[Rondec]

I think the issues with the M40 had to do with compromises due to its size and it was a little fiddly to use due to its size. The DA 40 is based on the same optical formula but has auto focus, which makes it easier to use on digital cameras, but it doesn't have an aperture ring.

[Skodadriver]

I bought a lot that had the -M 40mm F2.8 in it, I thought the lens, a Tamron 28mm F2.8 with PK-A Adaptall mount and an original Pentax M42-PK adapter in the lot would be worth the £47 I paid. I sold on the Tamron 28mm and the Pentax 40mm on and realised enough money to not regret the purchase.
The Pentax 40mm was tried out on digital and I had a little trouble using it due to it's tiny size, the few images I took were, for me, a little lacking in colour and contrast. I have no doubts now that I should have used a hood. It was quite sharp.
I think that I should have used it with film (and a hood) where I might have appreciated it more, except for my turning the aperture ring when focussing.
The pentagon shapes provided in the bokeh was, to me, not nice.


Much as I was happy bagging a Tamron PK-A adapter and original M42-K adapter, this thread is making me wish I had kept the -M 40mm and learned to use the focussing ring.

[redpit]

One of my favourite lenses on K-1! I use it as a body cover whenever no other lens is attached on my K-1. Great rendering and bokeh and real easy to focus. I have to post some pictures especially from street photography.

[Cambo]

Haha maybe. I'll do some research into Pentax digital cameras, especially full frame, but I keep spending on Pentax lenses for the SP500 and MX, so don't have much left for a new Pentax body and len(s) :-)

My reasoning for Fuji really is form factor over much else, I love the connection to film slr set ups with the shutter dial on top, aperture rings etc. I like to not go into the menus etc.

---------- Post added 01-08-18 at 11:11 AM ----------



Awesome. Is this with a digital Pentax Full Frame and 40mm lens?

Nope. K3ii and DA 40 limited.

[mikesbike]

I have the M40 on my Super Program as my ready-to-go standard lens. Very neat on such a quality, compact body. Great on the ME Super also. Since it is complementary in being MF only, I don't have to mess around getting out my DA 40 or FA 43mm for use on this MF body. The M40 build quality is excellent, even looks forward to the Limited series to come.

[GUB]

I feel my copy of the M40 2.8 is just a little softer than I expect from that era of lenses (M50 1.7 A 50 1.7 etc) but I also feel the raws from it edit up really well and seem to have just a little more 3d pop. I took the comparison shots the other day because I was never sure whether to use my 40 xs or the M40. As you can see the 40xs is the clear winner. The near to corner crop is not as simple as it appears as the 2 40s seem to have a totally different field curvature with the M 40 being more focused on the leaves behind. The complete image is via the 40xs and you can see the violent drop off of sharpness in the extreme corners. Shots ex K1 jpg unedited. Love someone else to do a similar test to see if it is repeatable.

[cyberjunkie]

It's the first Pentax lenses I bought, long long time ago.
It came on a beautiful MX, black version.
I still have both
Later on, at different times, I acquired all the others!
One more than those already mentioned actually, the Cosina-made 2.5/40mm.
This thread reminds me of an old idea. A collective test of the pancakes. It never materialized...
My educated guess is that they should all perform in a similar way. Main differences being coating and aperture blades. They are all Tessar design, made when the Tessar f/2.8 patent was long expired.
The only exception is the Konica. Faster, different design, better bokeh, likely a tad sharper. I tried it on m4/3, but the plan was to convert it to PK. Difficult to do because of the different register and design/focal.

I like the SMC DA Limited cause it's a tiny, very well made AF lens. Though I'm not sure it performs better than the old Pentax-M. The right way to compare them would be to use enlarged LiveView and focus in manual. On tripod, preferably multiple times.
Would be nice to know if any forum user ever attempted to do that...

EDIT:
Just saw GUB's post.
Interesting.
Can you try to reduce the variables and shoot a flatter subject?
Would be a good counterproof

Cheers

Paolo

---

Last edited by cyberjunkie; 01-10-2018 at 04:23 AM.

