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01-06-2014, 11:21 PM   #1
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Lens Breathing

Pentax has found a niche with bodies and lenses sealed against the elements, and tolerant of cold. It's a great thing. I work in sloppy conditions, with amazing photographic opportunities in them (like tropical rainforests) and so after the K3 came out I jumped ship from Canon EOS and became a Pentaxian. I miss a few things, but mostly I'm happy with the move.

I do have one lingering fear, though. Many of the WR and DA* lenses either lack internal zoom, or internal focus (e.g. 100 macro, DA* 60-250, 18-135 WR kit lens). Since they are water-sealed, but expand in volume when zooming or focusing, they suck ambient air into the body and lens. If that air is dry and spore free, then it is just fine. But in rainforest conditions, I have the sense it greatly increases the likelihood of sucking in a fungal spore that can then grow on internal lens elements.

It is also true that in a lowland rainforest field-station, electronic equipment is (when possible) kept in labs dehumidified with air-conditioning, and the coldness of the equipment causes lenses to immediately fog when they hit the warm moist air outside. That's not serious in an internally focusing and internally zooming lens where the fog forms on the outside and can be wiped off the filter, but in a breathing lens I suspect warm moist air will flow in and condense inside, where it may drip and create all kinds of trouble. In principle one can refrain from zooming or focusing until the camera and lens are warm. But in practice, it will be very hard to know when the internal elements are warm enough.

For the moment I'm going to address this by using a "dry closet" inside the air conditioned lab (a box with an incandescent lamp within it to raise temperatures, and lower relative humidity). But long term this isn't always an option.

So what I'm getting at is this: If Pentax wants to be the DSLR for extreme field conditions, should it be redesigning the current breathing lenses so they focus and zoom internally (like the DA* 300)? For many reasons, those non-breathing designs are likely to be more robust, and thus a better fit for the niche Pentax is carving out.

01-07-2014, 01:23 AM   #2
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Maybe a spore might get in but not moisture, so no fungal growth should occur?
01-07-2014, 01:43 AM   #3
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QuoteOriginally posted by BretW Quote
I do have one lingering fear, though. Many of the WR and DA* lenses either lack internal zoom, or internal focus (e.g. 100 macro, DA* 60-250, 18-135 WR kit lens). Since they are water-sealed, but expand in volume when zooming or focusing, they suck ambient air into the body and lens. If that air is dry and spore free, then it is just fine.
If they can suck air in and out, then they are not sealed. They are weather resistant, not water-proof. This is exactly how my K-5 got killed during a very fine drizzle. It wasn't fog, but not rain either, the air was saturated with thicker droplets. Real rain would have been better. The DA 18-135 pumped and the air, including the moist, got in. I didn't expect it at that time, as the same combination had survived giant poordowns before.

Mind you, the DA 18-135 is still my most used lens though. It gets all the work when the weather is bad... Which is 99% of the time in my place of the world.
01-07-2014, 01:44 AM   #4
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Bret,

I whole heartedly agree with you. The WR lenses should be designed that way, at least the DA* lenses anyhow. Unfortunately they are not. I have 3 and am not overly concerned about them, then again, I am not shooting in a rain forest. I am in an extremely dense oak forest and swamp, haven't had any issues yet, but we will see. The lenses are pretty robust, but don't underestimate this equipment just yet. If I were you I would use them without fear. Just me, that's probably why I am buying bodies every couple years......

01-07-2014, 02:23 AM - 1 Like   #5
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This topic is getting frustrating.

We need to remember that *air* does not share the same permeability as *water*. Air, especially as a gas vs water in a liquid, is far more capable of bypassing the sealing spots. I have the DA 18-135, DA* 16-50, DA* 60-250 and used to have the DA 18-55 WR. I have extensively tested the HD 55-300 WR. They all telescope. All of them.

Yes if you zoom in/out VERY quickly you will hear the suction. Open a flap (say remote port) and it will be more pronounced of a hiss.

Again, this is air. Water does not have the same ability to fit through small spaces. If you look VERY closely at where the telescoping tubes meet, there's sealing along the edges, blocking water from entering once collapsed.

