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Thread: P-65+ issues with extreme wides

  1. #1
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    Apr 2008
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    P-65+ issues with extreme wides

    I've heard trough the grapefine,that some shooters are having not so good results in the corners with their Phase P65+ and extreme wides.
    Anything wide than 47mm and from Schneider and Rodenstock.
    Any comments from current users?
    Could it be that the pixel pitch of the P65+ is doing the damage?

  2. #2
    Sr. Administrator Jack's Avatar
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    Oct 2007
    Los Altos, CA
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    Re: P-65+ issues with extreme wides

    Not sure exactly what you're asking. When used at optimal apertures, I am getting excellent results from my Phase 28 lens, though the extreme corners are a bit soft. A crop to 30mm effective or so and it goes away. On the Rodenstock 40HR I got sharp corners even with 8mm shift.

    The pixel pitch of the P65+ is 6 microns, and does extend to basically full-frame 645 --- so yes that could be an issue, especially older lens designs. However, I personally have found most lenses designed for digital, like the Mamiya "D" lenses or Rodenstock HR series, to be excellent. However, ALL lenses exhibit resolution falloff to a certain degree as you move away from the center. I have found both Schneider's and Rodentstock's MTF charts to be pretty accurate in helping predict this.

    "Perfection is not attainable. But if we chase perfection, we can catch excellence."

  3. #3
    Subscriber Member tashley's Avatar
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    Jan 2008
    South of England
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    Re: P-65+ issues with extreme wides

    I'd re-iterate what Jack says. The 28D is good but not right to the corners (I suspect some are better than others) and my Schneider 35XL is very good even with shift. However it may be that the problems you've heard about are less to do with sharpness and more to do with lightness falloff and there are indeed problems here. If you use a centre filter (and you'll lose a stop or two if you do, which means that on anything but a very bright day you will always need a pretty reliable tripod setup) this problem goes away but if you don't, electing instead to re-balance the brightness across the frame using software, you will in effect be exposure compensating the corners upwards by up to a couple of stops and this will mean risking quite noticeable noise increases in some scenes, depending on what is in the corners (shadowy areas in particular will start to look a bit grungy) and this will likely be worse if you use Zero Latency rather than a wakeup cable, depending on ambient temperature and the length of time you leave to back 'on' for.

    The other issue is colour shift and the need, on technical and field cameras to make LCC shots through an opaque panel. The Dalsa sensor is less prone to colour shifts than the Kodak sensors, but the problem is still there and it still needs dealing with and when you do apply the LCC shot you've made, you may want to choose the option not to correct light falloff or only to apply it partially or you may run into the noisy corner issue.

    However, in my experience with the system so far, these issues can be worked around with experience and good technique and are in no way to be seen as a deterrent!



  4. #4
    Subscriber gogopix's Avatar
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    Nov 2007
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    Re: P-65+ issues with extreme wides

    I use the P65+ with the Contax and Alpa. For some reason on a recent shoot in Ireland I saw vignetting with the Schneider 35mm, and otherwise fantastic lens. However, in C1 it takes about 10 s to remove, and once done can be applied to others (I guess there is a way to make this a pre-set, but other than knowing they exist have not tried for this.
    Strangely the Zeiss 35mm on Contax does not vignette.
    Neither has the color casts of previous Phase backs, so I think Jack and Tim have it that the Dalsa is better behaved.


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