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 p.1 #3 · Radio Popper PX Review | |
Nice review.
But the ironic thing about Radio Poppers is they finally got the Strobist (David Hobby) and others to actually try and understand how the Canon wireless system really works. This message isn't anti-RP but rather to explain some of the quirks of Canon flash you might not be familiar with if using them with conventional PW in manual mode.
There's nothing really ground breaking about the RPs in terms of functionality. The potential for convenience, shooting manual or ETTL and switching between them shot-to-shot, and high speed sync with multiple flashes was always there, but many would try Canon wireless once or twice without really understanding how it worked (and to some extent what changes in methods were needed to make it work) and then abandon it in favor of using the Canon flashes like dumb manual flashes with Pocket Wizards.
The Achilles Heel of the Canon system has long been the ST-E2, introduced back with the ETTL only 420ex flash as a way to move it off camera. The ST-E2 range is limited because its wimpy and has a heavy red filter over its flash tube. Its the source of the mis-information (spread by Stobist) that the system doesn't work because it uses IR. If a 580ex is used as master there is no IR involved and when the slaves are kept within the specified ranges of 40' indoors and 25' outdoors and an arc of 40-degrees on either side of the camera the system works quite well without the need for adding radio triggers. It doesn't require line of sight, there is no IR involved when a 580ex masters, and there are no problems indoors or out if the sensor on the slave (the little gray window on front of the base) is oriented towards the Master and kept shaded from direct sun outdoors.
The fact some users want to exceed the specified range doesn't mean the equipment sucks, only that its not the right tool for the job. Adding the RP to the Canon flash is like adding a pipe to the end of a crowbar to increase leverage, but you still need to understand how to use a crowbar to get good results.
Part of the blame for users not understanding how Canon flash works are the manuals which provide ambiguous and sometimes misleading information on how to use wireless. Radio Poppers are a great way to extend the range of Canon flash, but you still need to understand how to use Canon wireless effectively to get the most out of the flashes. That is especially true in ETTL mode where the camera metering controls flash exosure. ETTL will be a new adventure in ratio and exposure control. High-speed FP flash will be another new skill to master.
For example in the 580ex flash manual implies three flashes are needed to create a two light key / fill pattern.
Canon designed the system on the assumption there would be a Master connected to the hot shoe, directly or on a flash bracket nearby or held overhead, which is why the OC-E3 cord is only 2' long. What isn't clear from reading the manual is that the Master is always in Group A by default (in ETTL or M) or that you only really need two flashes to do to create a key & fill or fill + backlight pattern.
Some don't grasp the importance, in the technical sense, using of fill over the camera or using a bracket. To me it seems common sense to avoid shaded fill (which results in dark voids in the lighting pattern on the face) and much simpler to lug around one stand instead of two. But then that's how I learned to use flash.
The underlying technical goal is to record the scene with detail over the entire range of the scene. The way that is done indoors is to raise the shadows with fill the overlap a second "key" flash to create the highlight pattern on top of it. Doesn't matter which is added first, they will overlap and have the cause and effect of matching the scene to the sensor. Outdoors we typically start with ambient light with a 10-12 stop range and must capture it with a sensor that can record about 6 stops with detail. The only way to actually reduce contrast to fit the sensor is: 1) shoot into the shadows of the ambient so the flash will not overlap in the highlights; 2) expose first to keep the ambient highlights light below clipping; 3) add flash in front to create a highlight pattern over the ambient sky fill; 4) add a second flash for additional fill is the sky-lit shadows are darker and "harder" looking than desired.
