Brain Teaser: The Glowing Christmas Jar

It's Friday, so let's have a little fun this morning. I captured a single exposure of this plastic, Christmas-themed jar last night.

The question is – can you figure out what technique and / or tools I used for lighting the jar?

Note: The only editing I did in Photoshop was add the watermark and apply a small Brightness/Contrast adjustment.

Submit your answer in the comments. I'll let you know if you're right. [Sean]

The Reveal

Site visitor Nancy just emailed us the correct answer (she said she forgot her Disqus password so was unable to comment).

"Possibly cross-polarized (polarizing filter on lighting, polarizing filter on lens, set at right angles to each other to eliminate the facing-forward reflections).
Clue - rainbow stress marks on the plastic."

Indeed, she is right. I first opened up a blank / white document in Photoshop giving me a large blank white background via the laptop's WLED screen. The clear plastic jar was placed on a black laminate board on top of my laptop's keyboard (I used a couple of books to raise the height a bit).

As the WLED is a polarized light source (no filter required for it), I was able to use a polarizing filter on the 24-105 f/4L to block all light coming directly from the screen. However, the light passing through the plastic gets diffused (and changes directions, rendering it unpolarized), so the light passing through it is visible.

Here's a picture using the same exact exposure settings with the CPOL turned so as not to block the light coming from the screen (you can see my framing actually caught the left edge of the screen):

Once the polarizer was rotated to block the laptop's WLED light, the shot atop this post was the result. Here was the simple setup:

Thanks to everyone who participated! I enjoyed reading the responses and I think there were some great ideas presented.