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09-24-2011, 11:30 AM   #1
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Lens Comparison DA17-70 vs DA18-135 vs. FA43.

Having just received my 17-70 back from Pentax, I thought before I sell it, I should do a comparison of the same image, at the same aperture on a tripod, to see if there is a difference between the DA17-70, DA18-135 and as a check or benchmark, an FA43. I selected an aperture of f/5.6 so that none of the zooms would be at a wide open state. I was surprised by the results. First, the speed did not fully compensate for the different lenses. The FA43 is very bright and the DA17-70 is quite dark. In fact, the K-5 put my DA17-70 at a speed of 125 sec vs 250 sec with the DA18-135 and strangely the FA43 also shot at 125 sec. I don't get that at all. There were no clouds in the sky and they were all shot in the same basic minute or so that it took to swap lenses so that was strange. Oh and the front window looks strange because there was a seal break and water got in. Yes it could be cleaner too.

I haven't placed an image in a post for some time so I hope this works okay:
Here is the FA43 image:


Here is the DA17-70 image:


And finally the DA18-135



I don't understand why the speed would not be different on the 43. I expected it to be much faster. If anybody has an answer, I would like to here it.

I also took the same images in raw and then looked much closer in Lightroom. Naturally the FA43 gave the most detail of the brick but the DA18-135 was not far behind. My main lens for the past 2.5 years but hopefully no longer was the 17-70 and close up I saw much less detail with it. Are there any other conclusions that can be drawn from this comparison? Did I set it up right (I'm no pro).

09-24-2011, 11:42 AM   #2
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Do you have the EXIF on that last image? My suspicion is since your composition is a little different and the bright sunny area fills more of the frame with the 18-135, the K-5's metering determined you needed a much shorter exposure than the more similar compositions you achieved with the 17-70 and FA43, despite the fact that they are at the same aperture.

As to why the FA43 is so much brighter than the DA17-70 at equivalent f-stops and identical exposure lengths, well... I'm not entirely sure, but I have also noticed that my FA43 has a tendency to overexpose scenes much more readily than my other lenses. I think I remember reading somewhere that the calculations your camera does to determine how much light is really getting in at the various f-stops on the FA Limiteds is a little wonky in auto-aperture mode. My guess is your aperture blades open up to a little wider than expected for f/5.6.

[edit] I take back my earlier assertion about the 1/250th exposure length on the 18-135. You pretty much have the exact same composition as the other two images... for some reason it looked different to my eyes on first pass. Hm... I would guess your metering mode would matter here. Matrix/pattern should have given the same exposure length -- were you on spot or center-weighted per chance?

Last edited by v5planet; 09-24-2011 at 11:55 AM.
09-24-2011, 01:31 PM   #3
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Matrix metering but spot focus. I foolishly picked a spot right where the shade ends on the brick. Then again, I didn't lock exposure to the focus point so it still is very strange. The full details are in the forum gallery where I loaded the photos.
09-24-2011, 01:46 PM   #4
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First Conclusion

My initial conclusions is that the 18-135 is a darn fine lens. The 17-70 should have been for sale a long time ago. The FA43 is a funny lens that is sometimes great and sometimes not.

09-26-2011, 05:04 AM   #5
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I sold the 17-70 and am keeping the 18-135. I have noticed metering 'issues' with non-DA lenses too.
09-26-2011, 08:06 AM   #6
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It's a damn shame that Photozone dissed the 18-135mm. The lens he reviewed is nothing like my copy, which has very good resolution across the frame and great colour and contrast. Having said that, I don't know why it would optically outresolve the 17-70mm.
09-26-2011, 06:46 PM   #7
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Maybe I am crazy but those all kind of look the same to me? Except that the first is lighter? I am sure there are differences that can be seen bigger, though.
09-27-2011, 06:08 AM   #8
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QuoteOriginally posted by audiobomber Quote
It's a damn shame that Photozone dissed the 18-135mm. The lens he reviewed is nothing like my copy, which has very good resolution across the frame and great colour and contrast. Having said that, I don't know why it would optically outresolve the 17-70mm.
I'm not sure it out resolves the 17-70, difference in samples? But it does not have SDM and it is WR.

Nothing against PZ, Klaus has a high benchmark, but the only review that counts is yours.

09-27-2011, 06:19 AM   #9
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QuoteOriginally posted by Spotmatic Quote
I'm not sure it out resolves the 17-70, difference in samples? But it does not have SDM and it is WR.
Sorry, my post was unclear. The OP said that he sees much less detail from his 17-70mm compared to his 18-135. I said: "I don't know why it would optically outresolve the 17-70mm". I should have been more clear. An 18-135mm should not outresolve a 17-70mm. I believe the 17-70 has some sort of problem.

Last edited by audiobomber; 09-27-2011 at 07:05 AM.
09-27-2011, 07:09 AM   #10
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If those are straight out of camera results, I like the one from 1770 the best, at least at this small size ...
09-27-2011, 10:32 AM   #11
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QuoteQuote:
If those are straight out of camera results, I like the one from 1770 the best, at least at this small size ...
Me, too :-)
09-27-2011, 06:04 PM   #12
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A close up

Okay, I'll try to provide some more information about those shots including a very close up crop. First, here is the FA43. I did a .23 minus on the exposure in Lightroom. Normally I shoot raw exclusively but for this test I shot JPG and then imported to Lightroom and exported unchanged except for Lightroom's defaults and for this post, the crop and the slight change of exposure on the FA43


Here is the DA17-70 Again. Same photo as above, but cropped down to those same few bricks.


Finally here is the DA18-135. As with the DA17-70 it is the same photo as above in the original post but cropped down to what you see here.


Previously the area I looked at to see the detail suggested that the 18-135 had an edge over the 17-70. Now when I look at this spot I would say that the 17-70 has slightly more detail. Although, when I look at the yellow parts of the pine tree branch, I would say the 18-135 might be better. The FA43 just doesn't shine in this type of test but I'm sure that if I had a wide sample of photos the FA43 would stand out.

One last difference, I have a ND filter on the 18-135. I just leave it on there all the time so I had forgotten about it. As far as the rest of the EFIX details, they should all be in my gallery on this site.

Comments appreciated. I wasn't trying to slam any lens, but rather to see how well the 18-135 could do against the 17-70 (which is for sale) and I included the FA43 only because it is the only other lens I own.
09-27-2011, 06:46 PM   #13
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Not much difference in the last two. I guess I'd still take the 17-70.
09-27-2011, 07:00 PM   #14
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Thanks, Glen. What seems remarkable to me is that both zooms seem to perform pretty well compared to a very great standard. I have the 17-70, and it seems fine, but I don't have a lot to compare to. Well, that's not exactly true - it is not quite as good as my DA 40. Thanks. Glenn
09-28-2011, 01:41 AM   #15
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QuoteOriginally posted by SpecialK Quote
Not much difference in the last two. I guess I'd still take the 17-70.
Same here. And look at the photos again on a better monitor, I can see the color difference even more obivous between all the samples.
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