Is there an inherent level of stronger sealing in the DA* 50-135, 200 and 300? Yes, because they are 100% self-contained (the DA* 55 does not have internal focus, and has a slight amount of telescoping inside its open body). But there is *no* evidence to support that any of the zooms are less sealed and thus more prone to failure than the aforementioned primes and 50-135. None. If I had to pick just one to rule them all, I'd go with the DA* 16-50. That is the tank of tanks as far as my weather sealing experience goes, including zooming in and out while rain coated all telescoping tubes at full extension.

Just dry your gear appropriately (I use a standard bath towel) when you retire for the day, and let it dry with the tubes at full extension. I then keep everything in a regular cupboard lined with silica gel packets on the shelves.

Seriously, let us please put this myth to bed.

-Heie
01-07-2014, 02:42 AM   #6
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Hi Alex,

but do your explanations adress the doubts of the OP and Clavius experiences? They were'nt talking about liquid water getting into the lens but rather the possibility of water vapor in extremely humid environments penetrating the lens seals while zooming. Just asking.
01-07-2014, 02:52 AM   #7
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That's different - because again, it's not water, but water *vapor*. Vapor is a gas. The DA* 300, 200, and 50-135 will all have the same vapor inside unless you attach the lens before heading into the elements, and then don't detach until you get back.

The main issue is the humidity, and the only way to combat that is SLLLOOOOOOOOWWWWWWWWWWWW temperature adjustment (air conditioned to outside rainforest; cold overnight freezing to indoor heated domecile). I keep my gear in the camera bag for 6+ hours to adjust at a snail's pace - do it too quickly and then you get the "sweating can of coke" effect, mostly on the inside because the air will be warmer than on the len's surface. I notice this most in my distance scale windows.

What happens is the humidity (water laden air) changes into dew (droplets) because of the dewpoint, which is exactly what happens on your lawns, windshields, etc. every morning. This is why it is CRITICAL to allow your gear to 'stabilize' slowly when transitioning between extreme temperature/humidity difference in environments (the two most common I explained above).

Also note that chemically (physically?), warm air has much more ability to retain water, which is why humidity levels in the winter never reach those in the summer, however summer levels can reach very low humidity (which is why 110F/43C in Arizona feels much better than 90F/32C in Florida/Costa Rica or any other place that has typically dreadful levels of humidity. The higher the temperature, the higher the concentration before saturation (actual wetness). This is the same reason why boiling water can dissolve more salt, sugar, etc. than room temperature water.

-Heie

Last edited by Heie; 01-07-2014 at 03:04 AM.
01-07-2014, 02:59 AM   #8
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QuoteOriginally posted by Heie Quote
This topic is getting frustrating.

We need to remember that *air* does not share the same permeability as *water*. Air, especially as a gas vs water in a liquid, is far more capable of bypassing the sealing spots. I have the DA 18-135, DA* 16-50, DA* 60-250 and used to have the DA 18-55 WR. I have extensively tested the HD 55-300 WR. They all telescope. All of them.

Yes if you zoom in/out VERY quickly you will hear the suction. Open a flap (say remote port) and it will be more pronounced of a hiss.

Again, this is air. Water does not have the same ability to fit through small spaces. If you look VERY closely at where the telescoping tubes meet, there's sealing along the edges, blocking water from entering once collapsed.

Is there an inherent level of stronger sealing in the DA* 50-135, 200 and 300? Yes, because they are 100% self-contained (the DA* 55 does not have internal focus, and has a slight amount of telescoping inside its open body). But there is *no* evidence to support that any of the zooms are less sealed and thus more prone to failure than the aforementioned primes and 50-135. None. If I had to pick just one to rule them all, I'd go with the DA* 16-50. That is the tank of tanks as far as my weather sealing experience goes, including zooming in and out while rain coated all telescoping tubes at full extension.

Just dry your gear appropriately (I use a standard bath towel) when you retire for the day, and let it dry with the tubes at full extension. I then keep everything in a regular cupboard lined with silica gel packets on the shelves.

