Saturday, September 15, 2007

First Formal Test of the DA* 16-50/2.8

A Polish gear testing site has carried out the first DA* lens formal test and the test report is published as follows:-

http://www.optyczne.pl/92.1-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Wst%C4%99p.html

(A free online Polish to English translator can be found here)

Yet, below is a better human-translated summary on the test:-

http://forums.dpreview.com/forums/read.asp?forum=1036&message=24830862

Well, let's go on to see about the key findings of the test:-

1. Resolution:

See the following report page for the 50% MTF test results, measured in the lp/mm:-

http://www.optyczne.pl/92.4-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Rozdzielczo%B6%E6_obrazu.html

As a short note for what the test is measuring and what information the results can tell, it is to measure the maximum resolvable line-pairs per millimetre (lp/mm) for the black and white lines in the resolution chart for the difference between the black and white levels not less than 50% (ideally, black is at 0% and white is at 100%, so the maximum difference can be 100%).

From the first chart, we can see that MTF / resolution figures are good at the image centre. It can be seen that the optimal focal length is at 30mm, which is the middle of the zoom range. The maximum obtainable resolution figure is about 44 lp/mm. At both extreme ends of the zoom range, i.e., at 16mm and 50mm, resolution drops at about the same amount. As for the optimal f-stop, it is at f/5.6 where the best resolution can be obtained for all focal lengths. At f/2.8 wide opened, the resolution deteriorates and can be as low as at about 27 lp/mm at 50mm.

So, one would ask me how to judge those figures. Is 44 lp/mm or 27 lp/mm good or bad? First, you can compare Photodo charts and figures to have an idea. Do note that Photodo tested the Pentax lenses in a different way for the MTF. They used fixed test target with patterns of different lp/mm and then measure the MTF percentage. So, the higher the percentage, the better is the result. On the other hand, remember the latest popular measurement unit of LW/PH (Line Widths per Picture Height). Normally, a 2,000+ LW/PH figure is considered as high resolution for a 10MP DSLR, e.g. for those Imatest figures or those eye judged resolution charts by DPR. To convert the unit, 44 lp/mm simply means 1,408 LW/PH for an APS-C sensor at about 16mm height. 27 lp/mm is equal to 864 LW/PH. Although those figures are not directly comparable. I would say the highest obtainable resolution of 44 lp/mm is fair to good enough but the 27 lp/mm should be bad.

Well, now that we go to the second chart, which summarises the results for the edge performance. As you can see, the performance drops further. The poorest performance occurs at 16mm and followed by 50mm and then 30mm is still the optimal focal. But now that the highest lp/mm figure at edge is just 39 lp/mm (at 30mm at f/5.6) and the worst now drops to 16 lp/mm (!?), at 16mm at f/2.8, which undoubtedly is a very poor result.

Finally, it can be noted from the captures of the resolution charts for the existence of colour moires of which this phenomenon was also found by other reviewers before, for the K10D.

2. Chromatic Aberration:

http://www.optyczne.pl/92.5-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Aberracja_chromatyczna.html

They conclude that the CA is terrible, especially at the widest focal and/or wider opened, it performs worse. You can also see the obvious CAs from the sample pictures posted, in addition to the CA chart.

3. Distortion:

http://www.optyczne.pl/92.6-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Dystorsja.html

The distortion figures obtained are indeed rather terrible at 16mm, at an unbelievable huge amount of -4.1% (barrel) whereas at 30mm there is virtually no distortion (0.1%, pincushion) and at 50mm it is good (0.71%, pincushion). But then at the wide(st) angle, such a huge amount of distortion is ridiculous and IMHO practically it is just unusable! The Pentax DA 16-45 has a distortion of -2.52% at 16mm but yet I already notice its distortion when shooting landscape, I really cannot imagine what will happen for a -4.1% barrel distortion - which is worst than most lenses, including most cheapo kit lenses at 18mm.

4. Blur pattern:

http://www.optyczne.pl/92.7-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Koma_i_astygmatyzm.html

Interestingly, they measured how the image blur at this part of their test. As you can see from the red beam point. At centre (pictures at the left column), the red point reproduction is near perfect and at edges (pictures at the right column), the image formation is sketched in a certain directional way and thus causes blur.

