EOS Flashes

Canon EOS Flashes

Canon 7D: Auto-ISO Flash Setting

If you have your Canon 7D set to Auto-ISO and you slip your flash on, whether it's a Canon flash or a third party flash, like Metz... What are the rules for the Auto-ISO? That will depend on the mode:

  1. Tv or Av or P or CA or Full Auto: The ISO speed will be set at ISO 400
  2. Av Fill-in Flash: If the pre-flash detects over-exposure at ISO 400, then the ISO will drop to as low as ISO 100.
  3. P or CA or Full Auto & bounce flash: The ISO speed will be set between ISO 400 to ISO 1600 depending on the pre-flash.

Flash: Guide Numbers

Not only Canon flashes, but all brands express the power power of their flashes with the Guide Number. Canon numbers their flashes with the guide number. The guide number is the distance at a specific ISO at a specific zoom head position.

Why is the Guide Number so important?

  1. It allows us to calculate the right exposure. Without the right guide number, no correct exposure. It's that simple.
  2. It allows us to compare different flashes.

Canon: Remote Wireless Flash

For the first time, Canon has finally introduced a camera that can operate other eTTL flashes wirelessly without having a separate master flash mounted on the camera. The small built-in flash can be used as a “controller”. The pop-up flash will control either the 4xx, the 5xx series or many other compatible flashes like the Metz flashes.

All the flashes must be within a clear line of sight. The pop-up flash will do a “pre-flash”, a visible flash with the proper commands to the other flashes.

Non Canon Flash Not Working

I have this old, very old flash. It used to be the standard, the work horse of all professional photographers in the 70s. Yes, that's the 1970s. Every professional photographer had a Vivitar 283 flash. That was before the Canon EOS Speedlights or the Nikon Creative Lighting System.

I got a few photos in the manual mode, it worked. But when I switched to the Live View mode, it stopped working. The flash didn't fire at the right time. What happened?

I thought that my Vivitar 283 had packed it in. Tried again it in the regular manual mode and it worked again. So it was something I did.

Canon: Flash Exposure Compensation

I wish Canon had a flash system as good as Nikon's. I'm not saying that it's bad, underpowered, I'm saying is not as sophisticated or as flexible as Nikon's. When dealing with flash, you must deal with exposure compensation. Exposure compensation is topic that you have to feel, there are no hard rules.

  • The exposure compensation does NOT work in manual mode.
  • The flash exposure compensation does NOT work in manual mode.

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div class="boxtip" markdown="1"> Canon splits the exposure compensation between the camera and the flash.

Flash & Shutter Speed

My preferred mode is Aperture Mode. It's from all these years when the cameras only had aperture priority or manual mode. I'm not saying it's better, I'm just saying that's how I think.

Not long after buying my Canon 7D, I bought a Canon 580EXII flash. Load the camera, load the batteries, a couple of test shots. No problem, it seems to be working. Then I turned around, took another photo and all hell broke lose.

The flash fired, but something wasn't right. Chimping time! Take a look at the LCD, nothing then I hear the mirror slapping down. A 5 seconds exposure. What happened?

Flash: Gary Fong Diffuser

Here's another good one from What The Duck. Disclosure: I do own one of these from Gary Fong. I bought mine, many years ago, when the price was reasonable and I didn't know what I was doing.

Gary Fong: Flash Diffuser

Gary Fong: Flash Diffuser

The diffusers' job is to spray light everywhere, and hope or pray, according to your religion, that some of the light sent everywhere will bounce back on the subject of the photo. This implies that:

1.

FEC: Flash Exposure Compensation

Contrarily to Nikon's flash system, Canon's doesn't add the flash exposure compensation if it is set both on the camera and on the flash.

If you set the flash exposure compensation on the flash of -1EV and the of -0.5EV on the camera, the flash takes priority and the total exposure compensation is -1EV. The exposure compensation on the camera is ignored.

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div class="boxinfo" markdown="1"> To contradict the previous statements: The Canon's Flash Exposure Compensation is in addition to the fill-in flash automatic reduction of the flash output of around -1.5EV to -2EV.

Flash: Auto Focus Assist Light

Most of the Canon flashes have a big, monster red eye. It's the auto focus assist light. On my 508EX-II, it's made of 3 LEDs. When the ambient level of the light is low, it will illuminate to help the auto focus of the camera. But sometimes it doesn't work.

The modern E series of the Canon flashes use a bar code pattern to illuminate the subject. These red and black stripes give enough of a contrast to allow the camera to focus. The maximum distance of the assist light depends on the flash, but it's between 10 and 30 feet or 3 to 10 meters for the center focus point.

Fill-in Flash and Program Mode

If you turn on the flash and you are in Program mode and if the average light reading is fairly bright, the e-TTL-II will default to fill-in flash. Canon's fill-in flash setting automatically applies a -2 flash exposure compensation for the Canon 7D. No user input is required.

  • What's a fairly bright light reading? Around 13EV or f/8 @ 1/125s @ ISO: 100 or brighter. It's a sunny day, and extremely bright cloudy day.
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