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Canon FD 50mm and 135mm with same f-stop - striking difference

Discussion in 'Adapted Lenses' started by Marshland, Sep 25, 2014.

  1. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    While doing some low-light tests, I was surprised by the difference here:

    Canon FD 135mm f/2.8
    [​IMG]

    Canon FD 50mm f/2.8 (cropped)
    [​IMG]

    Both images were shot manually with identical settings on an NEX-6, attached to a Lens Turbo II. Some slight post-processing but exposure levels are identical. Both lenses are of FDn type, with S.S.C. coating.

    Is this purely because of a relatively poor T-stop performance for the 135mm?
     
  2. shaolin95

    shaolin95 TalkEmount Top Veteran

    942
    Jul 3, 2013
    Well that is very weird to me!
    I am going to test that with my 100mm and 50mm to see what I get. I wouldnt expect Tstop to be THAT dramatically bad really.
     
  3. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    Yes, seems weird to me, I did think that maybe the 135mm lens wasn't opening up fully (it's an f/2.8 lens) but I'm pretty sure it is.
     
  4. shaolin95

    shaolin95 TalkEmount Top Veteran

    942
    Jul 3, 2013
    Yeah I was going to ask if you checked that it was really opening since you know the FD lenses require a more careful adapter installation so maybe you didnt notice it was not engaged. But yeah now I got curious about trying my lenses today! :D
     
  5. HabsFan

    HabsFan TalkEmount Veteran

    257
    Apr 10, 2013
    Ontario, CAN
    It could also be that your 50mm (assuming it is faster than 2.8) has an issue with its apperture. Maybe it is stopping down less than you think. If it has been cleaned and taken apart, it's possible that the aperture was adjusted. Maybe compare to an E-mount AF lens?
     
  6. fractal

    fractal TalkEmount All-Pro

    Jun 17, 2014
    Southeastern PA
    Chris
    Any chance you changed the ISO?
     
  7. shaolin95

    shaolin95 TalkEmount Top Veteran

    942
    Jul 3, 2013
    I downloaded the images and they show the same settings
     
    • Like Like x 1
  8. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    Same settings for both images, same ISO, shutter speed, lighting.

    < If it has been cleaned and taken apart, it's possible that the aperture was adjusted. Maybe compare to an E-mount AF lens?

    It's a 50mm f/1.4, I've no idea if it's been cleaned and taken apart, there's no evidence that it has been. I'll do more tests with other lenses when I have the time.
     
  9. HabsFan

    HabsFan TalkEmount Veteran

    257
    Apr 10, 2013
    Ontario, CAN
    The only reason I say this is because I've had to adjust the aperture on a few lenses that I have owned. In my case, the aperture was not fully wide open when set at the wide open position. You could see the blades closed down a fair amount. On some of the lenses, it was possible to adjust in such a way that you go past the 'wide open' setting so that it would not stop down as much. Usually the aperture mechanism slot is 'ramped' so that the shape closes down faster at first and slower once you are stopped down more.
     
  10. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Wow, that is quite a difference.

    I have always wondered how consistent the F-Stops were from maker to maker.
     
  11. 986ster

    986ster TalkEmount Regular

    35
    Jan 15, 2013
    What adapter are you using? My fotoga requires the adapter ring to be fully clicked over to the 'lock' position in order to properly control the aperture. Sometimes it looks locked, but needs another little twist.
     
  12. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    It's the Zhongyi Lens Turbo II, I'm aware of the issue you describe from using other adaptors but it's not the case here.
     
  13. roundball

    roundball TalkEmount Hall of Famer

    Oct 8, 2013
    USA
    Your thread got my curiosity up and I ran comparison tests on three Canon FDn Lenses on the same NEX-7 body.
    50/1.4
    135/2.8
    80-200/4.0-L@200
    The body was set to Manual Mode, Spot Metering, Daylight WB, ISO100, 1/250.
    I put the small "Spot Meter Circle" precisely on a fully lit sun spot on a tree trunk 50 feet away.
    Tests were run as fast as I could dismount / mount lenses and no conditions changed during the 60 seconds I tested them.
    The Manual Mode exposure scale showed me having correct exposure when I reached F8 on all 3 lenses.
     
    • Like Like x 1
  14. Dan Euritt

    Dan Euritt TalkEmount Regular

    191
    Jan 11, 2014
    • Like Like x 1
  15. AK47J

    AK47J TalkEmount Veteran

    231
    Jan 31, 2014
    Central Oregon
    Run the exact same experiment without the Turbo 2
     
  16. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    Apologies for the delay in responding.

    Some more test images, with similar lighting to the original images but not quite the same. Shot manually with the same settings each time. Both have exactly the same post processing.

    Canon 50mm f/2.8 (with Lens Turbo 2 and cropped, slightly out of focus):
    [​IMG]

    Canon 135mm f2/8 (normal adaptor):
    [​IMG]


    Unfortunately I don't have an E-mount lens of that speed, so had to stop back to f/5.6 for all of the following images, shot with slightly different lighting to the images above.

    Sony SELP-1650 at 50mm (cropped):
    [​IMG]

    Canon 50mm (with Lens Turbo 2 and cropped):
    [​IMG]

    Canon 135mm (normal adaptor):
    [​IMG]

    Again the 135mm is the least exposed but could I guess be explained by T-stop differences.

    I'll try again without the LT2 on the 50mm lens when I have time.
     
  17. unlo

    unlo Sony ******

    Jan 19, 2014
    Ohio
    Matt
    I find the same issue with my Minolta glass
     
  18. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    Interesting to hear that unlo.

    FWIW, here's a photo of the Canon FD 135mm fully open, or at least as far open as mine will go:
    [​IMG]
     
  19. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    FWIW, some final tests, this time the Lens Turbo 2 isn't in use on any of the lenses. I've included my Canon FDn 50mm f/1.8 lens for additional comparison.
    All shot using exactly the same settings.

    Canon FD 135mm f/2.8 @ f/2.8:
    [​IMG]

    Canon FD 50mm f/1.8 @ f/2.8 (cropped):
    [​IMG]

    Canon FD 50mm f/1.4 @ f/2.8 (cropped):
    [​IMG]
     
  20. Marshland

    Marshland TalkEmount Regular

    28
    Aug 3, 2014
    By the way, if anyone's able to do a similar test using a Canon FD 85mm f/1.8 or Canon FD 100mm f/2.0 for comparison, I'll be very interested to see the results.