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Posts posted by MattGrum

  1. There must be a way to express something more comprehensible to the less involved that isn't so highly accurate, but still does the trick, don't you think?

    Would really make sense nowadays, I believe. With the exploding megapixel counts of sensors and everything.

    ​MTF charts published by lens producers are already greatly reduced in complexity, in that in general they only show contrast for two spatial frequencies (usually 10 and 40 lp/mm) and two aperture values (usually wide open and f/8) and two image plane orientations (sagital and tangential). The "full" MTF is a four dimensional quantity which is difficult to represent in 2 dimensions. I put "full" in quotes because it also depends on focal length for a zoom lens, and, to an extent, on the focus distance thus it can be a six-dimensional object.

    I hope you can appreciate why it's impossible to boil a six-dimensional function down to a single number. You could simplify it further and measure the MTF at a few distances from the image centre (centre, top/bottom edge, left/right edge and extreme corner), but it's been heavily simplified already and that would cut a lot out.

    You could try averaging the figures but the range you average over would be fairly arbitrary and subject to differences between manufacturers. And the idea that manufacturers attach a resolution figure to the lens in order to sell them would just open the flood gates to clever ways to inflate the score by carefully choosing what to include/exclude.

  2. So for Canon to price the 5DS so highly, they must believe that almost all Canon users are locked into the EF platform via their investment in EF lenses. The problem here though is that barely any of the current EF lenses resolve 50MP

    Firstly lenses don't "resolve" a certain number of megapixels, what happens is contrast starts to go down as details get closer together. This is characterised by the MTF of the lens. The sensor has it's own MTF. System resolution is determined by the product of the lens MTF and sensor MTF, thus an improvement in either can lead to an improvement in system resolution.

    Secondly most EF lenses will provide excellent results with a 50MP sensor over the most important central region of the image, as demonstrated by years of FF lens use on APS-C. I'd bet many would perform adequately even at the borders. They certainly wont be any worse than on a 22MP sensor, whilst at the same time you will get less alisaing on demosaicing artifacts by virtue of oversampling.

    It is sad to see the artificial segregation of the camera through downgrading video features and ISO settings. I'm very much hoping Sony can manage a line-skipped 1.1x crop 4K video from their next 50MP sensor, that should resize down to a very nice 1080p file.

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