[pentax_amateur]

I have done a quick and non-scientific test of these two lenses with surprising results. I was mostly interested in their performance wide-open. DA18-55 is a cheap kit lens, but it did better than the much more expensive DA16-85!

Camera: Pentax KP on a tripod, lenses with hoods, shots taken at the same (or close) f-stops.
File: DNG
Post-processing: minor exposure correction to match the two images. No sharpening, contrast, CA correction, or de-noising.
Image presentation: I up-sampled the images from 24Mp to 96Mp. All image pairs represent the center of the frame, except for one.

Results:
18mm/f3.5: tie.
18mm/f8: DA16-85 looks smoother, but has a lot more CA!
55mm/f4.5-5.6: tie in sharpness, but DA18-55 has significantly less CA.
55mm/f4.5-5.6 EDGE:This is the edge of the frame. DA18-55 looks significantly sharper!

Overall, I would say DA18-55 wins, despite being 8.6 times cheaper!
What is going on here?

Attached Images

       

[Adam]

What is going on here?

In the F8 shot, I'm seeing quite a bit of moire from the 16-85mm shot, which indicates that it is sharper. The AA filter simulator feature would help reduce that.

[Bertrand3000]

Why did you up-sample the images to 96 megapixels? I fail to see how doing this can be helpful, even for comparison purpose. Comparing straight 24 Megapixels with 1:1 crop would probably make some sense.

Back to the images you have shown us.

For 18mm F3.5, I do not see a tie, I much prefer the 16-85 image, more detailed, without CA, unlike the 18-55.

For 18mm F8, it's true that the 16-85 is the one with CA. On the other hand, why the 18-55 image has been taken with a shutter speed four times quicker? Were you in a kind of changing weather with sun going on and off? Harsh lighting at the time of shot could explain the 16-85 CA.


For the 55mm shots, it's another thing, the 18-55 indeed looks better.

That said, that is not proof by itself of sharpness (or lack thereof). It could be a focus issue. You also have to take into account field curvature, which means plane of focus curvature. Edge may be, or not be, in focus. You shot wide open with long focal length, so the depth of field is thin.

If i were you, I would try to shoot at 55mm at a smaller aperture (the same for both), auto-focusing on something far in live view to rule out any focusing error, and compare 24M images. You might get more reassuring results.

[Buntzbooze]

The last comparison at 55mm looks pretty conclusive in favour of the cheaper lens, assuming correct focus was achieved. I dare not look at the edges of my 16-85 photos, especially at wider angles, my copy is quite badly decentered.

[normhead]

Sample variation and comparisons featuring just one lens can be misleading.
The first issue you have an unfocussed issue. Your test shots need good hyper-focal positioning, which is hard to determine with AF.

You can tell you missed the hyperfocal point with your two where the 18-55 is better, because the the railing is bigger and softer than it should be. A characteristic of out of focus elements in a photograph.
At ƒ8 the the 16-85 comes out on top easily. The greater depth of field means the placement of the sharpest part of the focal plain is not as critical. It would be interesting to see what the results would be if you adjusted the AF on the lens so the two lenses were both focused on the same part of the image, when pointed at the same spot. n a busy image though, just knowing what exactly the AF picked out to focus on can be a challenge.

If you try this again try using Live View and the focus assist to make sure the position of the sharpest part of the focal plane is in the same position for the two cameras. If relying on AF you need to take at least 5 images at each set up , refocusing each time, and choose the best of each, but also note what percentage of the images are acceptable.

Looking at Optical limits for reference
Pentax SMC DA 18-55mm f/3.5-5.6 AL WR - Lab Test / Review - Analysis
Pentax HD DA 16-85mm f/3.5-5.6 ED DC WR - Review / Test Report - Analysis

It really shouldn't be much of a contest especially on the edges.

[caliscouser]

I've tested both head to head. (Disclaimer there is always the factor of sample variation) Here are my general notes:

- 18-55 is sharp in the middle at the expense of the edges
- The 16-85 has more even sharpness across the frame
So if you just test the center it's going to make the 18-55 look good.

The 18-55 needs really stopping down to get decent edge performance. For some reason it does well at f11 when other lenses start falling apart because of diffraction.

At the mid to long end the 16-85 starts degrading. At 50mm the DA*16-50 blows the 16-85 out of the water (at least with my copies)

The 18-55 and 16-85 rendering is very similar. Definitely different to the DA* and the Limited which each have their own character.

The 16-85 does exhibit a bit of lateral CA, not as much as the 16-50, but more than 18-55 (in the middle)

[pentax_amateur]

Why did you up-sample the images to 96 megapixels? I fail to see how doing this can be helpful, even for comparison purpose. Comparing straight 24 Megapixels with 1:1 crop would probably make some sense.

I find it a lot easier to compare upsampled images. With 1:1 scale I find it really hard to discern any differences even if they are there.

On the other hand, why the 18-55 image has been taken with a shutter speed four times quicker? Were you in a kind of changing weather with sun going on and off? Harsh lighting at the time of shot could explain the 16-85 CA.

True, I missed that. Lighting conditions were actually not changing at all. I ended up correcting the exposure for the two shots +1 and -1.

You shot wide open with long focal length, so the depth of field is thin.

The object distance is 280m (measured in Google maps), giving hyperfocal distance of about 40m.

[normhead]

I've tested both head to head. (Disclaimer there is always the factor of sample variation) Here are my general notes:

- 18-55 is sharp in the middle at the expense of the edges
- The 16-85 has more even sharpness across the frame
So if you just test the center it's going to make the 18-55 look good.

