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The EOS 70D’s pop-up flash can act as a wireless commander for off-camera Speedlites, no extra transmitter required — Canon calls it the Integrated Speedlite Transmitter, and it’s a genuine feature most cheaper Rebel-series bodies from the same era don’t get. The catch, and the thing that decides which flash is worth buying, is that it only speaks Canon’s older optical protocol: a series of light pulses read by a sensor on the receiving flash. It has no radio hardware inside it at all.
That single fact splits the market into two groups. Any speedlite with an optical slave mode — usually labeled S1 or S2 on the back panel — will fire the instant the 70D’s built-in flash pops up and sends its signal, for free, with no accessories to buy. That covers most budget manual flashes from Godox, Yongnuo and Neewer. Canon’s own EX-series Speedlites go further and hold full E-TTL II metering over that same optical link, so exposure is calculated automatically rather than guessed.
Radio is the trap. Canon’s newer RT-series flashes (the 600EX II-RT, 430EX III-RT, and third-party equivalents like the Yongnuo YN600EX-RT II) are built around a 2.4GHz radio link that talks to a matching radio commander — and the 70D’s pop-up flash isn’t one. Mount an RT flash on a 70D expecting wireless range through walls, and it does nothing off-camera unless it’s switched into optical slave mode (giving up the radio benefits it was bought for) or a separate radio transmitter, like Canon’s ST-E3-RT, is added in the hot shoe. Godox’s V-series and TT-series flashes have the identical problem with their own 2.4G “X” system — a Godox flash triggers other Godox flashes over radio, not the 70D’s built-in optical flash, unless it’s also set to S1/S2.
None of this matters if the flash never leaves the hot shoe. Every Speedlite below reads exposure through the same TTL contacts regardless of its wireless system, so as an on-camera bounce flash any of them works normally. The wireless story only bites once a flash comes off the camera.
The picks below split roughly along that line: cheap manual flashes that trigger directly off the 70D’s built-in commander for free, TTL Canon and Yongnuo units that hold full metering over the same optical link, and radio flashes worth buying only if a commander is already part of the plan.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | Canon Speedlite 600EX II-RT | $470–$580 | Amazon · eBay |
| 2 | Canon Speedlite 430EX III-RT | $280–$320 | Amazon · eBay |
| 3 | Canon Speedlite 470EX-AI | $380–$430 | Amazon · eBay |
| 4 | Canon Speedlite 90EX | $55–$75 | Amazon · eBay |
| 5 | Yongnuo YN568EX III | $85–$110 | Amazon · eBay |
| 6 | Yongnuo YN560 IV | $60–$75 | Amazon · eBay |
| 7 | Neewer TT560 | $45–$60 | Amazon · eBay |
| 8 | Godox TT600 | $55–$70 | Amazon · eBay |
| 9 | Godox TT685C | $65–$90 | Amazon · eBay |
| 10 | Godox V860III-C | $165–$200 | Amazon · eBay |
The picks, in detail
Canon Speedlite 600EX II-RT
Canon’s flagship Speedlite and the reference point for output: guide number 197′ at ISO 100/200mm, a two-way 2.4GHz RT radio system, and full E-TTL II metering. On the 70D it works perfectly as a hot-shoe flash, but its radio side goes unused unless paired with a separate radio commander, since the 70D’s own wireless is optical only.
- Guide number 197′ (60m) at ISO 100/200mm zoom
- Built-in 2.4GHz RT radio, up to 5 groups / 15 units
- E-TTL II metering with high-speed sync to 1/8000s
- Weather-sealed body, -7 to 90 degree tilt, 180 degree rotation
- Highest output and fastest recycle in Canon’s lineup
- Can be set to optical slave mode to trigger straight from the 70D
- Weather sealing survives outdoor shoots
- Radio system needs an ST-E3-RT or second RT flash to use off-camera on this body
- Expensive relative to third-party flashes with similar output
- Heavier than the 430EX III-RT on a body the size of the 70D
Canon Speedlite 430EX III-RT
The mid-tier Canon option: smaller and lighter than the 600EX II-RT but with genuine Canon color and exposure matching. Like its bigger sibling, its 2.4GHz radio link doesn’t talk to the 70D’s built-in optical commander, so the practical off-camera path on this body is switching it to optical slave rather than relying on its radio master mode.
