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100-400mm G-Master lens and "moisture resistance"


andyfowlie
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This week I spent a few days shooting golden eagles from a hide in Northern Finland.

 

I normally shoot wildlife with Canon long lenses and use Sony (A7Riii) for landscapes, but on this trip I took along the 100-400mm GM lens to try it out for this kind of shooting.

 

I am sad to say that it did not pass the audition. The image quality, focus speed and focus accuracy of this lens are all great but it could not handle the weather. Within less than an hour condensation had built up inside the lens (behind the front element) making it impossible to shoot with. The lens is said to be "moisture resistant"... but it could not handle the conditions. It was a basic Finnish day, about -5C, dry and a little cloudy with occasional snow and the lens was protected from some of the elements by an overhanging roof... it could have been a lot harder conditions. The difference in temperature between the hide and the outside world was enough to cause the problem.

 

My companions in the same hide had no such issues with their Canon 100-400mm, Nikon 200-400mm and Olympus 40-150mm zoom lenses. It was an embarassing situation to be a Sony shooter :(

 

I contacted the retailer where I purchased the lens and have been told that this is a common problem and does not mean that the moisture resistance of the lens is faulty.

 

I am pretty disappointed.

 

Has anyone else had any similar issues with this lens or have you had more positive experiences in the same situation?

 

Andy

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Did the condensation go away immediately when you entered a warmer environment?

Does this also happen when temperatures are just above the freezing point?

Hi,

 

The condensation went away gradually when taken to a warmer environment... it took an hour or two, a little longer in the more serious case where the condensation formed and then froze inside the lens.

 

I have not seen this in other situations such as when using at around zero degrees, it was this hide situation where there was a temperature gradient between the hide and the outside which seemed to be the trigger. There may be other situations which would cause this also but that it the one I encountered.

 

Andy

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Did the condensation go away immediately when you entered a warmer environment?

Does this also happen when temperatures are just above the freezing point?

 

This question is aiming at the proper direction, IMO.

 

I always try to first understand what happened, and why (analysis). From there I would try to address the root causes to fix / remedy the issue (sythesis).

 

In this particular case, Andy reports, that the condensation happened inside of the lens, right behind the front element. This is important - I'll come back to that later on.

I conclude, the moisture, which eventually condensed, was inside the lens all along. It did not enter from the outside. (Else I hope Andy would have mentioned that). If this assumption is correct, then it's not an issue of poor (i.e.: not enough) sealing.

 

Let me try to explain, with a little physics involved:

What we call "air" is actually a mixture of different elements in gaseous form. In particular, there is almost always some amount water vapour contained in the air. Depending on surrounding conditions (temperature, air pressure), each volume of air can carry only a limited amount of water in gaseous state. If conditions change, for instance: temperature drops, air pressure drops, then condensation may occur.

 

The following is the so-called "Mollier h-x Diagram" and details the relation of different physical properties of humid air. Raw graphics taken from this link (page 12), annotations added by myself:

 

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The vertical lines mark states of constant water content. This is an absolute amount of water, unit is grams of Water per kilogram of perfectly dry air.

The horizontal lines mark states of constant temperature, in degrees (Celsius).

The curved lines mark states of constant relative humidity, in percent. The lowest of these lines is the "saturation" line, where we have 100% relative humidity. The air cannot hold more water in gaseous state than that.

 

Let's suppose, at the moment of manufacturing (sealing) of the lens, the surrounding air had a content of 4 grams of water per kilogram of perfectly dry air. I've marked this as a green line.

