One lens one story #4
The XF35mmF1.4 R is probably the most loved lens by the X-mount users.
It was criticized for its slowness when it first came out, but now that the issue has been resolved, it is praised for the great image quality it produces and for setting the new standard for the prime lens.
When you take a look at the MTF chart however, it doesn’t seem like much of a lens. The response is high at the center, but the response falls short at the peripheral area. It will be classified as “decent lens” at best.
To tell the truth, The lens designer didn’t give much consideration to the MTF chart. To put it the another way, the interest wasn’t only limited to the spec that can be seen in the catalog, but it was far greater.
Let’s review the MTF chart that are used in the catalog.
-The distance to the subject is constant from the center to the peripheral, meaning the subject is two dimensional.
-The subject is set at infinity
-The score is determined on the frequency range of 15l/mm and 45l/mm (in case of APS-C format)
There are a few problems with this.
1. It doesn’t describe how three-dimensional subject will appear.
2. Not all lenses are used most often with the distance set at infinity. The chart doesn’t indicate the performance of cross range and mid distance.
3. The latest sensor depicts high frequency range higher than 45l/mm. The influcence of 60l/mm is far greater for the actual sharpness of the images.
XF35mmF1.4 R worked on these problems.
The designer created the lens with the idea that the short to mid distance is the most often used range. And he made sure that the subject in the range will be at its highest quality, utilizing the full potential of the sensor.
To achieve this, there are trade-offs of course. The image quality is not constant from the center to the peripheral area. But it is rare that a photographer would shoot something that is two dimensional with this lens. If you could ignore the catalog spec, then the actual design is far more practical in reality.
“Image quality” over “Spec”
The popularity of XF35mmF1.4 R proves this. There is something more than just the catalog spec.
Continue to read Episode 5
One lens one story – Episode 5: XF27mmF2.8 Part 1