#168. Is the new Zeiss 35/2.8 Z better than the RX1 ?

By now, it’s pretty certain the new Sonnar T* FE 35mm F2.8 ZA will be a stellar performer on the equally new Sony A7 and A7R cameras. Brilliant samples such as the one below by ijsvogel at Dyxum have shown us just how good.

(c) ijsvogel at Dyxum

Click here to access ijsvogel’s samples at Dyxum.

But the pressing question in everyone’s mind, is how good, compared to the extraordinary 35mm lens in Sony’s RX1 and RX1R cameras?

Until we have A/B comparison tests on identical targets, all we can do is assess what elements we already have in hand : official MTF curves and official sample tests.

Starting with the MTF curves, what can we see ?

The RX1’s Sonnar 35mm f/2 MTF curves (10lp/mm and 30lp/mm). (c) Sony

Above are the MTF curves at 10lp/mm and 30lp/mm for the RX1. Below are those for the new Sonnar T* FE 35mm F2.8 ZA at 10lp/mm, 20lp/mm and 40lp/mm. For comparison purposes, the 30lp/mm curves for the Sonnar T* FE 35mm F2.8 ZA would be roughly half way between the blue and green curves on the graph below.

If you are not MTF litterate, a brief intro to reading these curves is provided in a previous post.

Sonnar T* FE 35mm F2.8 ZA MTF curves

What this tells me is that the image quality from both these lenses will be virtually undistinguishable at F/8.

But at full aperture, the RX1’s Sonnar seems a tad better corrected than the Sonnar T* FE 35mm F2.8 ZA, particularly in the corners, where the difference would probably be visible. Though the difference will not be that big in real life pictures, remember the RX1 is achieving these results one stop more open than the Sonnar T* FE 35mm F2.8 ZA !! That’s remarkable and, in my mind, the RX1 possibly has the best 35mm ever designed !

Still, lenses do not operate in a vacuum. Used on the 24Mpix A7, the Sonnar T* FE 35mm F2.8 ZA will not be quite as sharp as the RX1, but on the A7R things are a little different :

• at F/8 and up to the edges, where the tangential curve falls quite low, the Sonnar T* FE 35mm F2.8 ZA will probably resolve 80lp/mm which the A7R sensor will be able to exploit. Over almost all of the frame, there should be more resolution in the A7R/Sonnar T* FE 35mm F2.8 ZA combo than in the RX1 image.
• at F/2.8, things are different and I’m guessing the difference (in favour of the A7R) will be clearly visible in the center 20 mm and gradually less, the RX1 actually being sharper in the corners.
• at F/2, well … there’s only one winner 😉

But there’s more to be learned from the specifications. The RX1 has 9 blades whereas the Sonnar T* FE 35mm F2.8 ZA only has 7 ! This is likely to make a difference in out of focus highlights, such as in the sample below, by dcfever.

As you can see, heptagons are present instead of the smoother shapes that would be produced by a lens with more blades. Note that the 9 blades in the RX1 have sometimes been criticised for not being as circular as hoped for but the bokeh from that camera is superb, so maybe we shouldn’t make too big a deal of it all.

Still, I cannot help feeling that Sony have deliberately held back on some aspects, probably in order to keep the RX1 at the pinnacle for a longer stretch of its life cycle.

But all this matters very little as I am just writing this to keep my mind occupied until the lens is mine 🙂 Whatever the charts and blade numbers suggest, I’m pretty confident this will be an outsanding lens (check out the nice bokeh below :)) on theA7R and cannot wait to use it !

Official Sony sample for the Sonnar T* FE 35mm F2.8 (c) Sony