Condensation/moisture during shoot at beach

[AfroKen]

I was taking photos at the beach before and during sunrise in a fairly cool, windy area in Northern California, with a strong off-shore wind. After at least 45 minutes of photographing the surf while doing long-exposures between 10-30 seconds, I started getting visible droplets on the photos when reviewing the photos in the LCD, something I hadn't seen through the viewfinder (maybe I just couldn't see this?). The lens/photos/filters did not appear to be foggy, however.

Since I saw water droplets rather than a specific fog, I assumed that somehow, my exterior filter was being splattered even though it was an off-shore wind. The next morning, I tried it again, being extremely vigilant with covering the filter and wiping it periodically even though I didn't see anything on the exterior filter. And again, after 45 minutes or so, the same thing began occurring.

The strange part is that when I took the camera back to the hotel to wipe down the filter and lens, I didn't see any evidence of water droplets anywhere on either the two ND filters or the lens. ????

Also, I was using a Nikkor 18-200mm VR lens and had two Tiffen 0.9 ND filters attached, the first of which, as it turned out, seems to have a loose filter (the actual glass revolves when I clean it, and if I shake the filter, it noticeably rattles).

I suppose I have at least a couple of questions here:
1. Could the loose filter somehow create condensation?
2. Regardless of the filter, how can I prevent this when on extended shoots at the beach, particularly when doing long-exposure photography? What techniques or equipment do pros use in situations like this?

Now, I do know that you are supposed to keep the camera at a temperature similar to the temperature that you are going to be shooting at, which I thought I did, although I did keep it in the camera bag. But would this account for the water droplets appearing in the photos at least 45 minutes after I had begun shooting? Wouldn't the condensation occur almost immediately?

Equipment (just in case it matters):
Nikkor 18-200mm VR lens
2 Tiffen 0.9 ND filters attached to the above lens
Nikon D90 camera
Feisol tripod

Thank you very much for your time in answering this. I do realize that this is sort of a long description and is somewhat confusing since it has a few different components to it. But I would love to do more long-exposure photography on the beach, but would love to resolve this problem first.

 

[tirediron]

This scenario doesn't make any sense to me unless somehow there was wind-born moisture hitting your filters, which given an off-shore breeze makes about as much sense as a 5 gallon can of sail-boat fuel. Can you post a picture or two?

 

[AfroKen]

No, it doesn't make any sense to me either, to be quite frank. That's why I asked in part what pros do to keep moisture out of the lens as an overall stopgap measure.

I'll try and post some photos soon. I just got back from this trip.

Thank you very much for your reply.

 

[Big Mike]

Are you sure that the spots aren't from a dirty sensor?

 

[AfroKen]

No, I'm not sure. Great point. I never even thought about that, I was so worked up about the filter and lens. Thanks for your response!

 

[Big Mike]

Stuff on the filter/lens is much less likely to show up in the photos. Well, you mentioned long exposures...so if you are also shooting at small apertures, then stuff on the lens/filter is more likely to show up....but still not as much as dust on the sensor.

Dust on the sensor usually looks like dark blobs.

 

[tirediron]

Are you sure that the spots aren't from a dirty sensor?

D'ohhhhhhhhhhhh... never even thought of that! I think you've got it Mike.

 

[AfroKen]

 

[AfroKen]

 

[AfroKen]

Stuff on the filter/lens is much less likely to show up in the photos. Well, you mentioned long exposures...so if you are also shooting at small apertures, then stuff on the lens/filter is more likely to show up....but still not as much as dust on the sensor.

Dust on the sensor usually looks like dark blobs.

I just uploaded two photos that were taken back to back.
-no dark blobs
-even though they are taken less than a minute apart, the water droplets look very different

By the way, the slight shift in perspective is mostly due to the rocks. It was extremely rocky, not sandy, and was quite challenging to keep the tripod secure. Anyway, these are 15 second exposures with a very small f-stop.

Again, I really do appreciate the help. I know that, at least on the surface, it doesn't seem to make a lot of sense....which is the reason I'm posting this!!! These are my first attempts at long exposures on the beach, and I want to get better at it. Thanks again

 

[spacefuzz]

I will assume the stuff on the bottom is the rocks and not insane noise?
If its condensation in your lens you should be able to look through it and see water droplets on the indavidual elements. Are you by any chance attaching your lens or changing them while out on the beach? To me it almost looks like water splashed on one of your ND filters, and then if they rotate that would explain the shift. They can be quite small dots of water and still cause small distortions so if there was a fine mist coming off the waves.... When shooting long exposures on the beach I usually have to wipe down my lens every 5-10 minutes.
Otherwise at home look at your back elements and see if there is any water residue there. If none of that is the culpret then I would try to get the sensor cleaned? Do you have a shot from the start of the photoshoot by chance?

 

[AfroKen]

I can try and dig out some photos later, thanks. I thought I did wipe down the lens, but maybe I was not vigorous enough.

And yes, the "noise" (haha) down below are all rocks, mostly black, but different variations of black and grey with the occasional whitish-colored rock. I was shooting at ISO200, so there's not really any camera noise to speak of.

 

[KmH]

I get the distinct impression the spots are small particles of dust, sand, or mist in the air directly in front of the lens and are partially in focus because of a small aperture.

Was it foggy that morning?

Regardless the ISO setting, under exposure promotes the visibility of image noise and every digital image has some amount of noise. Normally, at low ISO settings image noise is just not readily apparent.
http://www.adobe.com/digitalimag/pdfs/linear_gamma.pdf

 

[AfroKen]

Thanks. Do you think maybe I'm using too small of an f-stop? I did use F/25, which is absurdly small, as I was trying to make the photo look slightly "odd" and also get a longer exposure. But maybe this is too extreme? Bear in mind that this is my first time doing this. Most of the time I've done longer exposures, it's already been dark enough for me not to use ND filters.

 

[KmH]

Are you familiar with diffraction effects from a small aperture? Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks