# Speedlite AF Assist Beam: Issue for Very Low Light Events



## YuengLinger (Nov 26, 2019)

Thank you, Lukas Haupt, for pointing out in another thread (https://www.canonrumors.com/canon-to-release-new-firmware-for-the-eos-r-later-this-month/) the problem of the R not using the 600ex (or 580ex) AF Assist Beam.

You are correct. After doing some digging, including the user manual, I now see that this is an issue with IR beams, which is what the 600ex and the 580ex use. Darn!

And the little LED on the camera can be nearly useless. Even with the Rf 24-105mm f/4, if within seven or so feet of the subject, the lens barrel blocks the AF assist beam in a big area of the frame, _such as in the center._ With the lens hood on, things are much worse!

Seems like a hotshoe LED assist would work--but then no flash!!!

At least the series of strobe bursts still works. I have that disabled on my 5DIV, as it is unnecessary and distracting, but, on the R, it has to be used. 

Sigh...Always something with tech.

Any interesting work arounds? Apparently this is a problem with mirrorless, not some EOS R bug. 

Does anybody feel like this is a "gotcha" that wasn't mentioned in reviews and hype? Even the user manual kind of avoids the topic directly except on page 295, "An LED AF-assist beam is fired by LED-equipped external flash units."

The 600ex is apparently IR, even though we can see the red grid! 

Here's a link spelling it out: 









Why Mirrorless Autofocus Means Trade-Offs


Mirrorless cameras like the Sony A7 don’t use a traditional phase detect autofocus. While this enables popular features like eye tracking autofocus, it brings a number of tradeoffs, which could be a deal-breaker for certain applications. Two Systems Enter The phase detect system, typically used...




fstoppers.com


----------



## Mt Spokane Photography (Nov 26, 2019)

Year old news? I guess a year + after it came out, people have forgotten that there are limitations. I did some tests on mine when I first received it in mid October 2018. It was known then that it used the on camera AF light and not the one on the Flash. 

The good news is that it focuses in low light that is too low for me to see the subject unless I wait for 15 minutes for my eyes to fully adjust.


----------



## Ozarker (Nov 26, 2019)

YuengLinger said:


> Thank you, Lukas Haupt, for pointing out in another thread (https://www.canonrumors.com/canon-to-release-new-firmware-for-the-eos-r-later-this-month/) the problem of the R not using the 600ex (or 580ex) AF Assist Beam.
> 
> You are correct. After doing some digging, including the user manual, I now see that this is an issue with IR beams, which is what the 600ex and the 580ex use. Darn!
> 
> ...


The 600EX-RT is "near infrared light pattern", not IR... which is why we can see the grid at all, except on the R. IIRC the ST-E3-RT doesn't have a light? With the upcoming firmware installed you probably won't need a work around. Sure kinda starting to feel like things were pushed out the door a little too soon with this thing going on a year later.








Canon Speedlite 600EX-RT Flash Specifications


Is the Canon Speedlite 600EX-RT Flash right for you? Learn all you need to know about the Canon Speedlite 600EX-RT Flash in The-Digital-Picture.com's review!




www.the-digital-picture.com


----------



## Kit. (Nov 26, 2019)

CanonFanBoy said:


> The 600EX-RT is "near infrared light pattern", not IR...


"Near infrared" (NIR; as opposed to "far infrared") is infrared in the region of frequencies near the frequencies of visible light. We see the pattern of light because the light emitted is not _fully_ infrared, although there is not much power contained in the visible part of its spectrum. If we could see in infrared, the pattern would appear much brighter.


----------



## Joules (Nov 26, 2019)

Would be funny if the Ra wasn't just a cash grab to draw some Astro shooters in the R system but an experiment with IR sensitive sensors that would influence future bodies  
Were there any rumors hinting at new flashes coming with the upcoming higher end R bodies?


----------



## neuroanatomist (Nov 26, 2019)

YuengLinger said:


> Seems like a hotshoe LED assist would work--but then no flash!!!


The Canon 320EX flash has both a strobe and an LED, the latter intended for video. When using PDAF (viewfinder AF) on a DSLR, the main flash fires for AF assist, but on a DSLR in live view, the LED light is used for AF assist. I don’t know what it would do on the EOS R, but that might be something worth checking out.


----------



## YuengLinger (Nov 26, 2019)

Mt Spokane Photography said:


> Year old news? I guess a year + after it came out, people have forgotten that there are limitations. I did some tests on mine when I first received it in mid October 2018. It was known then that it used the on camera AF light and not the one on the Flash.
> 
> The good news is that it focuses in low light that is too low for me to see the subject unless I wait for 15 minutes for my eyes to fully adjust.



One cannot forget what one never knew.


----------

