DA* 55/1.4 Vs FA 50/1.4 - A Measurebating Shootout

Here is a very interesting shootout on the two "similar" Pentax lenses of different generations with some unique and effective measurebations:-

http://www.informatik.uni-bremen.de/foto-ag/DA55/DA55.html

The test report is concisely and clearly written and all the findings and observations are self-explanatory. Still, I extract some of the more interesting sentences below which I would add the comments of mine:-

"Disclaimer: This is a test by a layman, who does not really know what he is doing."

This guy is surely not a layman! His tests are cleverly and carefully designed. They are all simple and effective. I have rarely seen people who could do such excellent works at that high level! He even measured bokeh and has been able to qualify the difference in an easy way! He also plotted the spatial frequency charts which give us a general idea on the MTF response and changes from low to high spatial frequencies! "Layman"? :-o Well, he is just an humble guy who does not like to say loudly (unlikely me ;-D). Indeed, I would say he is just an excellent "measurbator"! (Thumb Up)

"AF Speed: The big disadvantage of the DA55 is that it is much slower compared to the FA50 in AF speed (measured using Audacity). The DA55 is about 3 times slower than the FA! I am wondering why this is so and what Pentax has to say about it. Isn't it a confession of failure that an almost 20 year old lens focusses so much faster?"

Oh, yes. Why's that? The SDM was found to be slower, but now this time it is even *much* slower!!? It is not about the travel and throw of the mechanical movement range of the focusing part of the lens, nor it is about the weight of the lens element to be focused, as it is found that:-

"Throw of the focussing ring:
FA85: ca. 90 degrees (superfast AF)
DA55: ca. 110 degrees (slow AF)
FA50: ca. 120 degrees (fast AF)"

So, the FA 50 has longer travel but the FA* 85 undoubtedly has much heavier glass, but neither of them is as slow as the DA* 55. Now, the culprit? IMO it *must* be the SDM, which is inferior in terms of speed (weak torque?), which is even much slower than the old type Pentax body-driven screw-type AF! (but why?)

"Bokeh:
Circle of confusion in the background:
(below the brightness across the ring is shown)"

He simply plotted the lightness response curve and it shows the "bright ring" bokeh which quite some Pentaxians have been puzzled about (provided that they know it)! Amazing! Well Done, Mr. ! You're my Hero!

And, his series of bokeh test shots are well thought and well done. More importantly, they are simple enough but yet clearly presented.

In the end, I don't think the DA* 55 is anything that really worth to invest, with its three time higher price tag than the old FA 50. Yes, it is somehow sharper from corner to corner when the lens is wide opened. Except this, there is no clear advantage optically and in image quality. But what's the real point for a portrait lens to have corner to corner sharpness when wide opened?

Furthermore, it is bulkier and heavier and subjectively I regard the outlook of the lens is Ugly, and so do all the DA Star lenses. In contrast, the FA Star lenses are beautiful (Sad). And yes, it is weather sealed and has the USM. But so what? Especially considered that the USM focuses rather sloooowly despite it is *almost* silent (but not totally). And, as the tester said, it is really ridiculous to have a lens made almost 20 years later, it is yet focusing far slower than a lens made with the technology of late 80s! OMG!