- Guide number 141′ (43m) at ISO 100/105mm
- Built-in 2.4GHz RT radio, master and slave modes
- Recycle time 0.1-3.5s, Quick mode to 2.5s
- Runs on 4x AA batteries, 295g
- Noticeably lighter on the 70D than a 600-series flash
- Reliable Canon TTL exposure with no third-party guesswork
- Doubles as an optical slave for free off the pop-up flash
- Radio master/slave features go unused without an RT commander on the 70D
- Costs roughly double a similarly-specced Godox unit
- Guide number is modest for a flash at this price
Canon Speedlite 470EX-AI
The one flash here that measures the room: point it up and it reads the distance to the ceiling and the subject, then sets its own bounce angle automatically. It has no radio hardware at all, which on the 70D is an advantage — it’s built entirely around the same optical wireless system the pop-up flash already speaks, so there’s nothing extra to buy for basic off-camera use.
- Guide number 154′ (47m) at ISO 100/105mm
- Auto Intelligent Bounce measures ceiling and subject distance
- Optical wireless receiver only, no radio
- Tilts 120 degrees up, rotates 180 degrees, 4x AA batteries
- Auto bounce genuinely saves guesswork at events
- Optical-only design matches the 70D’s built-in commander exactly
- Full E-TTL II metering
- Premium price for what is essentially a bounce-flash specialist
- No radio option if the kit grows later
- Heavier than a standard flash due to the swivel motor
Canon Speedlite 90EX
The smallest and cheapest flash Canon currently sells with real E-TTL metering. It’s built for the compact EOS M line, but its standard hot shoe and optical wireless mount it on a 70D without issue. It can also command up to three groups of optical slave flashes on its own, making it a genuine, if low-power, alternative to using the 70D’s own pop-up flash as commander.
- Guide number 30′ (9m) at ISO 100
- 2x AAA batteries, 1.76oz (50g)
- Controls up to 3 optical wireless slave groups from about 23ft indoors
- E-TTL / E-TTL II compatible
- Cheapest genuine Canon TTL flash available
- Tiny enough to keep in a bag permanently as backup
- Works natively with the 70D’s optical wireless system
- Guide number is too low for anything beyond close fill light
- No manual power dial for off-camera control
- Slow recycle time at full output
Yongnuo YN568EX III
A budget alternative to Canon’s own TTL flashes that uses the same optical wireless channels the 70D’s pop-up flash already understands, so it slots into master/slave setups without a radio add-on. Output and build feel roughly on par with Canon’s 430-series at a noticeably lower price, though the menu system is less polished.
- Guide number 190′ (58m) at ISO 100/105mm
- E-TTL / E-TTL II with high-speed sync to 1/8000s
- Optical wireless master/slave, 4 channels, compatible with Canon EX-series
- 270 degree rotation, -7 to 90 degree tilt, 2.5mm sync port
- High output for the price
- Optical wireless works directly with the 70D’s commander, no radio needed
- Can act as master for other optical slave flashes
- Menu and button layout is less intuitive than Canon’s own flashes
- Optical-only wireless, same range and line-of-sight limits as the built-in flash
- Build plastics feel less durable than Canon’s
Yongnuo YN560 IV
A pure manual flash with no TTL contacts to worry about, which keeps the price low and the operation simple: set power on the flash itself in 1/3-stop steps. Its S1/S2 optical slave modes fire directly off the 70D’s pop-up flash for free, and its own 2.4GHz radio receiver adds an upgrade path if a dedicated transmitter is added later.
- Guide number 190′ (58m) at ISO 100/105mm
- Manual power 1/1 to 1/128 in 1/3 and 1/2 stop steps
- S1/S2 optical slave modes plus built-in 2.4GHz radio receiver
- 24-105mm zoom, expandable to 18mm with built-in diffuser
- No TTL to fight with — power stays exactly where it’s set
- Optical slave triggers for free off the 70D’s built-in flash
- Strong output for a manual-only flash at this price
- No TTL metering, so exposure is trial and error
- Radio receiver needs a separate RF-603/602-style transmitter to use over radio
- Menu is entirely physical buttons, no touchscreen
Neewer TT560
The cheapest usable off-camera flash in this list, and a common first purchase for anyone testing whether off-camera lighting is worth pursuing before spending more. It’s fully manual with S1/S2 optical slave built in, so it fires off the 70D’s pop-up flash the same way the pricier manual options do — just with a lower guide number and a slower recycle.
