Some help understanding flashes

[twcull]

Hi everyone,

I'm in the process of finding / purchasing a new body to upgrade from my Canon 350D, I'm looking at the 50D/60D/7D at the moment and would like to buy a mountable flash. The problem is I know nothing about flashes, E-TTL II etc means very little to me. Can someone please link me to an article to explain it in laymen's terms? I find it all a little overwhelming.

I'd like a flash for portraits / sports / events / clubs and to try and learn a new aspect of photography. Any suggestions or assistance is greatly appreciated!

Thanks,
Thomas

[Mike367]

In TTL flash, the flash fires a small pre-flash, which the camera uses to measure reflectance off of the subject (determined by focal point) and determine how much "juice" to give the main flash for correct exposure. All this happens just before the shutter opens and the main flash fires. It is important, therefore, to keep the focus point on the subject; if you focus and then re-compose before fully depressing the shutter, the camera will read the pre-flash reflection from wherever you've moved the focus point ( in the frame) to, (usually the background) giving you an incorrect flash exposure.

In Nikonspeak, you can avoid this by using the FV function: 1. focus 2. FV this fires the pre-flash and stores the exposure info in memory. Now you can re-compose and it will fire the flash at the power determined when you pressed the FV button; it will always use this power level until you turn off the FV (Flash Value) lock. I'm sure Canon has a similar function.

When using TTL. I like to use the camera in manual, set for how I want the background, and let the camera set the flash value for the subject. I often dial in flash exposure compensation if I want to change how it exposes the subject.


Read this: http://neilvn.com/tangents/index/flash-photography/

[inkista]

Ok. Because I've needed to do this for a while, I'm copy'n'pasting a post I did on basic flash features for a Nikon shooter, but translating it into Canonspeak.

========
Just to back it up and slow it down a little, here's what some of the jargon being thrown around with flashes means:

eTTL-II. This is Canon's (digital) automatic flash exposure system. The camera and flash can "talk" to each other. The camera tells the flash to send out a burst of a known brightness, then meters this "pre-flash" burst, and based upon the metering results, can then set the flash power to where the exposure system thinks it needs to be for a good exposure. This is similar to having Av or P mode on the camera: the system automatically sets the power output level on the flash for you. (TTL, btw, stands for "through-the-lens", which is how the metering is done).

eTTL becomes important with on-camera flash (where the flash is mounted on the camera's hotshoe) because your main technique with on-camera flash is bouncing. This is where you point the head of the flash at a reflective surface (wall, ceiling, floor, window, whatever) and use the reflected light as your main source of illumination. You do this to spread out (diffuse) the light and make it softer. This eliminates that harsh-in-the-headlights look most newbies associate with flash.

But when you bounce the light, you increase the distance the light has to travel, and you'll have to compensate for this by increasing the flash power. eTTL can do this for you automatically.

The bouncing is also why you want to look at tilt and swivel on the head. The more directions you can point the flash, the more lighting directions you can choose from. Ideally, you want a flash that can swivel 360° around [most, however, will only do 270°], and that can tilt to be set straight up [90°].

Another thing to look for on a flash is the power output. However, guide numbers (which supposedly tell you this) can be very deceiving, thanks to another flash feature, which is a zooming head.

When a flash has a zooming head, the spread of the light from the flash can be controlled, so that the wider the lens you're using, the wider the spread of the light. BUT the tradeoff for this spread is how far you can throw the light. The wider the spread, the shorter the distance the light can travel. The narrower and more concentrated the spread, the farther it can travel. Some manufacturers use the narrowest spread when they give the guide number, which makes the flash look more powerful. So, always check the iso AND focal length that was used with the guide number when comparing. It can be hard to get an apples-to-apples comparison on these things, so don't always trust that a bigger guide number means a more powerful flash. Sites like speedlight.net are helping us get there, though, by actually testing to find the GN of the flash with all the other factors being equal.

The guide number of a flash, btw, is a way to calculate the distance the light will travel, given a specific aperture. Your guide number = distance x f-number. So, if you're shooting at f/8, and your flash has a guide number of 40 ft, @iso 100 (zoomed to 35mm), and you use those settings, you can expect your light to travel about 5 feet before falling off.

Recycle time is how long it takes for the flash to gather up enough juice from those tiny little AA batteries between flash bursts. Typically, this will be measured at full power, since the lower the power setting on the flash, the less juice it needs, and the faster it can recycle. Anything between 3-7 seconds at full power is pretty good.

Wireless eTTL is the Canon proprietary system for wireless control of off-camera flashes. You're unlikely to find this on third-party flashes, although some makes like Nissin/Metaz/Yongnuo are adding some form of it to their speedlights. This is a near-infrared light-based proprietary signalling system that has fuller function than most other off-camera triggering systems. You can use eTTL, remotely command power levels, and use high-speed synch. Generally, the wireless eTTL function will be slave-only (in which case you need a master unit), or master-in the pop-up. Right now, only the 1D Mark IV, 7D, 60D, and 600D have a master in the pop-up flash, and it cannot accomplish high-speed sync; for that you'd need a master speedlight unit (ST-E2, 550EX, 580EX, 580EX II).

