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12-24-2013, 06:28 PM - 1 Like   #1
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55-300 DA vs WR comparison

I've acquired a 55-300 WR, with the plan being to replace my DA with it if it works out.

DA, lower right corner, 300mm f5.8, 100% on a K5:



WR, lower right corner, 300mm f5.8, 100% on same K5:



This is the only difference in the images - that's why I'm posting these crops; the other 3 corners and center are too close to call, so posting them would be pointless. Incidentally, a difference is still there (although slightly less noticeable) at f9.5, the only other tested aperture.

I haven't tested all the other focal lengths equally yet, and I haven't tested to see if this difference will hold up at infinity. I did test the upper-right corner at infinity, ironically, because I felt my DA was a little weak there, but then cleverly forgot which lens made which image, so it's back to testing for that again tomorrow.

I went through 4 DAs before settling on my copy, but don't plan on doing that for the WR - just too much work. Two of the other DAs weren't close - one side or the other was seriously off. The third was close, a little better some ways, a little worse others. I'd call this close enough to be manufacturing tolerance not not toally unacceptable, although it's still annoying that I should be able to tell the difference between the corners with just 16mp at iso200 (and not even a K5iis at that.) Put the lenses on higher resolution bodies and of course you'd see more differences.

I'd be interested if everybody thinks this degree of difference is acceptable, or not.

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12-24-2013, 08:00 PM   #2
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Instead of sending it back, why not send it in for adjustment? If the service center puts it on the optical bench, it should end up perfect.
12-24-2013, 10:02 PM   #3
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QuoteOriginally posted by Kozlok Quote
Instead of sending it back, why not send it in for adjustment? If the service center puts it on the optical bench, it should end up perfect.
I've gone through this with Sigma - multiple round-trips - and I'm guessing Pentax will react similarly. The Sigma issue was with an EX lens, incidentally, which is marketed, at least, as somewhat more-than-consumer grade. Even with a problem much more obvious than this, you have to get the manufacturer to agree there's a problem. You even have to get them to agree as to the definition of a "corner." Maybe it's the actual corner, which is what I'm showing here. Maybe it's about 20% in from the corner. Sigma took test shots with my lens, but their test camera was a K100 (although by this time the K20 was available.) And their test target didn't come close to the actual corners of the frame. So even problems that were very obvious to me on my K200 weren't nearly as evident in their tests.

Experiences vary, but I'm not even sure it's possible to adjust many of the parameters that would cause this behavior in a "consumer" lens. And of course once you go that route, you lose the ability to return the lens to the retailer. Given the range of service experiences that have been reported here on the forum, it doesn't seem like a wise gamble to keep a lens that underperforms, although in theory I agree that a basically hand-(re)built lens could potentially have tighter-than-factory tolerances. But it's a long way from theory to practice. I think it would be very risky to assume that servicing could improve the performance of any lens that's just marginally (or even not-so-marginally) sub-optimal. If the front element falls out, you're probably good with servicing. This situation, not so much.
12-24-2013, 10:28 PM   #4
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QuoteOriginally posted by tibbitts Quote
I'd be interested if everybody thinks this degree of difference is acceptable, or not.
I'd say it's not unusual. If you haven't read these blog posts, I recommend them:

LensRentals.com - “This Lens Is Soft” and Other Facts

LensRentals.com - Notes on Lens and Camera Variation

LensRentals.com - The Limits of Variation

12-25-2013, 09:29 AM   #5
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QuoteOriginally posted by nater Quote
Thanks for the links. I'd read the lensrentals article on centering but not these. Some variation is certainly expected, but quantifying the differences into what's acceptable or not is difficult. In the case of the first two 55-300DAs, it wasn't close. You could have barely identified the numbers on those two.
12-25-2013, 01:46 PM   #6
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May I suggest a different test? Shoot around with it normally for a week, then look at your photos. Are they ruined by blurry corners? If so, return the lens. If you can't tell if they are or aren't, stop worrying and have fun with the lens
12-25-2013, 04:52 PM   #7
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QuoteOriginally posted by clawhammer Quote
May I suggest a different test? Shoot around with it normally for a week, then look at your photos. Are they ruined by blurry corners? If so, return the lens. If you can't tell if they are or aren't, stop worrying and have fun with the lens
I went out today with both lenses and made about 30(60) comparison photos of actual subjects that I typically photograph, both wide open (at various focal lengths) and about two stops down. I'll look at them when I get a chance and decide which lens to keep, and report back what I find.