- Guide number 38 (ISO 100)
- 8 manual power levels, 1/128 to 1/1
- S1/S2 optical slave modes plus PC sync port
- 4x AA batteries, 0.1-5s recycle time
- Lowest price of any usable flash here
- Optical slave works immediately with the 70D’s built-in commander
- Light enough for small light stands
- Guide number is noticeably lower than the Yongnuo or Godox equivalents
- Center-pin-only hot shoe means no TTL communication at all
- Recycle time lags at full power
Godox TT600
The rare budget flash that covers both wireless systems at once: S1/S2 optical slave for triggering directly off the 70D’s built-in flash today, plus a built-in Godox 2.4G radio receiver for a future upgrade to a dedicated transmitter. It’s manual-only, but the guide number and recycle time punch well above its price.
- Guide number 197′ (60m) at ISO 100/200mm
- Manual power 1/1 to 1/128
- Both optical S1/S2 and built-in Godox 2.4G radio wireless
- 24-200mm zoom, 14mm wide panel, 0.1-2.6s recycle
- Covers optical and radio triggering in one flash
- High output-to-price ratio
- Works with the 70D’s built-in commander with zero extra cost
- Manual only, no TTL metering
- Radio side needs a Godox X-series transmitter to use off-camera over radio
- AA-powered, so recycle slows as batteries drain
Godox TT685C
A TTL step up from the TT600 with the same dual-wireless design: E-TTL II metering over Godox’s own 2.4G radio system for other Godox flashes, plus S1/S2 optical slave that fires for free off the 70D’s built-in commander in manual mode. It’s the closest third-party flash here to matching Canon’s own EX-series feature set.
- Guide number 197′ (60m) at ISO 100/200mm
- E-TTL / E-TTL II with high-speed sync to 1/8000s
- Built-in Godox 2.4G radio, master/slave, plus S1/S2 optical slave
- 20-200mm zoom, -7 to 90 degree tilt, 360 degree rotation
- Full TTL metering at well under Canon’s price
- Optical S1/S2 works with the 70D’s commander out of the box
- Godox radio system is a genuine upgrade path if the kit grows
- TTL is only available over Godox’s radio, not the 70D’s optical link
- Needs a Godox X-series transmitter for off-camera TTL/HSS
- Plastic build feels less rugged than Canon’s own flashes
Godox V860III-C
Trades AA batteries for a removable lithium pack rated around 480 full-power flashes per charge, with a noticeably faster recycle than any AA-powered flash in this list. It shares the TT685C’s dual optical/radio wireless design, so it triggers off the 70D’s built-in flash via S1/S2 for manual use, with full TTL reserved for Godox’s own radio system.
- Guide number 197′ (60m) at ISO 100/200mm
- 7.2V/2600mAh lithium battery, about 480 full-power flashes, 1.5s recycle
- Built-in Godox 2.4G radio plus S1/S2 optical slave, manual only
- 10-level LED modeling light, high-speed sync to 1/8000s
- Lithium battery recycles far faster than AA-powered competitors
- No more swapping AA batteries mid-shoot
- Strong output and HSS for the price
- S1/S2 optical mode drops to manual power only, no TTL through the 70D directly
- Costs more than the TT685C for mostly a battery upgrade
- Replacement lithium packs are a Godox-specific purchase
Buying tips
- Enable wireless flash from Menu, Built-in flash func. setting, Wireless func., and choose the option that shows only the external Speedlite icon so the pop-up flash fires as a commander only, not as visible fill light.
- Set a Godox or Yongnuo manual flash to S1 mode when the 70D is in manual flash mode, or S2 mode when it’s in E-TTL — S1 fires on the first pulse, S2 waits for the second and ignores the metering pre-flash.
- Keep line of sight between the pop-up flash and the receiving flash’s sensor — optical triggering fails behind subjects, around corners, or in bright sunlight that washes out the pulse.
- Budget for a radio transmitter, such as a Canon ST-E3-RT or Godox X2T-C, separately if buying an RT or Godox-radio flash — the 70D contributes nothing to a radio link on its own.
- Four rechargeable NiMH AA batteries recycle a full-power flash faster and more times per charge than alkalines, which matters most on 600EX II-RT-class flashes with large guide numbers.
- A used or budget flash with a lower guide number is not necessarily a problem — bounced light off a ceiling loses several stops anyway, so raw output matters less indoors than outdoors.
- Check the foot before buying: some very cheap flashes ship with a plastic locking pin rather than a metal foot, which wears the 70D’s hot shoe contacts faster over hundreds of mounts.
- If a flash lists compatibility with Canon E-TTL/E-TTL II but not a specific camera list, it will still work on the 70D — that designation, not the body name, is what determines TTL metering support.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.