Lens weather sealing for zooms

Hello all

I am a novice but have had some experience with micro 4/3 for about 10 years. I am considering purchasing the Panasonic 14-140 f3.5-5.6 zoom as an all-around travel lens but I have a general question about weather sealing. My previous zoom was the Panasonic 45 -175.  Since it's length didn't change with zoom range it didn't suck in and push out air as you adjusted the focal length.  With the Pana 14-140 every time you adjust focal length you are encouraging air movement inside the lens.  It seems to me that a weather sealed lens would be less likely to entrain dust particles as opposed to a non weather sealed lens.  Hence I am trying to decide whether it's worth spending the extra $200 or so dollars to buy the newer version of Panasonic 14-140.

From reading this forum it seems like most of you would say it's a waste of money but I can't get over the idea of all these little dust particles settling on the inside glass (plastic) haha.

Thanks

dkrohn wrote:

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From reading this forum it seems like most of you would say it's a waste of money but I can't get over the idea of all these little dust particles settling on the inside glass (plastic) haha.

Thanks

An external zooming lens offers no protection against water, solids, or against condensation. A "dust and splash resistant" external zooming lens offers only limited protection against water and solids (and none whatsoever against moisture). By design, because the lens must breathe large volumes of air in operation, the protection is limited by the type and size of the water repelling mesh used to "filter" the air inlet. No matter what marketing spin the manufacturers wrap around it. Fine dust will find it's way onto the interior surfaces and over time will fog the glass. So will moist air. If you do not want that, get an internal zooming lens instead.

This is what my user manual of my PL100-400 says:

SQT1200-4 Operating Instructions

An interesting twist: the above is the international Operating Instructions SQT1200-4 that came with my lens. The US American Owner's Manual SQT1199-1 has a slightly different text. It does NOT say "The dust and splash resistant of the lens will not prevent the entry of dust or water droplets completely. Take the following precautions to provide satisfactory dust and splash resistance performance...." .Maybe this means US customers can have the lens internally cleaned for free?

SQT1199-1 Owner's Manual

Chris 222 wrote:

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Contrary to internet forums lore, the displaced volume of air on most zoom lenses is actually very small.

1) It depends on the lens in question.

- For Zooms like the 12-40pro I agree with you, this lens expands very little and the volume of displaced air is very small, Therefore the amount of fine dust (dust finer than what the hydrophobic filter mesh can retain) is very small, and it will take a very long time before you can see a dust coat on the inner glass surfaces. It does happen after some time though, and on that particular lens it is the lens surfaces right before and after the aperture that are first affected.

- For a Zoom like the PL 100-400, the displaced volume is quite large. This lens expands by 7.9cm. The external diameter of the expanding tube is 6.3cm. Lets assume an inner void diameter of only 5.0cm. The area is 2.5cm*2.5cm * 3.14 = 31,40cm2, over 7.9cm expansion that is 31.4cm2 * 7.9cm = 272mL. That is almost the volume of a CocaCola can. For each time the lens is zoomed the whole range from 100mm to 400mm. And that is quite often, because you transport this lens collapsed to 100mm. Assume in one day of use, you fully zoom this lens 30 times, you are pumping 8L of air through it. After 100 days of use that would be nearly one cubic meter. If that air was laden with fine dust, that will show up as fine deposit on the internal lens surfaces.

Also, this lens is open at the back. Better avoid zooming it without a WS camera attached, as you suck in unfiltered air from the rear.

2) For a tele lens like the PL 100-400, it only takes two zooming strokes to completely exchange all the air inside. If that happens to be moisture saturated warm air, like in the tropics, and you then bring the lens inside an airconditioned cool hotel room, the humidity in the air will condense onto the inner surfaces. And that can become messy, if those surfaces are already coated with some fine dust. Cause when the droplets dry, they will leave visible drying marks behind. Also, ideal conditions for fungi (spores introduced with the dust), they will thrive finding both water and food (dust)! So when coming into a cool room from a moist outdoor, better cycle the zoom action a few times to replace the moisture laden air inside. And when coming from a cold airconditioned room out into tropical conditions, let the lens warm itself up before using it.

The above means that the useful life of some external zooming lenses can be shorter, than what you can expect with internal zooms. It depends on the environment, and on how careful you use the lens. And note, some lenses like the PL 100-400 simply cannot be sent to the service center for internal cleaning, because they cannot be opened without losing alignment. If you do not like that, better choose an internal zooming lens - it will be larger and heavier though. Like the 40-150pro, this lens is sealed and does not breathe air, making it ideal for things like dusty action sports.

As you say, exfending lenses suck in air with moisture and dust. I use even my Olympus pro lenses like the 12-100 as if it were not sealed in any way.
Also be aware, that having moisture of any kind inside the camera or lens at once voids any warranty.

However, I find there is also no reason to get overly terrified. I never had problems with a few drops on lenses, even those with bad BQ like the O 4-5.6 40-150R. And for 3 years I used my Ricoh GR together with the GX7 in the same environment. And while the GR had twice problems with dust (the lens didn't move in and out any more, and if, only with some screeching sound) and eventually died with the infamous sticky aperture syndrome, which might or might not have to do with dust, the GX7 and my M43 lenses never had any problem in spite of many many lens changes.

Peter

dkrohn wrote:

Thanks for everyone's responses. I decided on the mark II PL 14-140 probably because I like to waste money as opposed to worrying that a used lens was returned due to being a poor copy. Does anyone have recommendations for someone that does a good lens cleaning?

Just to be sure, only the mark II of the 14-140mm lens is splash proof.  Note, there have been 3 versions of the 14-140mm.

The first version had a different aperture range (f/4-5.8) from the second version.  The third version (i.e. mark II) has the same aperture range (f/3.5-5.6) as the second version.