[rbefly]

First off, I don't have any amazing insights, insider information or even self-indulgent, official-sounding proclamations to make regarding the performance of this lens. For that (and much more!) you can click on either the 52-page thread, the 131-page thread or (time permitting) the 774-page thread.
What I DO have, and haven't seen posted yet, are numbers. As in, size, weight, aperture, filter size and (of course!) price.
But we already have those numbers, right?
For the Pentax DA Limited 20-40mm f/2.8-4.0 zoom, yes we do. I meant the numbers for Canon and Nikon. You know, the 'other guys'?
Neither one offers an exact 20-40mm match, but between them, they have four lenses that come pretty close. One Nikon and one Canon are constant f/2.8, the another pair are constant f/4.0. What may (or, may not) surprise you is that the new DA is faster (overall) than two, smaller and lighter than all four and (drum roll, please!) less expensive than three, within $160 of the fourth. Oh, one other difference; All 4 C/N's are APS-C and FF compatable. We'll have to wait to see if the Pentax is or is not. Meaning the DA zoom may vignette on a camera that Pentax doesn't offer anyway, at least right now. That makes perfect sense to me. YMMV.
As promised;
Pentax DA Limited 20-40mm f/2.8-4.0 zoom. Filter 55mm, size 71 x 68.5mm, weight 283 gr, 10.0 oz. Price $1,000. W/R, DC motor.
Canon EF 16-35mm f/2.8L zoom. Filter 82mm, size 88.5 x 111.6mm, weight 635 gr, 23 oz. Price $ 1,700. W/R, USM.
Canon EF 17-40mm f/4.0L USM zoom. Filter 77mm, size 83.5 x 96.8mm, weight 475 gr, 16.2 oz. Price $840. W/R, USM.
Nikon 17-35mm f/2.8 ED-IF zoom. Filter 77mm, size 83.8 x 106.7mm, weight 745 gr, 26 oz. Price $1,450. W/R, SWM.
Nikon 16-35mm f/4.0 ED-VR zoom. Filter 77m, size 81.3 x 124.5mm, weight 680 gr 24.5 0z. Price $ 1,250. SWM.
Disclaimer; Prices, weights and sizes are from B + H Photo, they may vary slightly on other sites. Weight conversions are accurate in grams (from B + H, again), my ounce(s) conversions may not be!.
What I'm able to deduce from this is that Ricoh/Pentax tried to hit the middle of these offerings. The DA Ltd's variable-aperture, so derided by many, permitted a much smaller lens in every dimension. It may also have helped the size and price factors that the FL doesn't go as wide as the Nikon/Canon offerings, perhaps better-informed minds, regarding manufacturing and design costs of WA zooms could could enlighten us further. Compared to the constant f/2.8 zooms, it's one stop slower at the long FL's, equal at 20mm. Compared to the constant f/4.0 lenses, it's faster at 20mm and equal at the longer FL's. A compromise. The price is very competitive; slightly more than the f/4.0 Canon, less than any of the others. How it compares optically, we'll have to wait and see.
Ron

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Last edited by rbefly; 11-11-2013 at 04:02 AM. Reason: Add new data

[seventysixersfan]

I am not familiar with nikon and canon lenses-- do the ones you listed have Weather resistance and silent focusing motoring? What about Construction material -- are they plastic or metal?

[filoxophy]

Compact Camera Meter

(Pentax 18-55mm has similar dimensions as the 20-40mm).

[rbefly]

I am not familiar with nikon and canon lenses-- do the ones you listed have Weather resistance and silent focusing motoring? What about Construction material -- are they plastic or metal?

Hi seventysixersfan,
To be honest, I don't know about the WR, focusing motors and construction. I'll have to research the individual Canon and Nikon sites to find out. Good question, though! I'll post (here) when I get some data.
Ron

[seventysixersfan]

Otherwise you do make a good point in comparing sizes, weight, speed, and most importantly, price. Maybe $1000 is not too unreasonable....

[carrrlangas]

But... Comparing full frame lenses to an APS-C specific (we´ll have to wait for the tests to see if it covers FF image circle) doesn´t make much sense to me because of different Angle of view and all things that come with that (max aperture, size, weight, etc).
Shouldn´t we look for 30-60mm zooms if looking at FF glass? are there any? 24-50 comes to mind but 24 is pretty wide compared to 30...

[SpecialK]

Shouldn´t we look for 30-60mm zooms if looking at FF glass?

The crop factor applies to all lenses equally, so no.

[carrrlangas]

The crop factor applies to all lenses equally, so no.

but, FF glass in the 20-40mm range will always be heavier, bigger, slower... it has to cover a bigger circle... Althogh If you only use a crop sensor, then yes... it´s the same thing...

[rbefly]

but, FF glass in the 20-40mm range will always be heavier, bigger, slower... it has to cover a bigger circle... Althogh If you only use a crop sensor, then yes... it´s the same thing...

Hello carriangas,
Yes, I'm trying to compare the (closest focal range) Nikon and Canon wide-angle zooms to the new DA Ltd zoom. Pentax can hardly be criticized for an unfair comparison, simply because Canon and Nikon chose to make their lenses fit two different formats. Pentax made the DA to fit the cameras they offer.
Canon and Nikon seem to actively be steering their users towards FF, and have minimal new offerings in the cropped-format (only) lens lineup. If they choose to follow this course, they will leave a void in the smaller format and Pentax can use it to introduce a fuller and more varied APS-C lens selection.
Their loss is our gain!
Ron

[carrrlangas]

True, and good point. It´s just good to clarify that the comparison only applies for crop sensor cameras.

[starbase218]

The crop factor applies to all lenses equally, so no.

That is assuming you would use these C/N lenses on a crop body, while they are designed to cover fullframe. Not really a fair comparison imho.

[thibs]

That is assuming you would use these C/N lenses on a crop body, while they are designed to cover fullframe. Not really a fair comparison imho.

It is if it is clear you compair in this context.
You could do the same on an FF bofy and you'd (most probably) get the DA Limited to vignette so badly the FF lenses would take a good laugh.

I see no problem in this comparison. As long as it is clear you're working on a specific format: APS-C.

[SyncGuy]

Hmm....

Why is it that i have to pay for a whole cheese when all i need are a few slices?

[MBT74]

The numbers I'd like to see are the f stops for each focal length range. Is only 20mm at f2.8? What the max f stop at 25mm etc?

[rbefly]

Otherwise you do make a good point in comparing sizes, weight, speed, and most importantly, price. Maybe $1000 is not too unreasonable....

For seventysixersfan and any others who may be interested, I took a look at the Canon and Nikon home sites regarding the construction features of the four lenses. Here's what I found;
Both Canon zooms feature the 'Ultra Sonic Monitor' (USM) which reduces focusing noise. I don't know how this compares to the DC motor used in the new DA Ltd zoom, but would assume they're both pretty quiet.
Both Canon zooms are described as 'Weather-Resistant'
The Nikon 17-35mm f/2.8 zoom features a 'Silent Wave Motor' (SWM) for focusing. It is described as having a 'rugged construction and professional grade dust and moisture resistance to withstand even the most trying conditions'. I've shortened this to 'W/R' on the first post.
The Nikon 16-35mm f/4.0 zoom features SWM.
Neither site goes into detail about metal/plastic used in the lens construction. I would guess (always a dangerous tactic!) the higher-priced f/2.8 zooms, clearly aimed at the advanced/pro market, are more sturdy than the f/4.0 versions. How much metal/plastic/composite materials and in what ratios? Got me.
I've added the focusing motor initials and 'W/R' for all lenses in the initial comparisons, where appropriate.
Ron