photographing polished granite and I'm going MAD

[Ascheids]

I'm trying to create a system of photographing 10' x 9' polished(mirror like finish) granite slabs. This is one of the hardest things I've ever done. Any dark colors reflect everthing it faces and with mixed lighting in the warehouses they are stored in, trying to get accurate color is a huge struggle. Mercury, florecent and natural light make it a constant battle, even with a custom white balance. I've been using a lot of angled shots with constant lighting. 2 lights set up at 45 degrees on each side of the slab and hiding the camera behind a huge black drop cloth, but this does not work for all the colors. Does anyone have any ideas on this? I would love to hear them.

[zacker]

tried a Cirlcular polarizor yet? it will get rid of reflections. it might help you.

[cosworth]

Tripod, RAW and a white card all after you shoot with a polarizer.

Tripod kills the shake and gets the image nicey nice nice. RAW you use to adjust white balance with the white card. Colours are then dead on. Polarizer makes the mirror finish go away. Polarizer reduces exposure about 2 stops hence tripod.

[DavidEB]

I can see it's a challenge.

check out light, science and magic (http://www.amazon.com/Light-Science-Introduction-Photographic-Lighting/dp/0240802756/sr=8-1/qid=1164759541/ref=pd_bbs_sr_1/002-7999628-0344016?ie=UTF8&s=books)

look at the section on soft light sources and critical angles. It covers the theory behind what you're trying to do.

I haven't tackled slabs that big but I do pottery (http://www.pbase.com/davideb/pottery), which is the same concept. your light source has to be diffuse -- source at least as large as the subject. The light source should be outside the critical angle of the camera (see the section in the book).

You might try scaling up the light tent (http://photography-on-the.net/forum/showthread.php?t=139812) approach -- a large family camping tent with semi-opaque walls, so you have non-directional light, set that up outside either on a cloudy day or in the shade, and then use a long shutter.

polarizers only are effective if the light source is polarized -- not for most artificial lights.

also, if you want the whole slab in focus, you have a problem -- you may need to be shooting it face-on, in which case you see the camera reflection. A very large f-number might give you the needed depth-of-field for a shot outside the critical angle. I've never tried it, but a tilt-shift lens would let you get the slab in the plane-of-focus without seeing the camera reflection.

good luck.

[PacAce]

Use strobes or flashes set to both sides of the slab to provide even lighting. Use black gobos or boards to shield the other lights in the the area to keep them from reflecting off the surface of the slab.

[SRPhotographic]

If I'm not mistaken, granite is a grey stone. Why not convert to b&w?

[woffles]

They sell large panel diffusion scrims to soften light, you might need something like that possibly double walled to prevent hot spots. A white sheet stretched out with the light above it might work.

[PhotosGuy]

with mixed lighting in the warehouses they are stored in, trying to get accurate color is a huge struggle. Mercury, florecent and natural light make it a constant battle You need to overpower those lights. but this does not work for all the colors What I said above, + some colors in nature can't be duplicated in RGB, & if you go to prof print as in for catalogs, CMYK may not be able to duplicate the colors either. Add a disclaimer, "Stone varies, & the colors you get may not be the colors you see here"? ;)

[chtgrubbs]

This should be photographed the same way you would copy art under glass. You need for the surface of the stone to "see" only black. First, you need to shut off all lights except the photograhic ones. This may mean coming to the location during non-business hours. Now put one or two lights on each side of the stone at a 45 deg. angle, just like copy lights. Use an incident light meter to measure the light across the stone and adjust the angle of the lights so that the light is even all the way across the face of the stone. On a piece that big you will probably want two lights on each side to get even coverage. You DO NOT want a large diffuse light source as this will only contribute to the problem of specular reflections. I like Lowel TotaLights as they give a very even light output from a small source.

If the warehouse space is big enough your shooting lights will not illuminate the background behind the camera enough to reflect in the stone. If they do, then you will need to put a black background behind the camera. You could hang a 9 ft black seamless paper behind the camera. It may require two rolls of seamless side by side in order to be large enough, or maybe you could get a 24ft black muslin. Drape the camera and tripod in black so they do not reflect in the stone, and use a remote release or self time so you will not be in the shot.

Polarizing the light sources and using a polarizer on the lens may help bring out the colors, but you can't rely on polarization alone to remove all reflections, especially from and uncontrolled environment.

[tweatherred]

...Polarizing the light sources and using a polarizer on the lens may help bring out the colors, but you can't rely on polarization alone to remove all reflections, especially from and uncontrolled environment.

Interesting, I posted a question on that very technique earlier today:

http://photography-on-the.net/forum/showthread.php?t=245372

[wayne_eddy]

have you tried just putting it on a flat bed scanner .... or putting the scanner on it!

[DocFrankenstein]

You'll need HUGE diffusers which overpower the ambient.

I doubt the polarizer would help much.