I think longer zoom lens likely to attract more dusts.
It is normal. Even my PNS camera got dust.
dust if everywhere, theres no escaping it. anw a spec of dust if not gonna affect image quality. even shattering the front element of ur lens is not gonna significantly degrade ur image quality (still usable). go search google, there are some blogs where unlucky ppl shatter their lens and yet still can use them cos the electrical systems are fine. at wide apeture the lines and shards of glass dissappear (same effect as shooting thru a wire fence)
Canon 550D Sigma 17-70mm f2.8-4 HSM OS | 50mm f1.8 II | 55-250mm f4-5.6 IS | Di622 | BP-550D
Ha ha, so u really think they are so different?
For a air and water they are different but very close, as long as air can flow in water will too. The different is so small and only if u look at it from the micron level than u will be able to seperate water and air. Only way control this at constant pressure and testing parameters is to use a membrane where the pores of the membrane is so so so small in the scale of micro level that it only allow air in and not water. This material is so expansive and heavily patent that I am sure no camera company will use it in their lens.
So u think the camera maker is a membrane manufacturer?
Certainly weather seal is not a 'water tight', 'air tight' proof.
However i think it is more water proof than air proof if we just paid a little attention to the nature of weather.
1) Rain or droplet fall from high to low position due gravity.
2) Air does not 'obey' gravity and can flow into any tiny hole when there is wind or changes direction due to a change of temperature (hot air rise and cold air take up the 'empty' space.
A simple test:
Tho air and water show a similar properties in surface tension
1) Pocket of bubbles (in a cup of water) rushes upward only no matter how hard you shake in diff. direction
2) How hard you throw a cup of water it will still fall to the ground.
Thu more Lens more 'water proof' is a combination of factors (nature and human) and water tension but 'air proof' will have much less advantage.
if L lens is water proof ...
i think i bathe with my lens everyday haha ...
den i can bring my camera + lens go snorkling WITHOUT buying EXPENSIVE underwater casing haha ... can save alot money + take WONDERFUL photo
Water Resistant does not mean you can go diving also... they are classified by their degree of water resistance to indicate how well can it is sealed against ingress of water + pressure.
L Lens (same type of Lens) will have diff price with diff. degree of water resistance.
I suggest you read up on what "weather-resistant" means. Simple water splashes are fine so long as there is no additional barometric pressure on the seals.
my new 50 1.8 has more dust than my zoom lenses. no idea why.
Canon.550D|EF-S 18-55mm| EF-S 55-250mm| EF-S 18-55mm 1:3.5-5.6| EF 50mm 1:1.8|Di866