[tibbitts]

The difference in the lenses is more than sufficient to dramatically affect creativity. As a practical example, for a recent photograph I was standing across a lake, with a shoreline of ice-covered trees a couple of hundred yards away. Even at f11 or f16, when I display the image and just glance at it, the branches in one corner are noticeably blurrier than the other three. The objective was to have that backdrop of trees be uniformly sharp - and that's really necessary for the photograph to have the intended effect.You don't have to be looking for the difference - it jumps out at you. In fact, that's the kind of situation that led me to do these seemingly endless tests. I didn't set out to test lenses - I set out to determine why my pictures were glaringly inconsistent across the frame. I would prefer the the manufactures test lenses, so I don't have to.

Obviously the maximum sharpness from a 55-300DA/WR at 250-300mm isn't going to be equivalent of a very high-end lens, and I'm sure my picture might have been more effective if I'd taken it with a 36mp ff sensor and elite 300mm prime. But my contention is that any reasonable-quality lens should be uniformly sharp/not-sharp in each corner, when viewed at 100% on, say, a 10 or 16mp sensor.

By reading other posts, there's absolutely no evidence that more expensive lenses are any more consistent, so I don't think that simply paying more is necessarily a solution.

[tibbitts]

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.

I have not tried fine-tuning, partly because some of my tests have been on a K200 (it focuses fine with all my other lenses, so I'm not going to change its only default for just one lens), and partly because I can't manually focus (live view on a K5, or through the viewfinder on the K200) any better than autofocus does. These lenses aren't like my Tamron 17-50, where I'm needing -10 (and maybe could use even a slight bit more) on the K5. The 55-300s seem to autofocus well, after a little hunting occasionally. In any case, I do recognize that some lenses need some help with focus adjustments, but none of my tested copies have needed that. The centers are certainly uniformly sharp across all the copies I've tried.

Having complained so much, I will say that these lenses can produce images that I'm very pleased with, and do so maybe 80% of the time in actual use. They have much higher contrast than my older lenses, and there's not much to complain about in the center 2/3rds of the frame. It's the other 20% of the time that's so disappointing. And even with all the testing I've done (hundreds of purely test pictures at this point with just these lenses), I still haven't determined under exactly what circumstances they fail. The one thing I've learned is that you can't just take pictures of test targets on the wall at various focal lengths. You need to test every combination of focal length and focusing distance, and that's not something I really want to do. I haven't tested my other lenses to the same extent, because they've not let me down to the same degree in routine picture taking. It was the failures in actual use that triggered all the testing. Previously, the bad copies of lenses that I'd had were at least somewhat uniformly bad - I could reproduce the failure across multiple focal lengths and distances. Not so with these lenses.

[tibbitts]

Here's another example, DA on the left and WR on the right, 300mm. The left side of the images look similar to me; the right sides, not so much:

[kh1234567890]

That is bad. I'd send it back.

[tibbitts]

That is bad. I'd send it back.

Since I'm out of time at amazon I'll send it back, but the annoying part is how inconsistent the results are - but only outside of about the center 60% of the frame. And it's not unique to 300mm or any other focal length. Two of my copies were horrible at 55mm. It's almost as if all the lens components don't register in exactly the same position every time the lens is zoomed/focused. Unlike with some Pentax lenses (16-45), the physical tolerances on these seems not-too-loose, so I can't explain that.

Of the actual pictures I've made with the DA over the past year, I'm very pleased with most of them, but it's frustrating to know that the kind of performance in the example with pop up at random times. And it's bad enough to completely ruin some pictures - actually a good percentage the types of pictures I usually take. Realistically there isn't usually time to examine each image in detail, or to completely rezoom/refocus after every shot, so you don't know you have a problem until it's too late.

[tibbitts]

I received a replacement 55-300WR to test against my 55-300DA. Here's the lower left at f5.6, WR on the right, DA on the left. Yet another disappointing 55-300. This one does outperform the DA at 200mm+ in the upper right.

[kh1234567890]

Are you going to persevere or just give up and keep your old SMC since that appears to be the only DA 55-300 that Pentax had ever managed to set up properly ?

[tibbitts]

Are you going to persevere or just give up and keep your old SMC since that appears to be the only DA 55-300 that Pentax had ever managed to set up properly ?

I wasn't as careful in testing when I got my DA. My first DA was glaringly blurry at 55mm on the entire left side. So I exchanged it for another, which was fairly uniform across the frame at with the test chart, and seemed ok in practical tests (couple of hundred images.) Basically I declared victory too soon. Subsequently, I used the lens at 300mm to photograph a (large) bird across a pond, with a uniformly distant background of foliage. Foliage in the upper right was blurry. So I tested with printed characters at several hundred feet, and sure enough the upper right was obviously worse than my 100-300F. Everywhere else, the DA was better. So as a practical matter, my DA is fairly good 55-200ish lens. Subsequently I tried two more DA's (4 total), one of which was worse overall than mine, and the other of which was different (better at 300mm), but inconclusively better or worse overall, so I kept mine.

I'm tired of testing 55-300s. I want Pentax to test them so I don't have to. Probably if 90% of these lenses - probably the actual defect rate - got returned, that would get some attention from Pentax. But not enough consumers test lenses - I know I didn't. Or maybe they just care about center performance, especially with telephotos, in which case any of my copies would have been acceptable.

I wouldn't mind paying more for a lens with consistent performance with the same range and features. I don't need or want the physical size/weight of a Tamron 70-210 or 60-250DA, and since I'd be very satisfied with the performance of a combination of the 55-300s, I don't think I should need to carry more weight just to get consistency.

[kh1234567890]

I'm tired of testing 55-300s. I want Pentax to test them so I don't have to. Probably if 90% of these lenses - probably the actual defect rate - got returned, that would get some attention from Pentax. But not enough consumers test lenses - I know I didn't. Or maybe they just care about center performance, especially with telephotos, in which case any of my copies would have been acceptable.

It seems that Pentax lens testing only involves shining a light into one end and checking that it comes out of the other

You'd have thought that while they were changing the design to incorporate WR they would also try to make centering setup easier for themselves. Unless the WR changes consisted of only sticking in some neoprene foam strips inside and a rubber o-ring on the mount.

[tibbitts]

It seems that Pentax lens testing only involves shining a light into one end and checking that it comes out of the other

You'd have thought that while they were changing the design to incorporate WR they would also try to make centering setup easier for themselves. Unless the WR changes consisted of only sticking in some neoprene foam strips inside and a rubber o-ring on the mount.

I'm curious to know if the most directly comparable (but generally less expensive) lenses - the nikon and sony 55-300s - have the same variation issues, but I don't have any access to that equipment. I know the pentax is faster at the wide end, and maintains a relatively wide aperture through the zoom range, but that doesn't matter to me relative to being able to have consistent performance across the frame.