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 p.1 #3 · wireless flash- 2nd flash or PW or? | |
The Canon flashes are not designed for use with softboxes. The problem is the location of the slave sensor, which is the little gray window on the front of the base under the flash head. A simple solution to that problem would be to make the sensor a plug in module which could be extended on a cord outside the box, but Canon hasn't adopted that suggestion yet 
Influenced by the Stobist site, which advocates the use of cheap manual flash, many wanting to move a Canon flash off camera add a radio trigger. That solves the signaling dilemma, but turns a very sophisticated flash unit into a dumb brick.
By the time I bought a Canon camera I'd been using a pair manual flashes in a key over bracket fill with optical triggers for over 30 years and was well versed in getting correct exposure and a variety of lighting styles. I used my manual Vivitar 285HVs for the first year with my 20D then opted to switch to the 580ex to take advantage of the ETTL metering and high-speed flash mode. Having used optical triggers and knowing that the 580ex sent commands via the main flash head I devised a diffusion solution that would function in the same way as a soft box -- bouncing diffused light forward with minimal spill - but not block the sensor:
You will find a template for making them at the URL in the photo or by clicking the WWW button below which links to my tutorial site.
I routinely use the flashes at distances beyond the specified ranges of 40ft indoors and 25ft outdoors. Its simply a matter of keeping the base of the slave where the sensor is oriented towards the master on my flash bracket and out of direct sunlight outdoors which will blind it.
In the shot above the slave flash was on the stage out of frame to the left and I had opened the top flap of the diffuser on the bracket and was bouncing most of the fill off the high 30' ceiling. No problems with signaling. It's just a matter of understanding how the equipment is designed to work and finding ways to work within those design parameters.
WIth respect to lighting technique you first need to realize how fill works in a two-light scenario. The key light creates shadows, the fill reveals detail in those shadows. When a single light is moved off axis it will create shadows but they will be unfilled except for whatever ambient light there is because THE SENSOR CAN'T HANDLE THE SCENE CONTRAST. Regardless of whether you turn on fill or key light first when the fill is placed over the camera the key -- the only practical place it can fill all the shadows the camera sees - the key light overlaps the fill.
A 2:1 lighting ratio on a face describes the fact the light reflecting from the highlighted side if the face is 2x brighter. But to create that ratio we need two lights of equal strength:
H:S
1:1 fill illuminates entire face
1:0 key light overlaps, creating highlights over the revealed shadow detail
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2:1 reflected ratio
In a 3:1 ratio the key light is 2x (1-stop) brighter than fill (the constant in the ratio notation)
H:S
1:1 fill illuminates entire face
2:0 key light overlaps, creating highlights over the revealed shadow detail
===
3:1 reflected ratio
So you see fill, and the shadow detail it reveals is the foundation the lighting pattern is built on. Here's a lighting exercise showing the four basic roles for lights:
Fill to lift the darkest shadows to the point the camera can record detail in them at the f/stop selected for DOF.
A separately controlled background source to control subject / background contrast:
A "key" light overlapping fill to create highlights and the illusion of 3D
Back "rim" lighting to enhance the illusion of 3D
With two flashes I use two basic strategies, depending on whether or not I can control / predict the direction of the nose to the key light:
Short lighting: Placing the off camera flash 45 degrees from the nose and shooting into the shadow side:
Backlight + Downward Fill:
The trick to getting flattering light in front is raising the flash on a bracket so it mimics the downward direction and pattern of natural light. The flash on a bracket also will produce very flattering single flash shots indoors and out:
Making the light look hard or soft with a two light strategy does not require huge modifiers. All that is needed is to reach up to the master over the camera and turn the wheel of a 580ex in ETTL ratio mode to change the ratio of key and fill. The workflow is quite simple:
Set the ratio based on how light or dark you want the shadows. Knowing that is simply a matter of experience which can be gained very quickly by doing a test like this:
Then with camera in M at 1/125th and flash in ETTL at FEC =0 fire a test shot, see where the exposure of the highlights is correct using the overexposure warning in the playback, then adjust FEC as needed to override the camera metering's best guess. With a bit of experience you will be able to anticipate how much FEC is needed. Needing to add FEC doesn't mean the camera got the exposure "wrong" in simply is a fact of life due to the fact the camera must calculate the flash based on pre-flash using rather large zones on the viewfinder.
When the shooting situation is static, like a portrait session, I use M mode on the face. Placing the off camera flash at 6ft and shooting from 8ft with both on 1/2 power results in a 3:1 ratio with perfect exposure at f/8 @ ISO 100 with my diffusers. There are no variables and no camera metering so the exposure is always f/8 with that set up. The ratio produces detail in the darkest shadows in a dark suit to the bright highlights in a white shirt and everything in between:
Outdoors high speed flash allows shooting at f/2.8 in direct sun and turning this scene that exceeds the range of the sensor...
into this one that fits the range of the foreground to the sensor perfectly...
By sticking with Canon you get all the advantages of ETTL and Manual in one unit. If you have a clue how they need to operate (i.e., not blocking / blinding the slave sensor) they work quite well within the specified ranges. Mind you Canon didn't design them to be fired from 600. But also realize that 99% of your shots will likely be taken within 25-40 feet for the simple reason that the flashes can't effectively light beyond those distances.
The ideal solution is to use the Canon system as is, then if necessary for extreme conditions add radio triggers. Usually if adding radio triggers you will also be placing the flashes in places difficult to reach to adjust power. That argues for buying a solution that retains remote control of power and ratio. There are two solutions that do that: Radio Poppers which appears to be a well performing product created by a somewhat unreliable start-up company, and the new Pocket Wizard system where you get unreliable hardware (there are range problems) from a solid, well established company.
But for either you need two Canon flashes anyway, so the frugal prudent course of action in my view is buy a pair of 580ex flashes, learn to use them to the maximum of their capability, then and only then buy radio triggers if needed. I have conventional PW I bought at the same time as my 580ex to hedge my bets but find I never use them because I figured out how to make the Canon system work.
Chuck
Edited on Oct 30, 2009 at 02:17 PM · View previous versions
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