I pondered that sentence myself and wondered if "calculated MTF" might
mean what I suggested... that the lens MTF is back calculated from the
system MTF.
Chuck Norcutt
Moose wrote:
> Chuck Norcutt wrote:
>> I had not read this before and you raise some interesting and perplexing
>> questions. I knew they were using DXO something and, since they show
>> resolution in excess of the sensor resolution, I had assumed (bad) that they
>> were measuring the lens independent of the sensor and also with the sensor
>> since the tests clearly use a particular camera. You are right... where
>> does the lens resolution beyond the sensor Nyquist limit come from?
>>
>
> "Whenever the measured numbers exceed this value, this simply indicates
> that the lens out-resolves the sensor at this point - the calculated MTF
> values themselves become meaningless." Meaningless, but published.
>
> BTW, I really don't mean to slag their lens tests. I think they are
> valuable and useful. I suspect that the things they measure are probably
> fairly useful analogs for the more subtle things, i.e. those that do
> well mostly will do well in less tangible areas of performance.
>
> Hard too, to fault them for not measuring the unmeasurable. :-)
> Given the paucity of useful tests of lenses on FF sensors, I think they
> are a great service. The side-by-side comparison feature is great. In a
> short time, I can see just how the 50/1.8 I have compares to the 50/1.4
> in the areas they measure. At f1.8, the faster lens fall below the
> slower one, and performance at f1.4 is well below the standard of both
> lenses from f2.0-11.
>
> It looks too, like the f1.8 might theoretically be easier to focus
> manually, as it is significantly sharper wide open than is the f1.4.
> That doesn't factor in differences in MF focusing mechanisms. In any
> case, I can see that upgrading would be about build quality, a tiny bit
> of speed, AF speed/noise and bokeh, not sharpness, contrast and distortion.
>
> Moose
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