5. Vignetting:

http://www.optyczne.pl/92.8-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Winietowanie.html

Obvious vignettings are found at 16mm as tested, even at one-stop stepped down at f/4. At f/2.8 and 16mm, an average mean of -1.8EV light loss is recorded at the image corners, which is considered to be significant for an APS-C DSLR. Well, I can see slight de-centering defect, too. The de-centering can be a camera body body for a not perfectly centred CCD sensor, though.

6. Flare Control:

http://www.optyczne.pl/92.9-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Odblaski.html

As we all can see from the sample photos, the flare control is poor, at least the testers were disappointed with the results, especially when compared with the other Pentax lenses they have tested before.

7. Autofocus speed and accuracy:

http://www.optyczne.pl/92.10-Test_obiektywu-Pentax_DA*_16-50_mm_F2.8_AL_ED_IF_SDM_Autofokus.html

They found that the speed and accuracy are both good enough. This differs from a few of previous less formal tests I have quoted in my blog before.

So, the conclusion? I think I need not to go further to quote their conclusion. I think you have made up your own conclusion already at this point. This DA* lens simply doesn't perform, with worst performance at wide angle and wider opened. So, what's the point of getting this lens? Aren't two of the major selling points of this lens is that it is a fixed f/2.8 faster zoom with a 16mm wider angle? Even for the flare control, where Pentax usually excels, the lens yet doesn't perform here. A real disappointment here and I feel really very sad again here. Actually, this is rather sad for Pentax to produce a "Pentax" lens like this, not even to mention again it is a "Star" lens as labelled. It seems that Pentax has just put her long established Star reputation at risk, which is indeed the most disappointing thing ever seen in Pentax's history.

See Also:-

Shootout Again! DA* 16-50 Vs SIGMA 18-50/2.8

SDM = More AF Errors?

DA* 16-50 Vs DA 16-45, A Shootout

25 Comments:

CuriousOnlooker said...

I'm intrigued about these results. Yes, the CA performance is disappointing. However, if you look at the tests on the Canon 17-55/2.8 on the very same website, the Pentax DA16-50 achieves better resolution results than the Canon 17-55/2.8. The Canon also has more distortion than the Pentax. The Canon has -5.7% distortion at 17mm and 1.06% distortion at 30mm. The Pentax does much better at -4.1% distortion at 16mm and 0.1% at 30mm. Yes, the CA is an issue, but that can be corrected through software. All in all, the Pentax did very well and is certainly in line with its competitors.

Anonymous said...

The Canon 17-55 isn't as wide, isn't weather sealed, reviews worse and costs the same. So as the first poster said, Pentax are in line with the rest of the companies, indeed are exceeding them. Lets see a Canon version of the 16-50, it'd cost twice as much for no reason.

So what if Pentax called theirs a DA* lens? What do they have thats "above" it? It certainly can't be called a DA lens, they aren't weather sealed.

So effectively its priced at the market level, in fact its better value than the competition, as Pentax usually are, it reviews at or better than the competition, and its designated in the only lens range it can possibly go in to fit in the Pentax lineup.

If you want to call it too expensive, then all the other brands are hugely overpriced.

RiceHigh said...

I think we have been mistaken and mixed up the Canon 17-85/4-5.6 IS with the Canon 17-55/2.8 IS. I have checked the Polish site and read the Canon 17-55/2.8 test page here, for the distortion test.

So, the figure is actually -2.47% (barrel) at 17mm whereas the tester compares the 17-85 which has a -5.7% distortion at 17mm. Do note that the 17-85 is just a slow 5X longer range zoom which priced at about half of that of the 17-55/2.8 (and the DA* standard zoom as well). Thus, it will not be a big surprise at all for the comparatively inferior performance.

Yet, Canon has not labelled the 17-55/2.8 as a L class lens afterall, although its performance is already not bad overall speaking (CA would still be a problem, though). According to the test carried out by the Imaging Resource / SLRGear.com, the 17-55/2.8 actually performs quite well.

