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01-07-2018, 04:44 AM   #16
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My lone K lens (K35/3.5) has the same build quality as my M's (50/1.7, 85/2, 100/4, 135/3.5 and 200/4) both are better than my A's.
All my KMA-lenses are good enough for the purchase price by far.

Seb

01-07-2018, 10:09 PM   #17
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QuoteOriginally posted by cyberjunkie Quote
I thought most people would check the differences on Bojdar Dimitrov's site, or the new Pentax-K site that is replacing it (kmp.pentaxians.eu).

Paolo
Thanks for that link.

I'm a huge fan of the K series. Just a word of warning to those considering purchasing a K series lens - plan on adding an additional $50.00 to any price you see because the lens will probably need a CLA. Three of the last K series lens I have purchased had sticky aperture blades.
01-08-2018, 02:17 AM   #18
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QuoteOriginally posted by bassek Quote
My lone K lens (K35/3.5) has the same build quality as my M's (50/1.7, 85/2, 100/4, 135/3.5 and 200/4) both are better than my A's.
All my KMA-lenses are good enough for the purchase price by far.
Hi Seb,
I don't have the K 3.5/35mm, but I'm sure it's great.
My considerations are based on the wonderful performance of my 3.5/28mm, the two lenses are quite similar in concept, if not in design.
Both are held in high esteem by knowledgeable pentaxians, and both are relatively slow, and work more than decently wide open, from what I read.
Other lenses of the same vintage had faster max aperture, but it really was meant for easy focusing in low light, more than for actual use.
That leaves the door open to a creative use of their "flaws", but I'd say that normal and short tele focals are more likely to be used that way (unless the wides are focused at very close range, or the photographer looks for some nice flare).
It's really amazing to see how rather inexpensive lenses, released more than forty years ago, still perform at a very good level, matching modern FF zooms
It is true that zooms have AF, give proper EXIF, and don't need the green button procedure, but it is also true that K and M prime lenses are sturdier, easy to transport and work great in manual focus.

I'm happy to see that some answers to my original question have given a twist to this thread. Some have shared their personal preferences, across different Pentax series, for each focal.
It's an interesting development. When I read that kind of posts I try to rationalize WHY.
Most times it makes perfect sense, thinking (or checking, my memory/knowledge is not so great...) of the lens design. A couple of times it didn't, but I don't find it so surprising, each lens design typology has both good and not-so-good examples, and ALMOST identical layouts could perform in a completely different way. A simple Cooke triplet can be quite sharp (Zeiss Triotar), be softer and give strong bubble bokeh (Meyer Trioplan), have a nice bokeh with no bubbles at all (Feinmess Bonotar), or be completely unpredictable, often with terrible IQ, sometimes quite good, due to the extreme sensitivity of the Cooke design to assembly tolerances (Meyer Domiplan).

I think an often overlooked quality of vintage Asahi Pentax lenses is their consistence. Unless a lens has been damaged, or butchered by a botched repair attempt, the variance between different examples seems to be quite low. I guess they took good care of the assembly process, had competent workmanship, and engineered the barrels in a rational way using high quality build standards. I also guess they had an efficient quality control.
You can feel it using their objectives, after so long time.
This kind of mechanical quality is praised by many users of other camera systems. Plenty of raving reviews of the "feel" of Takumar and early Pentax lenses, on the Web!

If other users share their favorites (if some K series stands in the first, most favorite line), I might try to give it a thought myself....


QuoteOriginally posted by sibyrnes Quote
Thanks for that link.

I'm a huge fan of the K series. Just a word of warning to those considering purchasing a K series lens - plan on adding an additional $50.00 to any price you see because the lens will probably need a CLA. Three of the last K series lens I have purchased had sticky aperture blades.
I don't think it is so common. Probably you have been quite unlucky
I never had the same problem, maybe just a little sluggish towards the end, but I almost never shoot in diffraction zone. Though I am aware that the 28mm M sometimes has sticky diaphragm leaves.
I have seen plenty of sticky leaves, often completely frozen, collecting large format lenses. Leaf (central) shutters are very prone to it. Almost always it's the shutter, not the diaphragm. The two set of leaves sit close one to the other, and while the diaphragm leaves are manually actuated both ways (like in preset objectives), the shutter leaves are shut back by a spring. Unfortunately shutter leaves are very thin, and a tight fit, so that with a minimum of oil their resistance can't be won by the spring.
Sometimes it's possible to clean them with some Zippo fuel, a pair of tweezers, and a little of kitchen paper. Plus a lot of patience and a steady hand.
Often it's not enough, the shutter has to be partially disassembled, cleaned... and the leaves reseated!
Of all SLR lenses, according to my experience the worst affected are those made in the soviet bloc.
Even CZJ ones, which were the best of the crop. Interestingly, also West Germany lenses of similar vintage can be found with the same problem.
Pentax objectives, at least those i bought, do much better.


