To do this trial I used a foldformed pure gold and fine silver pendant. The pendant was photographed on the following backgrounds and in this sequence:
+ on non-reflective glass elevated above a white background.
+ on non-reflective glass placed on a white background.
+ object placed directly on the white background.
All other possible variables such as lighting, exposure time, white balance preset, etc. were kept constant. As one can see from the photos below, placing a support of glass under the jewelry will darken the background.






Above are the results after importing the original photo into PhotoShop and doing some corrections. I want a white background. So I chose a background point on each photo and using the curves tool, arbitrarily brought the R, G and B channels up to a 245 value (255 being white). Using curves the shadows were set at a value of 65.
The results were a bit harsh for the two photos that had the darker backgrounds due to the glass layer so I re-photographed the pendant both on the elevated glass and on the glass placed on the white background. But I placed a small piece of white on top of the glass so that I could see it in the upper left corner in the viewfinder. I could have cropped this out but have left a small amount in the photo to show how this was done.
Here are the original, un-corrected photos and below them are the photos after PhotoShop.




This time the background point to be brought up to white was chosen from the small white area in the upper left because I know that this should be white. Again the curves tool was used to bring the point’s R, G and B values up to 245 and the shadows were set at 65.
The moral of the story is that, yes, using a layer of non-reflective glass, either elevated or placed directly on the background, will darken the background in the photo. But by photographing the object placed directly on a white or partially white background the light areas can be corrected to white. Also, a small, croppable white sample placed on to of the glass can be used as a valid color correction point.
I have a page on my web site that explains the techniques that I use for jewelry photography.
