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08-19-2009, 08:52 AM   #1
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Vivitar 90mm 2.5 Macro question

I have a question for any owners of the Vivitar 90mm 2.5 Macro and matched 1:1 converter. I just sold a copy of this lens in the marketplace and the buyer noticed that when the converter was on the lens the aperture would not open all the way to 2.5.

For those with experience, is this a normal property of using the lens and converter together? I don't see why it would be. When testing the lens I didn't notice the problem and nothing seemed out of the ordinary, so I thought it might be a normal function of using the converter on the lens.

08-19-2009, 09:05 AM   #2
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QuoteOriginally posted by Votesh Quote
I have a question for any owners of the Vivitar 90mm 2.5 Macro and matched 1:1 converter. I just sold a copy of this lens in the marketplace and the buyer noticed that when the converter was on the lens the aperture would not open all the way to 2.5.

For those with experience, is this a normal property of using the lens and converter together? I don't see why it would be. When testing the lens I didn't notice the problem and nothing seemed out of the ordinary, so I thought it might be a normal function of using the converter on the lens.
Of course! It is normal for the lens to reduce the aperture when it is at the closest focusing distance and ESPECIALLY when a close focusing CONVERTER is attached!!! It's pretty similar to adding a teleconverter except not quite as big of a difference aperture wise.
08-19-2009, 06:25 PM   #3
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I thought that could be the case. However, the fact that the f-stop remains the same, at least as reported by the camera, when using my Sigma 1.4x TC threw me off. I also wasn't sure if aperture reduction when close focusing was a actaul physical closing down of the aperture, or merely a reduction in light which equated to closing the aperture to a certain degree. Thanks for the info.

Anyway, I'd still feel better if I heard from an owner of the lens and converter that this was a normal behavior for the lens.
08-19-2009, 06:48 PM   #4
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QuoteOriginally posted by Votesh Quote
the buyer noticed that when the converter was on the lens the aperture would not open all the way to 2.5.
What does "the aperture would not open all the way to 2.5" means exactly?

If I'm not mistaken, the lens has PK mount so "the aperture would not open all the way to 2.5" can't mean the camera body can not set the lens's aperture to 2.5.

With the exception of the Pentax 1.7X AFA, I've never seen a TC (including the ones with PKA mount) that modifies the aperture setting signal.

I don't have the particular lens and converter, but if "the aperture would not open all the way to 2.5" means the aperture ring on the lens can not be set at 2.5, there is some problem.

There are no electrical contacts between the camera body and the lens. The camera doesn't know anything about the lens and the converter. The lens doesn't know if the converter is there. Why is there the problem only when the converter is attached? I'm confused.

I know I'm no help. But I'm just curious.

Edit to add: At close range, the effective aperture is not the same as the setting of the aperture ring. The aperture markings are calculated at infinity. In general, at 1:2, the lens is 1 stop slower than the setting; at 1:1, 2 stops slower.


Last edited by SOldBear; 08-19-2009 at 06:57 PM.
08-19-2009, 09:23 PM   #5
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well i guess it is normal... i had a tamron 90mm f2.5 macro adaptall and a matched 1:1 converter.. .and whenever the converter is connected it acts as 180mm F5.. and the aperture setting on the lens starts from 5 (cannot be turned towards 2.5)... .. and yeah the camera shows different aperture readings..not sure why.. i used a PKA mount.... i once thought i had a 180mm F2.8 1:1 macro... seeing the pic properties.. . that would have been good.. .
08-19-2009, 10:19 PM   #6
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Here is a quote from the e-mail:
"When attaching 2X, to the lense, the*aperture value just stuck*between 2.5-4, can not*go to 2.5."

So, when the lens is on its own it opens all the way to 2.5 with no problem. However, it seems that when the converter is attached to the lens, the converter physically prohibits the aperture from opening all the way, with the max aperture being somewhere between 2.5 and 4 when the lens is attached.

QuoteOriginally posted by SOldBear Quote
What does "the aperture would not open all the way to 2.5" means exactly?

If I'm not mistaken, the lens has PK mount so "the aperture would not open all the way to 2.5" can't mean the camera body can not set the lens's aperture to 2.5.

With the exception of the Pentax 1.7X AFA, I've never seen a TC (including the ones with PKA mount) that modifies the aperture setting signal.

I don't have the particular lens and converter, but if "the aperture would not open all the way to 2.5" means the aperture ring on the lens can not be set at 2.5, there is some problem.

There are no electrical contacts between the camera body and the lens. The camera doesn't know anything about the lens and the converter. The lens doesn't know if the converter is there. Why is there the problem only when the converter is attached? I'm confused.

I know I'm no help. But I'm just curious.

Edit to add: At close range, the effective aperture is not the same as the setting of the aperture ring. The aperture markings are calculated at infinity. In general, at 1:2, the lens is 1 stop slower than the setting; at 1:1, 2 stops slower.
08-19-2009, 10:27 PM   #7
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The buyer has told me that he has used another copy of this lens, and the issue at hand did not occur.
08-20-2009, 07:41 AM   #8
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I have this lens and converter and I can say that the converter is a little bit tricky to properly install to the lens. Try this:

1. Set lens to F2.5.
2. Line up the red dots on the lens and converter and attach lens to converter.
3. Twist converter clockwise using the tripod mount portion of the converter until an audible click is heard.
4. Install the lens on the camera.

The lens should work at all apertures. The aperture should stay wide open when set to F2.5.

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