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06-24-2010, 07:47 PM   #16
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QuoteOriginally posted by Lowell Goudge Quote
someone commented that this may be also a function of focusing distance, does the aperture change if you focus to infinity and read F4? I did not see a response to that. Also how close to 70 does it get to and remain at F4?

I would be interested. it may be they are playing on permissable tolorances, and if so, that would be too bad, i.e. at 65 its F4 but at 70 it is 4.5 . Also can you tell us the filter diameter, and the diameter of the front element.

simply put an F4 lens at 70mm should be a diameter of about 17.5mm only.
Umm.. I responded with... " let me check.. this happens both ways ;(." So it happens both ends of focus ;/. Whether it is macro or not also. Umm... filter diameter is 72mm I believe...

I can't really explain how close to 70 does it get and remain at f4 because anything about 50mm is shown as 50mm on the data. So... I'm just going to take some pictures to show you guys. Please excuse the Sony P&S ;P.

Got some pictures up.

Excuse the blurry.

At F4.5


Here are the Focus ring adjustments that keeps it at F4.5 still





These two are about the threshold where they change from 4-4.5



At 70mm


This is just when it's below 70mm to show you it can actually go to F4.0


Sorry ;( going to sleep... and going away first thing in the morning... so might not be able to reply to the thread. Sorry!


Last edited by NecroticSoldier; 06-24-2010 at 08:29 PM.
06-26-2010, 09:32 AM   #17
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Not sure if this is related, but fwiw, I've also had/have trouble with a Sigma lens - I used it for a couple of years with no issues, then last year it started giving me trouble - the camera would no longer recognize it when mounted and didn't seem to be able to sense the aperture at all - it would just display f-- as for an M lens. After several mount/unmount operations, it would start to work. I'm not sure what it's wrong with it. Mechanically it looks ok, it is clean and it never fell or was subjected to any shock. There was a time when Sigma stood for Significant Malfunctions, so maybe it's just a case of that.

Consider servicing it if it's still in warranty.
06-26-2010, 04:29 PM   #18
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Is it possible that rather than f/4 not being f/4, maybe 70mm is a bit longer than 70mm, at which point max zoom can't do f/4? So yes, you are getting f/4 at 70mm, but as you go beyond it, the max aperture needs to decrease. Best idea I've got anyway.
06-27-2010, 12:07 AM   #19
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QuoteOriginally posted by Jodokast96 Quote
Is it possible that rather than f/4 not being f/4, maybe 70mm is a bit longer than 70mm, at which point max zoom can't do f/4? So yes, you are getting f/4 at 70mm, but as you go beyond it, the max aperture needs to decrease. Best idea I've got anyway.
;( I don't think so... because it stops right on 70.

06-27-2010, 01:27 AM   #20
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But what I'm saying is, maybe the zoom ring is off. It seems the change-over point is just at the beginning of 70. But as you get it set at full 70 on the ring, maybe that's pushing to say 73 in reality, and it still somehow registers and changes the aperture. Think of how some lenses focus past infinity. Now imagine that when the lens was assembled, it was done slightly off so that when it was focusing past infinity, it only showed as just being at infinity.
06-27-2010, 04:46 AM   #21
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One thing to consider in all internally focused lenses is that focal length is only accurate at infinity. That is part of the test standard. It would be worth also looking at the camera a little. Make sure you are in manual mode. In the film slr forum there is a thread about a pz-1 that would not go to f22. Adam made an observation that I confirmed that specifically in hyper program mode the camera would not permit apertures to be selected outside the possible metered range even if it was within the lens capability. Maybe it Is not allthe lens but the camera mode.

Regardless the other point raised about the lens being longer than 70mm this is easy to test, just shoot a distant subject of known height and distance and measure. The height on the sensor
06-27-2010, 10:52 PM   #22
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QuoteOriginally posted by Lowell Goudge Quote
One thing to consider in all internally focused lenses is that focal length is only accurate at infinity. That is part of the test standard. It would be worth also looking at the camera a little. Make sure you are in manual mode. In the film slr forum there is a thread about a pz-1 that would not go to f22. Adam made an observation that I confirmed that specifically in hyper program mode the camera would not permit apertures to be selected outside the possible metered range even if it was within the lens capability. Maybe it Is not allthe lens but the camera mode.

Regardless the other point raised about the lens being longer than 70mm this is easy to test, just shoot a distant subject of known height and distance and measure. The height on the sensor
I should do this when I get back home ;( currently at Vancouver airport... leaving to Hong Kong airport ;P.

Thanks for the info though, I never knew that!

Also... yeah maybe it might be the thing like infinity.
06-28-2010, 09:32 AM   #23
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I wonder if it's just mine... should I send it back to the guy who I bought it from to get a repair or something? because I don't think that US warranty works in Canada. I really like this lens though.

06-28-2010, 11:02 AM   #24
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Justin, A lot of us buy our lenses From Canada because in the onset, it's cheaper. Sometimes by 100's of dollars depending on the exchange rate. You might want to check and see exactly What type of warranty your lens has, ask the seller to set up a service return (if in Canada), and make arrangements to have it sent back to you. First though, find out exactly what you have.

06-29-2010, 07:46 PM   #25
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QuoteOriginally posted by JeffJS Quote
Justin, A lot of us buy our lenses From Canada because in the onset, it's cheaper. Sometimes by 100's of dollars depending on the exchange rate. You might want to check and see exactly What type of warranty your lens has, ask the seller to set up a service return (if in Canada), and make arrangements to have it sent back to you. First though, find out exactly what you have.

Thanks Jeff! Will do once I get home. Currently though... my lens is fogging on the front element every time I leave the hotel... Hong Kong! First time shooting here.
06-29-2010, 08:17 PM   #26
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Fogging? Are you staying in a refrigerator?

07-01-2010, 09:25 PM   #27
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QuoteOriginally posted by JeffJS Quote
Fogging? Are you staying in a refrigerator?

LOL! I guess so, going to Malaysia now ;D, had lots of fun in Hong Kong, the camera store was just loaded with Pentax. It was Pentax Heaven. I fit in also cause there's many photographers there.
07-02-2010, 02:40 AM   #28
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Just an added bit of info. A Tamron 70-200 I was using would only adjust aperture in 1/2 steps when maxed out on the long end, but setting just shy of max would let it meter in 1/3 steps, as I have things set to do. Only noticed it in playing around, no shots to check the EXIF. Will give it a shot when I get it back next week if you'd like. Just send me a reminder if you do, because I will forget.
07-02-2010, 03:30 AM   #29
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QuoteOriginally posted by Jodokast96 Quote
Just an added bit of info. A Tamron 70-200 I was using would only adjust aperture in 1/2 steps when maxed out on the long end, but setting just shy of max would let it meter in 1/3 steps, as I have things set to do. Only noticed it in playing around, no shots to check the EXIF. Will give it a shot when I get it back next week if you'd like. Just send me a reminder if you do, because I will forget.
Sure thing ;D I'mma come back from Malaysia next week. Hope I still remember.
07-07-2010, 12:52 PM   #30
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Just got the replacement copy, and it permforms the same way. At 200mm, f/3.2 is not available. But at a bit less than 200mm, it is. Also, if I go just a bit less than 200 @ f/3.2, and then zoom it to 200, the aperture automatically changes to f/2.8.
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