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05-28-2010, 03:59 PM   #31
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OK... I'm getting a little carried away here, I know, but it's likely not many people know about the 135mm STF (Smooth Transition Focus) lens, as Sony never seemed all that interested in marketing this lens, although it's one of the best in their lineup. As I was saying, it's unique too, since Nikon's DC thingy does not work in the same way, nor can it produce the same effect.


So hopefully no-one will mind if I link an article describing it in a better way than I ever could:

Sony 135 F2.8 [T4.5] STF SAL-135F28 review - dyxum.com

05-28-2010, 04:02 PM   #32
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All I can conclude is that this lens is officially the holy grail of Pentax lenses. Look, it's even shaped like a grail:



It's unusually rare, it's unparalleled in Pentax primes, and arguably unparalleled in non k mount primes. It may even bring King Arthur back from the dead, and honestly at this price, I'm not expecting anything less.
05-29-2010, 10:23 AM   #33
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It has arrived, it's condition is even better than what I expected from the photos. The only bit of oddness is that the lens reports 1.7 as wide open to the K-7, and at 1.8 it is ever so slightly stopped down from a visual inspection. I love the idea that this lens is secretly 1.7, but I doubt that is the case.

Other than this little bug, the quality of this lens is simply surreal, and the DoF control... yummy. A few people I noted reported it as slightly soft wide open, but I'm not seeing that.

Does anyone else have this aperture experience with this lens?
05-29-2010, 10:44 AM   #34
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QuoteOriginally posted by Clinton Quote
All I can conclude is that this lens is officially the holy grail of Pentax lenses. Look, it's even shaped like a grail:



It's unusually rare, it's unparalleled in Pentax primes, and arguably unparalleled in non k mount primes. It may even bring King Arthur back from the dead, and honestly at this price, I'm not expecting anything less.
I wouldn't say it's exactly the Holy Grail, especially if there is a CZ version for the non-k mount. and it is not exactly unparalled among Pentax Primes, although it's one of the best and somehow behind the 200/4 macro among others.

05-29-2010, 12:00 PM   #35
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Welcome to the 135 f1.8 club, enjoy the lens it's a great piece of kit.
05-30-2010, 11:19 PM   #36
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QuoteOriginally posted by Clinton Quote
It has arrived, it's condition is even better than what I expected from the photos. The only bit of oddness is that the lens reports 1.7 as wide open to the K-7, and at 1.8 it is ever so slightly stopped down from a visual inspection. I love the idea that this lens is secretly 1.7, but I doubt that is the case.
Yes, my copy does the same thing - that is, reports f1.7 wide-open. I didn't know that at f1.8 it is slightly stopped-down - I never bothered to check mine that closely. But I will say that wide-open (f1.7 or f1.8 - I don't remember which), my copy underexposes very slightly (maybe by 1/3 stop) compared to the other aperture settings.

QuoteOriginally posted by Clinton Quote
Other than this little bug, the quality of this lens is simply surreal, and the DoF control... yummy. A few people I noted reported it as slightly soft wide open, but I'm not seeing that.
I agree with you here - while it gets even better when you stop down, it is by no means considered soft at wide-open. FWIW, my A*135 wide-open looks sharper when viewed at 100% than my FA*200/2.8 @2.8.

I'll also say that you'll find excuses to shoot with this lens, even when it is not the most convenient (in terms of weight and/or FL) to do so. Enjoy!
05-30-2010, 11:27 PM   #37
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QuoteOriginally posted by photogerald Quote
Yes, my copy does the same thing - that is, reports f1.7 wide-open. I didn't know that at f1.8 it is slightly stopped-down - I never bothered to check mine that closely. But I will say that wide-open (f1.7 or f1.8 - I don't remember which), my copy underexposes very slightly (maybe by 1/3 stop) compared to the other aperture settings.
It would be interesting to compare the indicated f1.7 vs. f1.8 settings closely to see what the difference in exposure is, and also to see if there is a noticeable difference in the rendering of the bokeh (at f1.7 the aperture should be perfectly circular).
05-31-2010, 09:35 AM   #38
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QuoteOriginally posted by photogerald Quote
It would be interesting to compare the indicated f1.7 vs. f1.8 settings closely to see what the difference in exposure is, and also to see if there is a noticeable difference in the rendering of the bokeh (at f1.7 the aperture should be perfectly circular).
Agreed. It's also interesting that the k-7 when you stop down goes from 1.7 to 2.0 directly, but when you open up, it goes from 2.0 to 1.8 to 1.7. Which is to say the stop is only available when opening up.

As for exposure time, The camera picked the same shutter speed for both 1.7 ans 1.8 when I was playing with it.

Maybe I'll ping Pentax support tomorrow about this bug.

05-31-2010, 10:27 AM   #39
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Congrats on the lens!

As for the 1.7 aperture, I have a Vivitar 105/2.5 that sometimes reports an f-stop of 2.4, but I don't think it's the lens, more likely the camera, and the only difference is a slight change in exposure. Do you use 1/3 stops or half stops?
05-31-2010, 05:56 PM   #40
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QuoteOriginally posted by Clinton Quote
Agreed. It's also interesting that the k-7 when you stop down goes from 1.7 to 2.0 directly, but when you open up, it goes from 2.0 to 1.8 to 1.7. Which is to say the stop is only available when opening up.
I'm pretty sure my K20D behaves the same way.

QuoteOriginally posted by Clinton Quote
As for exposure time, The camera picked the same shutter speed for both 1.7 ans 1.8 when I was playing with it.

Maybe I'll ping Pentax support tomorrow about this bug.
Do let us know what they say.
05-31-2010, 05:59 PM   #41
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QuoteOriginally posted by farfisa Quote
Do you use 1/3 stops or half stops?
I like the control so I use 1/3 stops.
05-31-2010, 08:37 PM   #42
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QuoteOriginally posted by Clinton Quote
Maybe I'll ping Pentax support tomorrow about this bug.
The Sigma 28mm f/1.8 EX DG Macro AF lens also shows up as f/1.7 to all Pentax bodies when the lens is at f/1.8, which makes me now wonder if there is some design issue with the Pentax auto-aperture system which causes f/1.8 to get reported as f/1.7 for some lenses.
05-31-2010, 09:04 PM   #43
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QuoteOriginally posted by nater Quote
The Sigma 28mm f/1.8 EX DG Macro AF lens also shows up as f/1.7 to all Pentax bodies when the lens is at f/1.8, which makes me now wonder if there is some design issue with the Pentax auto-aperture system which causes f/1.8 to get reported as f/1.7 for some lenses.
I dont think it's a bug. it's rather that the Sigma 28/1.8 has an approx. aperture value of f1.7. it is probably playing in between 1.7 and 1.8 but rounded off at 1.8 instead. there are some lenses like this IIRC.
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