Fluorescence Photography Primer

Discussion in 'Photography' started by LikesFish, 27 Apr 2013.

  1. LikesFish

    LikesFish

    Joined:
    20 Jul 2007
    Posts:
    939
    Likes Received:
    15
    Location:
    Canada
    I have been asked by some people to explain how to take photos of the fluorescence, also called auto fluorescence, that is present in many corals in our reef aquariums. With some basic equipment and technique it is not too hard to obtain images such as this.

    [​IMG]
    _G0C1100.jpg by pwnell, on Flickr

    Overview
    Many coral contain natural fluorophores that causes the beautiful glow we sometimes see when only the blue LED's are on in the tank at night. The basic principle of fluorescence is that some molecules are able to absorb more energetic photons and emit less energetic photons in the process as opposed to reflecting or absorbing photons of certain energies. Since the colour of light is determined by the light's energy (wavelength), this means UV/Blue light can be absorbed and re-emitted as Green/Yellow/Red light. The same applies to other wavelengths, but the important thing is that in auto fluorescence the emitted light has less energy (hence a longer wavelength) than the absorbed light, hence changing the colour.

    Some terminology will make this easier. The light a molecule absorbs is called the excitation spectrum. The light that the molecule re-emits at a longer wavelength is called the emission spectrum.

    The problem with trying to photograph this at night is that the excitation light spectrum overwhelms the emission spectrum as both sources of light enters the camera lens. Fluorescence is very weak. Since the camera record light differently than the eye observes, it makes it much harder to take photos that look the same when visually observing the coral at night.

    Furthermore, the blue lights in your aquarium are not optimised to coincide with the excitation spectrum of the coral, hence evoking only a weak auto fluorescence response.

    Equipment
    To take good photos of auto fluorescence, you need at least the following equipment:

    1. DSLR Camera or a camera that accepts filters
    2. Yellow barrier filter
    3. Blue excitation filter / Blue light source
    4. Tripod

    In the list I have a choice between a blue excitation filter and a blue light source. I personally use a blue excitation filter in front of my Canon 600EX-RT flash as excitation source. However a blue light source such as the BlueStar flashlight will work well too. The important thing is that the blue filter creates light of the correct wavelength.

    The barrier filter is a filter you attach to the front of your camera's lens. This is a yellow filter that filters out the blue light from the excitation source. Think about the colour wheel - blue and yellow are complimentary colours so theoretically, if evenly matched, no light should be visible when a blue light is shone through a yellow filter. Since these filters are not lab grade this is not the case, the yellow filter only blocks a percentage of the blue light but it is still vastly superior to not having the filter at all.

    I recommend the Tiffen Yellow #12 filter to use with the NightSea BlueStar flashlight. It is critical that the yellow barrier filter and the blue excitation light source be matched to be complementary, otherwise the fluorescence will be weak. Make sure to choose the closest size based on your lens filter thread. It is usually best to pick a slightly larger filter and a step down ring if you do not find the exact size you need.

    A tripod is usually recommended due to the long shutter speeds that is required when using a weak light source such as the NightSea flashlight. When using a powerful flash such as the Canon 600EX-RT, a tripod is not needed but still very useful for composition and to make holding 10 things easier.

    Technique
    This is the easiest. Get your camera and your macro lens, or whatever other closeup lens you normally use to photograph your coral with. Screw on the yellow barrier filter to the filter thread on your lens. Place the blue excitation filter in front of your flash (not too close if you have a powerful flash, I melted a gel filter by accident with my flash), or get the NightSea blue light source ready.

    Mount the camera on the tripod and get your framing right. If you use a powerful flash, then you can take fluorescence photos even with the lights on. Otherwise make sure to do this with the lights off. Use a weak light to enable you to check your framing and focus. Set the camera to manual focussing of course, and manual exposure.

    Dial in a smallish aperture that does not induce diffraction, on an APS-C DSLR this is usually not more than f/13. Dial in a shutter speed that will give a good exposure with the light source you are using. Trial and error...

    Ensure the pumps are off and the coral is still. Start the exposure and shine the blue light source on to the coral. Hold it there for the duration of the exposure. Make sure not to cause any reflections. Once done, you should have a nice fluorescence photo like this:

    [​IMG]
    _G0C7072.jpg by pwnell, on Flickr

    The fun part is to try and figure out what fluoresces. I found only one of my thousands of feather duster worms fluoresces, was quite an intriguing find.

    Good luck!
     
  2. AdS Guest




    to hide all adverts.
  3. Bendor

    Bendor

    Joined:
    20 Aug 2011
    Posts:
    1,491
    Likes Received:
    30
    Location:
    Pietermaritzburg
    Awesome pictures! Thanks for posting.
     