Seriously, let us please put this myth to bed.

-Heie
+1 with Heie.

I may add that we should not misunderstood WR. WR means weather resistant, not water proof. It implies that we (the photographers) must take care of our equipment as well.

For the past 5 years, I have used my DA18-250mm (a non WR zoom lens) in atrocious conditions, incl. salty splash, sand, at sea, in tropical rainstorms, sub-tropical rain, mud, snow, ice... Probably not as bad as Heie, but still a wide range of hazards. I had no major issue. Even in a tropical rainstorm, I shot with my non-WR zoom lens and I had no problem. Why? Because I take care of my gears.

My 5 cents...


Last edited by hcc; 01-07-2014 at 03:28 AM.
01-07-2014, 04:01 AM   #9
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To answer the OP: operating a breathing lens (weather resistant or not) will eventually bring the ambient air into the lens and camera body. The humidity inside the camera will then eventually match the outside. Bring that camera into a cooler place and the water will condense out of the air inside the camera and most likely cause it to fail. This will be the case for any camera except for a waterproof camera designed for underwater operation which will not allow ambient air into the enclosure.

If it were me living in an extremely humid environment, I would invest in a dehumidifier cabinet and store my camera without a lens attached in the cabinet to permit quicker extraction of the humid air from the inside of the camera.

The problem is not the humidity per se, but the changing ambient temperature. As Alex alluded to, hot air has a greater ability to hold water than cold air. If you cool 35deg air at 95% RH to 20 deg it will result in condensation. The best is to dry the camera with 35 deg air at less than 40% RH before cooling to 20 deg (35 deg air at 40% cooled to 20 deg will result in 95%RH if I read my Psychrometric chart correctly) (All temperatures in Celcius)

Just my 5 cents too...
01-07-2014, 09:10 AM   #10
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No time for a full response just now, but I did want to clarify. I am not talking about liquid water getting in, I'm talking about vapor getting in and condensing to liquid. And that problem will be exacerbated by breathing.

Yes, the best way to keep that from happening in an internally zooming/focusing lens would be to leave it on the body, and I would probably carry two body/lens combos into the forest for this reason (probably 100mm Macro on a K5iis [for $ reasons], and 60-250 on a K3). It would not be not unlike the days of film when two bodies were carried for variable ISO. I would also point out that leaving lenses mounted is implicit in the WR concept under really rough conditions.

And yes, slowly allowing a lens to come up to temperature is good in principle, but in practice a photographer has to shoot when opportunity knocks. That is why I abandoned Canon for Pentax. The benefits of WR outweighed the losses by a large margin (I lost a 70-200L 2.8, 100mm 2.8 macro and 28-70L 2.8 to fungus in a remote part of Madagascar years ago--no electricity, high humidity and amazing creatures are often found together).

My only point was that internal zoom and focus are design features that should have a higher priority, given the niche Pentax has chosen to dominate (rough conditions). Breathing is a vulnerability when coupled with organic (and therefore fungus-edible) lens coatings.

P.S. I know that Pentax has designed the K3 and K5 not to suck in liquid water when lenses breath, but I have not figured out how it works given that rain can put water anywhere on the outer surface. The volume increases rapidly, ruling out the possibility that there is no path big enough for liquid water (like a goretex membrane). So presumably there must be a geometry that allows a droplet sucked in and then to leave the camera while air is sucked past it. But what does that look like? Is it like a kitchen-sink U-trap? A hooka? Anyone know?

Last edited by BretW; 01-07-2014 at 09:13 AM. Reason: clearity
01-07-2014, 03:30 PM   #11
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While I do not shoot in a rain forest I do shoot in green houses, which are just as humid and fungus laden. Never had an issue with any lens, either on film or digital. In fact, in simply humid conditions I think WR might be a liability because once in there is much less breathing than a non WR lens and therefore potentially rosk of sealing both spores and humidity inside.

