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Smallcleugh Mine - Photography with LED Lighting, (24/02/08)

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With my halogen lighting conking out yesterday and getting a late start, we ended up having a potter round the mine doing a loop to the Ballroom and exiting via Smallcleugh and Northend Flats. A sedate pace allowing lots of non rushed photography using LED lighting. Having started using the halogen lights before LED's had really come on in terms of light output power, I sort of got stuck with them and only because of lamp failure did I have a go with the LED's.

I know that many other explorers use powerful LED torches for their light sources, and they get fantastic results (just look at some of the photographs on Aditnow), however since I just use a compact digital I am left to the mercies of its internal settings for long exposures, which also tend to be limited to a maximum of around 4s if I am really lucky. This has always left me relying on the higher light output of the halogens for brute force lighting. Now with the higher output of LED's, our Retro2 units seemed to provide an adequate amount of light for my camera. This biggest problem that I did find though, was trouble with focusing at long distances, as you just could not get the beam, thankfully we had a demo Chinese mining light with a 1W side emitting LED with reflector and this helped out in a few situations, but it was still no match for a 50W halogen beam shooting down a passage (quite obvious really).

Another issue that I have found is that the colour rendering for bright colourful objects such as ochre is not very good. The oranges end up being lifeless and drained of colour. This could have something to do with the camera, and I need to look at playing with the white balance settings, but again these are limited on the compact. On a technical point, the spectrum of white LEDs is not well balanced and is somewhat lacking in red, hence why most white LED's are labelled as 'cool white'. You can get 'warm white' LED's, but the output is a fair bit lower. I suppose this stems from the fact that white LED's are actually blue ones, which use a phosphor to produce the 'white' light. That is why you get that bluish, almost UV tinge when illuminating white calcite flows. Maybe the way to go would be to create an LED light from red, green and blue LED's and that would give a better balance?

An interesting exercise would be to do some photography with a digital SLR at the same time with my compact using the same lighting and then compare the results. One thing that I did find today was that even though I did bring one half working halogen along, the weight saving was amazing, I forget how much I lump about in the name of photography - the halogens are powered by lead acid batteries. If nothing else LED's would do wonders for my back.