My lab just got a DA 50-200 f4-5.6. In the cause of better photography I
brought it home to test.
Physically it is delightfully light, but appears to be all plastic. This
is the first all-plastic DA lens I have seen. (I have not handled the DA
18-55.) Still it seems sturdy enough. It has one big design flaw: the
zoom ring is so large that it is quite difficult to remove the lens from
the camera. You grab the lens to twist it off, and all you do is zoom
the lens out to 200 mm. There's hardly any part lens to grab onto except
the narrow neck adjacent to the body. The box contains no soft case.
My purpose was to test it optically. I followed my usual test procedure:
images were of an adobe (mud brick) wall at a distance of about 40x the
focal length. All images were shot on a tripod, at ISO 200 in RAW, with
white balance set to shade. Images were important into Photoshop through
ACR with no sharpening or color noise reduction. Inside Photoshop each
image got Auto Contrast but no sharpening. Comparisons were done at
Actual Pixels.
The usual caveats apply: The test interpretation is only as good as my
eyesight. Also, I do these tests only for sharpness, and for my own
edification. If anyone else finds the results useful, that's great. If
not, please ignore this post.
DA 50-200 at 50 mm. vs. DA 16-45 mm at 45 mm:
F4: The lenses are close in the center, but the 16-45 is far sharper at
the edges and corners.
F5.6: The 50-200 is sharper in the center, but the 16-45 is better at
the edges and corners.
F8: The lenses are close in the center. I cannot call one or the other
sharper. The 16-45 is again better at the edges and corners.
DA 50-200 vs. SMC F 70-210 f4-5.6:
70 mm:
F4.5 (DA) vs. f4.0 (F) (i.e., both wide open): The DA lens is sharper in
the center, edges, and corners.
F5.6: The F is sharper in the center. The DA is sharper at the edges and
corners.
F8: The F is better in the center, but only slightly. It is also
slightly better at the edges and corners.
F11: Both lenses are matched in the center. The F is slightly better at
the edges and corners.
135 mm:
F4.5: The F is slightly better in the center. The DA is sharper in the
edges and corners.
F5.6: The F is much sharper in the center. The DA wins at the edges and
corners.
F8: The F is sharper in the center and at the edges and corners.
F11: The F is slightly better in the center, more noticeably better at
the edges and corners.
200/210 mm:
F5.6: The centers are very close. The DA may be slightly sharper at the
edges, and is noticeably sharper in the corners.
F8: The centers are very close again, but the F is slightly sharper. The
F is noticeably better at the edges and the corners.
F11: The F is sharper at the center, edges, and corners.
Overall the DA 50-200 performs pretty well, especially considering its
price. The design strategy to get to its price point was clearly to
skimp on edge/corner sharpness. Here it is consistently a bit weak. This
makes sense for such a lens. Most people will probably use it to
photography their kids, ducks in a pond, birds in a tree, and the like.
The edges of such images will be out of focus anyway, so the softness
won't matter. I occasionally photograph landscape elements and
architectural elements with telephoto lenses, so for me the edge
softness won't do.
The F 70-210 wins the majority of the head-to-head comparisons, but the
results are sometimes close. Keep in mind that my evaluation is at
Actual Pixels. At smaller magnifications one would see less difference
between these lenses. Overall I would have to say that the DA 50-200 is
nearly in the class of the SMC F 70-210. It may be Pentax's best
variable-aperture telezoom since 1987.
Based on these tests I won't buy the DA 50-200, or at least not right
away. My F 70-210 does just fine (as long as it doesn't start giving me
more images with purple bloom). If one needs a variable-aperture
telezoom, though, the DA 50-200 looks pretty good. If would buy it if I
didn't already have the F 70-210.
Joe