Anonymous said...

Thats funny, Ricehigh removed his comment that made him look like an idiot when the next poster tore him a new one.

Guess his commenting system is as fair and balanced as his "tests".

Way to shoot your already non-existent credibility in the foot there.

RiceHigh said...

I have removed my last comment because curiousonlooker and I have both made a mistake and mixed up the test results of the Canon 17-85 and 17-55. So, a correction is required. I'm just curious how come I cannot even update my comment to remove an error and make thing correct?

CuriousOnlooker said...

Yes, a correction was in order. We both made a mistake. I guess our Polish wasn't very good. :)

Anonymous said...

apparently 1 degree can make a huge difference as you can see from Klaus's comments at photozone:
Quote:
At 16mm the lens shows fairly heavy barrel distortions (~3.55%) - this is slightly higher than average but then we're also talking about 16mm here rather than 17mm or 18mm. Beyond the extreme wide-end the distortions are actually very well controlled with slight barrel distortions at 24mm and slight pincushion distortions at 35mm and 50mm."....unquote.
This lens is unarguably the "twin" to the Pentax. Apparently 1degree makes a difference...
Please compare apples to apples.
APPARENTLY Pentax should have stuck w/ 17mm and you probably wouldn't be babbling soooo much..... ;)

RiceHigh said...

If you want to compare at 16mm, just compare to the DA 16-45 at 16, as I've already mentioned in my this article. All in all, the distortion of the DA* is again considerably more, i.e., -4.1% Vs -2.52%.

So, afterall, what exact "apple" do you want to compare to? The Tokina 16-50/2.8?? Well, this time they are more or less the same in performance, as it's supposed to be. But don't you forget the Tokina is yet again being sold much cheaper than the "Pentax"?

Anonymous said...

Any 16mm-close to 50 f2.8.... The other one is an f4, which has a completely different set of design parameters than the f2.8.Compromises must always be made.
Don't buy the lens.
Did you ignore Klaus'es comments again?...tsk, tsk..
Klaus's comments at photozone:
Quote:
At 16mm the lens shows fairly heavy barrel distortions (~3.55%) - this is slightly higher than average (CAN YOU READ THIS) but then we're also talking about 16mm here rather than 17mm or 18mm. Beyond the extreme wide-end the distortions are actually very well controlled with slight barrel distortions at 24mm and slight pincushion distortions at 35mm and 50mm."....unquote.
You are the MASTER at selective knowledge I must say.
BRAVO.........

RiceHigh said...

The last time you've emphasized that it's the 16mm which introduces more distortion whilst 17mm will not (just because the Canon 17-55/2.8 has far less distortion here, at 17mm). Now, you say that it's also about the f/2.8 (just because the DA 16-45 yet has far less distortion here, at 16mm).

So, what's next then? Any more excuses? Would it be just because of that the DA* has a golden metal plate but the DA has a silver one?? Oh yes, there is a clear difference here and as such we can't compare them directly. Yes, we can all know about it now! Thank You for Your Great Wisdom! LOL..

Nonetheless, the *fact* is indeed very simple: With the DA* 16-50, the user will get more obvious barrel distortion at 16mm than the amount which a DA 16-45 user will get at the *same* focal, regardless of what aperture the two users are to select, i.e. for exactly the same f-stop and focal, from f/4 to f/22, say, and at 16mm. Still arguable??

Anonymous said...

Can distortion be corrected in post processing, if its noticable, which it pretty much isn't in real photography?

Can a slower lenses be corrected to be faster? Can it be corrected to be sharper?

RiceHigh said...

One can of course to waste time by sitting in front of the computer for hours to rectify for errors introduced by the camera or lenses, via software, but actually to certain extents only but not completely. If your "point" is valid, distortion, vignetting, CA are all NOT a problem then, as all those can be "cured" by the software at the "PP" stage.

Yet, it seems that you have still failed to read and learn from the Polish test report that the DA* 16-50 has been found to be NOT SHARP at near f/2.8 wide opened and/or at near 16mm.

