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04-30-2011, 10:30 AM   #1
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DA 35mm F2.4 - Plastic Mount Question

This lens is now ridiculously cheap in the UK (found for as little as 130 GBP) and the reviews all seem fairly positive...

I do however have some reservations regarding the plastic mount...

I know there is a member here of PF that broke his mount in a fall while horse riding and although he managed to replace his, I don't feel I have that capability to do such repairs...
Further more, as a regular mountain bike user I find it worrying that I may also break the mount in a similar manner during a fall... NB... Although I generally land on my head...

Has anybody else here broken the plastic mount on the DA 35 2.4 and under what circumstances?

How durable is this mount in general?
Will it wear out though 'normal' lens changing routines?

Advance thanks...
Dave

04-30-2011, 10:50 AM   #2
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QuoteOriginally posted by DaveHolmes Quote
that broke his mount in a fall while horse riding
Wow, that did not break the lens body but mount; all the shock must have absorbed by the mount, as a result nothing happened to the glass and rest of the lens body. A metal mount might transfer the shock to .......!
04-30-2011, 10:59 AM   #3
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There has been another DAL 55-300 with a broken mount here on PF.

To be honest, I would not worry. Metal mount might rip the bajonet of the camera.
04-30-2011, 01:28 PM   #4
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To be honest, I feel your concerns are totally unnecessary.
The fall, drop etc necessary to break the mount on the DA35 would do damage to any lens.
I have the DA35 and would highly recommend it, no qualms.

04-30-2011, 03:06 PM   #5
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I think it is no issue either. If you don't break the mount, something else has to give. I don think anyone buys a lens based on its maximum impact resistance...
04-30-2011, 04:09 PM   #6
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Original Poster
Cheers all... Don't think it'll be an issue either...

However... Think I'll pass on it as I have the Tamron 17-50mm 2.8 anyway and that's sharp enough...
Think LBA nearly took control there...
Gonna save for an FA50 f1.4 as That's a focal length I could use more in an AF-lens...

Cheers for the comments
04-30-2011, 06:20 PM   #7
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Metal feels better, but it is not stronger. It will just bend instead of snapping, and will transfer the force into the camera body.

If you are smacking the lens hard enough to break the plastic mount, I would be most concerned about messing with the optics (bumps that hard can do that).
04-30-2011, 06:30 PM   #8
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QuoteOriginally posted by paperbag846 Quote
Metal feels better, but it is not stronger. It will just bend instead of snapping, and will transfer the force into the camera body.

If you are smacking the lens hard enough to break the plastic mount, I would be most concerned about messing with the optics (bumps that hard can do that).
I agree that the plastic mount is perfectly fine and that if you smack a lens hard enough to break the plastic mount, you've hit it pretty hard and probably have other things to worry about (like the optics and their alignment).

That said, for the record, a given part made out of metal is most certainly stronger than the same part made out of plastic. Whether a piece of metal or plastic bends before breaking has to do with its ductility, not its strength.

05-01-2011, 03:49 AM - 1 Like   #9
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I find the 35mm F2.4 is a fantastic lens optically, so don't pass it up because of the plastic mount. I wish there were more like this. Metal build for me means mostly higher weight and price.
05-02-2011, 08:14 PM   #10
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QuoteOriginally posted by SpecialK Quote
I don think anyone buys a lens based on its maximum impact resistance...
LOL. But hey thats a new marketing line, first weather resistant WR, then impact resistant IR, no that won't work (Infra red), but how about AP - Armour Plated.
05-03-2011, 01:31 AM   #11
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QuoteOriginally posted by dgaies Quote
metal is most certainly stronger than the same part made out of plastic
A lens made out of metal is not more durable than one made out of plastic. Any impact that would break the plastic would also damage the glass, and metal would do an even worse job of absorbing the impact.

For lenses, metal and plastic are really just cosmetic. In fact, metal is at a disadvantage because it expands/contracts more to temperature changes.

Don't worry about the mount.
05-03-2011, 04:18 AM   #12
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QuoteOriginally posted by paperbag846 Quote
A lens made out of metal is not more durable than one made out of plastic. Any impact that would break the plastic would also damage the glass, and metal would do an even worse job of absorbing the impact.

For lenses, metal and plastic are really just cosmetic. In fact, metal is at a disadvantage because it expands/contracts more to temperature changes.

Don't worry about the mount.
I have no major concerns about a plastic mount on a lens; reread what I've written either in this thread, or other posts I've made, and you will see that this has always been my position. However, that does not take away from the fact that metals are inherently stronger than plastics, that's just a fact that cannot be disputed. The actual measured strengths of these materials is not a debatable point. This is what I actually do this for a living, measure the strengths and other properties of different materials.

Also, for the record, plastics expand and contract considerably more than metals due to changes in temperature. Steels and aluminums have a linear thermal expansion coefficient of about 5-13 microinch/inch/F while most plastics have a linear thermal expansion coefficient in the range of 50-125 microinch/inch/F. So for a given change in temperature, plastic expand and contract about 10x as much as metals (depending on the specific metal and plastic you are comparing).
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