed about this lens is distracting bokeh at the larger apertures. Highlights tend to look like flattened rings ('polo bokeh') and tend to 'swirl' around the centre of the image. As far as I'm concerned this is an f2.8 lens and I rarely use it wider than f4. The contrast is superb and this adds to the overall 'snap' of an image.
    4. At 85mm and above, CA starts to creep in. The 85mm lens is very sharp at f2.8 but there seems to be some kind of mechanical resonance at f4 leading to slight loss of sharpness at this aperture. This has been reported on the web by others (e.g. Gary Reece's data) so it seems to be a feature of the lens.
    5. At 135mm and above, the shutter speed must be 1/250 or faster if vibration is not to limit the lens performance. This is in spite of using an OM2000 on a tripod and using its timer (which pre-fires the aperture and mirror).
    6. At one time I also owned a 135mm and a 180mm, both f2.8. They are the same construction, a modified Ernostar. I found they tended to have higher CA, particularly the 180mm. That's why I now have the 200mm f4 and the 135mm f3.5 (this pair likewise have the same optical construction).
    7. The 24mm f2.8 is a superb lens. If I lost it, I would be happy to use the 28mm f3.5 and would probably not notice the difference (optically). The 35mm f2.8 I've never settled with.
    So the lenses I use are the 24mm f2.8, the 50mm f1.8 and the 85mm f2, with 100 ASA film. If I'm on safari or something like that and I take the longrer lenses, I switch to 400 ASA film so I can use a higher shutter speed.
    Here's a summary

  2. snapshot2000
    snapshot2000
    I have a lot of OM lenses and am really happy with them, except for the 24mm f/2.8. It would be about my favorite focal length, but has some serious wavy distortion on one side of the image that makes it mainly good just for lanscape use.

    Anyone else have a 24 with this sort of distortion, or do just have a bad one? The lens is perfectly sharp.

    Dan
  3. Jim Baker
    Jim Baker
    You have a fault somewhere. Since this is the only one of your lenses with this problem, that would seem to eliminate the camera. The shutter curtains take a few milliseconds to get across the negative so it seems to me that you have a vibration in the lens that takes about half this time to die down. You could test this if your camera has mirror and aperture prefire in its self-timer mode (e.g. the OM 4, OM 2000 and OM 2SP). If the effect goes away when you prefire the aperture then the problem is the linkages that stop down the aperture as the shutter is fired. If that is the problem, you should be able to get it repaired.
  4. snapshot2000
    snapshot2000
    I have several Om cameras, so I can easily check it on each of those bodies. I think it's shown up on more than one camera though. Maybe I could just hang up a line chart and see the distortion by looking through the viewfinder. It doesn't show with my 28 or 35mm though, and shows as a slight bowing/curvature in about the same area of the frame every time.
  5. Jim Baker
    Jim Baker
    It just seems unlikely to me that the lens would produce such local distortions. The lens elements are all sections of a sphere. It seems to me if a problem was due to the optics, it would be circularly symmetric e.g. the way a lens can get soft as you move away from the centre, or the way bokeh can swirl around the centre. I can't visualise how the lens could produce a localised distortion i.e. on one side of the image only. On the other hand, the curtains take a few milliseconds to move horizontally across the negative so I can visualise how a short vibration might produce an effect on one side only. I'd be interested to hear the effect of prefiring the mirror and aperture.
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