what kind of flash?

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Bill4282

Senior Member
I attended a party with low light and there was another person taking pictures. Every time he took a photo, he projected a red light grid pattern on the subject. he said his camera did it - Nikon 7100. I never saw such a thing and the store where he bought it was no help. Any idea how he did it? defective infrared?

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Horoscope Fish

Horoscope Fish

Senior Member
Bill4282 said:
I attended a party with low light and there was another person taking pictures. Every time he took a photo, he projected a red light grid pattern on the subject. he said his camera did it - Nikon 7100. I never saw such a thing and the store where he bought it was no help. Any idea how he did it? defective infrared?
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It wasn't the camera, it was the flash... Many flash units have an auto-focus assist beam that projects a red grid pattern.


To quote Nasim from Photography Life...
Nasim Mansurov said:
Autofocusing in extremely low light

So how would you make autofocus work in very dim situations? Here is a step by step process:

Mount a speedlight or a commander on your DSLR camera’s hot shoe
Change your focus mode to AF-S (Single Servo / Single Area AF)
Half-press the shutter release or the AF-ON button and you should see the red lights on the speedlight activate
A red beam will be projected onto your subject, which will allow your lens to immediately acquire focus

This method of focus acquisition is called “Active Autofocus” and it works by measuring the distance between the camera and the subject. Since the red beam quickly falls off with distance, it only works on relatively close subjects within 15-20 feet (which is plenty for most situations). It is a much more accurate method compared to the white “AF Assist” lamp on your DSLR, which is not only limited to even shorter distances, but it also has accuracy problems and is often blocked by lens hoods. All this is explained in detail in my “autofocus modes explained” article.
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Source: https://photographylife.com/how-to-make-autofocus-work-in-extremely-low-light
 
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WayneF

Senior Member
Bill4282 said:
thanks for the reply. even the expert at the camera store didn't know this.
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The camera body has a white focus assist LED to help focus in dark places. It is not very bright, and so has a short useful range (maybe ten feet), and it also can disturb the subjects flashing in their face (the flash flashes too of course).

Many hot shoe flashes have a red infrared focus assist LED that kicks in instead (it turns white camera LED off). Different flashes have different patterns, but often a grid of dots. It looks dim because our eyes can't see infrared (we see a little red). But it is actually much stronger, and is effective much further. I don't know how far, but 40 feet is easy with it.

It is slightly tricky to get either one of them enabled. The camera should be in AF-S mode, with a Single Point focus selected. Otherwise, neither light will likely ever be on. Same procedure as the camera manual documents for the white focus assist LED.

FWIW, you can see three focus assist patterns in the three speedlight reviews in link at the sig below.
 
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WayneF

Senior Member
That's great that it's working, but my understanding is different. Maybe the new menus are different? But on my Nikons, that AF Assist menu (white light) has to be on in the menu. Then the speedlights capability turns off the white light somehow, and the speedlights AF Assist works instead. It's the same AF Assist function. Remove the hot shoe flash, and the white light works again. But for me, neither will work if the menu does not specify AF Assist.

It's a little tricky sometimes to get it to work. There are some ifs and buts, but generally, the way I deal with it, it has to be AF-S with Single Point focus, which must be the center point. That is usually always my normal mode anyway. What's hard hard for me to remember sometimes, if you turn AF off on the lens, then no AF and no Assist. :)
 
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RocketCowboy

Senior Member
I've always disabled that white AF assist light in the camera menu, but have still had the infrared flash assist when in AF-S mode. It's been similar behavior whether using the SB-910 or the YN568. I'm always in single point focus too.


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Bill4282

Senior Member
my camera is a d90 and youngnou 568 flash. my menu calls it af illuminator. the flash doesn't turn off the illuminator, I had to and then see the red grid. all good - thanks to all for your replies.

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WayneF

Senior Member
RocketCowboy said:
I've always disabled that white AF assist light in the camera menu, but have still had the infrared flash assist when in AF-S mode. It's been similar behavior whether using the SB-910 or the YN568. I'm always in single point focus too.
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I have to agree. Upon rechecking, with Nikon or Yongnuo flashes, it does not matter if the AF Assist Illuminator menu is On or Off, both my D300 and D800 can work the flashes infrared AF Assist light.

Once realizing it took AF-S and Single Point focus in the center point, the main trouble I have on the D300 is with the AF-S switch, down below the lens release button. I accidentally hit that just holding it, and unknowingly easily knock it out of AF-S position. The newer D800 button there eliminates that problem.
 
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