Monday, June 2, 2008

ETTL vs Guide Numbers Setups

After my recent investigations into using Guide Numbers (GN) in meters and feet as well as also trying the charts and calculations out for the first time, I decided to see how using Guide Numbers compared to using ETTL.

The main aim of the tests was to see how long it would take me to set everything up and get a few shots off which I considered a good starting point for a shoot.

In the end I achieved pretty good results using both techniques and with a bit of practice would be able to do either one relatively easily. In summary I had the following high level observations:
  1. Using GN's for each flash made me think about each light when I was setting it up. Using ETTL made me take a slightly more "try and see" approach
  2. Both methods allowed me to get to good starting exposures relatively easily
  3. Using the GN allowed me to use Pocket Wizards and free up the 580EX II I had to use for the ETTL approach.
  4. I liked both methods - which surprised me :-)

Guide Number Shots


The shots below were taken using Tungsten White Balance with a 580EX II camera right with a Full-CTO gel on a shoot through umbrella and a 430EX background light with a Full-CTB gel on the curtains behind me. All of the shots were good enough as a starting point for a shoot.

This was the first shot out of the camera after using the GN tables to calculate the F-Stop from the distance including the light modifiers. The background light is using a Honl 8" Speed Snoot - which does not affect the GN calculation.

The second shot is the same setup, but with a white polystyrene board held camera left as a reflector. The shadow behind my head is my bicycle seat!

The shot below was the same as the one above but with the reflector held closer to my face making the face brighter.
This time the reflector was held further away from the face making my face darker butstill with some light filling in.

For this shot the reflector was removed.

The last three shots were taken with the light camera right moved at a higher angle. This shot as taken with no reflector.-

This shot had a white reflector camera left

This is the same shot as above with the white reflector but shot with an aperture 1 stop brighter. This is my favorite shot.

ETTL Shots
The shots below were taken using Flash White Balance with a 580EX II camera right on a shoot through umbrella and a 430EX as either the background or kicker light camera left behind me. All of the shots were good enough as a starting point for a shoot.

This was the first shot out of the camera after setting up the remote flash for the flash unit on my camera as the Master and the shoot through umbrella flash as a slave. Compared to my first shot above using GN's this shot is slightly brighter

The second shot below was shot with a magenta gel on the 430EX as a background light.

The next shot below was shot with the 430EX as a kicker light camera left. The ratio was set to 1:1 and the kicker light was too bright.

The following shot below was shot with the 430EX as a kicker light camera left. The ratio was adjusted to 1:8 and I felt that the kicker light was more subtle and acceptable.

The next shot is exactly the same as above but with a white reflector card camera left.

For these last two shots below I tried to replicate the first set of shots I did with the GN Tables. The first shot I found was slightly too dark.

I adjusted the flash exposure by 1 stop for the final shot which I fond was quite similar to the final shot in the first set.

I know that I've harped on about using the GN tables far too much and I hope that one day I will be able to setup and get close enough exposures with the first shots without using the tables or ETTL. For now though, I feel that both the GN tables and the ETTL setup with Canon are easy to use to quickly get acceptable results.

Finally I don't feel frustrated with using the flashes and am able to move on in the Lighting102 course.

Please feel free to leave comments or questions below or email them to me.

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