Canon lenses on Sony A7r very soft edges

[soboyle www.oboylephoto.co]

<p>Wanted to get feedback on other experiences with mounting canon glass on the Sony A7r. <br>

So far I've tried 3 different metabones IV adapters for my Canon EF 24-70 II, center is very sharp with good contrast, but the edges and corners are terrible, just fall apart at all focal lengths, even at f/8. The Sony FE 24-70 is better than the Canon lens at this point. <br />Everything I've read online says that canon glass is excellent on this camera. <br>

<br />So what gives? <br />Try another metabones?</p>

[ilkka_nissila]

<p>Microlenses, their design and positioning, and the thickness and other characteristics of the optical filter stack on top of the sensor may affect the imaging performance of the system that consists of the sensor and the lens. It is not all that surprising that a Canon lens which wasn't designed for the Sony sensor (neither was the sensor and its optics designed with that lens in mind) may have some issues in the corners of the frame.</p>

[alan_bryant1]

<p>Here's a rather technical article on the effect of the sensor's filter stack on adapted lenses. This might have something to do with it.</p>

<p>http://www.lensrentals.com/blog/2014/06/the-glass-in-the-path-sensor-stacks-and-adapted-lenses</p>

<p>I'm surprised it's still bad at f/8. Seems like that ought to be enough to compensate for the problems. I haven't used the 24-70/2.8 II but it's reputed to be very sharp.</p>

[golem_bngolem]

<p>After digesting the whole [linked] geek article<br>

about the effect of the glass sandwiches ahead<br>

of the sensors, one thing I'm fairly sure I got<br>

from all that info is that the SpeedBooster is a<br>

better compensated device than one would<br>

understand from Metabones's own website. It's <br>

claimed in the article that each SpeedBooster's<br>

optical design includes consideration of the<br>

glass sandwich thickness thaz native to the<br>

camera model line represented by the flange<br>

mount at the rear of that SpeedBooster as<br>

compared to the glass sandwich native to the<br>

lens line associated with the flange mount on<br>

the front of the SpeedBooster. <br>

<br>

This creates a puzzle. Some Nikkor lenses<br>

were designed for film Nikons with no glass<br>

sandwich while other Nikkors are designed<br>

for digital Nikons. I did NOT see any mention<br>

of there being 2 different SpeedBoosters for <br>

Nikkors. The same would be true of Canon EF<br>

lenses, whose history bridges the evolution<br>

from film to digital. Boosters for Minolta MD<br>

or Canon FD lenses face no such problem as<br>

these lenses lines were ALWAYS for film. <br>

<br>

Hopefully, a clarification will soon be posted<br>

here in reply [pleeeeeaaaaze?]. <br>

<br>

` </p>

[Marcus Ian]

<p>Golem, this is one of the reasons that nikon and canons have such thin filter stacks (as thin as possible, while still containing the filter elements). There are advantages to a thick filter stack, but a thick filter stack would have destroyed the IQ of every EF lens on the market when the digital EOS cameras came out - same goes for Nikon. </p>

[clgriffin]

<p>It does not seem this way with all my Canon glass, but definitely with the Sigma 50-500mm OS I get a vignette and distortion of image at the edges, more from the 50mm end, but also visible at 500mm. I checked several just now and edges are just fine on other Sigma lenses and Zeiss lenses and Canon glass. It may be that this one lens has an optical geometry that is different than most of the rest of the glass. I don't have a Canon 24-70 II to test.</p>