I often remind people that WR should be considered as insurance when primary protection fails, not as primary protection.
01-07-2014, 06:20 PM   #12
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QuoteOriginally posted by Lowell Goudge Quote
I often remind people that WR should be considered as insurance when primary protection fails, not as primary protection.
+1 with Lowell
01-07-2014, 10:20 PM   #13
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QuoteOriginally posted by Lowell Goudge Quote
While I do not shoot in a rain forest I do shoot in green houses, which are just as humid and fungus laden. Never had an issue with any lens, either on film or digital. In fact, in simply humid conditions I think WR might be a liability because once in there is much less breathing than a non WR lens and therefore potentially rosk of sealing both spores and humidity inside.

I often remind people that WR should be considered as insurance when primary protection fails, not as primary protection.
I don't see in what way this is useful.

Pentax has chosen to pursue photographers who wish to push the limits of DSLR equipment. You can argue that was a foolish choice on their part, or not. But I am within that demographic, and I am passing on some information about how I see the fitness of the system I have just invested in.

I think the move by Pentax was smart. People prefer photos that are uncommon, and one thing that creates uncommon shots is cameras that can be effective in conditions that most cameras can't handle. That is why I am here. On arrival I find that they have done some things right, and seem to have missed some opportunities to strengthen their dominance within this niche.

You want to shift responsibility back to me, and suggest I leave my equipment in safe conditions? Ok. But what's the point? I left Canon to gain the capacity to shoot in bad conditions. WR, DA* and the K5 and K3 are designed for that, but breathing lenses are a problem. They are an argument against WR--they are sealed against liquid water, but they inhale water vapor. The solution already has a name: internal zoom and focus.

Should I not have pointed this out? Should I only shoot things in a greenhouse? Should I go back to Canon?

What that I have said are you disagreeing with?

P.S. Greenhouses may have fungus in them, but 1) they have an exit door that you can take your camera through. And 2) the diversity of saprophytic fungi is orders of magnitude lower than any intact lowland tropical forest.
01-08-2014, 04:50 AM   #14
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Bret

What I am trying to point out is that while the cameras are sealed to an extent! they are simply not air tight, nore are they waterproof. I have been shooting for 30 years, have had my gear on kayaks, where it is has been totally soaked (non WR camera by the way) in tropical forests, out in rain, snow, etc, on beaches in dust, etc....

They have gone from very cold into a humid green house where everything condenses on them, etc....

I have never lost a single lens or camera because after use I clean and dry things properly, and even when out in inclement weather, I protect the cameras as best I can when not in actual use.

People shot for years before WR cameras came out, and did it successfully.

Does WR improve the situation, yes, of course it does, but it is but it is not the be all and end all of outdoor or extreme shooting. That is all I am saying.

When WR bodies first came out with the K10D there were tons of posts where people complained after going out in a driving rain all day, when they got home, they found their camera had fogged. Others complained that they fogged after washing them in the kitchen sink under a running tap, and didn't understand why, because it was the 50th time they had done it.

Moulds and fungus exist every where in the world in every environment (except perhaps a desert), and while I don't disagree with you that, for example, lenses that are internally focusing and zooming (I.e. Do not change physical length) are better than those which do, from the perspective of creating differential pressure across seals, any time you have a moving interface, such as a focus ring, aperture ring, zoom collar, function dial etc, you have an access point which is stressed when moved, which will let small amounts of air etc enter the camera and lens.

All WR does is reduce, not eliminate ingress etc. it has real and practical limits. As for the responsibility, yes, I am shifting it back onto you. It is your gear, you need to know its limits in practical terms, and care for your gear. It will last much longer of you do.
01-08-2014, 04:54 AM   #15
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QuoteOriginally posted by Lowell Goudge Quote
People shot for years before WR cameras came out, and did it successfully.
This is a red herring. The 'shot for years' wasn't an issue because back then, the cameras and lenses were mechanical and had no electronics that required protecting from water and dust.

QuoteOriginally posted by Lowell Goudge Quote
you have an access point which is stressed when moved, which will let small amounts of air etc enter the camera and lens.
Absolutely true.

-Heie
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