Can anyone put me wise please? I am using a basic digital flash camera underground. It works well, but a lot of the time the pics are ruined by hoards of white orbs. I have been told this is moisture? Sometimes the pics are perfect. I have tried wiping the lens, turning off lights etc, to no avail.
Can anyone tell me what this actually is/what causes them and more importantly, how to avoid them?
Many thanks in advance.
Mark

The problem is that your flash is reflecting off the moisture drops straight back into the lens. The moisture drops are in the air and come from breathing, streams, waterfalls, etc. They are not on the lens (normally) as they wouldn't reflect the flash if this was the case. The way to beat this is to get your flash away from the camera ( maybe a metre or more, this means the path of the reflected light is not straight back to the camera).
The camera probably flashes more than once and this can be a problem triggering slaves, although there are some products out there that deal with the problem of multiple flashes, thay have mixed results.  :-\
You might try turning the flash off, put the camera on a longish exposure (2 - 4 secs) and fire a flash gun manually whilst the shutter is open. Either with the camera on a tripod if you there is any ambient light or you can do it hand held if you have total darkness. I have used this method with my SLR to great effect. Ambient light is only a real issue if it is straight in front of the camera, in a cave light levels are quite low so it dosent seem to matter even if you hand hold the camera. It's a bit try it and see, but with a digi camera its no real issue to retake the shot.

If you want to use the camera flash to trigger a slave then you need an infra red filter (piece of exposed film is ideal, see who said film was obsolete) over the camera flash and use a slave that triggers off infra red (Firefly). 

Hope this helps.

Think Les has covered everything there.. I used to use a digital camera and the on camera flash, but like you Mark I found certain places were not suitable for taking snaps - pitches with even small amounts of water were a definite no-no, so these days my flash is permanently covered with a piece of exposed film!

Even one slave-flash is good, but you need to find out if your camera has a pre-flash and if it does can it be turned off.. If not you will need a slave that can handle pre-flash.

Les W said:

If you want to use the camera flash to trigger a slave then you need an infra red filter (piece of exposed film is ideal, see who said film was obsolete) over the camera flash and use a slave that triggers off infra red (Firefly).

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I used to use a bit of exposed film to cover the flash, but it is becoming as rare as rocking horse shit. I now use a bit of black insulation tape, which seems to work just as well and is far easier to get hold of.

Also incorporated into the tape is a very handy self attachment mechanism. 

Pretty much all compact digi cameras have this pre flash/anti red eye thingy. I have a Kodak easy share DX4330 which allows you to turn it off so you only get 1 flash, but even the newer Kodaks dont allow it. Trouble is, manufacturers are building for the lowest common denominator ie. snapp happy snapper with no clue what so ever They aren't designing for cave photograpy.

By the way, the premier trophy was won by a portfolio taken down the Gouffre Berger with a compact Kodak, in 2002 so you can get good results with a small snapper
He did use slaves though.

Les W said:

He did use slaves though.

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Egyptian or African?

Egypt is in Africa :read:

I believe he used Japanese slaves, each one loaded down with several cameras of their own and with a video camera and film lights

That's great, thanks very much Les, lads. I'd read a little bit about preflash and slaves. Used to get good results with an SLR and slave, maybe I'll go back there?
I like digital tho. I'll have a good look into it and try a slave. I have old film!
I'll let you know how I get on.
Thanks once again for clearing up the mystery.
Happy snapping,
Mark

Just tried using a piece of exposed film over the flash on my Olympus mju720, and this fired my cheap jessops slave unit with no problem, so hopefully this will work underground instead of using night mode with a 4 sec exposure and mini tripod which is fine for formations but caver's will not stand still that long.

Photoshop has a dandy feature called Clone Stamp which is very useful for removing those 'white spots'.

ian mckenzie said:

Photoshop has a dandy feature called Clone Stamp which is very useful for removing those 'white spots'.

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Although it's obviously much better not to have them in the first place. 

Having taken my digi SLR swimming in Scotland last year,  :-[ I now have a new digi SLR (courtesy of the insurance co.  ) I also have a lot of photos with water spotting on the images because there was water damage to the CCD and I didn't bother to get it fixed for some time (but continued to use the camera  )
Even with the clone stamp tool it is a long and tedious job to tidy them up.

Having taken my digi SLR swimming in Scotland last year,  :-[

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I was there when you went swimming - it was very funny - and you definately didn't manage to keep your feet dry!! :tease:

mak said:

Having taken my digi SLR swimming in Scotland last year,  :-[

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I was there when you went swimming - it was very funny - and you definately didn't manage to keep your feet dry!! :tease:

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I did manage to keep the camera dry though, it was my "rescuer" that dropped it due to a misunderstanding once I had "safetly" passed it to him.

I must admit to a small amount of perspiration in my wellies.  :-[

Les W said:

mak said:

Having taken my digi SLR swimming in Scotland last year,  :-[

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I was there when you went swimming - it was very funny - and you definately didn't manage to keep your feet dry!! :tease:

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I did manage to keep the camera dry though, it was my "rescuer" that dropped it due to a misunderstanding once I had "safetly" passed it to him.

I must admit to a small amount of perspiration in my wellies.  :-[

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As I recall it wasn't so much passed as thrown whilst you were coughing and spluttering mouthfulls of water :yucky:

Anyway you weren't the only one wet - firehose cave lives up to it's name - btw it's probably the hardest 157m long cave in the world!

Its certainly one of the wettest from what I saw 

I've just seen this on the BBC website, which is relevent to this thread. Somebody thought that the white spots were something supernatural!
http://www.bbc.co.uk/wales/mid/sites/weird/pages/danyrogof.shtml?2

aww bless 

Les W said:

The problem is that your flash is reflecting off the moisture drops straight back into the lens. The moisture drops are in the air and come from breathing, streams, waterfalls, etc. They are not on the lens (normally) as they wouldn't reflect the flash if this was the case.

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Possibly. But possibly not.  I have experienced this problem in photos where there was no moisture in the air. But what the photos had in common was a dark scene with bright areas. The obvious explanation is therefore lens flare; and lens flare in a digital camera manifests itself in a different way to that of conventional cameras. Chris Howes suggests that this is due to the anti-moiré filter in front of the CCD sensor. Also, of course, if you are using a digital SLR, you can get dust inside the camera. 

If it is lens flare then the way to reduce it is to use a smaller aperture, or subtly re-position your lights.

The technical term for these blobs is "orbs" and they are considered by some impressionable people to be evidence of paranormal activity. Search for orb+ghost+paranormal+digital+camera

Cookie said:

Les W said:

If you want to use the camera flash to trigger a slave then you need an infra red filter (piece of exposed film is ideal, see who said film was obsolete) over the camera flash and use a slave that triggers off infra red (Firefly).

Click to expand...

I used to use a bit of exposed film to cover the flash, but it is becoming as rare as rocking horse shit. I now use a bit of black insulation tape, which seems to work just as well and is far easier to get hold of.

Also incorporated into the tape is a very handy self attachment mechanism. 

Click to expand...

Any transparent plastic loaded with an organic dye will let infrared through. So, for example, a combination of a red and blue sweet wrapper will look black to visible light but transparent to infrared. A few years ago, I bought a several square metres of neutral-density theatrical lighting gel, which is excellent. I chopped it up into small squares and was selling them at a few pence a go. I have run out now, and I do not intend to buy any more because ...er... I cannot be bothered. But if any enterprising person wants to do this, the URL of the company is probably on my web site somewhere. http://caves.org.uk/flash/

The URL is on your site but the company charges approx £7 for delivery!!

I bought the same gel type from ebay.