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Wednesday, August 21, 2013

(Different) Optical Constructions of the Four DA18-55 Zoom Lenses

Source: http://forum.xitek.com/thread-866434-1-1-1.html (in Simplified Chinese)

1. Original DA18-55 - 12 Elements in 9 Groups, One Aspherical Element:





2. DA18-55II - 11 Elements in 8 Groups, One ED (Extra Low Dispersion) Element:





3. DA18-55WR - 11 Elements in 8 Groups, One Aspherical Element and One ED Element:





4. DAL18-55 - 11 Elements in 8 Groups, No Aspherical nor ED Element of Any:





After all, it seems that the optical formula and construction of the DA18-55WR should be the best. On the other hand, the optical design of the DAL18-55 is a cutting corner one, which should perform worst. Not even to mention about the cutting corner build of the DAL, which adopts a plastic mount and the quick shift focus mechanism is removed altogether.


Read Also:-

Standard Zoom Mega Shootout! (DA Vs FAJ Vs DAL Vs SA Vs FA!)

K-5D Mark III: DA 18-55 II Converted to a 24-80 FULL FRAME Lens!

Comments (16)

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For the pentax 18-55s, even if these differences in optical formula do exist.....I think the main thing is whether you have a sample that is correctly assembled, that is even more important than the slight diffences in optical formula. I happen to have a horrible 18-55 II, while my original old 18-55 is quite good. Another 18-55 Dal is somewhere in the middle.
When I compare them to my Pentax/tamron 18-250, that lens is much sharper in the 18-55 region that all kit-lenses. Bit more distortion, bit more vignetting, but sharpness is quite okay.
Anyway, the pentax sensors are that good nowadays , allowing higher iso, so you can select a somewhat smaller aperture, and then the kitlenses are reasonable.
Is it certain that the new 18-55 and the WR do not share the same formula? The drawings are identical.
2 replies · active 603 weeks ago
The diagrams are not identical, note the cross sections of the outer shells. In addition, only coloured elements are special ones, so the DAL has neither of them.
Arnold Stark's avatar

Arnold Stark · 603 weeks ago

The OPTICS diagrams of the DA II, DA-L and DA WR are identical except for the colouring of elements 2 an 9. However, the aspherical surface of the hybrid aspherical element No. 2 is visible in all three diagrams. And there could not be a different glass for element 9 without alteration of the lens elements surface curvatures. Thus your source is wrong, and original Pentax an KMP information is right.
Boring and crippled kit lenses in endless variations and 10x zooms with appalling image quality is all what's been thrown to Pentaxians in the last few years. Not a single new lens, really worth mentioning and remembering  .. Ah yes, a $7K DA560 for extreme birding. Ricoh is really showing us a birdie ...
Uncle Vova's avatar

Uncle Vova · 603 weeks ago

All of these lenses are not so bad to criticize them, but not so good to spend a lot of time on their discussion.
IMHO
The DA II has an aspheric lens. It is named AL, and confirmed on Pentax web site e.g. http://www.pentax.fr/fr/optiques-monture-k/DA-18-...

The new DAL WR is also named AL, cf. http://colors-k50.pentax.eu/images/front/0_0_0.pn...

And the old DAL is named AL, cf. http://img1.lesnumeriques.com/produits/152/9855/1...

I guess that the diagrams are missing colors and that all the optical formula are the same.
1 reply · active 603 weeks ago
The lens photo in the first official French link is wrong, it shows a DAL.
Indeed, there is a red II on the DA II
An the DA II and DA WR have the same focus ring, with distance info and quickshift.
Here are actual photos of the DA II http://www.lenstip.com/aparaty_image/3341_pen18-5... http://www.pentaxforums.com/forums/attachments/so...
I should not have trust Pentax website... but my point is still valid: it is named AL
5 replies · active 602 weeks ago
I trust that source post, the coloured elements are with something different, as it was reported that an element of the DAL lens deteriorated very quickly.
Arnold Stark's avatar

Arnold Stark · 603 weeks ago

The one thing that could deteriote quickly is the HYBRID ASPHERICAL ELEMENT (element No. 2)... ;-)
The material used and process of making it could be different, in order to save cost for making the DAL.
Arnold Stark's avatar

Arnold Stark · 602 weeks ago

The hybrid aspherical element is already the cheapest way to produce an aspherical element.
Maybe a different material also counts.
My original is the best one, the 2 DAL's I had were comical at best and downright awful IMO. WR one I had was also poor esp tele end
The design isn't that good even the original one wasn't that great, just not so bad.

A decent Tamron 17-50mm spanks the rear end off of any kit lens Pentax or otherwise, my advice is don't bother with any 18-55mm, as it happens the Pentax is the worst out of all the kit lenses
1 reply · active 603 weeks ago
Arnold Stark's avatar

Arnold Stark · 603 weeks ago

Your experiences contradict mine: My DA18-55/3.5-5.6 AL II and DA18-55/3.5-5.6 AL WR were/are surprisingly good, so that I would recomment either. The original DA18-55/3.5-5.6 AL performed OK on the *ist D but not so good on the K20D... ;-)

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