Friday, September 07, 2007

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

Here is a very recently published shootout test for the above two lenses:-

http://forum.pentaxfans.net/showthread.php?t=54131

(The report in Traditional Chinese, you can use Babelfish to translate)

Nonetheless, since Babelfish is not something one can fully understand :-D, I summarise the author's findings as follows (you may wish to read in conjunction with the full report with all those testing sample pictures posted):-

1. Purple fringing of the DA* is more obvious than the Sigma at the widest focal settings, for apertures from f/2.8 to f/8, i.e., at 16mm Vs 18mm respectively. The author compares the image corners.. ;

2. Exposures (i.e., for the image brightness) and colour/tone responses are more or less the same as tested at 50mm;

3. Resolution of the Sigma throughout the same aperture range (f/2.8 to f/8) wins the Pentax clearly, at the widest focals as compared. My comment is that this comparison may not be totally fair as the magnification of the Sigma at 18mm is slightly larger. As such if the same crops of the same image scene are compared, the larger magnification one will have the slight advantage. However, the difference seems to be so obvious that the Pentax should really have (much) less resolution. Also, the tester also tested at 34mm/35mm to verify his results on another day and yet again he found that the Sigma is still having better resolution;

4. Focusing accuracy test: The Pentax DA* back focused whilst the Sigma focused flawlessly on the same K10D!(?) The author remarks that this confirms the reported (back) focusing problem of the DA* lens, when SDM is used. He further writes that the focusing error could be the true culprit for the decreased and lower resolution as found. I think he is right for that suggested point as focusing accuracy is very important to keep the (high) effective resolution;

5. Distortion levels of both lenses are more or less the same and both are quite obvious. My comments are: I can see from the test images that the test chart/target are not shot "perfectly" on an optical bench for perfect alignment nor the target is perfectly flat. However, this is understoodable for what a non-professional measurebator could do with the limited resources he has. Still, the test shots can be treated as some kind of basic reference, IMHO;

6. The author is astonished at the high performance/cost to price ratio of the Sigma but however rather disappointed with the Pentax DA Star, which is expensive but yet found to be inferior and lose the shootout for almost all aspects under test;

Well, after reading this test and all the results, I feel rather disappointed (again). The DA* Star is again something let Pentaxians very down in general. It has focusing issue as verified, which has been reported over and over again since launched. The true cause can be either a design flaw, no matter hardware and/or software wise or a quality control issue. The DA* optically does not live up to the standard as supposed and expected. Actually, it has more obvious purple fringing, lower resolution, obvious distortion and so on - and the worse is that it cannot even win but just lose to the Sigma which is being sold at a price less than half of the DA Star.

My impression is that the DA Star is just something Pentax created to hurt seriously their long established reputation of their only true strong point, i.e., excellent optics, especially for the Star series, which should be their top-of-the-line, most luxury glass with the best possible optical quality and performance on the Earth, but still being sold at attractive and reasonable price levels - which all these favourable factors are true and valid for the old film FA* and F* or even A* lenses. But now that it looks rather sad and disappointed for those digital DA* "Star" are found to be performing just like some kinds of rebadged Tokinas which are actually being sold much cheaper. Still, the Pentax Digital "Star" are yet marketed with a "Star" price but lack the true quality and real performance which they should have (or at least as expected or supposed to be), as reported by many of the new users for what have been tested and verified repeatedly from many of the recent reports. (Not even to mention the unique optical characters which each of the old *true* Pentax Star lenses had - Sad. Really..)

Afterall, I believe that the consumers are brilliant, overall speaking. Reputations, no matter good or bad, are built over time and nothing can be hidden or cheated. So, if the DA* really don't perform, I'm afraid that Pentax is really endangering their brand name and just spoil their long-established good name of the Star and when the end of the Star legend comes, their old real fans must be upset (mostly).

16 Comments:

Anonymous said...

That BF is well within design parameters and if you sampled 30 copies of each lens would probably end up being the same... All that is required of AF is that the target is withing the depth of focus, at least for consumer based cameras. Canon pro are 1/3 Depth of focus (which is actually different than DOF, Read Doug Kerr's papers carefully)
If the focus line was "out of focus" (granted it is very close to that line) then that could be questioned. The DOF looks to be about 12mm w/ acceptable sharpness.
Again your ignorance is showing...
didn't we just talk about sample size (and numbers of iterations of each lens is important).
Dang your infuriating...

Anonymous said...

LOOK someone w/ Sigma and Pentax experience thinks the sigma is rubbish in comparison. Guess it's 1 against 1 now......
http://forums.dpreview.com/forums/read.asp?forum=1036&message=24734161
"Certainly head and shoulders above the equivalent Sigma lens which can only be described as rubbish by comparison, as a matter of fact after my latest skirmish with the 18-50 2.8 Sigma's both the Macro and non macro versions I have brought my last Sigma lens. I think I will sell my Sigma 105 macro and replace with a Tamron 90."

RiceHigh said...

> Anonymous said...
> That BF is well within design parameters and if you sampled 30 copies of each lens would probably end up being the same...

But the key problem for this case is that SIGMA under test is more accurate..

RiceHigh said...

> Anonymous said...
> LOOK someone w/ Sigma and Pentax experience thinks the sigma is rubbish in comparison. Guess it's 1 against 1 now......

