[Adam]

I've noticed that DA's and FA's (and old M42's) are tend to be smaller and a little bit less brighter than competitors lenses. Why is that? What Pentax did differently in terms of construction to get there?

Also, why rangefinder lenses are even smaller and brighter than SLR-ones?

Pentax generally favors compact size over speed, and that's one of the selling points of the system. Canon and Nikon have only recently started making slower, more compact lenses, while Pentax has been at it for years.

Adam
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[tuco]

Heck, my Nikkor 20/2.8D, 24/2.8D, 50/1.4D and 85/1.8D are on par, in general, with my Pentax A or M lens I have in terms of size. My Nikkor 24-70/2.8 is a little over an inch taller (though heavier but a FF lens) and about the same diameter as my DA* 16-50/2.8. But, yeah, Nikon does like to make physically large lenses, no doubt.

[Rondec]

I think Pentax lenses are somewhat smaller. The classic example to me would be the comparison of the FA 31 limited with the Sigma 35mm f1.4. Both are full frame compatible, both pretty sharp (Sigma is probably a little sharper and 1/2 stop faster), but the FA 31 is 345 gm and Sigma 35 is 665 gm -- quite a difference. Same is true for FA 77 versus competitors.

I think that Pentax makes some compromises, doesn't try for the ultimate in border sharpness and often is satisfied with slightly smaller maximum apertures as compared to competitors. I guess one other thing is that other companies have in-lens motors, while Pentax doesn't on many of their primes. Not having stabilization needed in the lenses also tends to decrease overall size.

[Rondec]

This is one of the worlds biggest lies, that full frame lenses are bigger and heavier than APS-c lenses. Just look at Pentax, the DA 300/4 is an APS-c lens but is heavier than the K300/4 and substantially heavier than the M or A 300/4. And a whole lot bigger too!

Especially for tele lenses there are only really three main things that determine the size and weight
- aperture, F4 on 300 mm requires a front element diameter of 75mm after aperture = focal length / diameter
- lens mount diameter. The K mount is the K mount, it has a physical size, regardless of what is inside it, the lens barrel size at the mount must be , as a minimum the mount diameter
- optical/mechanical design. Optical design elements and groups plus correction for aberration all add weight, telephoto factor, and by this I mean the amount of physical length reduction by adding lens groups , to achieve the apparent focal length adds weight but duces length. (Remember telephoto does to mean more than normal, but lenses which are physically shorter than the focal length as indicated by the apparent magnification) . As others have noted, mechanical design, integrated motors, integrated automatic aperture controlled in lens electronically (canon) integrated OS all add size and weight.

Although Pentax may be much lighter and compact compared to canikon, many of their current offerings are still heavier than past ones.

I think the DA *300 is full frame. Certainly the DA 15 f4 is smaller than a full frame 15mm lens, so having a smaller image circle does make some difference.

[thornburg]

Yep, many have tried them and some work. https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/31629-da-lens-...ts-thread.html

Thanks, that's a great thread.

Now why is the DA 50mm 1.8 not listed in the first post of it?

I also can't find a source for it in the thread, other than a mention of a chinese forum, which I can't read.

I was surprised to see that the DA 35mm f/2.4 is full frame!

[Lowell Goudge]

I think the DA *300 is full frame. Certainly the DA 15 f4 is smaller than a full frame 15mm lens, so having a smaller image circle does make some difference.

Is the DA 15 smaller than the K15mm? And lighter. Ok yes it is, but imam sure this is not related to speed or focal length, but different optical design the K is 13 elements, the DA is 8. I think wide anglenisnone area whe new optical materials has simplified design,

As to the DA300' while it may perhaps cover full frame, it is still heavier, even with the use of plastics, than the K300! Which uses no plastics.

Sensor size determines NOTHING

It is materials, lens designs, and trade offs

[Rondec]

Is the DA 15 smaller than the K15mm? And lighter. Ok yes it is, but imam sure this is not related to speed or focal length, but different optical design the K is 13 elements, the DA is 8. I think wide anglenisnone area whe new optical materials has simplified design,

As to the DA300' while it may perhaps cover full frame, it is still heavier, even with the use of plastics, than the K300! Which uses no plastics.

Sensor size determines NOTHING

It is materials, lens designs, and trade offs

Do you really think that? "Sensor size determines NOTHING?" Obviously on a k mount camera, with the same register distance, there will be limitations to the size of the lens, but certainly for a DA 70 limited to be full frame compatible, it would have to be bigger than it currently is. Same with the DA 40 and the DA 35 limiteds.

[Joel B]

Is Pentax the only maker to specialize lenses for the smaller sensor?

[fs999]

No Canon (EF-S) and Nikon (DX) have lenses for smaller sensors.

[Nesster]

Do you really think that? "Sensor size determines NOTHING?" Obviously on a k mount camera, with the same register distance, there will be limitations to the size of the lens, but certainly for a DA 70 limited to be full frame compatible, it would have to be bigger than it currently is. Same with the DA 40 and the DA 35 limiteds.

I beg to differ - the DA 70 probably needs a minor tweak to be full frame compatible at a decent quality across the frame (I use mine with film cameras)... and the DA 40 is based on the film version of the same and covers a full frame fine.

Leaving aside plastics and screw drives etc, the old manual focus Pentax lenses are small, like the old manual focus Olympus Zuikos, and do a fine job covering the full frame. With modern plastics etc the af versions don't need to be much larger, and will weigh less.

