Why does the Canon 430EX III use flash pulses for AF assist by default instead of the infrared beam?
Asked 12/17/2015
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On a Canon 700D with a Speedlite 430EX III, I found Custom Function F05 for the AF-assist beam emission method. The default is setting 0, which uses a small series of flash pulses, while setting 1 uses the infrared AF-assist beam.
The infrared beam seems less distracting and works well for me, so I'm wondering why Canon made the flash-pulse method the default. What are the limitations of the infrared assist on this flash, and is there any downside to leaving F05 permanently set to infrared?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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The 430EX III is a bit "special". Canon builtin flashes optionally use a series of preflashes for focus assist, but Speedlites up until this point have instead only used the (less confusing/irritating) IR focus assist beam. Perhaps as a cost-cutting (or market segmentation) measure, in the 430EX III the IR assist is only available when using the center AF point, and preflashing is used otherwise. Because of the limitation to the center AF point, the IR beam is not enabled by default.
Please refer to eg. this thread for details, including nice pictures showing the narrower-than-before beam pattern.
Originally by user14547. Source · Licensed CC BY-SA 4.0
user14547
10y ago
0
Generated from our catalog & community — verify before relying on it.
On the 430EX III, the infrared AF-assist beam is more limited than on some earlier Speedlites, which is why flash-pulse assist is the default.
Main tradeoffs:
- The IR assist beam on this flash only supports the center AF point.
- Its usable range is more limited than the brighter flash pulses.
- If you use off-center AF points, the pulse method is more broadly compatible.
So if Canon made IR the default, some users would get worse AF-assist coverage without realizing why. Using flash pulses by default is the safer general-purpose choice.
If you mostly use the center AF point and the IR beam gives reliable focus at the distances you shoot, there’s no real problem with leaving it set to infrared. Just be aware it may stop helping as effectively if you switch AF points or shoot farther away.
Also note that not every pre-flash you see is AF assist. Canon systems can also emit flashes for E-TTL metering, red-eye reduction, or modeling flash, depending on settings.
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UniqueBot
AI10y ago
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