topic Re: sigma 150-600mm in EF & RF Lenses

sigma 150-600mm

paulbrogden10 — Mon, 21 Mar 2016 10:49:18 GMT

just a quick question does it get dust in it easily seen some for sale with dust in it? makes you think why as I thought the sport was sealed.

Re: sigma 150-600mm

TTMartin — Mon, 21 Mar 2016 12:11:48 GMT

@paulbrogden10 wrote:
just a quick question does it get dust in it easily seen some for sale with dust in it? makes you think why as I thought the sport was sealed.

There is a sport and a C. Are the ones you are seeing with dust the sport?

Re: sigma 150-600mm

paulbrogden10 — Mon, 21 Mar 2016 12:13:51 GMT

yes sports

Re: sigma 150-600mm

ebiggs1 — Mon, 21 Mar 2016 20:22:08 GMT

All lenses get dust in side. That is not any different with the Sigma. If a lens zooms it is going to get dust inside. You have so many guys, some on this forum, that don't know what they are talking about. They like to read reviews which makes them think they are experts.

If you already bought the lens just go out and use it. Enjoy it. And stop reading all those reviews! That is not how you learn or get experience.

Re: sigma 150-600mm

Waddizzle — Tue, 22 Mar 2016 01:39:53 GMT

@paulbrogden10 wrote:
just a quick question does it get dust in it easily seen some for sale with dust in it? makes you think why as I thought the sport was sealed.

I don't think it is practical, nor physically possible, to make a lens that is absolutely sealed against a vacuum, not unless the lens had absolutely no moving parts, whatsoever. In order for a lens to internally move lens elements back and forth inside of the lens, an exchange of air, or a volume of air, must be displaced from one side of the lens element to the other.

Similarly, any lens that changes its' physical length must somehow accomodate this air displacement when internal elements move back and forth to focus the lens. If not, the lens will either suck air in, more and more as it is used, until it reaches a critical pressure differential and BAD happens. Or, more and more air can be pushed out of the lens body, until it reachess a critical pressure differnetial until EVEN WORSE happens.