Speedlite external metering a new name for thyristor flash

This is a look at an often missed function of the Speedlite 580EX II flash, but first a bit of a history lesson.

Recalling the times before digital, the days when there was no electronic communication between lens, camera and flash. Back in those days photographers relied on each part of the camera system to perform optimally on it's own; frequently with manual input from the photographer to ensure needed info passes from one device to another. A flash I owned had a blue and orange scale on the back and a matching switch with blue and orange positions. The blue corresponded to f/8 and the orange was f/4. There was a range of distances that the flash could reach for each of the settings. All that was needed was to set the aperture on the camera lens to either f/4 or f/8 to match either blue or orange on the flash. The flash fired, measured the light coming back and quenched the output when it decided enough light had been output; often it was linked with the term thyristor after the semiconductor switch that was used in the circuitry. 

Some photographers in more recent times used big old hammerhead Metz flashes and they had a similar arrangement often with a big distance scale dial on the top of the flash head; mostly these guys were wedding photographers with a medium format film camera.

Enough of the history, many of those medium format camera wielding photographers now have a digital SLR and they complain that these modern flashes don't work as good as their old one.

That brings us to the Speedlite 580EX II, it's the first Canon EX model Speedlite that has the self-same thyristor function, Canon call it external metering sensor and hide it in the flash custom functions.

Flash Custom Function 5, flash metering mode has four options, the last two 2: External metering: Auto and 3: External metering: Manual are the new "thyristor" modes. The Speedlite 580EX II has a little circular window on the front lower left corner on the picture above, that's the sensor that measures the flash and tells the flash gun when to stop firing in these thyristor or external metering modes. Remember to point that window at the subject when you use these modes!

2: External metering: Auto

Wth this setting the flash will be sent the ISO speed setting and the aperture in use from the camera automatically. Using this the flash works out the range and will indicate it in meters or feet on the back of the flash display panel. Even flash exposure compensation can be set. When the picture is taken the flash will fire and the metering of the light reflected from the scene is measured by the Speedlite 580 EX II's sensor, not the cameras metering. Also this means you don't see a pre-flash it's not needed.

3: External metering: Manual

With this setting the flash performs like the "good ole" Metz models of yesteryear. You need to tell the flash the aperture you want to use, you need to tell the flash the ISO speed you are using and then it works out the distance and will show the range scale on the back. When the picture is taken the flash fires and the metering sensor quenches the light when the flash determines enough light. You also don't get a pre-flash. Even better for the low tech, you can put the PC socket on the side of the flash to use and fire the flash with a PC sync cable or even a pocket wizard.

To get the custom functions on the flash, press and hold the Cfn button on the flash and perform a great sequence of dial turns and button presses to set Cfn 5 to 2 or 3. Alternatively if you have one of the following EOS models EOS-1D Mark III, EOS-1Ds Mark III, EOS 5D Mark II, EOS 50D, EOS 40D, EOS 450D or EOS 1000D you can put the flash on the hotshoe and go in to the camera menu for flash control and set the flash custom function there.

One application of the External metering: manual setting is for light painting. If you think that you want to light up that big building at night and you only have one flash, then set the camera on a tripod, choose the aperture and ISO, select bulb mode, open the shutter with a remote release and then walk around the scene firing the flash using the test button on the back to light each part of the scene.

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Multi-controller

The EOS cameras that feature a multi-controller (that's the small joystick on the back of the camera) also feature a Custom Function to allow you to use the multi-controller to select an AF point. On the EOS-1D/1Ds Mark III it's available in the latest firmware version and can be accessed using CFn III-09 and then either option 3, 4 or 5. On the EOS 50D and 5D Mark II, it's found in CFn III-3 option 1.

This is a very useful Custom Function to play with as it allows you to quickly select a different focusing point without having to first press the focus point selection button. However, it has a drawback - most notably if you're shooting a lot of shot in portrait orientation. Unless you have abnormally long thumbs, reaching the multi-controller button from the vertical shooting grip is all but impossible and you need to resort to the 'normal' method of AF point selection with the AF point selection button and the main and quick command dial.

It's not a major issue, but is something to be aware of, and for that reason, it might be worth putting that custom function into the My Menu settings on the camera so you can quickly change it as you need to.

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Sharpen your EOS-1D and EOS-1Ds response

The EOS-1D models have the distinction of being Canon’s fastest reacting cameras. By this I mean they have the shortest shutter release time lag of any model; but did you know that with some tweaking of the settings you can make the camera even faster?

When you press the shutter release there are several mechanical things that need to happen; the camera needs to lift the mirror, set the aperture on the lens and then release the shutter to start the exposure. In the camera instruction manual for the EOS-1D and EOS-1Ds Mark III cameras the text says that if the aperture of the lens only has to stop down 3 stops or less then with the custom function C.Fn IV-13 set to 1 the release time lag drops by 20%. Normally it’s 55 milliseconds. So why is this not the default?

Canon chose to prioritise stable release time lag and so the default is to have the function deactivated and the sedate 55ms lag is what you get regardless of the aperture you choose. In 55ms the camera has time to close the aperture of any lens to its selected value. But if you tend to shoot mostly at or near to the maximum aperture of your lenses then setting this custom function will speed up the camera response by 20%.
Say you shoot football with a 400mm f/2.8L IS USM lens and only ever shoot wide open or at f./4 or f/5.6 then you’ll always get the faster release lag if you use this custom function.

If you have an older camera then you’ll be glad to know EOS-1Ds Mark II, EOS-1D Mark IIN and EOS-1D Mark II also have this feature available through personal function Pfn-26. You need to set personal functions using the EOS Utility software and a firewire cable.

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Using a Macro RingLite MR-14EX as a master flash

The Macro Ringlite MR-14EX and also the Macro Twinlite MT-24EX can work as a master flash in the Canon Speedlite system. Problem is they are mostly thought of as macro flashes and in the brains of the designers they are not configured to fire more than additional background flashes. In this post we'll explain how this can be improved upon.

These specialist flashes are great if you only want to use an addtional Speedlite 430EX II or 580EX II as a background illumination source with the slaves set in group C. If you are thinking a bit more creatively and thinking to use the MR-14EX as a low powered portrait ringlight then you may need to control some additional flashes in groups A or B linked to the tubes on the ringlite.

The key here is custom function 5 in the ringlite or twinlite. Setting this to 1 instead of the factory default of 0 will enable the flash to trigger other wireless speedlites in groups A or B. That's all for today's top tip.

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