  4. Perky Pets

    Perky Pets Sponsor

    Joined:
    24 Jun 2010
    Posts:
    2,807
    Likes Received:
    116
    Location:
    Cape Town
    very cool , tks
     
  5. crispin

    crispin

    Joined:
    22 Jan 2008
    Posts:
    12,223
    Likes Received:
    160
    Location:
    Lilliehammer, Norway
    lovely write up, many thanks
     
  6. Nemos Janitor

    Nemos Janitor

    Joined:
    7 Feb 2009
    Posts:
    8,384
    Likes Received:
    286
    Location:
    Joe's Mountain
    Great stuff Waldo. Thank you very much. :thumbup:
     
  7. Nemos Janitor

    Nemos Janitor

    Joined:
    7 Feb 2009
    Posts:
    8,384
    Likes Received:
    286
    Location:
    Joe's Mountain
    Waldo, on the 100mm macro lens, do I remove the 67mm uv filter or do I just order a 67 mm yellow filter and fit with the UV filter? The uv filter fitted to the lens is a Nixon NC 67mm.

    Would this yellow filter also be OK to use for underwater photography. Or, would a filter be required on the UW housing? I got an ikelite for my 350D.

    Light source for the UW setup will be the Ikelite strobes DS161. Do you know if the blue filter will fit these strobes? I know the DS161 are video strobes and the 350D does not have that facility, but a 5D 111 is imminent. Or perhaps a 6D. Not sure yet.

    I do not have a flash as yet for my topside photography. I assume that the EX600 is preferred along with the blue filter rather than the special blue LED light source. AI my thinking correct?

    Thanks Bud.:thumbup:
     
  8. carlosdeandrade

    carlosdeandrade

    Joined:
    24 Dec 2010
    Posts:
    8,230
    Likes Received:
    228
    Location:
    North Riding, Jozi
  9. LikesFish

    LikesFish Thread Starter

    Joined:
    20 Jul 2007
    Posts:
    939
    Likes Received:
    15
    Location:
    Canada
    Never take photos with a UV filter on when you are not outside and using artificial lighting. It creates internal reflections. Just order a 67mm filter and swop the UV for the tiffen.

    The filter can be used underwater but I would mount it with the rest of the camera in the underwater housing.

    The blue filter can be ordered cut to size so just give them the dimensions.

    Well I got really great results with the 600 + filter, as I can stop motion with it. But both will work.
     
    Nemos Janitor likes this.
  10. Nemos Janitor

    Nemos Janitor

    Joined:
    7 Feb 2009
    Posts:
    8,384
    Likes Received:
    286
    Location:
    Joe's Mountain
    Did not know that I should remove the UV filter to do pics of fish in my tank. Thanks for the tip. :thumbup:

    Great advice. Will order the filters.
     
  11. Nemos Janitor

    Nemos Janitor

    Joined:
    7 Feb 2009
    Posts:
    8,384
    Likes Received:
    286
    Location:
    Joe's Mountain
    Waldo I have attempted to remove the Nicon HC 67mm filter from the canon macro 100mm EF IS USM lens.

    It is extreamly tight and I am afraid of damaging the lense.

    Was thinking of warming the lens up in case the cold temp or ATM were influencing.

    I do not want to introduce other issues within the lens. What do you suggest? I am inclined to leave it be but would like to take pic's without the filter to compare.
     
  12. LikesFish

    LikesFish Thread Starter

    Joined:
    20 Jul 2007
    Posts:
    939
    Likes Received:
    15
    Location:
    Canada
    Absolutely do not change the temperature of the lens. There is a trivial way to remove the filter. The idea is to apply pressure from the front of the filter thread, like a flat palm pushed on the front of the lens (be careful not to smudge it) then turn the lens or your hand. Do not grab the filter by its sides.

    Alternatively use those loops you get to open up a bottle of jam. Can also place the lens face down on a large piece of rubber and twist it.
     
  13. Nemos Janitor

    Nemos Janitor

    Joined:
    7 Feb 2009
    Posts:
    8,384
    Likes Received:
    286
    Location:
    Joe's Mountain
    Thanks Waldo. What you say we're my concerns. Will try to remove in the morning. :thumbup:
     
Recent Posts

Loading...
Similar Threads - Fluorescence Photography Primer Forum Date
Green Star Polyp Fluorescence Photography 19 Jul 2013
Aiptasia under full colour fluorescence Photography 10 May 2013
Bryopsis algae under fluorescence excitation Photography 16 Jan 2013
Fluorescence in green star polyps Photography 28 Dec 2012
Other fluorescence photos Coral Pics 15 Nov 2012
Fluorescence in Zoanthids Coral Pics 12 Nov 2012
Fluorescence 2 General Images 5 Jul 2012