Moreover, if one really want highest possible lens speed and the best image quality out of a lens, fast primes should still be the way to go, frankly. The point of a zoom is mainly for convenience. But still, the fact is that some zooms are made better than the others on Earth and normally more expensive ones *should* be better. Enough said.

Anonymous said...

The point is valid, post-processing is PART AND PARCEL of photography. If any of a camera or lenses limitation is a problem in a shot, then they are fixed. And if you actually knew how to take photos or process them, you'd know in a damn high percentage of photos you don't have to do any major fixing, because the problems aren't VISIBLE to anyone but anal retentive pixel-peepers!

And thats a damn amusing statement you saying "waste time in front of a computer" when your entire life consists of wasting time whining about a camera brand! Who the hell is wasting time, you or the guy post-processing a photo that makes him money or a piece of art?

So what if its not sharp at f2.8 at 16mm? A lens that isn't sharp wide open isn't rare, especially zooms. Funnily enough, there are 30 odd more mm to use, and a crapload more fstops. Thats sorta the point of a zoom lens.

Brilliant statement, a ultrawide zoom isn't as good as a prime. If you wanted to shoot wide open, at ultrawide focal length, yes, you should get a prime. So why the HELL do you expect the DA* 16-50 to be prime-level optically? Last I checked, its not a prime!

And what lenses are you comparing the price of the DA* 16-50 to? I don't know any other fully weather sealed 16-50's f2.8s for ~$1000 USD. You are comparing apples to apples aren't you, or are you comparing it to some non-sealed Canon lens that still costs $1000?

Oh wait, you ignore the other features of the lens that cause it to cost more than the mid-level varieties. Enough said.

Anonymous said...

"Still arguable??"
Actually yes, to a point. The lens had to be designed to be a f2.8. Now I assume you can't just make the aperature larger on the f4 to make a 2.8. You have to redesign the lens. Therefore your optical characteristics will all change. One optical formula is different than another. The distortion at 16mm seems not too surprising to Klaus.Could Pentax done better? Probably, but at a cost and a long time ago I said that Pentax lenses would try to stay in the $1000 price point. No more 2-3000+ lenses.
So the 16-50 f2.8 is probably the best they can do AND keep the price. It is not the best they can do price be damned. Cosina, I believe, used to start backwards, develop the best regardless of price and keep shaving the parameters and materials down till they reach a price goal....
All sort of compromises occur. Now since the Tokina is still selling and Tokina doesn't mind the "quality" then that says SOMEONE has some faith in it. Not Past Pentax star quality? Neither were all the pancake primes in comparison. If Pentax produces lenses of that caliber and sells them for a profit, they will price themselves out of the market and HOYA will be happy to sell the camera business.
As to cheaper a brand name lens will always sell for more than a non-branded lens, reardless of the fact they are equal. You only get into real problems when you are lesser. Regardless the Tokina is not available to Pentax anyways.
As to extreme dissimilarities in price, wait 6 months and it won't be such a big price difference. My guarantee........
Your expectations are way to high or you just choose to always see the bad. Take your pick..

Anonymous said...

"But still, the fact is that some zooms are made better than the others on Earth and normally more expensive ones *should* be better. Enough said."

You say that a lot but it is never enough is it......... ;)

Can you give me an example of a cheaper 16-50f2.8 in Pentax mount??? THERE ARE NONE.....

Anonymous said...

what's next then? Any more excuses? Would it be just because of that the DA* has a golden metal plate but the DA has a silver one?? Oh yes, there is a clear difference here and as such we can't compare them directly. Yes, we can all know about it now! Thank You for Your Great Wisdom! LOL..

Have I told you you were an idiot lately....
LOL :)

Anonymous said...

Hey Mr Rice I love this line from Mr. Kerr
"Remember, we are never in the case of Canon cameras working with an actual ISO speed value."
What do you think???
Nevermind.
http://forums.dpreview.com/forums/read.asp?forum=1019&message=24459281
http://www.openphotographyforums.com/forums/showthread.php?t=3652

arz said...

Sadly you are right this time. This 16-50 DA* is not a *, it's even not better than a Sigma, sad, sad, sad ... it should have been on par with the Canon 17-55 f2.8, but Pentax (or Tokina ?) engineers are sleeping.

