How can the Pentax 40/2,8 be so small?

[Griffin]

And why don't they make more lenses this way? Is it related to the focal length and image circle? Are there any drawbacks on this design? I'm just curious.

[jwnash1]

the Voigtlander Ultron 40mm and the Canon 40mm are pancake lens also. I do not know exactly why but it certainly seems to be something about the 40mm focal length that lends itself to compact or pancake lens style.

[buzzardkid]

The Konica Hexanon 1.8/40 is pretty small too...

[BlackXList]

I've read time and again that the Pentax 40 2.8 isnt a great performer, that these days it's markedly overpriced, and I already have the outstanding Konica Hexanon 40 1.8, but none of this seems to dampen just how much I'd like to have a play with the astonishingly small Pentax one

[flyalf]

The Perar is a bit smaller, and its built for FF. Please see
http://japancamerahunter.com/2012/02...super-triplet/

[mugent]

Even the standard 50mms you us to get for oly, Pentax etc.. were small, and fast, and good quality, these days, lenses tend to be much bigger, I think this is part AF systems, but more because people want a 'pro' look, either for ego reasons, or because clients expect a 'pro' look.
If someone showed up to my wedding with a Minolta tc1, it might just not look the part...

[leicapixie]

i have the 40mm Pentax lens. It is actually too small! Mine the film version, not auto focus or anything..Maybe they are all same? I own a Nikkor 45mm GN lens which is pretty small but focuses the wrong way! The Nikkor is both sharper, better flare control and easier to use. Busy with a Minolta 45mm. Much larger but bigger aperture, f2.
A Pentax ME/MX with the 40mm is a very compact unit.

[dct]

For an SLR designed lens, the Pentax 40/2.8 is really small, though it includes AF.
I cannot believe that a 40mm FF prime lens (up to f2.5) for any SLR or mirrorless mount has to be essentially bigger. It could be even smaller for APS-C or 4/3 sensors. Shouldn't it?

[Bille]

Obviously most people dont care a lot about size in SLR lenses. I find the bulk of a Canon 50/1.2 L ridiculous compared to manual lenses of the same speed.

The EF 50/1.2 L is almost 9cm in diameter at around 600g. Progress?

[Bille]

Originally Posted by dct

For an SLR designed lens, the Pentax 40/2.8 is really small, though it includes AF.

The 43/1.9 Limited (AF) is almost as small and covers full frame. So does the manual 40/1.8 Hexanon.

[bastian a.]

I think there is a recent Pentax 40mm pancake and an old one from the 70s or 80s. Athe first with AF, the second without.
Which lens do we talk about? So far about both I think

[Ernst Dinkla]

Originally Posted by Griffin

And why don't they make more lenses this way? Is it related to the focal length and image circle? Are there any drawbacks on this design? I'm just curious.

Often the design for a lens like that will be based on a Tessar or alike, the more if it is not faster than f2.8. The 40mm focal length helps too if used on an slr, shorter and a retro focus optical solution has to be used, longer the telephoto solution to keep the lens shorter than the focal length. Not all are Tessar designs though. the recently introduced Canon 40mm is a 6 element design. With Tessar types the resolution degrades more to the corners than with Gauss, Plasmat etc designs. Bokeh is often one of things sacrificed in pancake lenses.

--
Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectra...ctrumviz_1.htm
December 2012, 500+ inkjet media white spectral plots.

[BlackXList]

Almost sliding off topic here, has anyone tried that Canon 40mm? opinions?

I think it's somewhat disingenuous to criticise the fact that the Canon 50 1.2 for being "almost 9cm in diameter at around 600g" because the front element is 72mm as opposed to 49 in the Pentax model, so there's a lot more glass in the Canon model, plus the neccesary gubbins to shift that extra glass around, so it's not just due to newer designs being bloated

That said I do greatly enjoy my Pentax lenses on my ME Super and it's very handy that it slips into a jacket pocket

[Bille]

Originally Posted by BlackXList

I think it's somewhat disingenuous to criticise the fact that the Canon 50 1.2 for being "almost 9cm in diameter at around 600g" because the front element is 72mm as opposed to 49 in the Pentax model, so there's a lot more glass in the Canon model,

The larger filter covers the whole lens, not only the front element which should be about the same in diameter as any other 50mm f1.2 lens.

Here is a picture:
http://www.kenrockwell.com/canon/rebel-xti.htm

[BlackXList]

You're absolutely correct there, my mistake, even so the amount of glass in it is significantly more than the other Canon 50s (differing max apertures I know) plus the autofocus mechanism of course, so I think it's a little odd to expect parity with older manual focus designs.

