[Pentaxor]

Don't know which particular picture you mean but I've found two comparison images that illustrate the differences between F 1.7/50 and A 1.2/50.
I can't see if the focus is the same but it must be close.
The F weirdly seems to exaggerate the sharper portion of the image - the flower (especially distinct on the petals) while the A renders the whole scene with smoother transitions - can be seen on contrasty edges.
F: Pentax-F 50/1.7 @ f/1.7 photo - Sean Carpenter photos at pbase.com
A: Pentax-A 50/1.2 @ f/1.8 photo - Sean Carpenter photos at pbase.com

Objective tests aren't even possible - especially not when it's only one person doing the rating. Firstly there is the human factor which allows for a great variety of of testing errors and also if the person diong the test is photography-affine he7she is most likely prejudiced. The larger the testing group the more objective the results get.
The same can be seen here all the time: people logically tend to suggest the lenses they own.
But this is statistics and has nothing to do with this.

Still, can somebody give a description on M42 lenses or provide a link?

I can assure you that I've done the testing objectively as possible, without any prejudices.

as you've mentioned yourself and the test that you saw, it did verify my finding with regards to sharpness of the F1.7 at wide open and the smooth rendering of the f1.2. at f1.8.

I did some independent testings several times. tripod use, with/without lens hood, lighting condition, focusing distance and at varying stops. and I had to redo some shots just to make sure that the initial testings that I've done are consistent with the newer ones. so the margin of error there is lessened to a wide degree and bias is not even a factor. besides, what can I possibly achieve by prejudice? my point here is to only state facts. facts that determined my preference of a lens over the others, of which I tend to use more often because of those facts.

anyway, what I meant by below f2.8, I meant something at lower apertures like f3.2 and onwards. not something f2 and higher. you might had misunderstood me in that area.

so anyway, if there is anyone that had done some testing that had a different or opposite result from what I did, and the results by Sean Carpenter, I would be happy to see it.

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Last edited by Pentaxor; 03-06-2010 at 12:40 AM.

[Just1MoreDave]

...Before I look for M42 lenses: Could someone tell me how using them works precisely?
If you set the aperture on the aperture ring is the aperture stopped down immediately or is there an aperture release switch?
I'm specially asking in respect to the SMC Takumar 1.4/50.

That lens, like most Takumars, has a switch for the aperture. With the possible exception of some lenses I'm not aware of, the Super-Takumar and newer lenses all have this switch.

In AUTO, the aperture is fully open no matter where the ring is set. Pushing in the chrome pin on the mount stops down the aperture to whatever the ring is set to.

In MAN., the aperture blades move to wherever the ring is set. The chrome pin has no effect.

You can use the switch in different ways. You can use AUTO this way: choose an aperture, focus wide open, then flip the switch to MAN. and shoot. You can use MAN. and just move the aperture ring. The switch will not always be in a convenient location so with a large collection of M42s, you may need both techniques.

The Takumars designed for open aperture metering have a mechanism that will lock the AUTO/MAN. switch in AUTO if there's no adapter, cap or older M42 camera attached to the lens.

[Just1MoreDave]

...Objective tests aren't even possible - especially not when it's only one person doing the rating. Firstly there is the human factor which allows for a great variety of of testing errors and also if the person diong the test is photography-affine he/she is most likely prejudiced. The larger the testing group the more objective the results get.
The same can be seen here all the time: people logically tend to suggest the lenses they own.
But this is statistics and has nothing to do with this.

I can assure you that I've done the testing objectively as possible, without any prejudices.

I'm going to have to agree with Egg Salad here. This has nothing to do with you or your abilities or results. It's just how science works.

However, my contention with lens testing is that even a perfect tester and a perfect test only produce accurate results for the lenses in the test.

[Egg Salad]

Ok, thanks everyone.
For now it looks like nothing will change. Either the lenses I want aren't available or if they are they are overpriced for me.
Funnily even the M42 SMC Takumar 1.4/50 sells for way more than I paid for my K-mount 1.4/50. Must be because of wider compability (Canon users and such).
But yes a M42 lens would be easier to work with for me.

Penatxor I agree with Dave agreeing on me - I didn't mean one person can't test properly. But it is nearly impossible not to be influenced in some way. If you like well-made metal lenses like me you may rate another more plasticky lens lower although its optics are just as good - just because of the feeling it gives you while usiing it. But granted doing a test several times considerably lowers the relative systematical error of the series.

Dave, I also have yet to see someone testing a lens he/she doesn't own.

[Clinton]

FWIW, the bokeh on the Pentax-A F1.2 at 1.2 is stunningly fun, but the aperture blades aren't rounded so stopped down to say 1.4 or 2.0, your bokeh gets sadly hexagonal.

[Egg Salad]

Hexagonal bokeh is impossible with this lens. With its 9 aperture blades bokeh could be octagonal+1 (don't know what's greek [or latin?] 9).
Don't know if I'll ever see it on my own pictures.