Architect1776 Loc: In my mind

Why do UHH people and reviewers panc over some zoom lenses that extend when zoomed out talking about dust and moisture as a fault.
Yet the Z 24-70mm f2.8 and Sony 24-70mm f2.8 trombone in and out when zoomed with no concerns expressed here Or in reviews. Would this not change balance and allow dirt and moisture in as the lens is zoomed?

Longshadow Loc: Audubon, PA, United States

They are worried about dust and moisture getting sucked into the lens upon extension.
Some lenses more than others.

Simplest fix: Don't extend it.
Oh, wait......

Grahame Loc: Fiji

If you used extending lenses in environments where they become subjected to horrendous fine dust, salt spray, rain and your own sweat you would understand the concerns, which are obvious.

Buyers have choices and the smart ones buy gear that gives them confidence in the situations they use it.

Architect1776 Loc: In my mind

Then why all the panic over some lenses yet silence on others even though they all do the same thing as far as balance and sucking crud in?

imagemeister Loc: mid east Florida

Lenses bigger than 70-200 suck MORE air and therefore, more contaminates ....

larryepage Loc: North Texas area

I have both internal zoom and traditional zooms among my equipment. For the most part, I use them interchangeably. The fact is that internal zooms also draw in and exhaust air when zoomed, even though the volume of air moved is less than with traditional designs. It's easy to determine that this is happening, since my cameras each "breathe" through a vent port in the viewfinder area.

I've never known this to be a problem over the last 50 years or so, because I generally don't use my cameras in unsuitable environments. When I do, I'm careful to either avoid or at least minimize doing things that unnecessarily suck contaminants into my lenses and cameras. If there's junk in the air, I'm not likely to end up with a very good image.

My thinking is that a lot of the hysteria probably comes from comments made by today's reviewers. In particular, Tony Northrup has a habit of speaking quite derisively about traditional zooms, calling them "pumpers" or "old fashioned pumpers" multiple times in each review. He clearly does not understand that any time lens elements are moved to change effective focal length, provision must be made for allowing air to enter spaces which have become larger or exhaust spaces which have become smaller. It would not be physically possible to turn the zoom ring without allowing air to move and equalize internal pressures.

So chalk it up to ignorance, just like much of the other established lore that blocks folks from learning the things that would be truly helpful to know.

Longshadow Loc: Audubon, PA, United States

I have one that extends.
I'm not concerned in the slightest.

Grahame Loc: Fiji

Is there no end to you drama? Peoples valid sensible concerns and awareness now become "panic" in you mind.

bdk Loc: Sanibel Fl.

living on the beach for 5 years, salt, sun,sand, and lots of fog. My sigma 600 is still working perfectly.

Longshadow Loc: Audubon, PA, United States

I'll be there are some people who are just waiting for their lens to fill up with dust and humidity, this are VERY concerned.....
Same thing happens with some bridge and point-n-shoots who's lens extend and retract.
Same thing.
Does anyone worry about those?
I don't worry about them either (we have one of each).
Goes along with changing lenses. Dust and humidity can get in that way too.
Forget the fact that ALL cameras breath with changes in barometric pressure.
Who worries about that?

Grahame Loc: Fiji

They can also be designed so that there is a balance between the areas so that nothing is drawn in or exhausted out, simply exchanged.

Grahame Loc: Fiji

Where will you be?

Bill_de Loc: US

Some lenses is the answer. The Nikon 200-500 sucks in and expels more air than their 70-200. Not only is the volume of air different, but the 70-200 is better sealed.

The environment, of course, makes a big difference.

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Longshadow Loc: Audubon, PA, United States

That would be interesting.
Where is the air stored?
Fully extended and contracted are two different size cylinders, different volumes.
Would contracting compress the air or extending vacuumize it.
Not like a piston in a constant sized cylinder.

Grahame Loc: Fiji

Let's make it really simple for you.

Imagine a round hollow cylinder sealed (capped) at both ends. Within that cylinder you have a disc that can move from one end to the other. Within that disc you have a hole. When the disc moves towards the left the air passes from the decreasing volume left chamber through the disc hole to chamber on the right which has got larger.

Secret, the components within the lens, and lens barrel have not increased or decreased from their initial volume and the chambers are common to one another.