[charjohncarter]

As far as I can tell there are three such lenses: M, limited, and the Mark Newson K-01 lens. Which are you talking about or does it matter. I think it might, because the OP asked about image circle; two are APC-s and the other may be FF.

[charjohncarter]

You might want to look at these, it seems it is a good performer. Not like someone above says:

http://www.pentaxforums.com/lensrevi...cake-Lens.html

and this is the K-01 lens which is good just not quit as good. But at $249 it is a deal:

http://www.pentaxforums.com/lensrevi...m-f2.8-xs.html

Sorry no image circle information on these sites.

[oceanpriest]

Originally Posted by charjohncarter

As far as I can tell there are three such lenses: M, limited, and the Mark Newson K-01 lens. Which are you talking about or does it matter. I think it might, because the OP asked about image circle; two are APC-s and the other may be FF.

yes, it covers the image circle of fullframe, tested

Originally Posted by charjohncarter

You might want to look at these, it seems it is a good performer. Not like someone above says:

http://www.pentaxforums.com/lensrevi...cake-Lens.html

and this is the K-01 lens which is good just not quit as good. But at $249 it is a deal:

http://www.pentaxforums.com/lensrevi...m-f2.8-xs.html

Sorry no image circle information on these sites.

both da 40 limited and da 40 xs (mark newson k-01 lens) cover image circle of fullframe
http://www.pentaxforums.com/forums/p...ts-thread.html
http://www.clubsnap.com/forums/penta...old-200-a.html
http://www.clubsnap.com/forums/penta...8-40mm-xs.html

[LKeithR]

A "really" tiny lens is the Industar 50-2 50/3.5 M42 lens. Here's a shot of one with my old Pentax ME with M 50/1.7 lens mounted and the DA 40 2.8 Limited keeping them company. The 40 would be smaller if it didn't have the rear cap on but it's still not a whole lot smaller than the M 50...

[charjohncarter]

Thank you OceanPriest, at least someone answered one of the OP's questions (finally). I use an ZX-5 similar to your camera. I don't understand why more cameras were not made this way: shutter speed DIAL and APERTURE ring. You really know where you are, and if you want; complete auto. The auto is for the digital types that want to shoot film once in a while.

To help the OP maybe a little (as I only have one close to 40mm lens); my 40mm lens (maybe it is a 42mm) on my (RF) Olympus 35RC is really the best lenses for 35mm I have.

[btgc]

Over time I've come to conclusion pancakes aren't my dish, I leave it for kids Seriously, focus ring on Revuenon 45/2.8 (quite similar design to other manual focus 40-45mm pancakes) is very narrow (one line of knurling), it's slower and thus very little harder to focus than Rikenon 50/2 lens which by many ebay sellers is wrongly described as a pancake (which it isn't, but is just a little bigger) but has proper 6 elements instead of 4 in real pancake (well, good photos aren't by number of optical elements, we know) and is a bit brighter. And costs 10-20 times less than that

This is like w/ phones - there were time when everyone wanted to go smaller but now when phones aren't just phones and screen is everything, they instead get bigger!

[gavinlg]

Originally Posted by Bille

Obviously most people dont care a lot about size in SLR lenses. I find the bulk of a Canon 50/1.2 L ridiculous compared to manual lenses of the same speed.

The EF 50/1.2 L is almost 9cm in diameter at around 600g. Progress?

The 50L is also one of the best fast 50mm lenses in existence - so it sort of makes up for its weight problem.

[Griffin]

Thanks for the replies all. I was really interested in the boring technical stuff about how this lens is so small and if it would be possible to make other focal lengths this small. I was in fact referring to the manual focus lens, but the one for digital Pentax' cameras is pretty much the same size (or so it seems from web pics).

My conclusion is that a Tessar design, combined with the 40mm focal length, hits some sort of sweet spot size-wise, whereby the various elements/groups can be placed closer together. Am I correct?

[charjohncarter]

Tessar has 4 elements in 3 groups, while the manual Pentax 40/f2.8 has 5 elements in 4 groups. So probably not a classic Tessar. Someone that knows more about lens design might jump in, I'm certainly not the person to ask.

[tom.w.bn]

Originally Posted by Bille

The larger filter covers the whole lens, not only the front element which should be about the same in diameter as any other 50mm f1.2 lens.

Here is a picture:
http://www.kenrockwell.com/canon/rebel-xti.htm

They use the ring-usm autofocus. Lot's of advantages but on the downside it makes the lens bigger because the AF is around the lens elements.