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11-25-2008, 02:31 PM   #1
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Newspaper killed the DA* (50-135 content)

For the past few months there have been three lenses whose siren calls rang the strongest: The FA31, FA77, and the DA*50-135. After getting a 10% ebay coupon, coupled with the prospect of 25% ms cashback, I could no longer resist my growing LBA.

My initial impressions were all to my expectations. The lens is a comfortable size and weight, and the build quality is fantastic. The SDM speed is by no means fast, but the lens pleasantly whirs into focus and surprises you with a silent focus lock. As for the colors, sharpness, and bokeh? Well..

These were just some snapshots from around my house, but I think we can definitely check off bokeh and color on the list.

After waiting out the weekend for my tripod to arrive (somehow, my slik sprint mini was starting to seem ridiculous), I snapped off some shots comparing the DA*50-135 and the DA50-200.

At first glance, the DA* is slightly warmer and sharper. But, if you click on the links for the full sized images, you can see the DA50-200 truly begin to fall behind. Its biggest failing for me was not so much a lack of absolute sharpness, but rather, its rather nervous bokeh. Whereas the DA handles the spectral highlights somewhat unpleasantly, the DA* blurs the background into buttery goodness.

So all's as it ought to be, right? Well, it is at this point that I decide to sabotage my happiness.

The Newspaper Test.

I can hear the resounding thuds of palms impacting photographers' foreheads already. Don't get me wrong, once a lens earns itself in my lineup I don't sit around testing its sharpness. However, when I purchase a new piece of gear, part of me needs to know that it's better than the thing it's replacing.

Just as I feared, decentering rears its ugly head. I tried everything to make sure it wasn't so; I tightly taped the paper by all four corners and sides, I meticulously leveled the tripod, I tried to get the camera as perpendicular as possible. Yet, it was to no avail, no matter what I did the left side lagged behind the right.

If I look at the DA* shot only after a while I think that it's not that bad--and it really isn't. Most real world shots will have the left 15% of the frame well outside of the DOF. Also, the leftmost column isn't that much worse than the rightmost one. However, as soon as I glance over at the DA test shot, let alone the M135 f3.5, it begins to bother me again.

Okay, so 15% of the frame of my lens is a little blurry. There is almost no way that this matters, but nevertheless knowing it's there sits in the back of my mind. It's like listening to Muse and noticing Matthew Bellamy's sharp breaths, only to wind up hearing nothing but his gasps for air for the rest of the album.

I don't know if I should try seeking an exchange at this point. There's no guarantee I'd receive a perfect copy, and given the track record on the *s, there's the possibility of getting something worse. I guess I'm in sort of a state of let-down lethargy, where I neither feel like trying to send it back, nor do I feel like going out and taking pictures with it. Anyhow, I'm looking forward to some advice on this to edge me out of my melancholy and push me towards one direction or the other.

EDIT: When I wrote this post I was at an impasse at what to do with the lens, and I wanted some help to decide. I did not mean for this post to spread FUD about this excellent lens, nor did I intend to crucify pentax a-la RiceHigh. I had meant to work this post into a review of the DA*50-135, but due to thanksgiving I have run a little behind. For now I will post the results of my latest, and final test:

-------DA*50-135 @ 135mm, f5.6 ---------------- DA50-200 @ 138mm, f5.6-------

Crop of center column of text:

DA* on the top and DA on the bottom.
Click for 100% pixel view

Crop of the text left or right of the center column:

DA* on the top and DA on the bottom.
Click for 100% pixel view

The test was set up as per Class A's suggestion, although with the distance at 10m instead of 20. I focused manually to achieve focus lock with the center AF point, and the focus confirmation seemed to coincide with the sharpest text. For the DA, I zoomed in to 200mm for focusing and then zoomed back out. Then, I panned the image to the left and right. All shots were taken with the 2s self timer.

The DA* shots exhibit a little more depth of field in front of the box, and the DA more depth of field behind it. I'm not sure what's up with this as it happened consistently and neither lens showed much of a problem on the focus chart.

Now, the results. As you can see, the DA50-200 is rather horribly decentered. Not only is the left side sharper than the right, somehow the middle-right section of the lens is worse than the extreme right. The DA*50-135 is the clear winner here. Despite the DA* being at the weakest part of the zoom, while the DA is at its strongest, the * remains sharper even on its bad side.

The apparent superiority of the DA50-200 in the newspaper test is most likely down to two things: the DA*'s close distance performance, or lack thereof, and the DA's good side matching with the DA*'s bad side. Also, I was only looking to show the decentering problem on the DA* rather than comparing the two lenses for sharpness. As such I didn't spend a lot of time finding the best set of images.

Anyway, the verdict? I'm going to keep the lens. The biggest irritation with the $750 lens was not so much the apparent problems, but rather, that my $200 DA50-200 seemed less problematic. If I had to estimate it quantitatively, I'd say that the left 10-15% of my DA* is 20-30% softer than the right. In any event, this is getting rather esoteric, so this test will be the last sharpness comparison done with this lens.

