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04-26-2011, 12:00 PM   #1
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55mm f1:8

I've just got a takumar 55/1:8 m42 screw lens to use with my new k-5; I've also the chance to exchange it with a pentax K 55/1:8; does anybody know which lens in better to use with my camera?

Thanks
Elena

04-26-2011, 12:02 PM   #2
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Assuming your Takumar is the SMC version, then I believe the two(K and Tak) are identical safe the mount. In which case, I'd say go with the K as it doesn't need any adapters.

Otherwise, the SMC-K normals were excellent performers.
I remember reading that the SMC-K 55/2 was slightly sharper than the 55/1.8 but I can't for the likes of me remember where I saw this test. Either way, the 55 K's will not disapoint.
04-26-2011, 02:30 PM   #3
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You shouldn't see any difference in image quality whether you use an S-M-C / SMC Takumar or an SMC Pentax-K. I have the S-M-C Takumar 55/1.8 and it provides very pleasing results.

Choosing between the TAK and the K could be a matter of temper: With the K you don't have to bother with the M42 adapter - but you do have to bother with the green button to get the proper exposure. (I always tend to forget, when time is of essence!). With the TAK you can shoot in Av mode and leave things to the camera automatics.

I don't know for sure, but I believe most people would advice you to go for the K-version now that you have the oportunity. If we are talking similar prices(???) I think I would go for the K version myself also.

B.R. / Steen G. B.
04-26-2011, 02:57 PM   #4
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I would make the swap. I once had both of them for a short while and I simply hate using adapters (I borrowed the K from another forum member). If, however, you intend to purchase More M42 type lenses, then it really won't matter. You can just leave the adapter on the camera and it becomes a screw mount camera. One advantage the M42 may hold for you is the ability to shoot in Av mode since you don't have to work around the crippled K mount with it.



04-26-2011, 03:28 PM   #5
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Make the swap, but test the lens first to make sure that the new lens is similar or better (there is still sample to sample variation!)

Same lens, otherwise. Great lens.
04-26-2011, 04:01 PM   #6
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If they M42 is SMC they're identical optically and insofar as coatings, flare resistance, and colour rendition. The K might be more convenient, I don't shoot digital, so I don't know about "green Button" vs. Av mode.

If the M42 is a Super or Auto-Takumar they'll have different coatings, which will subtly alter your colours. The Auto-Takumar might be different optically and will have different coatings than either of the others.

If possible you might want to make a few exposures with each, and see which you prefer.
04-26-2011, 06:33 PM   #7
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QuoteOriginally posted by Stone G. Quote
With the TAK you can shoot in Av mode and leave things to the camera automatics.
That has never worked well with my K-x. With Av, the exposure is rather off with all my M42 lenses and the fact that it is inconsistent across apertures makes it impossible to find an Ev adjustment that works for all of them, so I don't even bother and shoot in M.
04-26-2011, 08:09 PM   #8
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QuoteOriginally posted by Stone G. Quote
With the TAK you can shoot in Av mode and leave things to the camera automatics.
Ikarus (above) is correct and the quoted statement from Stone G. is wrong. Consistent and accurate stop-down metering is limited to M mode on newer Pentax dSLRs (like the OP's K-5). In Av mode the camera will suffer from the same stop-down metering ills as the K10D, K20D, and others of that vintage. And, despite reports to the contrary, no amount of aluminum foil will fool the camera into behaving else-wise.

That being the case, a K or M series lens using the green button in M mode is much, much more convenient than a M42 lens using the same mechanism. The flow is easy. Meter once using the green button and shoot using that setting until either the subject or light changes.


Steve

(has mostly non-A-contact glass...has considered upgrading to a new body just to get the improved stop-down metering...)

(BTW...I own the Pentax-K 55/1.8 and have shot with the Super-Tak 55/1.8. Both are excellent lenses with essentially identical optical design, but the nod goes to the K 55 for convenience and ease of use when paired with a K-mount body.)


Last edited by stevebrot; 04-26-2011 at 08:15 PM.
04-26-2011, 11:50 PM   #9
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QuoteOriginally posted by stevebrot Quote
That being the case, a K or M series lens using the green button in M mode is much, much more convenient than a M42 lens using the same mechanism. The flow is easy. Meter once using the green button and shoot using that setting until either the subject or light changes.
It's a matter of taste, I guess. For manual shooting, I prefer M42s with auto-switch or better yet, preset mechanism over the Ks and Ms. Green button stop-down metering is too sluggish for my taste, at least on the K-x.
04-27-2011, 08:49 AM   #10
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QuoteOriginally posted by stevebrot Quote
Ikarus (above) is correct and the quoted statement from Stone G. is wrong. Consistent and accurate stop-down metering is limited to M mode on newer Pentax dSLRs (like the OP's K-5). In Av mode the camera will suffer from the same stop-down metering ills as the K10D, K20D, and others of that vintage. And, despite reports to the contrary, no amount of aluminum foil will fool the camera into behaving else-wise.
I have a way to test this statement. See how this sounds or try it out yourself.

