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05-29-2012, 04:35 PM   #1
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how much weight can lens threads hold?

So I have been playing with front mount wide angle lenses (yea I know the issues about image quality loss and such). I got a lens on ebay recently and was a little worried that it would be too small around. I couldn't have been more wrong. What I received was a box with a brick in it!!!! The lens is a century optics 0.7x lens that weighs 22.4oz. The rear element (the glass, not the whole lens) is about 72mm and the front element is about 92mm. This is a rather huge, heavy beast. The lens that I at least initially want to try it with is a tamron xr (not xr di) 28-200mm with 62mm plastic filter threads. I was also thinking about trying it with some primes to get a fast wide lens (like a 35mm 1.7 cheap).
Can the lens threads even take that much weight? Fyi the tamron is internal focusing so the weight is not bearing on moving parts when auto focusing. It would bear on the zoom but I have already learned when using heavy attachments to point the camera up or down to take the weight off the lens when zooming. The lens would be primarily used at the wide end where the lens is at it's shortest too. If I were to try it with some old MF primes, the weight of the lens would be bearing on the moving parts when manually focusing.

05-29-2012, 04:56 PM   #2
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My heaviest lens is a Rubinar Makpo 1000/10 mirror weighing 1760g / 8lbs 3.9lbs with an M42 thread. I mount it on my K20D with no problem. Your midget 1.5lb lens is nothing in comparison. In other words: Don't sweat it!

Last edited by RioRico; 05-29-2012 at 07:07 PM.
05-29-2012, 06:01 PM   #3
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I think he's talking about the filter ring actually. A plastic one, in fact.
05-29-2012, 06:26 PM   #4
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QuoteOriginally posted by RioRico Quote
My heaviest lens is a Rubinar Makpo 1000/10 mirror weighing 1760g / 8lbs with an M42 thread.
There is some problem in your conversion. A pound is 454g. Your lens is only 3.87 lbs, not 8 lbs !

QuoteQuote:
Your midget 1.5lb lens is nothing in comparison. In other words: Don't sweat it!
I beg to differ about not sweating it, it really depends on what kind of adapter and mount you have .

I have a Rokinon 800mm mirror which is 936g, a little over 2 lbs. It is already a problem with a cheap T-ring mount to the point where the lens is so front-heavy that there is some visible space between the t ring and the camera where dust could get in. Unfortunately, that lens doesn't have a dedicated tripod mount.
I'm in the process of getting a better T-ring. See this thread : https://www.pentaxforums.com/forums/pentax-camera-field-accessories/187107-wh...t-adapter.html .

05-29-2012, 06:46 PM   #5
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It is a front mount wide angle lens so it will be attaching to the front of a regular slr lens with the filter threads. It is the filter threads on the front of the main lens that I am worried about breaking, not to mention any other sort of damage with that much weight hanging off the front.

In other words, I put my tamron 28-200mm on the camera and screw this 1.5lb wide converter to the tamron lens. I'm worried about breaking the filter threads on the front of the tamron. Likewise if I were to use it with an old manual focus 50mm, that weight would be on the front when focusing.

The wide angle is this lens here

Century | .7X HD Wide Angle Converter for Canon XL | 0VS-07CV-XL2

It is a bayonet mount but I have a similar smaller lens and it was easy enough to convert to filter threads. I'll post some pics in a bit.
05-29-2012, 06:57 PM   #6
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QuoteOriginally posted by ripit Quote
It is a front mount wide angle lens so it will be attaching to the front of a regular slr lens with the filter threads. It is the filter threads on the front of the main lens that I am worried about breaking, not to mention any other sort of damage with that much weight hanging off the front.

In other words, I put my tamron 28-200mm on the camera and screw this 1.5lb wide converter to the tamron lens. I'm worried about breaking the filter threads on the front of the tamron. Likewise if I were to use it with an old manual focus 50mm, that weight would be on the front when focusing.

The wide angle is this lens here

Century | .7X HD Wide Angle Converter for Canon XL | 0VS-07CV-XL2

It is a bayonet mount but I have a similar smaller lens and it was easy enough to convert to filter threads. I'll post some pics in a bit.
Interesting, that is one heavy wide converter. And expensive, also. At 0.7x you will only get down from 28 to 19.6mm focal length. You can find 18-200 or 18-250 lenses that would serve you better, for much less.
05-29-2012, 07:01 PM   #7
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The picture doesn't do it justice about how big and heavy it is (seems to look smaller in comparison than in real life). Must be the angle I shot at. Top left is the ist-ds kit lens for size comparison. Bottom is a similar bayonet mount lens that has been converter to filter thread mount. Top right is the new lens.
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05-29-2012, 07:08 PM   #8
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QuoteOriginally posted by madbrain Quote
There is some problem in your conversion. A pound is 454g. Your lens is only 3.87 lbs, not 8 lbs !

I beg to differ about not sweating it, it really depends on what kind of adapter and mount you have .
I corrected the numbers. I shouldn't use a calculator before the painkillers wear off...

05-29-2012, 07:09 PM   #9
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QuoteOriginally posted by madbrain Quote
Interesting, that is one heavy wide converter. And expensive, also. At 0.7x you will only get down from 28 to 19.6mm focal length. You can find 18-200 or 18-250 lenses that would serve you better, for much less.
It is for an obsolete mini dv camcorder (a very expensive broadcast quality one in its time) and has a proprietary bayonet mount. While people usually try to get a couple of hundred for these older obsolete ones, sometimes they go cheap. I paid 29$ shipped for a new one (no reserve ebay auction from a camera dealer). You have to love front mount tele and wide converter crappy resale values.
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