The 18-55 needs really stopping down to get decent edge performance. For some reason it does well at f11 when other lenses start falling apart because of diffraction.

At the mid to long end the 16-85 starts degrading. At 50mm the DA*16-50 blows the 16-85 out of the water (at least with my copies)

The 18-55 and 16-85 rendering is very similar. Definitely different to the DA* and the Limited which each have their own character.

The 16-85 does exhibit a bit of lateral CA, not as much as the 16-50, but more than 18-55 (in the middle)

The old DA*16-50 featured a very sharp centre with less detail at the edges. (Images for the way people take pictures, not for the test charts.)
CA can be affected if lenses are just slightly out of alignment, nothing you can do about it. But everything sounds in the range of possibility. Thanks for posting. You can never have too much information, or more to the point, you need a lot of information. There's more depth to the analysis with every new data set.

---------- Post added 02-27-21 at 11:38 AM ----------

The 18-55 needs really stopping down to get decent edge performance. For some reason it does well at f11 when other lenses start falling apart because of diffraction.

I would really like it if one of our optical geniuses explained how this is possible. Falconeye? Digitalis? Bdery? anyone?

[pentax_amateur]

Your test shots need good hyper-focal positioning, which is hard to determine with AF. You can tell you missed the hyperfocal point ...

With object distance of 280m, focal distance 55mm, and f3.6 I get hyperfocal distance of 42m. That's hard to miss

---------- Post added 02-27-21 at 09:48 AM ----------

My surprise here is that 8.6 times more $ does not produce an obviously superior image.

[caliscouser]

My surprise here is that 8.6 times more $ does not produce an obviously superior image.

Test the edges at 18mm on both lenses and the differences will become clear.

If your priority is center image sharpness then you won't see much difference.
If you're shooting wide-angle landscapes at infinity then the differences are clear.
So depends on what you are looking for in a lens.

To produce a 16mm with good sharpness across the frame, limited distortion, limited CA is optically much more difficult and costly than doing it at 18mm
That's what you are paying for, plus the extra reach, the WR, the DC motor, etc

[Des]

18-55 is sharp in the middle at the expense of the edges- The 16-85 has more even sharpness across the frameSo if you just test the center it's going to make the 18-55 look good.

That is consistent with the PF comparison between the DA 16-85 and DA 18-135: at 85mm, the 18-135 was sharper in the centre, but the 16-85 was much more even across the frame. HD Pentax-DA 16-85mm F3.5-5.6 Review - General Image Quality | PentaxForums.com Reviews @Heie got a similar result at 85mm, although the 16-85 was better in the centre at its widest and at 50mm: HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database

Just one point about the OP's comparisons at 55mm: the 16-85 was tested at f4.5 and the 18-55 at f5.6. Even with a 0.3EV aperture disadvantage, the 16-85 looks better in the centre to me. As Adam says, the purple in the wires might be moire rather than CA. The edge difference is explicable by a focusing issue as Norm pointed out.

There is a valid point to be made that a cheap kit lens can even be in the same ballpark as a mid- to high-level lens. But I am not convinced that the 16-85 is a waste of money!

[normhead]

With object distance of 280m, focal distance 55mm, and f3.6 I get hyperfocal distance of 42m. That's hard to mis

There's evidence to the contrary right in your images.
Don't be so quick to blame the lens.
But there's another possibility, hand held your movement was more than shake reduction could compensate for. SR is good, especially for people trained in stabilizing non SR film cameras.

What is going on here?

Possibly a faulty test.
Possibly too much dependence on SR.
Possibly not enough samples.
Possibly a decentered lens.
When your results are different from everyone else's, usually it's not everyone else.

IN this poll taken at 35mm, the DA 18-55 receive 6 votes out of 84 votes.
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/302815-35mm-find-prime-2.html
Sorry the images are no longer available... but you get the idea. it's unlikely the 18-55 is the better lens overall, although no one but you knows the exact circumstances that lead to these results. Maybe with your copies yours is better. Good copy of one, poor copy of the 16-85. Anything is possible. I wouldn't even try a test like this without a tripod and calibrating both lenses first personally.

We don't know what's going on. We didn't do the test. We can only guess.
Another question for you though.... why is the noise so bad in the second image for the 18-55? Also, I you think you can't miss focus at 280meters based on a 42 meter DoF you'd be wrong. That would only be a 7.5% error, when you consider that half the DOF is in front and half is behind the image. You'd only need a 22 meter error at 280 meters to miss acceptable focus.

[StiffLegged]

I find it a lot easier to compare upsampled images. With 1:1 scale I find it really hard to discern any differences even if they are there.

Then forgive me for saying there probably isn't any real difference, viewed at 100%. I would also want to know if you have checked AF calibration on both lenses for the camera you shot these tests with. The differences between accurate focussing and hoping it's accurate are unmistakeable – I have an 18-55 that recently needed considerable AF adjustment to focus accurately while other lenses needed none.

[tibbitts]

Then forgive me for saying there probably isn't any real difference, viewed at 100%. I would also want to know if you have checked AF calibration on both lenses for the camera you shot these tests with. The differences between accurate focussing and hoping it's accurate are unmistakeable – I have an 18-55 that recently needed considerable AF adjustment to focus accurately while other lenses needed none.

I would guess the OP was either using live view AF or MF.

[pentax_amateur]

I would guess the OP was either using live view AF or MF.

I used AF-S via the viewfinder, but I do like the idea of calibration. I will try to calibrate my lenses and repeat the test.