Photographing color change garnets? Questions!

[Quantz Studios]

Kenny, something we agree on. I'm a trained artist and that was also the hardest hurdle to jump- drawing what your eyes SEE, not what you think you see, or think you know. Once you are able to do that, a whole new world is opened up to you. Same thing with colors- In drawing II, when we started using pastels, the first thing my instructor did was take our blacks and grays from our pastel sets and hide them from us. "How do we do dark and shades now?!!" With, color... Who would have thought, that instead of using black or grey to put that shadow the apple casts on the banana, you grab the brightest magenta you have and smear it into the yellow and- viola, a gorgeous natural-looking shadow that doesn't muddy up the colors like gray or black!

But art is art, gems are gems, physics is physics and photography is photography... None of them is simple, easy, or straightforward across the board or easily related in totality. This thread is a topic that can be dissected and discussed until we're all blue in the face. But it could get very interesting!

If you want cheap stuff to experiment with... you could even try finding some color-change... you know what... Its inexpensive and would be sure to show you a complete, dramatic and 100% color change- Unlike some inexpensive and low-end natural materials.

 

[chrono]

White balance is extremely important when photographing cc stones, lest the background colour becomes tinted and the stone shows too much blue. My quick and dirty method, although unprofessional looking, is that hand shots require almost no tweaking or colour correction. For some reason, the camera sensor adjusts better with a body part than a white object in the background. My CC garnets also shift beyond 2 colours so the light source is important.

 

[corundum_conundrum]

If you want cheap stuff to experiment with... you could even try finding some color-change... you know what... Its inexpensive and would be sure to show you a complete, dramatic and 100% color change- Unlike some inexpensive and low-end natural materials.

Haha...that unnameable and verboten substance.

 

[kenny]

Actually I'm gem shopping now.
I'm not sure what the point is, though ...

Anyway, here is my plan for a somewhat scientific test ...
Comments please with supporting reasoning if you have a suggestion how to better conduct this test ...

1. Record florescent light's color temp in degrees Kelvin, let it warm up for an hour with the gem under it, so the light and the gem are stabilized and stop changing color. (is an hour enough?)
2. In the position that the gem will be I'll hold a calibrated 18% gray reflectance card that I bought from a photo store and hold it parallel to the camera's sensor plane.
3. Press my Nikon D600's Manual White Balance button, since AUTO white balance is only a sloppy guess at each lights' color temp.
4. Place gem on grey card and take a pic. (Unlike a white or black background a gray card is closer to the MIDDLE of the camera's exposure range or latitude, where the sensor is more linear than near its upper or lower extremes or shoulders of its curve.)
5. Do same with a tungsten incandescent (old fashioned light bulb) light source.
6. Do same with full direct sunlight when the sun is directly overhead.
7. Do same with evening sun. (Sorry, I'm not flying to all latitudes between equator and a pole.)
8. Load all pics into computer.
9. Look at all pics ensure all gray backgrounds are still neutral gray, and if not correct them.
10. Post all images.

The color of the gems will just look however they look in all 6 pics.
Then what?
What have I proven?
Am I suppose to then report whether the pics match my recollection of the gem's color in those light sources?
(That seems like a can of worms, given my previous posts in this thread.)

What is the problem we're trying to solve here, anyway?

One issue I notice with the above procedure is I will not be using so-called full-spectrum electrical light bulbs - which someone here posted are so essential when evaluating/photographing color-change gems.
I just don't feel like spending the money ...
Perhaps they DO something to the gem or the light coming from it that my cheap not-full-spectrum) light bulbs do not do.
Even then, what's the point of getting expensive 'full-spectrum" bulbs.
Few mortals have them, so is what they tell really useful?

Besides, what's the difference between a 4000K bulb and a full spectrum bulb? even light output at all wavelengths?
If so are they not useless for telling use what the gem looks like under "tungsten" or 'fluorescent' or daylight?
And keep in mind the camera can properly white balance to light sources that are not 'full-spectrum'.

There are so many aspects to this.