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 15, 2013

ultimitsu wrote:

Bart Hickman wrote:

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.

that maybe so but how do you know it is not closer to the sensor than canon 55-250 ?

I don't know for sure on that lens, but I do know the Canon 55-200 does reach the rear element.

I know the comparable DSLR lenses not only go all the way to the rear, but they stick out slightly.

that is because the mount is deeper to begin with.

Exactly.  My point is a telephoto lens doesn't care about flange distance.

At 210mm, the rear element is way back--a couple inches from the sensor at least.

Are you sure ?

Positive.  I can see it.

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.

what you mean? PZ shows centre, border and extreme border figures.

Normalized means the resolution is in terms of lines per picture height, not pixels.  If the lens is the limiting factor, adding resolution won't change the results.

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.).

I will improve both centre and edge.

It will not.  It'll improve much more in the center assuming the lens was limited in the center in the first place.

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.

I dont see why not. their flange back distance is very short, and none of their lenses perform well in the corners, you put 2 and 2 together...

So you're basing this conclusion on circumstantial evidence.  That's fine as long as we got that straight.  Until now, it sounded like people had direct knowledge of the root cause of edge sharpness being low, even on telephoto lenses.

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.)

Both true. Being half the price is just part of the bonus (though can sony justify twice the price just for a hood and non-rotating front for a Telephoto zoom?). it got has better IQ and more range.

The MSRP isn't half the price.  Sony just seems to be holding street price up high.  Sort of like a lot of m43 lenses are also a bit pricey because people value the small size.  I think the cheaper plastic construction, plastic mount, rotating front element, no hood could easily explain the MSRP difference.

Again, there are no steep light angles on these telephoto lenses--the rear element is so far from the sensor.

Bart

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