High-speed sync is the ability to use a shutter speed higher than your camera body's max. sync speed. Most camera bodies have a maximum flash sync speed in the neighborhood of 1/200s. Because of the way that camera shutters work, physically, a faster shutter speed means that part of your sensor will be covered by a shutter leaf during the exposure if you use a faster shutter speed than this, and you'll get dark bars at the top/bottom (or both) of the frame. High-speed sync means the camera and flash can time pulses of light from the flash as the shutter gap sweeps over the sensor, so the entire frame can be illuminated by the flash. The trade off is a loss of power output from the flash. Again, this is a feature you're unlikely to find on 3rd-party flashes.

Sync ports are a way, other than the flash hotshoe, to tell the flash to fire. The most common interface used is a PC (Prontor/Compur) jack, but some flashes have 1/8" monojacks (so you can use audio cables from Radio Shack, rather than PC cables), and studio lights will have 1/4" monojacks or HH ("household") plugs that are household wallsocket type connections. This may or may not be relevant to you, depending on how soon you find the Strobist website and what type of remote triggering you want to try using. There are, however, remote triggering methods that can use the hotshoe, so a sync port is not a have-to-have.

External battery ports are if your flashes see a lot of heavy use, and you would prefer not to keep popping sets of AAs in and out of the flash all the time. They can also speed up the recycle time, but be careful. Because the battery packs can pour out more juice, an incompatible 3rd party pack could help you fry your flash.

Stroboscopic mode is where the flash can send out multiple flashes very quickly, so that you can get echoed discrete movement, almost like a time-lapse. The 580EXs can do this; the 430EXs can't, unless they're slaved to a 580EX.

"Dumb" optical slave is another simplistic way to set off a remote flash without using wired sync methods. Typically, you're looking for whether or not an optical slave can ignore an eTTL pre-flash, and how sensitive it is. This can save you having to get YA radio trigger in a multi-light setup, be a way to use your speedlight off-camera with a P&S, or to help add your light to someone else's setup. Handy feature. However, none of the Canon EX speedlights have one (Canon assumes you'd prefer spending money on wireless eTTL); but a lot of the 3rd party cheaper alternatives include one and possibly one that can ignore a pre-flash. I use a Yongnuo YN-560 off-camera this way with a P&S camera built-in flash.

Those are pretty much all the main features I can think of when it comes to flashes, and why you might or might not want them.

For on-camera flash bouncing and your first speedlight, the usual advice is: save up and get the top of the line OEM flash (580EX II). You'll have the most power (so the most range for bounce surfaces) and a head that swivels 360°, as well as a flash with all the bells and whistles to go Strobist, full manual and off-camera. Subsequent additional lights, getting lower-cost manual-only strobes can be a much better buy. But it's always good to have at least one speedlight to pop onto the hotshoe that can do all the fancy stuff.

If you can't afford the top-of-the-line OEM, then get the mid-range OEM (430EX II), or look into the 3rd party TTL-capable and wireless-TTL slave-capable flashes, like the Metz Mecablitz 500 (and up) models, the Nissin Di-822 and Di-622 II, and the Yongnuo YN-565EX. Like all 3rd party equipment, though, you do have to worry about future compatibility. The Metz and Nissin units have upgradeable firmware which can ease this worry, but the Yongnuos are supercheap and do not. Also, the Yongnuo gear doesn't have a great reliability reputation, so if you are buying from Yongnuo directly on eBay, consider what shipping a bum unit back to Hong Kong might be worth, and see what local dealers are offering. There are advantages to going with one of the 3rd party flashes, though, since the Nissin and Yongnuo models sport PC sync ports AND dumb optical slave modes: features that do not exist on the 430EX II.

If you can't afford those, then there used older models (580EX, 430EX, 550EX) and 3rd party alternatives, but they won't have the same range of features, and their future-compatibility isn't quite as assured. I would suggest looking at this list on speedlights.net for 3rd-party alternatives if that's the way you're leaning.

When you're looking at a second or third flash for an off-camera Strobist setup, then it's time to consider the all-manual cheapies, like the Yongnuo YN-560, or Lumopro LP160.

My two last words of advice: before getting into flash photography, you really want to be happy and comfortable shooting in M mode. If you aren't, you might want to consider waiting until you are before getting a speedlight. And if you are thinking of heading straight for Strobist stuff, then you may also want to kick around the idea of whether or not a studio strobe might be a better way to spend the big bucks than a top-tier OEM flash.

[twcull]

Wow, so much information. Thank you very much for the post! It certainly helps

[inkista]

You're welcome.

BTW, if you are looking at 3rd party flashes, keep in mind that the terminology they use for dumb optical slaving, eTTL, wireless eTTL, and high-speed sync can be a little misleading. Highly recommend that you use the speedlights.net reviews (if there is one for the flash you're interested in), because they'll clarify which features are there or not. Just because a 3rd party flash does eTTL does not automatically mean it does wireless eTTL or high-speed sync and "wireless slave" can just as easily mean a dumb optical slave vs. wireless eTTL.

For learning flash photography techniques, I'd say take a look at the Tangents website/blog/messageboard by Neil van Niekerk before going to David Hobby's Strobist website/blog/Flickr group. Both have a ton of valuable information, but van Niekerk's information is more basic. Hobby pretty much assumes you already have some experience with on-camera flash, and you just want to learn how to take the flash off-camera for studio-type lighting set-ups, and so (imho) is more advanced.