Now, is this much? Is this humid or rather arid? That depends:

  • At 38°C (bullet point 1), follow the purple line to the left axis, the green line of absolute water amount intersects the curved line which indicates a relative humidity of 10%. This would be very arid. At this temperature, the air could theoretically hold ten times more water in gaseous state than the current 4 gramms per kilogramm of dry air. (Because ten times 10% equals 100% - full saturation).
  • If we cool this sealed volume of air off a little bit, to a about 25°C (bullet point 2), the green line intersects the 20% relative humidity line. At this temperature, the air could theoretically still hold five times more water in gaseous state than the current 4 gramms per kilogramm of dry air.
  • If we further cool this sealed volume off a bit to +11°C (bullet point 3), the green line intersects the 50% relative humidity line. At this temperature, the air could theoretically hold only two times more water in gaseous state than the current 4 gramms per kilogramm of dry air.
  • Further cooling this off, we finally arrive at the saturation line (100% relative humidity). The temperature is now a mere +1°C.
  • If this sealed volume is further cooled off, then condensation occurs. Inevitably. The temperature, where this occurs, depends only on the amount of water contained in the air at the time of sealing the lens. Assuming, the lens is indeed perfectly sealed.

When this lens was put to use in a cold environment, the glass front element, being a good conductor of heat, cooled off because it was exposed to the temperature of the environment. Eventually the inside surface of the lens took on the temperature of the outside, which in turn cooled off a layer of air right next to the inside glass surface, below the "dew point". Much like humidity condenses in winter on the inside of poorly insulated window panes. Although the air inside a room may still feel warm. That's because air is a bad conductor of heat, and you have low temperatures only locally, right next to the window pane.

 

Now comes the juicy part. :) What can be done about it for your lens?  (I happen to own the same lens, but never used it in the conditions you described).

 

1. Well, hope (or pray, depending on your inclination), that the lens is not perfectly sealed. In that case, gaseous water vapor could travel inside and outside of the lens, so the relative humidity inside the lens would always be similar to that of the lens's environment. Given enough time to accomodate changes in weather.

2. Try to not expose the lens to sudden changes in surrounding air humidity and/or temperature. If you know you are going to a wildlife shooting trip in cold temperatures, do not keep the lens inside a well heated room until immediately before using it. Because warm air from the inside can store much more water than the cold air outside.Rather, let it adapt in terms of temperature and humidity to the conditions to be expected. Leave it in your car during the night prior to shooting with it should be good enough.

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This question is aiming at the proper direction, IMO.

 

I always try to first understand what happened, and why (analysis). From there I would try to address the root causes to fix / remedy the issue (sythesis).

 

In this particular case, Andy reports, that the condensation happened inside of the lens, right behind the front element. This is important - I'll come back to that later on.

I conclude, the moisture, which eventually condensed, was inside the lens all along. It did not enter from the outside. (Else I hope Andy would have mentioned that). If this assumption is correct, then it's not an issue of poor (i.e.: not enough) sealing.

 

Let me try to explain, with a little physics involved:

What we call "air" is actually a mixture of different elements in gaseous form. In particular, there is almost always some amount water vapour contained in the air. Depending on surrounding conditions (temperature, air pressure), each volume of air can carry only a limited amount of water in gaseous state. If conditions change, for instance: temperature drops, air pressure drops, then condensation may occur.

 

The following is the so-called "Mollier h-x Diagram" and details the relation of different physical properties of humid air. Raw graphics taken from this link (page 12), annotations added by myself:

 

attachicon.gifMollier.jpg

 

The vertical lines mark states of constant water content. This is an absolute amount of water, unit is grams of Water per kilogram of perfectly dry air.

The horizontal lines mark states of constant temperature, in degrees (Celsius).

The curved lines mark states of constant relative humidity, in percent. The lowest of these lines is the "saturation" line, where we have 100% relative humidity. The air cannot hold more water in gaseous state than that.

 

Let's suppose, at the moment of manufacturing (sealing) of the lens, the surrounding air had a content of 4 grams of water per kilogram of perfectly dry air. I've marked this as a green line.

