Thursday, June 2, 2011

Balancing Flash and Ambient: Candlelight Photos

ISO 1600, f/2.8, 1/30. TTL flash.

Shooting in candlelight is easy if you know a few simple techniques.

We were having lunch at Disneyland's Blue Bayou, the restaurant inside the Pirates of the Carribean ride.  It was dark inside the restaurant, which was lit mostly by the votive candles at each table, and some small paper lanterns overhead.

If I had taken a photo with a camera on auto mode, the popup flash would have fired, and the ambient would have been underexposed, leading to a deer-in-headlights look with a totally black background.  Taking a photo without flash would have preserved the ambience but due to the darkness, noise would have been prominent, and the shutter speed would have been so slow that the subject would appear blurry.

Instead, here are techniques for candlelight shots:
1. Use the flash.  Using the flash would allow sufficient light so that we don't need to resort to ultra-high ISO or very slow shutter speeds.  If the flash exposure is too bright, just use flash exposure compensation to decrease the flash exposure.

2. Use a CTO gel on the flash.  A flash without any gel would give off whitish-bluish light with a color temperature of around 5500K.  The light would look much cooler compared to the warm color of the candlelight.  To match the flash color with that of the candlelight, we need a CTO (color temperature orange) gel, which will will mimic the orange tint of candlelight.

If you don't have a CTO gel on you, you can make-do by taking the shot in raw (as opposed to JPEG), then adjust the color balance during postprocessing.  The disadvantage of this alternative is that the background will look more red/orange than normal.

3. Balance the ambient exposure.  By default, when taking flash photos, most cameras will have a shutter speed that is around 1/60, which is probably too fast for a dark environment like this -- resulting in a totally dark cave-like background.  Instead, use manual exposure to get an adequate ambient exposure.  Just use a combination of higher ISO, wider aperture, and slower shutter speed, until the light meter shows around -0.7 to -1.3.

Why not zero the meter?  If you do, then you make flash blur more likely.  When the ambient is underexposed this way, flash blur is not obvious even though it may be seen on close-up.  For the same reason, you don't have to worry if your shutter speed ends up being quite slow.

That's all there is to it!

ISO 1600, f/2.8, 1/30. TTL flash.

I got feedback about the images being too orange or red (see comments).  Interestingly enough, on my laptop they look ok to me but on my office computer monitor, they do look too red (my iphone seemed somewhere in between).

Anyway, let's have a look at the histograms for the shots above:

The histogram shows the candlelights being clipped but otherwise there are no clipped channels.

Nonetheless, I looked around to see the how other photographers and filmmakers simulate firelight.  It seems that some photographers prefer to use a CTO (color temperature orange) gel while others prefer a CTS (color temperature straw, i.e., yellowish) gel.  In movies, there are likewise candlelight and firelight scenes that have a red/orange appearance while others have yellowish highlights.

To show the difference that this makes, here are the same photos, with a yellowish look this time (by fiddling with the white balance):

And for those who prefer a more neutral color, here's yet another version edited by co-author mshafik: