Bounce flash photography & The Inverse Square Law
If you find the title of this article a touch intimidating, please stick around and watch the video. It is important to understand how The Inverse Square Law affects bounce flash photography, and creates a specific result where the background appears brighter when the flash is bounced properly without on-camera flash modifiers. I know that is counter-intuitive, but that is what happens when you bounce your bare flash behind you instead of using a light modifier on your flash. The accompanying video, linked to below, explains this in hopefully clear, easy to understand ways.
The photograph at the top is typical of the results. Now this might not be the way you like your wedding receptions to be lit. Perhaps you prefer cross-lighting the dance floor with multiple flashes. That’s cool too. Working with just the single on-camera bounce flash gives really good results with no cross shadows and awkward shadows. Every photo works with the light fall-off pretty even from front to deeper into the scene.
The key to this is that the light source isn’t your flash on your camera — instead it is the wall and ceiling far behind you. That is your light source now, and the light fall-off will be much more gradual. This is explained in the video. In explaining the way that the inverse square law is implicated, it is only necessary to understand that you lose two stops of light every time you double your distance from your light source. Simple. An easy enough rule to remember. From there on, everything will fall into place.
For those of you who prefer Youtube, here is the link to the video on Youtube : Bounce Flash – That one thing you need to know.
On-Camera Flash Photography – revised edition
This book is explains a cohesive and thorough approach to getting the best from your on-camera speedlight.
Particular care was taken to present it all with a logical flow that will help any photographer attain a better understanding of flash photography.
You can either purchase a copy via Amazon USA and Amazon UK, or can be ordered through Barnes & Nobles and other bookstores. The book is also available on the Apple iBook Store, as well as Amazon Kindle. Also check out the Amazon Kindle store.
Learn more about how the cover image was shot.
Another example from a different event – a Bar Mitzvah party – but the results are very similar. Notice how the hands in the front are as well lit as the boy’s face as he crowd surfs. From there on, the light fall-off is still there, but not abrupt. All the important elements in the frame are similarly well exposed. All because the flash was bounced off a wall behind me on the stage … and then the light fall-off is less rapid. All because of how The Inverse Square Law works at longer distances.
Seriously, check out the video – it is all explained in there.
Camera settings and gear used
- 1st image (at the top) : 1/100 @ f/3.2 @ 2500 ISO
- 2nd image : 1/80 @ f/4.5 @ 2500 ISO
- manual flash, on camera, bounced with the black foamie thing.
- Ambient exposure was about 3 stops under.
- Sony A9 (B&H / Amazon)
- Sony 24-70mm f/2.8 GM (B&H / Amazon)
- Profoto A1x flash for Sony (B&H / Amazon)
- Tutorial on Bouncing your flash
- The list of articles on bounce flash photography
- Black foamie thing : modifier for on-camera bounce flash