Flash Basics: Flash Photography
A Short Guide to Flash Photography by Kenneth Caleno
On-camera flash basics: (forget the built-in flash) Using a hot-shoe mounted flashgun, directed straight at the subject is very flat lighting, possibly the very worst of all. There are ways that we can modify the on-camera flash to control our lighting.
We can diffuse the flash by means of clip on plastic domes, (think non-coloured Tupperware-type pots that will fit over flash head). Or we can bounce our flash from ceilings, walls, off of reflectors, etc.
Balancing the light between existing light and flash is quite simple. Just remember that the shutter speed controls existing or ambient light and the aperture controls the flash effect. You set your camera's mode to Av (aperture priority) selecting aperture to desired depth of field (i.e. for weddings F8 does the job).
Get a reading from subject and take a note of these settings. Now select M (manual) mode and use the settings you got from Av mode. Fit your flash to hot shoe, use manual flash. Try first maximum sync speed (usually 1/250 sec or 1/500 sec). Then come down from here just adjusting shutter speed, and checking on monitor, until ambient light looks right.
As for power setting, I like to start at a quarter power. Then I can go down two stops to 1/8 and 1/16 power, and up to a half and full power. Note: My flashguns only span from full to 1/16 power. For interior shots use the same method. I.e. If ambient light reads 1/125 @ F4, you will need to set aperture to F4. Then set the shutter speed at 1/500 (if this is your camera’s maximum sync speed, or 1/250 @ F5.6 if that is your maximum sync speed, and bounce off ceiling.
Adjust power of the flash until it looks right in the monitor. This gives a ratio of 3:1 as a basic starting point. A big advantage, especially when photographing people, is to have the flash off-camera, so wherever you wander to get different angles, your lighting will remain constant. If flash is on camera, you would need to make adjustments each time you move out of the pre-set range of focus.
Your flash can be triggered by radio transceivers (wireless flash triggers) or by means of PC cables. For wrap around, or cross-lighting, you could place your subject between the sun and your off-camera flash. Then using the sun as fill and your flash as the main, or "key" light.
Ideally, indoor images should not show that flash was used. So, for this to take place modification is required. I use a black computer mouse-mat which forms a half snoot and is rubber banded to the underside of my flashgun when bouncing off of ceilings etc. This ensures no direct light lands on the subject.
You can choose of course, to use automatic mode for flash, or TTL, (through the lens). I just prefer the manual mode. Problems occur when using flash under fluorescent illumination, where you will get a severe green cast over your images. The solution is to use a gel (Window green) over the flash window, and a magenta filter (FL-D) over the lens.
These filters will lose you one stop of light, but the lens filter alone will do the trick, if you aren't using flash. Why this works is green over the flash window equalizes foreground and background color temperature, and the magenta on the lens absorbs the green from both sources to neutralize the image.
Most cameras will let you select the front or rear curtain flash set-ups. Front curtain flash fires as soon as the shutter opens, while Rear (or second) curtain flash fires just before shutter closes. For most types of photography the front curtain will do the job. If the subject is on the move however, rear, (Second) curtain flash is the way to go.
The reason being that if you were to use front curtain flash on a moving subject, the movement defining blur, especially against a black, or at least a dark background, would appear in front, and not behind the subject, giving the impression that the subject is going backwards.
On the other hand, if you were to use rear (second) curtain flash for say a portrait, and you are trying to capture a certain mannerism, you would not want the flash to fire too late and miss the emotion.
Using at Weddings
If you shoot at a party or wedding reception, indoors at night using the auto or programme flash setting you will end up with ultra black backgrounds and not the scene you saw. This setting is usually either 1/250 or 1/500 second,
That is because the flash fired too fast to record any background detail.
Solution: set camera to shutter priority or manual mode, and adjust speed to between 1/30 and 1/8 second. These are normal settings for fairly dark conditions and because of the actual flash speed, blur won't be a problem. This is known as "dragging the shutter".
When using the dragging method, keep the flash set to auto or TTL. Unless you are comfortable with doing this, you could complicate matters. If you only have a point and shoot camera, use the night setting. This is so the camera will automatically set the shutter speed to allow background detail to be captured. BUT, you will need a tripod/monopod as for night mode, shutter speeds are likely to be a lot slower than 1/8second.
Flash doesn't reach as far as you like? Up the ISO! Twice the distance, four times the speed.
For instance: If your flash has a Guide number (GN) of 25(metres (80 ft), the best you can expect is a realistic distance reach of 20 metres (60 feet) at ISO 100. So at ISO 400 you will get a realistic reach of 120 feet (40 metres). At 1600 ISO, a reach of 240 feet (theoretically), but noise will play its part at high ISO's.
If you are using an automatic flashgun, that does not give you fill-in values. Just double the ISO you are using. Meter the scene, select an f-stop for the DOF you want. Set auto flashgun aperture to same f-stop, and take your shot, this will give a 2:1 ratio, and your fill will be 1 stop darker that the main subject.
Flash Basics: About the Author:
First Name: Kenneth
Last Name: Caleno
E-mail Address: email@example.com
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Country: New Zealand