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Thread: Pentax 645Z vs A7RII IQ and bang for the buck

  1. #151
    Workshop Member Bryan Stephens's Avatar
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    Re: Pentax 645Z vs A7RII IQ and bang for the buck

    Quote Originally Posted by jerome_m View Post
    It is the same sensor, but the multishot process emulates a higher resolution sensor and increases the sample frequency. One will see better the limitations of the lenses.
    Yes and no. It emulates the output of a higher res sensor, but the input is identical to the 50c sensor in single shot mode. It takes multiple single shots (I believe between 2 and 6) and combines them, so it really is not the same as if it were a true 200mp sensor. If it did behave in that manner, you would REALLY need some impressive glass to get optimal results, any any shortfall would be magnified.

    I think even the impressive 60XL or the 40HR would show any possible flaws at that pixel level
    Bryan

    “You don’t take a photograph, you make it.” — Ansel Adams

  2. #152
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    Re: Pentax 645Z vs A7RII IQ and bang for the buck

    Quote Originally Posted by Bryan Stephens View Post
    If it did behave in that manner, you would REALLY need some impressive glass to get optimal results, any any shortfall would be magnified.

    It does behave in that manner. I don't really want to discuss the underlying reason, but this is a consequence of the transfer functions of the lens and sensor being linear. If you had stepping motors of infinite precision, you could actually completely characterise a lens with a single pixel moved around.

    As to the glass being impressive, not that much. Multishot backs of that sort increase the resolution by a factor of two, but the MTF of the lenses will not suddenly go to zero when one samples twice as much. One sees the defects of a given lens more clearly, but the lenses do not suddenly turn to mush just because one has 4 times more pixels, just as good lenses from the film era did not suddenly turn to mush when 24x36 SLRs went from 6 mpix to 24 mpix.

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