Now, is this much? Is this humid or rather arid? That depends:

  • At 38°C (bullet point 1), follow the purple line to the left axis, the green line of absolute water amount intersects the curved line which indicates a relative humidity of 10%. This would be very arid. At this temperature, the air could theoretically hold ten times more water in gaseous state than the current 4 gramms per kilogramm of dry air. (Because ten times 10% equals 100% - full saturation).
  • If we cool this sealed volume of air off a little bit, to a about 25°C (bullet point 2), the green line intersects the 20% relative humidity line. At this temperature, the air could theoretically still hold five times more water in gaseous state than the current 4 gramms per kilogramm of dry air.
  • If we further cool this sealed volume off a bit to +11°C (bullet point 3), the green line intersects the 50% relative humidity line. At this temperature, the air could theoretically hold only two times more water in gaseous state than the current 4 gramms per kilogramm of dry air.
  • Further cooling this off, we finally arrive at the saturation line (100% relative humidity). The temperature is now a mere +1°C.
  • If this sealed volume is further cooled off, then condensation occurs. Inevitably. The temperature, where this occurs, depends only on the amount of water contained in the air at the time of sealing the lens. Assuming, the lens is indeed perfectly sealed.

When this lens was put to use in a cold environment, the glass front element, being a good conductor of heat, cooled off because it was exposed to the temperature of the environment. Eventually the inside surface of the lens took on the temperature of the outside, which in turn cooled off a layer of air right next to the inside glass surface, below the "dew point". Much like humidity condenses in winter on the inside of badly insulated window panes. Although the air inside a room may still feel warn. That's because air is a bad conductor of heat, and you have low temperatures only locally, right next to the window pane.

 

Now comes the juicy part. :) What can be done about it?

 

1. Well, hope (or pray, depending on your inclination), that the lens is not perfectly sealed. In that case, moisture could travel inside and outside of the lens to always be similar to lens' environment. Given enough time to accomodate changes in weather.

2. Try to not expose the lens to sudden changes in surrounding air humidity and/or temperature. If you know you are going to a wildlife shooting trip in cold temperatures, do not keep the lens inside a well heated room until immediately before using it. Rather, let it adapt in terms of temperature and humidity to the conditions to be expected. Leave it in your car during the night prior to shooting with it should be good enough.

 

 

Ah... some science has arrived. Excellent. Thanks a lot Chrissie for the effort put into your comment!

 

Additional data points:

- condensation also formed on the outside of the front element, but that is not so problematic as you can remove that easily enough

- the problem continuously worsened during the 11 hours or so spent in the hide, it did not stabilise or start to reduce

- the temperature itself is not the problem in my opinion, I have used the lens without issue in colder temperatures, it was the difference between the temperature inside the hide (where the camera body and some part of the lens was) and outside the hide (where the end portion of the lens protrudes).

 

If it was as you guess Chrissie, that there is such an amount of moisture sealed inside the lens as would be problematic in use, then wouldn't that show up also in the case of using purely in cold temperatures?

 

Finally... if the lens is indeed sealed... then it is a major failure on the part of Sony to have a manufacturing environment that includes such an amount of moisture in the air that would be problematic in low temperature use.

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Glad you liked it - I've enjoyed thinking about this as I have the same lens.

I'll come back to your questions in maybe four to five hours time from now, as I'm still in the office and also have to provide some "actual" results for what I'm being paid for ...  :rolleyes:

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Guest Jaf-Photo

A weather-sealed lens is not air-tight. Therefore, they are susceptible to condensation at quick temperature changes. Even more so than unsealed lenses which allow for quicker equalisation.

 

That's why you (well not you) avoid quick temperature changes such as letting the camera cool slowly in the bag before shooting.

 

Also, weather seals are not water proof. They make it harder for water to enter and run inside the lens. Think of it more as splash resistance.

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Ah... some science has arrived. Excellent. Thanks a lot Chrissie for the effort put into your comment!

 

Additional data points:

- condensation also formed on the outside of the front element, but that is not so problematic as you can remove that easily enough

- the problem continuously worsened during the 11 hours or so spent in the hide, it did not stabilise or start to reduce

- the temperature itself is not the problem in my opinion, I have used the lens without issue in colder temperatures, it was the difference between the temperature inside the hide (where the camera body and some part of the lens was) and outside the hide (where the end portion of the lens protrudes).