I have come to accept that most modern zooms will not be perfectly centered, so that when one goes looking for problems he will invariably find them. Also, if there's a place to have weaker performance, the extreme left side is the best place for it to be. I've noticed my horizontal compositions tend to put the subject on the right hand side, and obviously portrait oriented shots will also have the subject on the right hand side. I've proven to myself that, without a doubt, the DA* is superior in every respect (except shooting newspapers), and this lens has earned its place in my bag.

Last edited by Kirivon; 11-27-2008 at 03:08 PM. Reason: added content
11-25-2008, 04:30 PM   #2
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These threads about the two (main) primo zooms worry me.

If I, say, got hired by a newspaper tomorrow and they let me bring my own gear (or, more likely, were such a dodgy newspaper we had to bring our own gear) I'd love to get one or two K20D's and these lenses.

But if it were such a case of Russian roulette to get a good copy...*sigh*. It's not like there's any camera store down here that has half a dozen of these lenses in stock sitting on the shelf for instant returning and swapping. After you wait the 3 weeks for the lens to come in, it's another 3 weeks for another lens.

I really hope Pentax can again start making all their lenses themselves soon. Tokina doesn't seem to be giving much of a toss. Or, if Hoya does indeed own Tokina, they should start telling Tokina to pull their head in.
11-25-2008, 04:43 PM   #3
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The DA* 50-135 is not a macro lens, and as such, it might have a very hard time rendering a flat subject at close range 100% sharp corner to corner. I really would try to check if you slightly alter focus forth and back to see if that part that is not perfectly sharp can be brought to sharpness. That would mean that focus at close range is not perfectly flat, not necessarily a de-centered lens. Macro lens and general purpose lenses are not designed with the same goal, which might explain your results.
11-25-2008, 06:23 PM   #4
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As far as I know, the DA*50-135 lens isn't meant for taking newspaper photos

Don't worry, as long as you are happy w/ the real world shots, you'd be fine. Just enjoy using it and forget about the newspaper ...

11-25-2008, 07:26 PM   #5
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what exactly is decentering........ and does it pose a problem in "everyday" shooting by an amateur?
11-25-2008, 07:27 PM   #6
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I have never once taken a shot of newspaper with my 50-135.
11-25-2008, 07:58 PM   #7
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Your 50-135mm performed beautifully on your everyday shots with great color and bokeh. I think mine does too, but I would not want to put any one of my lense to the newspaper test just to find "decentering" so I can drive myself crazy looking for the "perfect" lens.
11-25-2008, 09:27 PM   #8
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For that price I would like to get a decent (newspaper) performance that even my 60eur fa28-70 zoom can do..

11-25-2008, 10:16 PM   #9
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QuoteOriginally posted by pasipasi Quote
For that price I would like to get a decent (newspaper) performance that even my 60eur fa28-70 zoom can do..

Check out the terrible de-centering in these shots:

Terrible, huh? (Moral of story: I have no idea, nor do I care, how my lens would
capture newsprint.)

Last edited by jsherman999; 11-25-2008 at 10:25 PM.
11-25-2008, 11:23 PM   #10

Thanks Jay...

A very good showing... this proves the old "believe only what you see not what you read in a newspaper.

But I am trying to switch systems and here you are gonna make me buy this lens.

It has always been my dream length / speed zoom.
11-25-2008, 11:44 PM   #11
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I would just like to mention that the 50-135mm is reported to not perform at its best at closer focusing distances.

Like the others have said, I've never done such a test with my 50-135mm(the 16-50mm is a different story, but it turned out alright), yet I've been nothing less than stunned by what it produces.
11-26-2008, 12:03 AM   #12
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I am also in the ''I have no idea, nor do I care, how my lens would capture newsprint.''

Should you not be using a Macro lens for shooting newspaper?
11-26-2008, 01:27 AM   #13
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QuoteOriginally posted by Kirivon Quote
I don't know if I should try seeking an exchange at this point.
Only you can decide how much the apparent decentering bugs you. Judging from your audio analogy, I think it would stay in the back of your mind, even if you are basically happy with the images.

Going against the general opinion here, although of course only real world performance matters, I believe for a high end product like this lens with the associated price tag you have every right to expect proper centering.

In another thread I contributed a posting about how you can check for decentering in an alternative way. If I had bought this lens new, I'd return it as often as it takes to get a proper copy whether the flaw is in your face during normal usage or not. But other's milage certainly does vary.

All the things the lens does well (as beautifully demonstrated by jsherman999) don't go away if it is flawless.
11-26-2008, 01:32 AM   #14
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You will find that all DA* 50-135's give a similar result shootin a newspaper. I noticed it with mine then went on a rampage round the net checkin up on it... conclusion? My god this is one lovely lens.
11-26-2008, 02:47 PM   #15
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looking at the 50-135 review in photozone:

Pentax SMC-DA* 50-135mm f/2.8 ED [IF] SDM - Review / Test Report

there is some dramatic fall off of border resolution reported in that test, e.g. at 135 F2.8, the center resolution is 1915 and the border resolution is 1494, thats almost a 25% of resolution lost between the center and the border. But then again, there isn't one lens that doesn't have falloff of resolution between the center and border.

there is no perfection in this world, there is a manufacturing tolerance on everything. For a zoom sealed fast lens, i am amazed they can produce something this good.

I'm waiting for my DA 300 today, and I won't be testing it on a newspaper. But do what you think is best, its your money.

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