[leechris5666]

Under proper conditions, say temperature & humidity, how long a lens can be kept before it dies? How to vertify a lens dead?

[maximilianyuen]

Never heard of such a thing.....

[pongyee]

First of all, proper conditions varied from place to place. You may control the relative humidity or temperature, say, by keeping them in an electronic cabinet so that fungi might not eat up the coating of the lenses. However, other factors such as chemical changes of the glue used between the lens' group, mechanical failure of the motor and other moving part inside the lens' barrel (they would refuse to repair your equipments when the spare parts are being ceased from production ) .

Nowadays, they make lenses with moulded plastic...

[leechris5666]

Thanks pongyee c hing.

That means reasons for making a lens malfunctional can be:
1. fungi / mould growth,
2. chemical change of glue,
3. mechanical breakdown of moving part, & etc.

Few more questions:
Would lens deform / degrade over years affecting the picture sharpness? Is the span of life for a lens very long without the above unfavourable factors?