[D. Obermann]

...looks a little bizarre mounted as K-1 body cap...


...as well with a hood...



...but is serving the 35mm frame wide open without vignette or pentagon bokeh; sharp enough to count lashes....


(linked to ooc jpg)

[GUB]

Can you try to reduce the variables and shoot a flatter subject?
Would be a good counterproof

Yes I have been thinking the same. If I have surmised correctly that the 40xs has a more curved plane of focus then it will show with a shot of a wall as sharp only in the middle. This might also be a serious limitation in landscapes situations where everything needs to be at infinity. Give me a few days.

[GUB]

I did some shots of walls - including some at angles to try and show a curved plane of focus but really couldn't objectively demonstrate much. But this landscape test pretty well demonstrates my conclusions on my 2 lenses (M40 2.8 and 40XS 2.8). The only area where the XS is ahead is in the centre wide open. For a normal stopped down landscape shot the M40 is superior. Especially as I have kept away from the extreme corners where the XS collapses entirely. Remember this is on full frame. But I still would choose the M40 on APSC. Yes for portraiture the XS wide open might be better but then I would have shifted over to a fast 50 anyway.

[cyberjunkie]

... this landscape test pretty well demonstrates my conclusions on my 2 lenses (M40 2.8 and 40XS 2.8). The only area where the XS is ahead is in the centre wide open. For a normal stopped down landscape shot the M40 is superior. Especially as I have kept away from the extreme corners where the XS collapses entirely. Remember this is on full frame. But I still would choose the M40 on APSC. Yes for portraiture the XS wide open might be better but then I would have shifted over to a fast 50 anyway.

Thanks,
and well done!
Your conclusions confirm my (not so) educated guess.
It takes just a bit of common sense. A very mature optical design like the Tessar can be tweaked and optimized, but not improved beyond a certain point.
I believe that the improvements in the multicoating are not visible in practice (but measurable instrumentally), including the latest HD. Surface treatments of other kind can be very useful, but on a different level.
I think that the subtle tweakings in lens design were aimed at a better center IQ, sacrificing a little coverage (which translates in weaker border performance).
Most film era lenses were not designed for maximum sharpness wide open, so it's not surprising if the XS (and very likely the two Limiteds) are better wide open. Being DA lenses, it is also not unexpected to see a degradation in the borders of the FF frame.
BTW, stopping down a Tessar does not improve coverage * that much.

* when I use the word coverage, I don't mean the circle of illumination that a lens projects on the film/sensor plane, I mean the usable circle of coverage. Depending on the optical design, there is smaller or larger area at the border of the circle that has an image quality that can't be accepted for any photographic use.
That's exactly what happens if we stretch some DA lenses using them on FF. The corners, that were originally outside the APS-C frame, are now part of that degraded area. The details are mushy, but even the extreme corners are still illuminated.

Cheers

Paolo

[GUB]

I tried the A50 1.7 as well but it did not perform quite as well here as the M40. I am always uncomfortable about doing test shots at infinity as a lot of these old lenses don't quite get there and need a small adjustment to correct the tyranny of time.

[cyberjunkie]

True.
A slight mis-focusing can affect very much the perceived sharpness, looking at the image at 100%.
Most of the times we don't know much about the old lenses we acquire. Actually I am impressed by how well they work. Well, most of the times...

cheers

Paolo

[Kerrowdown]

Is the 40mm 2.8 Pancake really that bad?

The only real problem I had back in the day... was getting the old Kerrowdowns banana fingers around it, to focus the wee beast.

[Arjay Bee]

was getting the old Kerrowdowns banana fingers around it, to focus the wee beast.

Bring fingers to lens from the front not the top and bottom. We train ourselves not to do this with our other lenses to stop finger prints but with this lend the front element is so small as to not likely to be touched.

Here is my M40 copy on a K2. The quality refinish done by DC Shooter of course. Looks even spiffier on the smaller bodied silver MX - just no picture atm.