Tuesday, June 15, 2010

In Hindsight: Large Dimly-Lit Room with High Ceilings (Basic to Intermediate)

HindsightThis is the second of a series of entries where I examine some of the older pictures I took and analyze what I would have done differently to learn from my mistakes.

Issue: Lighting and Exposure

Situation: church with dim ambient lighting.  I wanted to have a decent exposure.

How I did it then: if I recall correctly, I tried to bounce the flash from the walls a la Neil Van Niekerk. I think I was either in Program or Aperture Priority.  My exposure settings turned out to be:
ISO 200, f/4, 1/6, flash used.

This was the result:

On the plus side, it appears as if flash was not used.  However, there are many problems with the exposure and lighting in the picture: white balance, underexposure, blur from subject movement.

Analysis:
1. White balance: most DSLRs don't do well with artifical light sources.  White balance is also often a problem when bouncing light, which takes on the color cast of the bounce surface.  When the two issues are combined, it's a recipe for white balance disaster.  There are two things that can be done to fix the white balance issue: a. take the shot in RAW. b. Use the appropriate gel on the flash if necessary. You have a lot of latitude with changing the white balance of an image shot in RAW. It would have been easy to click on any of the white object in the picture such as our kid's outfit to correct the white balance. 

Ideally, a gel should also be used on the flash to match the ambient light. Otherwise, there will be a difference in white balance between the subject (illuminated by the whitish/bluish flash) and the background (illuminated by yellowish incandescent light).

2. Exposure: ISO here was way too low given the dim ambient light as well as the bounced flash.  Because of the low ISO, and not so wide aperture (I think I was using the Tamron 18-250), the shutter speed was a glacial 1/6 - which naturally resulted in blurry subjects.  A high ISO is also needed when bouncing flash, because the light has to travel the distance to the bouncing surface and back, plus lose some stops of light depending on how reflective the bounce surface is.

How I would do it today:
Option 1: handheld umbrella
I think the ideal solution here to get soft light on the subjects is to use an umbrella (I would probably use a handheld umbrella).  Because the subjects and background are about evenly lit by ambient, I would underexpose the ambient by about 1 stop then use the flash with umbrella to provide the key light.  The ISO needn't be so high because the umbrella is more efficient than bouncing, but I would still probably choose 400 to 800 ISO.  Given that it's a group shot, I would probably choose an aperture no wider than f/4 to get adequate depth of field, and then adjust the shutter speed (or exposure comp) to get -1 stop underexposure for ambient.  I would adjust the flash exposure compensation as necessary to achieve a good overall exposure.

The result would probably look kinda like this shot, where I used a handheld umbrella in a mall where the ceiling was about 5 stories high.

D80, Tamron 28-75, f/2.8, 1/200, ISO 400, flash: TTL -1.0 FEC


Option 2: bounce.
Bouncing may be possible but it won't be easy. I would probably select 1600 ISO to maximize my bounce capability.  I would zoom the flash to 105mm to get the highest guide number (the bounced light will still be soft).  I would probably try to underexpose the ambient by 1 stop, and shoot as above.

The result would probably look a bit like this shot, where I underexposed ambient by 1 stop then bounced the flash to a ceiling that was about 20 feet high and about 20 feet away laterally.


D300, Tamron 17-50 VC, f/4, 1/50, ISO 800, flash: TTL @ -0.7 FEC

The following is another example of a similar type of shot (also 20 feet high ceiling, about 20 feet away laterally).  Ambient was also underexposed 1 stop using exposure compensation (I was on aperture priority).  Flash was bounced to the ceiling at high camera left at +1 FEC (to balance out the -1 EV exposure compensation for net 0 FEC).

D80, Tamron 28-75, f/2.8, 1/60, ISO 200, aperture priority -1 EV exposure compensation + on-camera bounced flash: TTL @ +1 FEC (net: 0 FEC).