RiceHigh said...

As we can see from the two Polish formal tests for the Canon 17-55/2.8 here and the Pentax DA* 16-55/2.8 here, the Canon has much more consistent performance resolution wise throughout the whole zoom range and has better resolving power too, overall speaking, no matter in the image centre or edge, and especially in the range from f/2.8 to f/8, in which the difference is obvious.

In fact, the Polish test results agree much with the measurbation test results as published by the SLRGear.com / Imaging-Resource for the Canon lens. So, it's again when measurbation shows its true value - It's at least scientific, more objective and formal afterall.

Anonymous said...

"Sadly you are right this time. This 16-50 DA* is not a *, it's even not better than a Sigma, sad, sad, sad ... it should have been on par with the Canon 17-55 f2.8, but Pentax (or Tokina ?) engineers are sleeping."
Please try to keep in mind that the lens is not a 17mm. It is 16 and offers a 3 degree increase in horz fov. I'd prefer to see full stats at 17........then say something.
http://www.frankvanderpol.nl/fov_pan_calc.htm
As to star quality.... star has just become a buzzword for expensive and/or fast optics. Doesn't take a rocket scientist to figure that out.
I'm sure the lens wasn't designed on a napkin during a lunchbreak andthen someone says "hey what the heck, lets make it and see if anyone buys it."

Anonymous said...

Ricehigh - "So, it's again when measurbation shows its true value - It's at least scientific, more objective and formal afterall."

The Canon lens is 27-88mm, the Pentax is 24-75. Not very scientific to compare those is it.

The Canon is also equally expensive, and has a well known problem of sucking in dust like a vacuum cleaner, vs a fully weather sealed lens with the Pentax. Whats the price of the Canon weather sealed L 16-50?

You are only "scientific" when it suits you to complain about Pentax.

Anonymous said...

So oh great and powerful Rice. Any reason not to post a bit of nice fluff regarding the 50-135 f2.8???
http://dc.watch.impress.co.jp/cda/lens_review/2007/09/19/7001.html
Oh yes I forgot you only selectively post the BAD stuff re: Pentax. My apologies.......

Anonymous said...

ricehigh i get the point of your blog, but i really think you should stop comparing a pentax k10d/k100d to a canon 5d they are in different leagues for the price you paid for the 5D i hope it performs the way it should, but you need to realize a couple things. 1)Pentax just started to get back in the game, the first dslr was made not long ago. 2)they are catching up and they will get there. 3)Pentax creates affordable equipment for all users . 4)you pointed out minor problems people have or should i say big problems others with the k10D, but again it has won a crap load of awards it must be doing something right.

you get what you pay for but with a camera like a K10D its a big bang for the buck, And also with all the test you are doing and sharing with the world you are bound to get feedback, and reading your site did not change my choice to buy the k10 D. keep up your freedom of speech i hope you get a nikon so you can do the test for all three and not just the 2, may suggest a D300?

Anonymous said...

Since this whole blog is a gossip column of sorts I thought I add a bit to it.........
A little bird told me....
"Picked up my second DA* 16-50 yesterday. What a world of difference from my first sample. The images were extremely sharp and the color was excellent. It’s hard for me to believe that Pentax allowed the first batch to be shipped to the dealer.
The excuse given by the Pentax Rep to the dealer was that the first batch of lens was calibrated by hand and the second batch was calibrated by laser.
The second sample is everything I had expected from Pentax"

arz said...

About the comparison Canon 17-55 vs Pentax 16-50, yes fov is different, BUT if Pentax wanted to do a * lens, engineers should have said to their marketing : no it's impossible, we can't do a 16-50 without horrible distorsions and CAs at 16mm, so it would be better to make a nice 17-50 or a 18-50 (I would prefer a really good metal made DA* 15-30mm or 16-30mm, this would have been the Pentax spirit, concentrate on glass, glass, glass). Let's hope that the new batches of DA 16-50 f2.8 will show improvements.

Post a Comment

Related Posts

 
Creative Commons License
RiceHigh's Pentax Blog by RiceHigh is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.