Where I notice resolution issues is foliage and branches, so that's what I tested with today. It's harder to get good comparisons outdoors vs. what I did in the samples above because you can't control the environment as well. In the time it takes to change lenses, the sun/clouds can shift a little, you can get a little more or less sun in the viewfinder affecting exposure just slightly, you can get wind moving the camera or subject, etc. But I do understand the point that resolution test target corners don't matter to everybody. If you photograph sports or animals, for example, you might not care about corners at all. But if you're photographing a scene with a wall of foliage, and the left and right sides aren't equally sharp (even at a typical aperture like f11 or so), that's a big issue. Obviously consumer lenses like these might not be super-sharp across the frame, but the choices in relatively portable autofocus tele zooms for Pentax is pretty limited.

Oh, something I've already tested: the 300mm lower-right weakness in the test target photos doesn't hold up at infinity. The lower rights of the lenses are pretty equal at infinity. The upper right in the infinity tests I've completed so far is very slightly better in the WR, although it's not as dramatic as in the test target photos.
12-25-2013, 05:38 PM   #8
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QuoteOriginally posted by tibbitts Quote
Oh, something I've already tested: the 300mm lower-right weakness in the test target photos doesn't hold up at infinity. The lower rights of the lenses are pretty equal at infinity. The upper right in the infinity tests I've completed so far is very slightly better in the WR, although it's not as dramatic as in the test target photos.
You could have some decentering, which you could test for yourself:

LensRentals.com - Testing for a Decentered Lens: an Old Technique Gets a Makeover

Incidentally, when I said the lens performance was "not unusual", I didn't mean to imply it was at at a level that shouldn't be corrected. From what you've posted and said, I would imagine some fine-tuning at a repair shop (such as CRIS) would improve the performance of the WR.

12-26-2013, 06:57 AM   #9
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QuoteOriginally posted by nater Quote
You could have some decentering, which you could test for yourself:

LensRentals.com - Testing for a Decentered Lens: an Old Technique Gets a Makeover

Incidentally, when I said the lens performance was "not unusual", I didn't mean to imply it was at at a level that shouldn't be corrected. From what you've posted and said, I would imagine some fine-tuning at a repair shop (such as CRIS) would improve the performance of the WR.
I would agree if not for my Sigma experience, which is that unless the images look like you'd smeared grease over the front of the lens, you're not going to get anywhere. I sent them images just like are posted above, and like the ones above, they were repeatable. I could test on both my camera bodies with different targets/environments and get the identical results (except to degree - more visible on a higher mp body, obviously.) Now, it's certainly possible that if you can establish what's considered a problem, some lenses might be correctable. I'm not sure a 55-300mm would be, however - I'm just not sure the adjustability is built in like it might have been in older, simpler (or currently some higher-end) lenses. You could replace the entire guts of the lens, of course, but then you'd probably be exchanging one problem for another, as in the 4/5 copies of this lens that I've now experimented with. Maybe someone who has expertise with that can comment. I'd say almost any side-to-side or corner-to-corner variation is likely some form of decentering, but I'm not really concerned with identifying what the optical problem is if I can't convince a manufacturer (or rep) that there actually is a problem. Most lenses probably have some decentering - I seem to remember lots of magazine lens test reports from the '70s and '80s, for example, where the phrase "centering was nearly perfect" was frequently used. So, not perfect, to a degree that could be measured. But there weren't that many tests of 300mm lenses back then, or 450mm depending on your viewpoint, so I'm not sure what that would have revealed. So it's a matter of how visible decentering is and to what degree it's acceptable.

If I could take the three uninspiring copies I've now had and combine the best of their performances across various focal lengths and focusing distances, I'd be totally satisfied with the performance of the lens. That tells me that the optical design can meet my expectations, if there are actually any copies that are built accurately enough.
01-14-2014, 09:37 PM   #10
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Here's another example of why I find these lenses so aggravating - and this isn't a test chart, for those who prefer "real" pictures. These are just screen captures from faststone, but hopefully sufficient to make the point. Note that the behavior at these much longer distances is different than from the 8ft or so range I had posted earlier.

