Just another SWAG (Schitty WAG) .... does my green font show up on yer screen correctly :D?

I work in optics, and have background in getting digital cameras to properly recreate color and hue correctly...

Definitely a built in white balance problem with the camera. You need to find a way to output RAW if you're going to compare at that level of detail.

Try this...3 pictures, one after the other, with the camera on a tripod. Recreate your wheel image. First, take an image with both wheels, then take away the small piece, then take away both and only image the ground. The three SHOULD look identical as you flip back and forth, but they won't. The camera is looking at the histogram of each color channel and finding the median (or some other internally decided value), and setting that to be "white". The full wheel is getting more sunlight and a brighter spot, so it's probably deciding the color balance. The camera might even have zone balancing, so it's setting each differently.

With RAW, you should be able to go between the 3 images and see the exact same colors/levels/hues between each, which is when you're looking at the actual raw pixel level data. THAT is what you need. The files will be huge (on the order of a Gb each).

Looks like the Nikon D7200 has a "manual preset" white balance, use that, the manual says settings from 1-6, see what "1" and "6" do on a test image.
Also, set output to NEF (RAW) and 14 bit depth, instead of jpeg. JPEG files have their own set of internal calibrations that change the picture even more...
ALSO, see if you can get an image using manual exposure and aperture settings, the auto settings might change the values between shots as ambient light changes.

In other words, take that expensive hi-tech camera and make it stupid, all of the bells and whistles are modifying your image behind your back, and you're critical enough that you can see it.

When you work on Photoshop, keep it in some high-bit format, like TIFF (or RAW, if it can keep the image that way). RAW file format is 3 numbers per pixel giving the RGB amplitude and nothing else. It's the actual data that the CMOS detector picked up.

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Centering on grey allows the highest detail threshold for each picture.

While that is true, a lot of people don't understand that the camera is going to attempt to do that with every picture. They expect a picture to be black if the object is black and white if the object is white.

Read this under the dying heading:

https://en.m.wikipedia.org/wiki/Anodizing

I think Porsche may have used a tin based inorganic dye vs an organic dye.

Inorganic is far more colorfast.

Again, I am not an expert!

Another test today to get more gold. On wood in the sun the colors are very accurate using the Nikon 7200. You can see the original piece is very close and is extremely close in person. The test piece is a little more gold. Even though the first parameters are closer to the original, the customer has chosen the more gold version. I can't blame them, it's a beautiful, subdued bronzy gold.

One more test to replicate the gold on a perfect surface, then one more on an entire manhole cover assuming all goes well, the set of 4 9x16 Club Sports.

http://forums.pelicanparts.com/uploa...1615413442.jpg

On the full-frame nikons there's usually a "WB" button and you use a scroll-wheel to cycle through the options. My 700 and 610 have little "sunshine", "clouds", "lightning bolt (flash)" and other options, as well as a fully manual setting.

And if you don't have a grey card, the cap from a 35mm roll of Kodak film was 18% grey I think. ;)

There are so many moving parts to what you are trying to do.
You think you see a color, but the brain is pretty tricky and lets you see what you think you ought to be seeing. The camera will see it differently. It's sensors are different than yours and it doesn't have a brain that says, "I know that should be black, so I'll let you see black."
So even if you clear the first hurdle and the camera sees and records exactly what you see (not likely), you then you have to display what the camera sees on something. Show the same image on two different monitors and they probably will not look the same. If you have prints made, who knows what they will look like.
The best you can do is a decent approximation.

Shaun - Taking photo's of the wheel to compare different anodize techniques should be treated like an experiment. Control the variables as best you can. This would include the back ground used, the lighting used, the angle the light hits the object, the camera angle relative to the object and lighting, all camera settings (ISO, aperture, shutter speed), even the distance from the object too.
Once you can get images with all those parameters the same, as much as possible, then you'll be able to really see differences in the anodize formula used.
Just my opinion from out here in the cheap seat in CA.

Also keep in mind the digital camera may be recording light that the human eye is unable to see, and in the photo print, it is printing it , or showing it on the monitor different than you see it with eyeball 2.0

A good example of this is many digital cameras can see the ir transmitters that are used in remote controllers ie tv remote.

Got a old film camera? It records the photons that pass through and hit the film.

A good explanation why some producers miss the old film cameras, even though so expensive to film using them.

most of this I gained from a conversation with a production friend at WDW, so I may have not understood perfectly.