I learned flash shooting weddings as Monte Zucker's full time assistant back in 1972. He is really the original "Strobist" because he introduced and popularized the used of dual flash for wedding reception and other event "candid" coverage back in the late 1960s when photo slaves became available. By that time many wedding shooters had learned that raising on camera flash on a bracket hid most of the shadows behind the shoulder and put the nose shadow under or behind the nose where it was more flattering. Monte introduced the idea of using a second flash off camera for either short lighting (when the direction of the nose to light was controllable) or rim lighting with the second flash behind the subjects when it wasn't. Both techniques create a much better illusion of 3D than direct flash and that's how Mr. Zucker came to be well known. Monte in those days used window light for all of his formal portraits, another hallmark of his trademark style, but still was classified as "candid" under PPofA print competition because studio lights were not used. His work started winning every competition he entered and that lead to requests for classes from other pros who paid $$$ for them. I got a 2 year "master level" education while he paid me 
I still use what he taught me because I've tried everything else since and haven't found anything else which matches the combination of results and convenience for candid shooting with hot shoe. Studio work is a different task I use studio flash equipment for. Keeping fill on a bracket puts it where it is needed to fill everything the camera sees, and makes the fill component a no-brainer. The only other equipment needed is a single light stand with another flash on it. I use a rolling IV stand, another clever and practical solution to making using dual flash practical at weddings learned from Monte.
The point? There are ways of making the Canon system work before resorting to radio triggers. Putting the Master 580ex on a bracket with a diffuser is part of what will make the Canon wireless system work better, but even when using Radio Poppers there is a compelling technical reason to keep a flash on a bracket over the lens, especially outdoors where scene contrast exceeds sensor range. RPs do not change the factors involved in producing flattering lighting on a face and you will need to become familiar with the odd quirks of the Canon system:
1) Master is always in Group A by default
2) If Master is used as the Fill (wherever you choose to put it) the A:B ETTL ratios will be the reverse of the H:S portrait lighting reflected ratio convention and A:B = 1:3 will not produce the same look as a conventional 3:1 ratio (2xkey + 1x fill : 1x fill)
3) A:B ratios are actually an incident ratio inferred from measuring the light reflected from each group pre-flashed separately. Here's what actually happens in ETTL mode between the time the shutter is fully presses and the main flash fires:
It all happens so quickly that the pre-flashes seem to merge into the main flash from behind the camera. If you see flash in the viewfinder its the pre-flash. The mirror blocks the viewfinder when the main flash goes off.
4) To quickly grasp what A:B ratios produce and how they differ from conventional H:S ratios do controlled tests like this and visualize the result:
Because I use the Master A as fill on a bracket the ratios from 8:1... 2:1 look about the same because fill is overpowering the off camera key light. Once FEC is used to dial in the highlights the metering does a good job of keeping the highlights the same and making the shadows progressively darker.
The test above was done in a way similar to the cross light diagram in the 580ex manual, with the main flash on the Master disabled. It still emits some light in the exposure because the coded "fire main flash" command is sent to the slaves after the sensor is exposed.
5) Once you can pre-visualize what the various ratios look like ETTL workflow becomes very simple:
a) set the ratio based on how dark you want the shadows to be
b) take a shot at FEC=0 or other known baseline
c) look at the playback with the overexposure warning enabled
d) adjust FEC as needed to keep the highlights in the clothing and other solid white objects below clipping.
The result will be a file exposed with both highlight and shadow detail, with everything in between looking "normal" because the process is engineered that way. Knowing how to interpret clipping in the RAW based on the camera feedback requires testing and comparison. Anticipate when exposing in the camera that the 16 bit RAW > 8bit JPG editing stage will cause some clipping of the highlights.
6) In ETTL mode Canon intends Group C as background light only. Its not factored into the setting if the A:B ratio or the exposure of the foreground. You set the A:B and then adjust the background lit with C relative to it with a separate group C compensation setting from the Master..
In M mode there is no metering so the A, B, and C flashes can be used in any role: key, fill, background, rim light.
7) In Av mode with ETTL flash focus / recompose can skew flash and overall exposure when AF and AE are locked with half-shutter press (the default). If you focus on a dark area and use shutter half press to lock AF, it also locks the ambient exposure. If you then recompose the scene and full press the shutter the camera will do a separate ambient/flash comparison to determine flash power. The second metering does change the shutter speed locked on the darker area with the half shutter press, so the camera may drag the shutter more than is needed for the recomposed scene in the viewfinder and blow the highlights with just the ambient. Any flash added will blow them more.
A solution is don't use Av with flash. Set shutter manually in M mode. If you do use Av with flash move AF lock to the * or AF-ON button and don't half press shutter to lock the ambient until after recomposing:
Lock focus with *
Recompose
Half press shutter to lock the ambient AE
Fully press shutter to pre-flash, meter flash, and make the exposure.
Chuck
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