First, a 135mm example at f8, DA on the left and WR on the right (100% crop from the upper left corner)

Followed by a 300mm example, with (just to confuse you) the WR on the left and DA on the right (100% crop from the upper right corner)

What's significant is that the rest of these images were identical between the WR and DA examples - so they were both out of focus and in focus in the same places, as would be expected from the limited depth of field - except for these two corners. So this isn't a case of focus simply being different between the images. If I'd provided a crop from the center or any of the other corners, I'm pretty sure everybody would agree they were identical for practical purposes, which is why I'm not including them.

I've tested my old 100-300F (the "bad" version) against the 55-300 incidentally, and while contrast and maximum sharpness isn't equal to what the newer lenses can accomplish, there's very little corner/edge deviation.

Performance of these lenses does improve with stopping down - at least through f11-13 at shorter focal lengths and f16-19 at the longer lengths. Maybe diffraction takes some minor toll, but what you get back in consistency across the frame (and of course the extra depth of field) much more than compensates - assuming what you're doing actually requires sharpness across the frame. If you only needed center sharpness (wildlife, for example), you'd probably be happy with any of these copies.

https://www.pentaxforums.com/forums/attachment.php?attachmentid=202227&stc=1&d=1389758001

https://www.pentaxforums.com/forums/attachments/10-pentax-slr-lens-discussion/202228d1389758001-55-300-da-vs-wr-comparison-135mm-f8-top-left.jpg
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01-16-2014, 03:37 AM   #11
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This is what my old SMC DA55-300 does at infinity (well, at 880 meters) at 300mm and f5.8 - centre and corners, CA corrected. This is my second copy, the first was decentered and I returned it. This one I can live with.

Judging from your experience Pentax QA/QC is still cr*p.
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01-16-2014, 04:39 AM   #12
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Knowing about the horrible QC at that time under Hoya (back in 2011), I compared two different new DA 55-300 to select one (hopefully) flawless one. One was totally unacceptable at the short end and so-so at the rest of the range, while the second one was actually very, very good in general but slightly decentered at 100 and 300mm. I decided to take my chance with this one and sent it in for adjustment, and it actually came back perfect. So it seems it is possible to adjust the 55-300. A different experience was less good, however. At a later time I also sent in my 18-55 WR, which also showed decentering at some focal lengths, but got it back with the claim that it is within manufacturer tolerances. So knowing this, I'd probably no longer take the gamble of getting a lens adjusted but would make sure to get a flawless copy from the beginning...
01-16-2014, 06:14 AM   #13
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Have you tried fine-tuning the AF on your new lens? Does that have any impact?

That being said, I think this level of difference is meaningless. Go out and take pictures, it will make you happier than worrying about such small sample variation.
01-16-2014, 06:57 AM   #14
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QuoteOriginally posted by bdery Quote
That being said, I think this level of difference is meaningless. Go out and take pictures, it will make you happier than worrying about such small sample variation.
That is exactly what the money grabbing multinationals like Ricoh are hoping that you will do so that they can get away with even less QA/QC.
01-16-2014, 09:02 AM - 2 Likes   #15
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QuoteOriginally posted by kh1234567890 Quote
That is exactly what the money grabbing multinationals like Ricoh are hoping that you will do so that they can get away with even less QA/QC.

The OP took the best, out of FOUR DA lenses, and compared it to one random sample HD lens. Both are perfectly acceptable but there is a slight difference. In one corner.

I make my living as an optical designer for test and measurements on fiber optics. My company manufactures products, and I'm responsible for defining what manufacturing tests and tolerances are required. so I can tell you that EVERYTHING , manufactured or hand-made, will have sample variations. The manufacturer sets the tolerances based on several factors. If you set tighter tolerances, the cost is higher (that's one reason DA* lenses are more expensive). There are industry standards that most companies follow (2 standard deviations tolerances, for instance). I'm positive that both these lenses fall within that range.

Now let's look at what Pentax does, in fact, guarantee about that lens. They guarantee the focal lengths, apertures, and... that's it. That's ALL there is. The rest is information about the lens, nothing more (coatings, WR, etc).

How is the slight difference in sharpness in one corner going to affect the creativity of the photographer, the artistic value of the images? Blatant flaws in a lens are of course unacceptable, but this? If you had no other lens for comparison, you would have found it plenty sharp.

I don't see your point about "money-grabbing companies". We live in a world where companies offer products that you can or cannot buy. They are not grabbing anything, they are putting products on shelves for you to look at. But their purpose is to be profitable, otherwise there won't be any products available pretty quickly.
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