lighting for taking photos of polished rock

Discussion in 'Digital Photography' started by James, Dec 2, 2005.

  1. James

    James Guest

    Hi,

    what type of light can I use that will allow me to take photos of polished
    rock. the surface of which is quite reflective. the stones will very in
    size from 12x6 to 40x40 inches and around 3 inches thick. my biggest
    problem is that I can't reposition the lights/tent/camera for each shot as I
    will be doing very many shots all the time (I.e. production line). the
    stones are often super heavy and can only be laid down flat on a skateboard
    type roller. right now I roll them into a photo both that is one size and
    bounce my lights off of the white walls which then give indirect light to my
    stone. but the problem is since the stones very in size the light has hot
    spots on some of the different size stones.

    Should I get one big huge light with a giant light diffuser box around it?
    any problems with doing that? what about shadows etc.. what about getting
    two huge lights with light diffusers. hot spots?
     
    James, Dec 2, 2005
    #1
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  2. Without knowing what you want as results, I can only suggest two ideas
    that may help or may be worthless.

    1. Polarize the light sources and the lens.

    2. Spraying a little water on the rocks can create quite a different
    effect.

    If either works great, if not, I am out of ideas for now.
     
    Joseph Meehan, Dec 2, 2005
    #2
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  3. James

    James Guest

    the result should have no hot spots or glare. the stone is like a plaque and
    is one flat peice. do you know of a liting figure that would work for my
    needs that doesn't need to be repositioned depedning on the size of the
    stone? since we take a lot of photos i don't want to have to adjust the
    lights or the tent or reflective materail each time. if i polierize the
    light, does that mean i would put a polerized lens on the camera? would
    there still be hotspots? can you recommend any lighting equipment that would
    work for this project?
     
    James, Dec 2, 2005
    #3
  4. I don't usually top post. but I'll follow your lead in that.
    You've got the idea with diffuse light. You need to spead it out
    as much as possible, without using an angle that reflects off the
    stone into your lens. Do you have to shoot at 90 degrees to the
    polished surface? If you can angle it a bit, you can place a
    black matte opposite to absorb the light and prevent a reflection.
    You have different sized stones, but they all lay flat, right?
    Diffuse side lighting and light from the general area of the
    camera lens, (under the camera), shouldn't reflect if you can drop
    the angle enough. In fact the light need not be terribly diffuse
    as long as the reflections are going in another direction and not
    back into the lens. Hmmmm. you might even be better off with
    non-diffuse light from the sides, and black, light absorbing
    material everywhere else.
    If you need to be at 90 degrees to the surface, lights can be
    arranged at a shallow angle so the reflections skip off to the
    sides and don't reach the lens. They can be directed right at the
    stone in that case and you have no diffuse lighting and
    reflections are absorbed in a "black room" environment. Yeah, I
    think that would be best.
     
    Fred Williams, Dec 2, 2005
    #4
  5. James

    m Ransley Guest

    A polariser on the lens should do for reflections.
     
    m Ransley, Dec 2, 2005
    #5
  6. James

    James Guest

    my camera needs to be directly above the stone. i have tried putting lights
    with no defusers on each side of the stone and "skiping" the light off it.
    but that creates really big hot spots. is there a type of light fixture and
    bulb you would recomend that won't do this? i have also tried using defusers
    but they barly make any light show up on the stone at all. im using this
    type of light, i have two of these:
    http://cool-lux.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=LK2000&Category_Code=DHMCKL
    and i tried using little white defusers for them. is it that this just isn't
    powerful enough for the size of my stone? on avg the stone is 30x15 inches.
     
    James, Dec 3, 2005
    #6
  7. James-

    Are you familiar with the "Blimp" light diffuser? It is like a
    translucent bag that goes over your flash, spreading its light over the
    inside of the bag.

    I don't have any references, but they are commercially available. They
    may not be best for your application, but others have found them useful
    for difficult lighting situations.

    Fred
     
    Fred McKenzie, Dec 3, 2005
    #7
  8. James

    Deedee Tee Guest

    Place one light on each side of the largest slab you must photograph,
    so that no reflection from the lights shows in the picture. Use black
    curtains around the setup to cancel any unwanted environment
    reflections. If you have uneven illumination on the slab, move the
    light sources higher up and further away sideways from the slab. This
    is the only thing you can do within your constraints. You need to
    place the lights at a distance from the slab of at least 4-5 times the
    width of the slab. Once you have a setup that works for the largest
    slab, you can photograph all the others by changing the camera height
    above the slab or the camera lense. I assume you are using a studio
    stand or repro stand, but if you are using a normal tripod you should
    add a horizontal arm to move the camera out and directly above the
    slabs.

    Usually there are fine scratches on the surface of polished rock, and
    probably these are better controlled with point sources of light
    (i.e., no diffusers). A point source of light may also add interesting
    sparkle from mineral crystals in the rock.
     
    Deedee Tee, Dec 3, 2005
    #8
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