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Lens review

Samyang 21 mm f/1.4 ED AS UMC CS

8 December 2015
Szymon Starczewski

4. Image resolution

The resolution test of the Samyang 21 mm f/1.4 ED AS UMC CS was based on RAW files from the Fujifilm X-E1 camera. They were developed by the dcraw program (with the 3-pass X-trans filter algorithm) and analyzed with the help of the Imatest package.

Let’s remind here that the best fixed focal length lenses from the Fujifilm X system tested that way are able to reach 73-76 lpmm and the decency level is situated near 42-43 lpmm. The resolution record, amounting to as much as 78 lpmm, belongs to the Fujinon XF 90 mm f/2 R LM WR.

The graph below shows MTF50 function values depending on the aperture we got in the frame centre and on its edge.

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Samyang 21 mm f/1.4 ED AS UMC CS - Image resolution


We like the performance in the frame centre very much indeed. At the maximum relative aperture the image is perhaps not very sharp but it can certainly be called decent. With the stopping down the MTFs increase swiftly and by f/4.0 they reach almost record-breaking values – those near 77 lpmm. It is really an excellent result - after all the much more expensive Fujinon XF 1.4/23 could only get to 70 lpmm or so.

Unfortunately the edge of the frame can spoil your good mood. Our graph shows clearly that near the maximum relative aperture the MTFs are weak and the lens has to be closed down to about f/4.0 in order to achieve a decent resolution…

What’s happened? The problem stems not from a bad design of optical construction but inferior build quality and quality control. The situation becomes clear when you compare the image resolution on the left and on the right side of the frame.

Samyang 21 mm f/1.4 ED AS UMC CS - Image resolution


As you can notice the differences are significant and only from f/5.6 the performance on both sides becomes similarly high. When you look closer at the very corners of the frame the situation is even worse and the crops below prove that much.

Fujifilm X-E1, RAW, f/1.4, left Fujifilm X-E1, RAW, f/1.4, right
Samyang 21 mm f/1.4 ED AS UMC CS - Image resolution Samyang 21 mm f/1.4 ED AS UMC CS - Image resolution


Of course you can always wonder what a performance of the perfectly centered lens would be. Unfortunately the poor quality control in the Samyang factories made it impossible to answer. According to our rules we always check only one specimen of a given model; the Samyang arrived to our office in perfect condition so we had no reason to consider it faulty; after all it was sent directly from the Polish distributor and they had got a brand new specimen straight from the factory.

At the end of this chapter traditionally we present crops taken from photos of our resolution testing chart saved as JPEG files along the RAW files we used for the analysis above.

Fujifilm X-E1, JPEG, f/1.4
Samyang 21 mm f/1.4 ED AS UMC CS - Image resolution
Fujifilm X-E1, JPEG, f/4.0
Samyang 21 mm f/1.4 ED AS UMC CS - Image resolution