Lens review

Sony Carl Zeiss Planar T* 85 mm f/1.4

7 October 2007
Arkadiusz Olech

4. Image resolution

We expect that prime lenses of companies like Zeiss will break records of resolution. A glance at the below graph shows that there are no records, because the maximum value of MTF50 function measured at RAW from Alfa 100 is almost 41 lpmm. It is clearly worse even from Sony 2.8/50, which reached over 44 lpmm. When we will have a look at the lenses of the same focal length made by the same manufacturers, Zeiss also does not come off well here. Nikkor 1.8/85 tested at D200 achieved at the maximum level 43lpmm and Canon 1.8/85 (tested at 20D) a little over 40 lpmm. But in the instance of 8MPix matrix of Canon the result of the level of 40 lpmm in fact match the result of 43 lpmm at the 10MPix matrix.

Sony Carl Zeiss Planar T* 85 mm f/1.4 - Image resolution

Before, however, we will start criticising Zeiss, we should take into account that in the photography breaking records is not what counts. The difference between 41 and 43 lpmm is almost nothing, since both levels guarantee sensational sharpness of achieved photos. When we will have a look at the graphs of resolution in global, and compare to one another the 85s of Zeiss, Canon and Nikon, this is the last that will obtain the most critical opinions. It will happen mostly due to the weak behaviour for the vicinity of the wide-open aperture. The comparison of Canon and Zeiss shows that in the centre of the image they both have very similar results, and both even with the maximum aperture achieve acceptable image quality (but in Canon the maximum aperture is f/1.8 and in Zeiss f/1.4 – to a portraitist, it is a significant difference).

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When we will have a look at the behaviour at the edge of the frame, Zeiss does not have its equal. It is significantly better than Nikkor and a little better than Canon. Here, Zeiss really deserves to be well praised, because even for the f/1.4 the difference between the centre and the edge of the frame is inconsiderable. The intention to achieve such an effect could be the reason why there are no records in the centre of the frame, for the stops in the vicinity of f/5.6. And I must admit that personally, I am ready to pay this price.

Sony Carl Zeiss Planar T* 85 mm f/1.4 - Image resolution

Honestly, in conclusion, it must be mentioned about one more factor that may determine lower MTF levels of Zeiss. Alfa 100, on which we test Sony lenses does not have a proper option of mirror lock-up. It only has its dummy. There is a two-second self-timer,in this role, which is realised by mirror lock-up. The problem is that those two seconds could be appropriate to test, for instance Sony 2.8/50, but with a focal length of 85 mm it could already have an influence on the presence of minimum and unrestrained vibrations. It is hard to say it this is really what happens hear, because until now Sony lenses cannot be tested on anything else.