Speedlite AF Assist Beam: Issue for Very Low Light Events

YuengLinger

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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:

 
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Mar 25, 2011
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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.
 
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Ozarker

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The Ozarks
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:

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.
 
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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.
 
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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.
 
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YuengLinger

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Dec 20, 2012
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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.
 
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