1 Vs 1? Are you kidding when you compare a few lines of brief comments without any photo against one who writes a detailed shootout report of all those head-to-head comparison shots posted? Your joke is really funny..

Anonymous said...

No, one "pseudo-science" detailed report is just as good as any other report. In the scientific community one report is only an open challenge to others to verify. Nobody with half a brain takes one or even 2 reports as gospel. And actually science can NEVER prove a theory (as in lens performance), only disprove. unless of course your some devine being. Anyways this is your own little universe so I guess you can make the rules, no matter how flawed.
You presented someone with I theory and I showed "evidence" to the contrary. You have every right to attempt to refute my evidence as I do yours. And let others decide. Simple isn't it.
.................
Theory
From Wikipedia
The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion.
In common usage, people often use the word theory to signify a conjecture, an opinion, or a speculation. In this usage, a theory is not necessarily based on facts; in other words, it is not required to be consistent with true descriptions of reality. True descriptions of reality are more reflectively understood as statements which would be true independently of what people think about them. In this usage, the word is synonymous with hypothesis.
In science, a theory is a mathematical or logical explanation, or a testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise falsified through empirical observation. It follows from this that for scientists "theory" and "fact" do not necessarily stand in opposition.
........................
and from the scientific method:
These steps must be repeatable in order to predict dependably any future results.
.................
And usually repeated by many COMPETENT authorities.
As it stands everything you post is a hypothesis at best, open to refutation by other RELIABLE sources, or more likely, just plain trash, depending on the methodoloy and expertise of the person performing the "experiment"..
None of anything I can remember you reporting is in a controlled enviroment with enough repeated samples to EVER be called scientific OR authoritative. Just conjecture and, should I say it again, hearsay. No juried articles ect. Just web pablum.....
And still, like my post on BF REFUSE to even acknowledge the facts I presented, INCLUDING Klaus'es observations that a completely centered lens is a rarety at the LEAST.....or any of the other facts I presented including the fact that a light meter on a grey card should show a histogram peak at 110 AND if you accept that fact and rework all your "pseudoscience" charts and tables will see that you only have a few anomolies in all your "tests", or that all your "tests" have way too small of a sample size. Testing 10 of one lens beats testing a dozen SINGLE samples any day. I'm done with you, your a hopeless zealot with no hope for redemption nor humility. I PRAY to some divine being that you are not involved in the "engineering" (IF in fact you actually are an engineer, AND you never ever stated your field of expertise and years of experience or training. For all I know your really a janitor at a McDonalds) of anything that, if it failed, could be life threatening because, even if presented with contrary facts, you would be too proud and pig headed to admit an error and blindly continue on the path that you chose.

Anonymous said...

Ricehigh babbles...
But the key problem for this case is that SIGMA under test is more accurate..
ONE freaking lens vs ONE other freaking lens. Give me 20 samples of each and repeat the test 20 times (on each lens) THEN open your piehole and make a statement. THAT's the way real people do "research"

Anonymous said...

STILL waiting for those side by side exposure shots between the Canon and Pentax... coward ... or is it more excuses again..

Laurens said...

Leaving aside sample variations etc. It is already well known that autofocus performance (of all camera brands) is not sufficiently good when performing resolution tests. The DOF is based on an allowable CoC for "normal" viewing distances. Max. resolution requires a far stricter max. CoC.

RiceHigh said...

For this case, it was tested that the Sigma focused more accurately than the DA* on the same K10D body. So, it is not really surprising that when the Sigma finally produced higher resolution than the Pentax.

One of the possible reasons for the back focusing found is possibly owing to the new SDM that was in use for achieving the AF. For more details, see:-
http://ricehigh.blogspot.com/2007/09/sdm-more-af-errors.html

Anonymous said...

A user on PentaxForums tested the 16-50 against the Tamron 28-75 and it kicked its ass in sharpness.
The Tamron exceeds the Sigma 18-50 in sharpness. Whoops.

Oh forgot, you only report things that fit your anti-Pentax crusade. Really should change your blog name to "Ricehigh's Anti-Pentax Blog" since there is absolutely no balance to it.

RiceHigh said...

You can always say that I'm a anti-Pentax-ian (but I say I am not), but the reviewer who carried out the test and wrote this detailed report is a Pentax fan. Why does he need to say something bad about Pentax and her latest "high-class" product?

Anonymous said...

You cannot seriously say with a straight face that you aren't anti-Pentax. How many of your blog posts are showing the advantages of the Pentax range, to balance out all the negatives you take so much pleasure in screaming about?

Or test against other brands, to see if its Pentax being inferior, or its issues that occur across all DSLRs? All tests need a control or an average to compare against.

Anonymous said...

Sell up All Your P Gears (Probably Worth Sh*t 2 u right now Or Dump em at my doorstep and i wont charge u!) Then Go shoot With da BIG BRAND!!!! Hopefully Dat Will put u out of your misery!!! Get a F...king life,man!!!

RiceHigh said...

The test compares SIGMA to PENTAX. Did you refer to the SIGMA as the "BIG BRAND" when you mentioned it??

Anonymous said...

> Did you refer to the SIGMA as the > "BIG BRAND" when you mentioned it??

Some Canon L lenses are also crushed when compared with Sigmas. Are you ready to call Canon being inferior than Sigma, too?

RiceHigh said...

Yes, if this is really the case, that L lens is crap, not only "inferior".

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