[kitestring]

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?

[VisualDarkness]

What do mean by "less brighter"?

[kitestring]

I mean you can find 1.2 or 1.4 easily for Nikon or Canon, but there is only one 55/1.4 for Pentax. And rangefinder lens have a number of options which goes down to f0.95

[cali92rs]

There's nothing real magical. Larger registration distance (or distance from the filmplane in the case of SLR/rangefinder) drives lens sizes larger. Faster aperture (smaller f number) drives lens sizes larger. And also focusing motors and vibration reduction methods (AF-S and VR in Nikon jargon, don't know the Canon jargon) make lenses larger because you have to package it within the lens.
So if you compromise on any of those factors, you will get a smaller lens. In the case of the DA limiteds for example, they are small because they aren't relatively fast and they don't have focusing motors nor in-lens vibration reduction

[lytrytyr]

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?

Small size was often an important design consideration for Pentax,
so they deliberately avoided large apertures
which would make a lens bigger.

(That said, the K or A50/1.2 aren't oversized, IMHO.)

What Pentax did differently in terms of construction to get there?

For pancake lenses, like some DA Limiteds,
they chose a lens architecture,
e.g., the Tessar type and its derivatives,
which give a compact lens having even resolution
(not necessarily the sharpest in the center).

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

Because the back of those lenses can be closer to the film/sensor
(no mirror to clear),
so more freedom in designing the lens.

[VisualDarkness]

Well, Pentax have old 1.2's too, and they are small for what they are too. Though they lack things like AF and similar that would increase the size. But still it's true that Pentax variants tend to be smaller than their equivalents from Nikon and Canon and is probably basically different design philosophies and priorities.

Like the limited series who sacrifices some speed (max aperture) and rely on screwdrive focusing, among other differances, to bring down the size and weight. Quite a special philosophy as most tend to do the Nikon/Canon way, until just recently with the mirrorless trend.

On the other hand it's not always true as the DA* 55/1.4 is bigger and heavier than the Canon 50/1.4 due to one extra element, stronger build and "shielded" sunk in inner lens tube.

Rangefinders (mirrorless) are so different it's hard to compare. One huge difference is that they lack the mirror so they can take lenses that protrude very far into the camera.

[Aegon]

Another consideration is that Pentax's DA line is designed for APS-C and, in most cases, does not cover FF. Whereas many of the bright primes for Nikon/Canon are FX/EF and are generally correspondingly bigger.

Umm, that's a lot of jargon. Pentax lenses are mostly designed to cover a smaller sensor size.

[VisualDarkness]

Well, lenses like the DA* 300/4 (smaller and lighter than most competitors), DA 50/1.8 and most of the limiteds seems to be fullframe compatible lenses. But yeah, when it comes to lenses as the quite compact 50-135/2.8 they get a lot smaller just by not covering fullframe.

[Kerrowdown]

Why Pentax lenses are smaller

So that they require less pixie dust to make them work their magic.

[Just1MoreDave]

The screwdrive mechanism allows for smaller lenses; the in-lens motors aren't enormous but add to lens diameters. In-lens stabilizer systems don't help either, not needed on Pentax lenses. Pentax bodies are smaller so smaller lenses make sense as a design goal. Even when AF or IS was not a factor, Pentax lenses were always smaller.

Lens speed is probably because Pentax can't afford to have every possible lens for sale, so they concentrate on what people will buy in reasonable quantities. Except for the DA560.

[thornburg]

Well, lenses like the DA* 300/4 (smaller and lighter than most competitors), DA 50/1.8 and most of the limiteds seems to be fullframe compatible lenses. But yeah, when it comes to lenses as the quite compact 50-135/2.8 they get a lot smaller just by not covering fullframe.

Wait, what? I was under the impression that all the DA lenses were APS-C only. Ricoh Imaging site says "Developed specifically for PENTAX digital SLR cameras" on the 50/1.8 page.

Has anyone tried it on film? Or adapted on a FF camera?

[Joel B]

So that they require less pixie dust to make them work their magic.

When I wax poetically about a certain lens having been sprinkled with pixie dust, I get looks like I've gone off my nob! Non camera people just don't get it. Now my m-135 might be small, but its not light. If I didn't know better, I would think it's one solid piece of glass polished on each end and wrapped in metal! It will live forever!!!

[Not a Number]

Now my m-135 might be small, but its not light. If I didn't know better, I would think it's one solid piece of glass polished on each end and wrapped in metal! It will live forever!!!

At the risk of going off topic:

Solid Cat
http://www.barthworks.com/nikon/vivitar800mm.htm

[Lowell Goudge]

Another consideration is that Pentax's DA line is designed for APS-C and, in most cases, does not cover FF. Whereas many of the bright primes for Nikon/Canon are FX/EF and are generally correspondingly bigger.

Umm, that's a lot of jargon. Pentax lenses are mostly designed to cover a smaller sensor size.

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.

[VisualDarkness]

Wait, what? I was under the impression that all the DA lenses were APS-C only. Ricoh Imaging site says "Developed specifically for PENTAX digital SLR cameras" on the 50/1.8 page.

Has anyone tried it on film? Or adapted on a FF camera?

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