We'll use a polarized-light-source technique to address a common problem: glaring flash bounce. We've all had it ruin a potentially awesome impromptu picture because we don't notice there's a window behind the subject. The flash bouncing off the glass creates a flare that throws off the exposure metering and creates a deathstar exploding glare.
Once you've mastered controlling reflected light, you'll find many different situations where tweaking the amount of bounced fill-lighting can make a huge difference in the final quality of your pictures.
Also, I'll do two flash units at the same time because it's super important that both flashes have the polarized plastic films aligned the same direction. That way when you calibrate the lens' circular polarizing filter in the last step, it will work correct for either flash.
Before and after demo
The before and after shots were taking under the worse condition possible. The flash pointed straight at a mirror.
These shots were taken back-to-back. I did not clean the mirror and I kept the camera settings the same between these shots. Pretty impressive results!
Step 1: Materials
Luckily, they are easy and relatively cheap to get online. At the end of the article, I list my favorite provider.
You will also need to buy a circular polarizing filter that fits your camera. Most people who do high-end digital photography already own one. If you don't, you probably should get one. They are great for outdoor photography in general.
One (or more) flash units.
If you have multiple units, you want to do the all at the same time. Don't forget your built-in camera flash.
- Circular Polarizing filter for lens.
- Electrical tape.
- Cutting supplies like small wire cutters, scissors, razors, etc.
- Some paper or tracing paper and a marker.
A permanent marker
Used click-off the correct orientation of the circular polarizing filter.
Step 2: Prep Materials
First, make a template of the shape of your flashes' front area. Depending on the shape of the flash, you might want to make the templates such that there's a little overlap (as I do for the built-in camera flash. See step 4.), so when you tape it into place, you don't cover any of the actual flash output. Or, you might make it smaller than the flash window area (as I do for the external flash), so it can fit flush with the recessed window.
I use some tracing paper and a marker (after verifying the marker doesn't bleed through the paper) to get the outline.
You can use whatever technique works for you. It really isn't that important.
What's important is keeping track of which way is up and front for the filter.
My mistake: In this write-up, you may notice I have the external flash flipped 180 degrees the wrong way! You can tell because the buttons that control the flash unit are facing the same way as the flash.
Step 3: How to Cut
**It's super important to keep track of the orientation of the film for each piece you cut.***
Which side is up and which side is front are kind of important, too.
To keep track, I cut a small rectangle of electrical tape and place it on each of the bottom edge of each piece. Also, mark the main piece of polarizing plastic film so you can go back and cut more later.
Cutting this stuff sucks
The plastic film I used was high-quality, thick stuff. Cutting it was harder than I expected. What I found that worked:
- Use a razor to etch outlines on both sides of the plastic. There is a thin film on each side that's fastened to a thick core. A deep etch will decrease the chance the surface will peel away as you cut.
- Once I etched both sides, I found some small wire cutters allowed me to cut through the touch plastic core.
- I suspect that glass cutting tools would be useful, but I didn't have any handy.
Step 4: Attach Filters
WARNING: Be very gentle with the internal flash!!!
It is a delicate piece and when you close/open it to make sure the polarizing film and tape aren't getting in the way, do it carefully.
Make sure to keep the correct side of the film facing front and down.
Step 5: Calibrate the Circular Polarizing Filter.
The circular polarizing filter should freely spin even when it's tightly attached to the camera lens.
There are two ways to figure out what rotation of the circular filter is correct.
- Get a handheld flashlight and the remaining bulk polarizing plastic (the piece you have left over cutting the smaller templates out).
- Orient it the same direction as the ones attached to the flash (remember the which-way-is-down tape?).
Slowly turn the circular polarizing filter while looking through the lens on the lens until the light dims. Note, the overall room might get brighter, just watch the actual beam.
Note: this might work best for OLED viewfinder based cameras.
- Aim at a mirror and just take pictures.
- Each shoot, just rotate the circular polarizing filter on the lens.
- It should be pretty obvious when you get it right.
Use a marker to delineate which rotation is the correct one and you're done.
No more fear using your built in flash!
Where to purchase the polarizing filter film
I highly recommend getting it from 3d-drt-3d merchant on eBay. (Disclaimer: I have purchased my polarizing filters from this merchant; however, he is not a personal friend nor do I make any money from endorsing him.)
http://www.ebay.com/sch/merchant/3d-drt-3d Look for 4x4 inch Linear Polarizing Filters.
As of the writing of this article, they were <$20 for 2x of them! Pretty cheap for camera equipment.
You even have left over material to put on your LED lighting!
If anyone can suggest other sources, please do so in the comments below.
Step 6: Conclusion & Examples
- Close-up of shiny metal or glass objects.
- Natural photography of wet objects like a frog or leaves.
- Portrait photography of subjects with glasses.
- Portraits with sweaty subject like athletes. You'd have to be in the shade with the flash for it to work.
Using polarized light isn't a magic bullet. There are cases where you want light reflections (like in the eyes).
But this technique allows you to control which of your lights sources are flat fills and which are highlight reflections. Because it offers a unique tool, it really should be a part of every photographer's toolbox.
I really encourage you to click through the pictures to see larger versions. All pictures taken with my Sony A77.
Example 1: Bathroom
Both shots taken with the same exposure and filters; however, the circular polarizer is NOT aligned correctly. The apparent exposure difference is caused by the camera's internal light-meter not picking up the glare. That results in a longer flash and better exposure balance without changing the metering.
Example 2: Slimy wood
This shot was taken on a rainy day with some clouds. The exposure on these shots may not be ideal, but look at the wet wood at the bottom.
Example 3: Wet foliage
By removing the flash lighting flares, we get a better dynamic range of the green in the plants.
Example 4: Tolerant pug in glasses
Lelu the Pug a real trouper when it comes to helping me take pictures.
This example is one where the polarized light technique may not be ideal. It does give dynamic range to colors and improves contrast and details around the face, but you WANT reflections in the eyes. This is where a round fill light without polarizing would have been a nice addition.