Part 3: Control Light and Get the Look You Want Using a Flash
I am going to explain this as easily as I can. In real life I could show you, which is how I learn easiest. I don’t want these written words to confuse you, or make you skip over it and class it “too hard”.
I am going to explain it to you in scenarios we might have all been in. Both the images below off camera flash were used. A very basic set up.
In both shots, I wanted the backgrounds as I saw them, but I wanted the subjects lit by flash. If I had of shot these images in natural light, I would have had dark subjects, or well lit subjects and blown out backgrounds.
All I used was a 580ex11 speed light for both these shots! The flash was fired into a 40 inch silver reflective umbrella (for wider softer light). My shutter speed was 200, my iso 100, and an aperture was f 7.2 for the family shot and 4.5 for the kite shot
How shutter speed effects flash photography
This element controls the ambient light. This means the light already in the shot. If it is at night, this means the lights from buildings, the stars and moon, or cars etc. If it in the afternoon, it is the golden light etc.
If I do not like the surrounding light of my chosen location or subject, OR if I want to make the background darker, I INCREASE my shutter speed to 200 (maximum). This cuts out as much light as my camera will allow in the background.
Two images one with the background purposefully darkened, one with the background left as it was to the naked eye.
HINT * your image background is still not dark enough?*
Just like with natural light photography, when using a narrower (bigger number) aperture, you will need more light for a good image.
2.8 lets lots of light in , however if you are shooting a family of 8 you will need a aperture of around 5.6 to get them all in focus, this new aperture will allow less light to your camera, making your image darker when using the same shutter speed .
This theory also works for flash. If your image is NOT dark enough in the background for your liking, increase your aperture from say 4 to 9 or 11 , you will see the image become a lot darker, (*however you will need to increase your flash power, or move it closer to your subject to get the flash power right when using small strobes. *)
If I like my background as I am seeing it with my naked eye, and want to incorporate it into my shot, I decide how much light I like on it by lowering my shutter speed to the effect I like, from 200-10 , depending on the image in mind.
Low shutter speeds when using flash is not such a crucial element to keep your eye on as it is when shooting natural light photography portraits. Flash freezes motion, so shooting at shutter speed 30 is no big deal. Once you get below 10 you will need a tripod or a BIG flash unit.
What does aperture do?
Aperture controls the power of the flash!
2.8 gives you lots of power, 22 gives you limited power.
2.8 lets in lots of flash light (and allows the camera to give you lots of light in the shot) Aperture 22 lets in a lot less flash light , and also makes the image darker as the camera needs a LOT more light to shoot at that aperture.
If the light on your subject is too strong at 2.8, and your shutter speed is 200 (or maximum), then increase (narrow down) your aperture to say 5.6 to lower the level of power the flash has on your subject.
Once you have reached an aperture which suits the look you are after, increasing or decreasing the shutter speed will NOT alter the flash strength on your subject, it will just allow more light l or less light into the background , or overall look of your image.
For instance, both these images were taken at the same aperture, but at different shutter speeds.
If I am using flash for newborn photography my flash power is dialled way down to approximately 1/8 as I like to use 2.8-3.5 for my newborn shots, and allowing this much light in when using flash indoors ( at full power) will almost always blow it out.
If I was using 1/1 power on my flash for newborns (full power) and wanted an aperture of 2.8 (full camera light power) the strength would be too strong, I’d have to move my light way back from my subject (losing softness!) or increase my aperture making my camera need more light, the image darker, but I’d lose my depth of field. I would then widen (lower) my aperture to suit the look I was after.
If I am shooting models or families outdoors, I am usually shooting them in a location chosen for the background colour and interest, so my depth of field is not so important.
To learn more about Wild Spirit Photography, visit our site and our blog. Check the MCP Blog daily through October 5th, for more “flashy” posts. And don’t miss out on October 6th for a contest to win a 2 hour Skype photography mentor session with me.