 

If it was as you guess Chrissie, that there is such an amount of moisture sealed inside the lens as would be problematic in use, then wouldn't that show up also in the case of using purely in cold temperatures?

 

Finally... if the lens is indeed sealed... then it is a major failure on the part of Sony to have a manufacturing environment that includes such an amount of moisture in the air that would be problematic in low temperature use.

 

 

Andy,

 

now we have to be a bit careful not to rush to premature conclusions. I was using assumptions to clarify the general mechanism of water vapor condensation as such.

I have no knowledge of the production process for Sony lenses.

I also don't know, if the lens is indeed perfectly sealed. According to Jaf, they aren't.

Also, I was using the "4 grams of water per kilogram of perfectly dry air" only as a sample case, because it fitted so nicely the case I wanted to demonstrate. For different initial amounts of water, only the respective temperatures change, while the principle remains the same.

 

That said, the problem of condensation within lenses does neither seem to be rare, nor be confined to Sony lenses either.

 

As a counter-measure, some lenses are filled with nitrogen and sealed as best as possible. Inert gases should btw also do the trick. Where there is no water vapor inside, there will be no condensation, regardless of how low the temperature. Sounds ideal, but I don't know if a lens can be retrofitted that way if it wasn't designed for that feature in the first place. It also  doesn't seem to be possible, to really seal a zoom lens which has moving barrel parts. 

 

Then I've found suppliers for lens-heating devices. This should also help in keeping condensation issues at bay.

 

And then I've read of zoos, where they have hot air jets (hand dryers at a rest room?) at the entrance of tropical houses where people entering from the cold outside could warm up their glasses and/or lenses, to fight condensation issues.

 

As for your particular situation:

front of lens in contact to cold outside, while barrel of lens inside a probably cozy and humid hide. That leaves me scratching my head for a while ... 

 

- the temperature itself is not the problem in my opinion, I have used the lens without issue in colder temperatures, it was the difference between the temperature inside the hide (where the camera body and some part of the lens was) and outside the hide (where the end portion of the lens protrudes).

 

I understand that you want to use some sort of camouflage during wildlife shooting, but does it have to cover two different clima zones?

 

Before I speculate any further: did you do any (frequent?) zooming action (zoom in, zoom out)  while inside your hide?

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Guest Jaf-Photo

Is that documented somewhere?

Several manufacturers have such lenses and It's stated in the documentation. In any case a filter is always a plus if you're out and about.

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Guest Jaf-Photo

Condensation typically happens when a warm lens meets cold air or vice versa. Typical examples are taking the camera out of a warm car in the winter or taking it out of an air-conditioned room in the tropics (and vice versa).

 

The dew problem only occurs during extended night-time shooting like time-lapse, so it's a marginal issue.

 

The trick is to keep the lens in the bag for some time before you take it out. If you're shooting in the winter, leave the camera bag on the porch for an hour before going out. That will allow for a slow adjustment to ambient temperature. Same with the car. Keep the camera in the boot if it is closer to air temperature and allow it some time to adjust before you take it out of the bag.

 

This is not really news to anyone who are used to cameras. The only difference these days is that modern lenses breathe less and therefore fog more easily. A vintage lens may only fog for a minute and then clear.

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Lots of good advice from Jaf-Photo and Chrissie... especially for anyone who has not seen it before... but it all misses the point to an extent.

 

There were 13 different lenses set up by six different photographers all in the same hide and all in the same conditions. These include Canon, Nikon and Olympus primes as well as Sony, Canon, Nikon and Olympus zooms. All lenses had been in the same succession of environments (residence, vehicle, walk through the forest) on the way to the hides.

 

The Sony 100-400mm was the only one to get this internal condensation problem... so it managed worse than all the competitor lenses in these conditions... this is the point, this is the part which sucks.

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Condensation typically happens when a warm lens meets cold air ...

 

If I may add a bit of precision here:

 

This seems to be the thread starter's case. IMO, that type of condensation did not occur because the lens was warm, but rather, because the warm air inside the lens contained more water vapor than the outside temperature allowed to keep in gaseous state. So part of the humidity inside the lens condensed on the inside of the front element, after this had sufficiently cooled off.

