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05-12-2008, 07:52 PM   #1
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Sigma 70-200 f/2.8 questions

In searching for some decent long glass I've arrived at this lens. Mainly because I do a fair bit of low light work for my church but also because I've found the Sigma 100-300 f4.5-6.7 to be rather poor and inconsistent for motorsport.

I've seen images from the lens with the Sigma 1.4x TC but how much does the IQ suffer with the 2x TC? I'd be looking at the 2x TC since 140-400 f/5.6 is plenty fast and long enough for what I plan to use it for.

Also what is the going rate for this lens used? I won't be looking at the new version with HSM since I don't plan on upgrading from my K100D for another year or two.

05-13-2008, 04:39 PM   #2
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Last few I have seen sell for approx $1000AUD. I have heard of some good copies and some average copies as well.

I am waiting for the Tamron 70-200 f/2.8 that is meant to be released soon ... and that's in the range of $700US ... so about $750AUD. I saw some test images on another website and it looked extremely promising.
05-13-2008, 07:18 PM   #3
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QuoteOriginally posted by nobbsie Quote
In searching for some decent long glass I've arrived at this lens. Mainly because I do a fair bit of low light work for my church but also because I've found the Sigma 100-300 f4.5-6.7 to be rather poor and inconsistent for motorsport.

I've seen images from the lens with the Sigma 1.4x TC but how much does the IQ suffer with the 2x TC? I'd be looking at the 2x TC since 140-400 f/5.6 is plenty fast and long enough for what I plan to use it for.

Also what is the going rate for this lens used? I won't be looking at the new version with HSM since I don't plan on upgrading from my K100D for another year or two.
I posted both of these a while ago because someone asked the same question

https://www.pentaxforums.com/forums/187646-post19.html
https://www.pentaxforums.com/forums/208249-post1.html

One thing you need to consider is exposure. I don't know how the K100D meters and behaves, but the K10D has some metering problems, and with the teleconverter either 1.4x or 2x (I have them both) it will over expose by 1 -1.5 stops but is consistent. You should as a minimum run a test just so you know how your camera behaves.
05-13-2008, 08:38 PM   #4
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I have that setup and it works well.. here are some samples in the same thread that Lowell linked

https://www.pentaxforums.com/forums/183940-post4.html


QuoteOriginally posted by Lowell Goudge Quote

One thing you need to consider is exposure. I don't know how the K100D meters and behaves, but the K10D has some metering problems, and with the teleconverter either 1.4x or 2x (I have them both) it will over expose by 1 -1.5 stops but is consistent. You should as a minimum run a test just so you know how your camera behaves.

Interesting that you mention this, I found the same to be true on both my istDS and my K10 with the Sigma 70-200 and 2xTC. I do not find an over exposure problem with my Tokina 400 f/5.6 and 1.5xTC so I *think* it is something to do with the Sigma combo (I have a feeling that the TC is not really 2x fooling the camera and letting in slightly more light).. just a theory


John

05-13-2008, 09:45 PM   #5
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Thanks for the replies, if the exposure problems are consistent then that's simple to correct. This combo looks very good to me simply because it can be useful for practically any situation.

Having said that I doubt I'd notice much difference between this and the M75-150 f/4 I'm using for low-light work. Even with a 1 stop gain I'll most likely still need to shoot at ISO1600. I'm wondering if upgrading to the K20D would be a smarter move simply for the better high ISO performance.
05-14-2008, 04:59 AM   #6
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QuoteOriginally posted by palmor Quote
Interesting that you mention this,
edit note: my comment on metering
QuoteQuote:
I found the same to be true on both my istDS and my K10 with the Sigma 70-200 and 2xTC. I do not find an over exposure problem with my Tokina 400 f/5.6 and 1.5xTC so I *think* it is something to do with the Sigma combo (I have a feeling that the TC is not really 2x fooling the camera and letting in slightly more light).. just a theory


John
John

I don't know the DS, but I own both the K10D and *istD.

The *istD meters perfectly with or without the TC. The K10D adds 1 1/2 stops (i.e. over exposes) with the TC.

I think the reason you don't see it with the tokina 400 f5.6 is because the maximum apature, either with or without the TC is above the point on the K10D where the metering is non linear.

the sigma 70-200 F2.8 on the other hand is right in the middle of the real non linearity with metering, and changing it to either F4 with the 1.4x or F5.6 with the 2x really changes what the camera sees. Unfortunately the contacts on teh TC pass right through and as a result, the camera still thinks it is at F2.8 and over exposes as a result.

see the attached link as you might find this interesting

Please excuse the title, as it relates to all the things I had been called when presenting my argument about metering.
https://www.pentaxforums.com/forums/241716-post69.html
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