# 600EX-RT AF Light Assist



## JRS (Sep 18, 2013)

I used to have an canon 580EXII and I remeber that when I choose the central focus point the AF assist light from flash only lights the center (iluminating only the center focus point). When I choose all focus points, the AF assist light illuminates all the focus points.

Now with the 600EX it don't seems to have the same feature, if I choose only the center focus point or all focus point, the AF assist light is the same, iluminating all AF points. Is it right or I have a unit with defect?


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## neuroanatomist (Sep 18, 2013)

Can't speak for the 5DIII, but on my 1D X the 600EX-RT's AF assist lamp lights up only a thin vertical strip if the center AF point is selected. If I select a point in an off-center column, or in 61-pt auto, the full-width AF assist rectangle illuminates.


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## JRS (Sep 18, 2013)

neuroanatomist said:


> Can't speak for the 5DIII, but on my 1D X the 600EX-RT's AF assist lamp lights up only a thin vertical strip if the center AF point is selected. If I select a point in an off-center column, or in 61-pt auto, the full-width AF assist rectangle illuminates.



That's how my old 580EXII used to work on my 5D3, I was expecting that the 600EX-RT would work the same.


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## polarhannes (Sep 18, 2013)

neuroanatomist said:


> Can't speak for the 5DIII, but on my 1D X the 600EX-RT's AF assist lamp lights up only a thin vertical strip if the center AF point is selected. If I select a point in an off-center column, or in 61-pt auto, the full-width AF assist rectangle illuminates.



This also applies for the 5D3. Single point AF centered position = vertical red light beam(a line,not just a small dot), off center position or 61-pt auto = large pattern. I just checked my setup and verified it.


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## JRS (Sep 18, 2013)

polarhannes said:


> neuroanatomist said:
> 
> 
> > Can't speak for the 5DIII, but on my 1D X the 600EX-RT's AF assist lamp lights up only a thin vertical strip if the center AF point is selected. If I select a point in an off-center column, or in 61-pt auto, the full-width AF assist rectangle illuminates.
> ...



So, maybe I have a problem, because I don't have that vertical light beam line when using only the center AF point.


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## neuroanatomist (Sep 18, 2013)

Just to confirm, are you in single point selection mode, and not the 4- or 8-point expansion settings?


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## JRS (Sep 18, 2013)

neuroanatomist said:


> Just to confirm, are you in single point selection mode, and not the 4- or 8-point expansion settings?



I'm not with my camera right now, but later I will try again and make sure I'm not making any mistake.


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## JRS (Sep 19, 2013)

I've checked and I'm using single point selection...







Tried lot of different setting and still can't get the AF vertical beam from flash 

I'm using the last firmware version, I will try to downgrade and see if it works.


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## neuroanatomist (Sep 19, 2013)

Weird. Just FYI, the diagram you linked shows Spot AF, not Single AF (I have no idea if that makes a difference, and you may be in Single AF anyway but just found a convenient image on Canon's website). 

Only other thing I'd suggest before calling Canon would be to try resetting the camera to the factory defaults. Interested to know what Canon says if you call them...


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## JRS (Sep 23, 2013)

I finally got the vertical beam.

But now the weird part: I can only get it using the 50mm lens, with the 24-105 I only get the vertical+horizontal beam. Didn't tried other lens yet.


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## neuroanatomist (Sep 23, 2013)

JRS said:


> I finally got the vertical beam.
> 
> But now the weird part: I can only get it using the 50mm lens, with the 24-105 I only get the vertical+horizontal beam. Didn't tried other lens yet.



Odd. I tried it with the lens on my camera at the time, which was the 24-70/2.8L II.


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## JRS (Sep 23, 2013)

neuroanatomist said:


> JRS said:
> 
> 
> > I finally got the vertical beam.
> ...



Tried with all my lens:

50mm f/1.4 and 135L I have the vertical AF beam assist.

24-105L, 17-40L, 70-300L and 15mm fisheye I have full-width AF assist.


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## neuroanatomist (Sep 23, 2013)

So your lenses that give the full AF assist array are all f/4 or slower. I'll try it on mine with the 70-300L mounted...


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## JRS (Sep 23, 2013)

neuroanatomist said:


> So your lenses that give the full AF assist array are all f/4 or slower. I'll try it on mine with the 70-300L mounted...



Yes, except the 15mm fisheye that is f/2.8.

Please let me know when you try with your 70-300L.


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## neuroanatomist (Sep 23, 2013)

JRS said:


> Yes, except the 15mm fisheye that is f/2.8.



I was thinking of the 8-15mm Fisheye zoom, sorry. I'll post results...


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## JRS (Sep 26, 2013)

neuroanatomist said:


> JRS said:
> 
> 
> > Yes, except the 15mm fisheye that is f/2.8.
> ...



Did you try with your 70-300L?


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## neuroanatomist (Sep 26, 2013)

JRS said:


> Did you try with your 70-300L?



Just now. Turns out there's nothing wrong with your 600EX-RT (or at least if there is, the same thing is 'wrong' with the three of them that I have).

I tried again with the 24-70/2.8L II, and the center point gives the thin vertical AF assist. The 70-300mm f/4-5.6L IS gives the full AF assist array even with the center point selected.

So...I tried it with a variety of lenses, and this is what I found with the center point selected (selecting a point away from the center column always gives the full AF assist array):


EF 16-35mm f/2.8L II - thin vertical AF assist line
EF 24-70mm f/2.8L II - thin vertical AF assist line
EF 28-300mm f/3.5-5.6L IS - full AF array
EF 70-200mm f/2.8L IS II - thin vertical AF assist line
EF 70-200mm f/2.8L IS II + 1.4xIII - full AF array
EF 70-200mm f/2.8L IS II + 2xIII - full AF array
EF 70-300mm f/4-5.6L IS - full AF array
EF 100-400mm f/4.5-5.6L IS - full AF array
EF 85mm f/1.2L II - thin vertical AF assist line
EF 100mm f/2.8L Macro IS - full AF array
EF 135mm f/2L - thin vertical AF assist line
EF 600mm f/4L IS II - full AF array (part of which is blocked by the lens  )

You found that your 50/1.4 gives the thin vertical line, whereas your 15mm f/2.8 fisheye and 24-105L give the full array, and likewise, my 100mm f/2.8L Macro also gives the full array, while other f/2.8 and faster lenses give the thin vertical line.

Taken together, that suggests that with the 5DIII or 1D X and the 600EX-RT flash, the determining factor is which AF 'group' the lens is in. Only *Group A* lenses give the thin vertical AF assist line with the center point selected, whereas Group B and slower lenses give the full array (the 15/2.8 Fisheye is in Group B, the 100/2.8L IS and f/4 lenses are in Group C, etc.).


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## privatebydesign (Sep 26, 2013)

Just for the fullness of the thread.

I get different light patterns on the 600EX-RT AF assist with center AF point only with my pre 2012 1Ds MkIII's too.


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## JRS (Sep 27, 2013)

neuroanatomist said:


> Just now. Turns out there's nothing wrong with your 600EX-RT (or at least if there is, the same thing is 'wrong' with the three of them that I have).
> 
> I tried again with the 24-70/2.8L II, and the center point gives the thin vertical AF assist. The 70-300mm f/4-5.6L IS gives the full AF assist array even with the center point selected.
> 
> ...



Neuro,
Thank you for your time testing all those lenses!

Good to know that there's nothing wrong with my flash 

And very interesting that only group A lens have the AF vertical beam, don't know why it is not on the manual.


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