 

... or vice versa.

 

This is probably the more obvious case. Like a can of ice-cold beverage, which collects water drops on the outside surface when in a tropical (or warm and humid) environment.

Bringing a cold (and dry) lens into a warm interior, its surface would collect condensed water on its outer surfaces.

 

The dew problem only occurs during extended night-time shooting like time-lapse, so it's a marginal issue.

 

There is no technical distinction between "condensation" (general term) and "dew", which is a specific manifestation of the former.

 

In any case, condensation occurs always as a consequence of humid air cooling off below the dew point.

 

In the first case (above), the warm air was inside of the lens. In the second case (above), the warm air was outside of the lens.

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Guest Jaf-Photo

There is a difference. Dew forms on the outside of the lens, crucially on the front element. That is the case even if the lens is at ambient temperature.

 

Inside condensation forms when the air trapped inside a lens is affected by outside temperature changes. This changes the water carrying ability of the inside air, just like you wrote.

 

Inside condensation is a problem because it can stain the internal elements and in the worst case lead to fungus.

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Lots of good advice from Jaf-Photo and Chrissie... especially for anyone who has not seen it before... but it all misses the point to an extent.

 

There were 13 different lenses set up by six different photographers all in the same hide and all in the same conditions. These include Canon, Nikon and Olympus primes as well as Sony, Canon, Nikon and Olympus zooms. All lenses had been in the same succession of environments (residence, vehicle, walk through the forest) on the way to the hides.

 

The Sony 100-400mm was the only one to get this internal condensation problem... so it managed worse than all the competitor lenses in these conditions... this is the point, this is the part which sucks.

 

Totally agree with you. I mean it is nice to figure out why things like this generally happen, but I would be more interested in why this happend only to the Sony lens. 

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Guest Jaf-Photo

We don't have the full picture. The Sony lens could have been kept in warm and humid air before the shoot, allowing moisture to build up. Maybe the lens was handled differently before or during the day.

 

We just don't know.

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We don't have the full picture. The Sony lens could have been kept in warm and humid air before the shoot, allowing moisture to build up. Maybe the lens was handled differently before or during the day.

 

We just don't know.

 

Or we could all just agree that the Sony lens sucks.

 

I mean andyfowlie stated "All lenses had been in the same succession of environments".

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Or we could all just agree that the Sony lens sucks.

 

I mean andyfowlie stated "All lenses had been in the same succession of environments".

 

 

After having spent something in the range of 2.500 bucks for this lens (like I did), this is understandably not an easy final word to speak.

 

But, it may be the only conclusion to draw, after all other possibilities have been exhausted. Which is currently not the case. I'm fully with Jaf on this.

 

I certainly trust Andy's honesty in telling us about all conditions, which he felt were relevant. Which of course do not include those conditions which were in fact relevant too, but were not recognized as such by Andy.  ;-)

 

These would fall in the category "unknown unknowns", to paraphrase Donald Rumsfeld.

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Or we could all just agree that the Sony lens sucks.

 

I mean andyfowlie stated "All lenses had been in the same succession of environments".

Not really. Maybe there's more moisture where the OP stores his lens? Maybe the Sony is more air-tight? Who knows?

 

But in all honesty, I would be wary with statements that a lens is faulty because is fogs up during temperature changes. That is typical behaviour and experienced shooters take precautions.

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Well, much as I am enjoying this "the lens is perfect but I am an idiot" theory, maybe we could get back to what I asked originally.

 

Other readers must own this lens as well.

 

I would like to hear about their experiences, positive and negative, of shooting in difficult conditions.

 

Andy

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Guest Jaf-Photo

You're quite good at reading between the lines. But as you not only asked a question but mostly described a scenario, I think it's fair game to comment on the scenario. In any case, I'm an A-mount shooter because I'm not too keen on the FE-mount system. So, I'll bow out.

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