Cheers,
and thanks for all your very interesting posts

Paolo

Last edited by cyberjunkie; 01-08-2018 at 03:19 AM.
01-08-2018, 11:04 PM   #19
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QuoteOriginally posted by sibyrnes Quote
According to the forum database, the K200 f4 takes a 58mm filter and the M200 f4 takes a 52mm filter - definitely a difference in optical formula. "Better" is a subjective term, but there are physical difference between almost all of the K and M series.

Yes, of course there is a physical difference. I was referring to what the lens does. I cannot see any difference when comparing the results of them side by side.

01-10-2018, 05:19 AM   #20
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I think aside from the perceived build quality, where the K series to me seem much better and generally more solid than the later lenses. Each lens ne DS to be reviewed on its own merits.

But there are some general points to consider.

Newer lenses will have superior coatings, and as a result will be better performing in terms of flair resistance.

Many Pentax newer lenses are smaller and lighter than their K predessors, if size and weight is an issue consider this.

Some newer lenses will be much better in terms of controlling lateral and longitudinal CA , but this is not always true for example my Takumar 200/3.5 preset performs better all round, sharpness, CA , and color rendition than the super tak 200/4 or SMC Pentax 200/4. As I said at the onset, each lens ne DS to be judged on its own merits.
01-13-2018, 06:24 AM   #21
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Already in the film days (20 years ago?) I had the next statement :

No M lens which replaced a similar K lens, optically outperforms that K lens, they are usually worse.

Why ?
The M generation had as major selling point compactness, and that had its optical consequences for the edges of the image field.
Central performance of a M lens is generally good, that is why the APS-C users don't notice this difference, on 24x36 thats different.
Lots of A lenses are repackaged M lenses.

Mechanically the K lenses which had their roots in takumars have brass in their focus heliocoid, the M generation has aluminum only. Aluminum on aluminum goes very bad without grease.
01-13-2018, 08:58 AM   #22
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I hope that this info might be of some help to those looking at this thread:

The Pentax Camera Lens Compatibility Chart

Pentax K-Mount Lenses Explained: The differences between various Pentax lens series

https://www.pentaxforums.com/articles/photo-articles/evolution-of-pentax-k-mount.html
01-13-2018, 10:04 PM   #23
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QuoteOriginally posted by glasbak Quote
No M lens which replaced a similar K lens, optically outperforms that K lens, they are usually worse.

Why ?
The M generation had as major selling point compactness, and that had its optical consequences for the edges of the image field.
Central performance of a M lens is generally good, that is why the APS-C users don't notice this difference, on 24x36 thats different.
Lots of A lenses are repackaged M lenses.

Mechanically the K lenses which had their roots in takumars have brass in their focus heliocoid, the M generation has aluminum only. Aluminum on aluminum goes very bad without grease.
This is exactly my opinion.
With a caveat: it is a general assessment. Some specific lenses don't follow the trend.
This is especially true of some A optics, which either have more elements (like the 4/200mm) or have a good build (like the A* and a couple more).
Regarding optical performance, here is an interesting link. It's about astro performance, so coma/astigmatism have more importance than with other subjects, but it's an eye opener on the simple fact that with the same technology, more elements mean more correction (read: better IQ).

Star test

Regarding mechanical construction, I think we should be aware that it plays a fundamental role, way beyond the number/shape of diaphragm blades affecting OOF highlights, or the pleasure of using a solid objective with a well dampened focusing helicoid.
A well designed barrel, made with the best materials, can greatly reduce inter-reflections, prevent bokeh vignetting (cat's eye or half moon bokeh), and allow to service the objective long time after it was made.
You are right, aluminium on aluminium is not not good! Many old lenses made of aluminium have the male and female threads cold welded. No way to open them! The quality of the material is not good and it's easy to break them if you apply too much force.
Modern time alloys are much better, do not oxidate so easily and are way stronger, but the optimal solution is brass on aluminium (let's forget about bronze, too expensive ).
Of course plastic and glue are at the extreme opposite of the spectrum... if we get some fungus inside an optical cell made that way, the only option is to replace it with a new one. If the spare is not available anymore, that' when we learn first-hand the meaning of programmed obsolescence!

Let's treasure our vintage optics, and use them th best we can. I am afraid that in forty years the champions of today's MTF charts will be out-of-whack doorstops, unless we have kept them in a safe like jewels. I'm getting sick of badly decentered expensive zooms with no external trace of damage. When there will be no spare focusing and zoom sleeves (all made of plastic, hence not repairable), old mechanical lenses would still be perfectly usable...

cheers

Paolo

01-14-2018, 02:19 AM   #24
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QuoteOriginally posted by cyberjunkie Quote
This is exactly my opinion.

Regarding optical performance, here is an interesting link.
So, you found my very first webpage, with the pictures I made 20 years ago !

About mechanical finish, there is a degradation in finish of the M lenses over the various production batches (cost cutting), the very first generation of the M 1:1.7 50mm has the best finish.
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