You need a Pentax DSLR, an M or K lens, a target with consistent, even lighing, and a tripod. I used a white wall. Set the camera up on the tripod, in M mode, lens properly mounted. Set the lens to a minimum aperture, f22 or whatever. Use the green button to meter and take a shot. Then go down one stop on the aperture ring, meter with the green button and shoot again. Do that for each whole stop until the lens is wide open.

Now set the aperture ring to its minimum aperture setting again. Unlock the lens and rotate it slowly while observing the aperture blades, which should close. Stop when the blades won't close any more. Switch the camera mode to Av. Take another series of shots at each whole stop, but this time, don't meter with the green button, just let the camera set the shutter speed by itself. Be careful not to rotate the lens itself when moving the aperture ring.

That test uses the same lens, position, light, subject, camera, etc. The only difference is metering mode. Anyone should be able to do it.
04-27-2011, 12:35 PM   #11
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QuoteOriginally posted by vabsit Quote
I've just got a takumar 55/1:8 m42 screw lens to use with my new k-5; I've also the chance to exchange it with a pentax K 55/1:8;
Wow, f/8's! I didn't know Pentax made lenses that slow! I have a Vemar 12/8 fisheye and Sakar 500/8 mirror, and even a Rubinar 1000/10 mirror, and an Edun 45/181 pinhole. Zowie, they need long exposures!

OK, punctuation matters. An aperture of f/1.8 isn't the same at f/1:8 -- and I'll bet that more than a few of us have excitedly bid on 50/1:2 lenses thinking they were ultra-cheap 50/1.2 ultra-steals. (Duh, yeah, me too, duh...) It doesn't help that some search engines can't distinguish between '.' and ':' and ';' and ',' embedded in search strings. Damn stupid computers...

CV: I was once a software engineer, ie programmer / codemonkey. We had a saying: "Computers are dumb. The only thing dumber than a computer is a programmer." Search-engine designers don't seem to have optimized their warez for lens(wo)men. Bother.
04-27-2011, 02:37 PM   #12
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QuoteOriginally posted by Just1MoreDave Quote
I have a way to test this statement. See how this sounds or try it out yourself.

You need a Pentax DSLR...
Not just any Pentax dSLR. I have done this exercise with my K10D and the two modes produce identical results. HOWEVER, Pentax changed the metering system on their more recent bodies starting with the K-7. On those bodies, non-detection of the A contacts in M mode uses different exposure computation logic than in the other modes. The user manual for the K-7, K-5, and K-r reflect that change (no more caution about stop down metering in M mode). The manuals for those cameras still indicate that YMMV in modes other than M.

While I did not have much time with the K-7 a year and a half ago during demo days here in Portland, I was able to do an green button exposure series in M-mode using an evenly-lit blank wall with my Pentax-M 50/1.7 from f/1.7 through f/22. The exposure series was dead-on linear.


Steve
04-28-2011, 07:12 PM   #13
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QuoteOriginally posted by stevebrot Quote
Not just any Pentax dSLR. I have done this exercise with my K10D and the two modes produce identical results. HOWEVER, Pentax changed the metering system on their more recent bodies starting with the K-7. On those bodies, non-detection of the A contacts in M mode uses different exposure computation logic than in the other modes. The user manual for the K-7, K-5, and K-r reflect that change (no more caution about stop down metering in M mode). The manuals for those cameras still indicate that YMMV in modes other than M.

While I did not have much time with the K-7 a year and a half ago during demo days here in Portland, I was able to do an green button exposure series in M-mode using an evenly-lit blank wall with my Pentax-M 50/1.7 from f/1.7 through f/22. The exposure series was dead-on linear.


Steve
With my K-7, I got (eventually) the correct sequence in M mode, and in Av, a half-stop overexposure at f16 and f22. At other apertures, everything was the same. With my DS, M was the same as Av. I think it's a useful test to sort out your lenses and your equipment, rather than what I might say.

That was with an M50/1.7. I started with a K55/1.8 to make it relevant to the thread, but my lens wasn't stopping down enough between f16 and f22, so I made an adjustment. When I took off the filter ring, I found my lens was assembled with two types of screws. I think it was done at the factory that way but can't tell for sure.

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