Canon Flash Part 1 – Choosing a Flash

This was going to be a single post but as usual I wrote quite a bit so instead I will spread this topic over 4 blog posts as follows:

  • Part 1 – Choosing a flash for your Canon EOS or PowerShot camera (this post)
  • Part 2 – Battery Selection
  • Part 3 – Battery Chargers
  • Part 4 – External Power Sources

Canon (along with most DSLR makers) have a fairly comprehensive selection of flashguns for many of the cameras. All of the EOS DSLR/Mirror-less models and many of the “higher-end” PowerShot fixed lens compact cameras have a hot-shoe and for some time this has had 4 extra pins as well as the central firing pin:


Canon refer to their flashguns as either “Speedlites” or “Macro Lites”, I don’t know why they decide to incorrectly spell the “light” part as everyone else refers to these types of flashes as “Speed Lights”, maybe it was to differentiate their models from the other manufacturers. In addition to this there are many third-party manufacturers who also make Canon compatible flashes and other accessories (such as wire-less communication devices i.e. Pocket Wizards) that work within the Canon Speedlite eco system.

Canon’s current Speedlites are as follows:

  • Speedlite 90EX (designed for the EOS-M Mirror-less camera)
  • Speedlite 270EX II
  • Speedlite 320EX
  • Speedlite 430EX II
  • Speedlite 600EX-RT
  • Macro Ring Lite MR-14EX II
  • Macro Twin Lite MT-24EX
  • Speedlite Transmitter ST-E2
  • Speedlite Transmitter ST-E3-RT
  • Canon also make the “HF-DC2 High-Power Flash” but this isn’t technically a Speedlite)

The most recent additions were the update to the Macro Ring Lite and the replacement of the “Speedlite 580EX II” with the “Speedlite 600EX-RT” as well as the addition of the ST-E3-RT. I have written a separate blog post about the introduction of the new Ring Lite, you can read that here.

The first for Canon (and this is ahead of the other DSLR and Mirror-less manufacturers too) is that the new Speedlite 600EX-RT flash and ST-E3-RT transmitter both support radio wireless flash if paired with another 600EX-RT flash. The “RT” in the Speedlite’s and transmitter’s name is for “Radio Transmission”; this is similar to the Pocket Wizards even though the two systems are not compatible with each other. In the past radio transmission required the addition of a radio transceivers/transmitters/receivers which introduced additional complexities and possible issues. They also required their own battery power too.

A number of third-party manufacturers have now released their own radio based wireless flashgun systems and some of these will work with Canon’s intelligent flash system “E-TTL II” too. However getting these in the UK with any kind of local support is difficult; I gave up trying to get a non-dedicated/manual flash system for the Fuji cameras that I owned and is one of the main reasons for going back to Canon, the radio wireless flash control cemented that decision.

So why would you need to communicate with flashes, doesn’t the hot-shoe deal with this?
If you have a single flash gun and this is attached to the camera’s hot-shoe then the light that the flashgun provides will not produce the best lit pictures. Yes you can bounce the flash of a wall or ceiling but the best pictures are produced when the flash is taken “off-camera”. There are a number of methods that can be used to do this and assuming you want to maintain TTL communications the main three are:

  1. Use of a camera system compatible TTL cable between the camera’s hot-shoe and the flash’s “shoe”
  2. Use an optical transmitter (this can be another flash or a dedicated transmitter) as a “Master” in the camera’s hot-shoe. The remote flashes or “Slaves” and can then be remotely controlled and fired
  3. As per number two but using a radio transmitter/flash in the hot-shoe and radio controlled slaves

You can mix 1 & 2 as well as 1 & 3 but not 2 & 3 – you cannot use optical AND radio in the same system at the same time (as of today’s blog post – who know what will be possible in the future).

What are the benefits of radio over optical based off-camera flash systems?

  • Optical requires line-of-sight between the flash and the transmitter
  • The distance of the radio systems is greater
  • Not affected by ambient light

The Speedlite 600EX-RT can be used on camera, be a master or slave in optical systems as well as a master or slave in a radio-based flash system (here I use the word “system” to describe any flash set-up whereby there is a master on-camera and one or more flashguns off-camera). The companion device the ST-E3-RT can only be used as a Master in radio based flash systems and it will only remotely control and fire the Canon Speedlite 600EX-RT. Canon only has one speedlite model of flash that can be used via radio at the moment; the rumour is that later this year the “Speedlite 430 EX II” will be updated and will have the facility to be controlled via radio as a slave.


As I want to ultimately use radio to control my flashes (and one of the main reasons for going Canon) I decided to get for now one 600EX-RT and one ST-E3-RT. The main advantage of the ST-E3 is that it is around half the cost of the 600EX model.


I am also lucky in that the 600EX was purchased quite cheaply second-hand. The flash did not come with its boxed, Gel holder, Gel Holder bag and the Gels for the holder; hence the price. I would have preferred it if it came with a box, however the missing gel holder and gels is not an issue as will use the Honlphoto Gel system that I already have when I need to gel the flash.


What are “Gels”?
Different natural light has different colours at different types of day and can also vary by your geographic location too. These different colours are referred to as temperatures or colour temperature and are measured in degrees Kelvin; Kelvin has the same gradation as degrees Celsius but Kelvin starts at absolute zero (zero degrees Kelvin), this equates to −273.15° Celsius or −459.67° Fahrenheit.

The light that is emitted from flashguns is balanced so as to be as close as possible to the midday sun (about 5100 to 5500°K). Sometimes this needs to be balanced to other types of light source i.e. Tungsten, Fluorescent light sources or the rising/setting sun. Other times you need to override the default temperature maybe to add a colour tint for example. The way to do this is to put a thin piece coloured of “gelatine” (hence the name gel) over the end of the flash (covering the flash head), this will then alter the colour temp of the flash.

Colour Temp

What do I have so far?:
From my previous venture with off-camera flash (with Canon and then Fuji) I already had a lot of the flash accessories; adding the new flash and transmitter almost completes everything I need as follows:

  • Canon Speedlite 600EX-RT
  • Canon Speedlite Transmitter ST-E3-RT
  • Manfrotto 5001B Nano Stand
  • Manfrotto MN026 Lite Tite Swivel Adapter
  • Frio Coldshoe Adapter V2
  • Honl Speed Strap
  • Honl HP-Filter 2 Colour Correction Kit
  • Honl Filter Roll Up (case for above Filters)
  • Rogue Flashbender (Small)
  • Wescott 43″ Optical White Satin Umbrella with removable Black Cover

What is left?
One omission is a 5-in-1 40″ reflector that will make the most use of the available/Speedlite light. Finally, I also need to look at powering the flash and you can read about this in my next few posts this week.