Mirrorless- Continuing to Under Perform

Started Apr 11, 2013 | Discussions thread
Bart Hickman
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Re: Mirrorless- Continuing to Under Perform
In reply to ultimitsu, Apr 13, 2013

ultimitsu wrote:

The 55-210 obviously isn't suffering from the short flange distance either (if anything, it's sharpest at 55mm where the rear element is closest to the sensor.)

It is suffering from it.

This is Sony, check the border.

http://www.photozone.de/images/8Reviews/lenses/sony_55210_4563_nex/mtf.png

This is canon 55-250, half the price, longer reach, 1/3 a stop faster, and exactly the same physical size.

http://www.photozone.de/images/8Reviews/lenses/canon_55250_456is_50d/mtf.gif

See how bad sony is in the border compared to the cheap canon?

I don't think it's because of the flange distance.  I have the 55-210--the rear element does not reach the rear of the lens--it's actually recessed even at 55mm.  The rear element is also nearly the same size as the sensor which is also not the case with DSLR lenses--the rear element is usually small circle.  I know the comparable DSLR lenses not only go all the way to the rear, but they stick out slightly.  At 210mm, the rear element is way back--a couple inches from the sensor at least.

Whatever is "wrong" with the 55-210, I don't see how it could be due to flange distance or light angle hitting the sensor.

As for the photozone results, they are normalized.  So if the sensor is limiting the resolution in the center (but not at the edges), it will appear to make a lens more uniform across the frame.  For all we know, if you put that Canon lens on a 24M sensor, it'll only get sharper in the center (and I would expect that the center will improve more.).

The similar Nikkor lens drops off towards the edges at the wide angle setting and that's with a D200 which means the drop off is actually a lot worse than indicated (again, the flange distance won't matter at the long end--the lens must telescope out regardless of flange distance.)

The Sony lenses aren't great, but I can't see how you can make any conclusion it has anything to do with flange distance.

Are Fuji X-mount lenses known for terrible edge IQ?  The X-mount also has a very short flange distance.  That new 18-55 large aperture kit seems to perform impressively well.

BTW, I think part of what makes that Canon cheap is it does not come with a hood and it has a rotating front element (which is unusually primitive behavior these days.)

Bart

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