Canon FD 35mm f/2.8 tested on Sony A7 against native Sony Zeiss Sonnar T* FE 35mm f/2.8 ZA

Started Oct 16, 2017 | Discussions thread
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jarek leo
jarek leo Contributing Member • Posts: 960
Canon FD 35mm f/2.8 tested on Sony A7 against native Sony Zeiss Sonnar T* FE 35mm f/2.8 ZA

This is a summary of my test performed back in 2015. You can find photos accompanying the original text written in Polish and substantiating my findings here:

Test summary

Thirty-five vs. thirty-five: Sony Zeiss Sonnar T* FE 35mm f/2.8 ZA and Canon FD 35mm f/2.8 tested on Sony A7

This is a test I performed in 2015 when analyzing lens options for Sony A7, my first full-frame mirrorless camera. The Sony Zeiss Sonnar T* FE 35mm f/2.8 ZA had very good reputation but I was not ready to pay the high price it commanded for such a slow lens. I decided to give the Canon new FD 35mm f/2.8 lens a try, although given the tenfold price difference and mantra repeated by some that film-era lenses were incompatible with modern sensors, that seemed like a battle lost by the Canon before it even started.The copy of the Canon I tested was manufactured in March 1980, and although the new FD series lenses were back then criticized for being overly plasticky, their construction seems decent by today’s standards. The IF design of the Sonnar makes it prone to some focus breathing, something not bothering the Canon, where the entire front of the lens is moved for focusing.

Vignetting. The small entrance pupil of the Sony causes it to vignette strongly at f/2.8 and the problem does not completely go away even at f/11. The Canon vignettes slightly at f/2.8 but the illumination evens out across the frame already at f/5.6

Distortion. Both lenses have minimum amounts of barrel distortion; they are so well-corrected that I would use them for architectural photography with no reservations.

Sharpness and contrast. I had assumed beforehand that edge image quality had to be better in the new lens made specifically for full-frame sensors. Results proved me wrong. At f/2.8 the central sharpness and contrast is slightly better in the Sony, while edges are worse – but acceptable - in ether lens; surprisingly the Sony is no better than the Canon, and the aforementioned strong vignetting is really disturbing on the Sony. Canon’s central sharpness and contrast improve by f /4 to Sony’s levels at the same aperture, while edges improve too and better the Sony, which does not show any edge improvement. At f/5.6 image quality evens out across the frame and it is difficult to pinpoint any differences between the two lenses; I would give a slight to nod to the Canon for edge sharpness; besides Sony still vignettes heavily. At f/11 the quality between the two lenses is indistinguishable. Perhaps the Sony has field curvature preventing it from achieving equal sharpness between center and edge until stopped down to f/11. At f/13 diffraction kicks in.

Chromatic aberration. I was truly puzzled by the results here, as new lenses should be better corrected than old ones. Not true in this case. At f/2.8 the Canon is virtually free from CA, which is quite visible in the Sony. This might follow from IF design of the latter. Certainly, Sony cameras have embedded profiles correcting images from specific lenses for CA, so perhaps this is why the designers did not bother to correct the lens better than they did.

Bokeh. Bokeh from either lens is mediocre at best.

Sony is not a bad lens by any means. On the contrary: it is a very good glass with a few shortcomings, such as strong vignetting, chromatic aberration and inferior edge sharpness image at large aperture openings; the two former faults are easily correctable by the camera firmware or later by image processing software. Against such background, the Canon looks truly excellent. For me autofocus alone did not prove to be a sufficient argument in favor of the Sony or justification of its high price tag. Regardless of the price, on virtually all counts I would give a slight edge to optical performance of the Canon. No wonder I kept the lens, and used the spare cash to finance some other photographic toys. I am not saying there is no progress in optical designs. There has been a lot of progress in the recent three decades, but it must have ignored slow primes.

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