We have to look at history and the marketplace to see where size became a major (market) consideration. Nikon and then Canon prioritized ruggedness and performance over many other considerations, for the pro market. The other manufacturers went along - riding on the size = rugged idea, plus manufacturing/design cost -- making things the size they turned out to be I would think is cheaper than going for size reductions, especially where the raw material cost was less important than manufacture tolerance etc. Perhaps larger glass elements made lens design a bit easier also, as one could 'throw out' the edges...

But Pentax (and in the early days, perhaps Miranda) went against the grain, already with their earliest SLRs. The vision was portability and gracefulness, a la Leica, for the practial amateur. In the M42 days, often the Takumar is the smallest in any given category.

Olympus in the early 70s changed the market. Everyone got on the smaller size bandwagon -- even Nikon offered smaller cameras and lenses for the amateur market. Olympus for a while had the pro cachet as well working for them.

In the long run, it has turned out the pro connection is the strongest marketing force in quality SLRs. Thus, despite periodic downsizing for the amateurs (which Canikon is again doing) it is the large 'professional' cameras that sit at the top of the pile.

[Rondec]

I beg to differ - the DA 70 probably needs a minor tweak to be full frame compatible at a decent quality across the frame (I use mine with film cameras)... and the DA 40 is based on the film version of the same and covers a full frame fine.

Leaving aside plastics and screw drives etc, the old manual focus Pentax lenses are small, like the old manual focus Olympus Zuikos, and do a fine job covering the full frame. With modern plastics etc the af versions don't need to be much larger, and will weigh less.

We have to look at history and the marketplace to see where size became a major (market) consideration. Nikon and then Canon prioritized ruggedness and performance over many other considerations, for the pro market. The other manufacturers went along - riding on the size = rugged idea, plus manufacturing/design cost -- making things the size they turned out to be I would think is cheaper than going for size reductions, especially where the raw material cost was less important than manufacture tolerance etc. Perhaps larger glass elements made lens design a bit easier also, as one could 'throw out' the edges...

But Pentax (and in the early days, perhaps Miranda) went against the grain, already with their earliest SLRs. The vision was portability and gracefulness, a la Leica, for the practial amateur. In the M42 days, often the Takumar is the smallest in any given category.

Olympus in the early 70s changed the market. Everyone got on the smaller size bandwagon -- even Nikon offered smaller cameras and lenses for the amateur market. Olympus for a while had the pro cachet as well working for them.

In the long run, it has turned out the pro connection is the strongest marketing force in quality SLRs. Thus, despite periodic downsizing for the amateurs (which Canikon is again doing) it is the large 'professional' cameras that sit at the top of the pile.

I have not shot my DA 40 (or when I owned it, my DA 70) on film, but from Falk's DA lenses on full frame thread, I think it is clear that both lenses have quite a bit of vignetting and soft corners, even stopped down. Falk graded them at +, meaning that they are both usable starting at f4 to f5.6 with soft corners. The only lenses that Falk gives ++ or +++ are the DA *200, 300, 60-250, DFA 100, DA *55, and DA 35 f2.4.

[asp1880]

I guess one other thing is that other companies have in-lens motors, while Pentax doesn't on many of their primes. Not having stabilization needed in the lenses also tends to decrease overall size.

The Canon EF mount even puts the aperture motor (servo, actuator, whatsitcalled) in the lens, driving lens size upwards.

The upside of that decision is that it's easier to build a 10fps sports camera and you don't have to put the diaphragm close to the bayonet but can place it more freely along the lens barrel. Perhaps that gives more optical design freedom.

Regards,
--Anders.

[thornburg]

I have not shot my DA 40 (or when I owned it, my DA 70) on film, but from Falk's DA lenses on full frame thread, I think it is clear that both lenses have quite a bit of vignetting and soft corners, even stopped down. Falk graded them at +, meaning that they are both usable starting at f4 to f5.6 with soft corners. The only lenses that Falk gives ++ or +++ are the DA *200, 300, 60-250, DFA 100, DA *55, and DA 35 f2.4.

It appears that newly posted results will land the DA 50 f1.8 on that list as well.

[monochrome]

Thanks, that's a great thread.

Now why is the DA 50mm 1.8 not listed in the first post of it?

I also can't find a source for it in the thread, other than a mention of a chinese forum, which I can't read.

I was surprised to see that the DA 35mm f/2.4 is full frame!

Hi! The Op started the thread in 2008; the samples were taken by various contributors and the OP (and a few others) voluntarily compiled the links into an organized, sorted table. Eventually the thread became stale and/or the OP tired of the work (not really likely as he still posts here).

(I'll note sidebar that hnikesch and crewl1 have done a similar service for users of the Q with K mount lenses and K>Q Converters and that isn't the only example - people here do some really amazingly generous things when you think about it).

IIRC the premise wasn't necessarily to show that some DA lenses were intentionally designed as FF. The idea was to show that - since many of these lenses are based on old FF designs - they might just possibly work on FF Some do, some don't, some are just acceptable.

What about the DA50/1.8? More than likely it is simply a case of no one thinking to post their review of sample images from the DA50/1.8 since it is a comparatively new release and a comparatively old thread.

[lesmore49]

Pentax's design focuses generally on small. They're not the only firm to subscribe to this less is more philosphy. I have Leica rangefinder equipment and Leica RF...bodies and lens are also relatively small....as our Olympus.

It's essentially differing design philosophy.

On the other hand however the medium format Pentax 6 X 7 was uber large.