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Author Topic: Autofocus assist  (Read 1634 times)

CanineCandidsByL

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Autofocus assist
« on: April 02, 2012, 10:33:21 PM »
Does anyone know if there is a continuous IR light source I can use that will work with Canon bodies to help out focus in low/no light?  I'm thinking either an IR LED panel or an IR flashlight.

Thanks.

EDIT:
Continuing to look into the problem, I found information that states canon doesn't use IR but near IR light and its projected in a pattern that's easier to focus on than just lighting the object with IR.  From that, it seems an IR light wouldn't do any good. But if anyone know different, please let me know.
« Last Edit: April 02, 2012, 10:39:55 PM by CanineCandidsByL »

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Autofocus assist
« on: April 02, 2012, 10:33:21 PM »

dturano

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Re: Autofocus assist
« Reply #1 on: April 02, 2012, 10:46:33 PM »
You have to have a bulky flash mounted but you can disable the flash and just assist.

Menu
External Speedlite Control
Flash Function Settings
Flash Firing
Disable

I'm surprised they don't make a small shoe mounted device for a reasonable price.  Also does the ste2 solve this? With the above in camera settings

PeterJ

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Re: Autofocus assist
« Reply #2 on: April 02, 2012, 11:16:28 PM »
Canon cameras don't tend to be very IR sensitive with their IR filter in place, a while ago I pointed my 7D at an array of IR LEDs and you could barely tell they were on. By comparison pointing a monochrome CCD camera without an IR filter at the same array of LEDs totally saturated the sensor.

If you were after a cheap DIY solution you could try a cross-type red laser module, but for safety / legal reasons it wouldn't be any good if the subjects are people or animals. Otherwise try a torch with a cross or cross-hatch cut out of thick cardboard and see how it goes. I think the only purpose of the pattern is to give a few lines with sharp contrast, I doubt it has to be all that precise and the IR assist on my 580ex looks a bit 'fuzzy'.

Edit - just realised after posting the IR filter is on the main sensor not the AF sensor, so maybe AF would work OK with IR. They might just stick with near IR so you can see it's working.
« Last Edit: April 02, 2012, 11:19:30 PM by PeterJ »

neuroanatomist

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Re: Autofocus assist
« Reply #3 on: April 02, 2012, 11:20:36 PM »
Edit - just realised after posting the IR filter is on the main sensor not the AF sensor, so maybe AF would work OK with IR. They might just stick with near IR so you can see it's working.

Exactly what I was going to point out!

A 430 flash or higher, or the ST-E2, project the near-IR grid.  None are wide enough for the outer points on a 5DIII/1D X with a wide angle lens, except the 600EX (the 580 and ST-E2 come close, the 430 not so much).  Note that the new ST-E3 doesn't have an AF assist.
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CanineCandidsByL

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Re: Autofocus assist
« Reply #4 on: April 02, 2012, 11:50:33 PM »
Wouldn't the grid be used to produce fine lines on the object which can then be focused on? That would be an advantage even in bright light when trying to focus on a subject which doesn't have enough contrast on its own.

I did find this info, but I'm not familiar enough with site to know how much I can trust it.
http://photonotes.org/articles/eos-flash/index3.html

neuroanatomist

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Re: Autofocus assist
« Reply #5 on: April 02, 2012, 11:58:35 PM »
Photonotes.org is quite reliable.

Fine lines aren't necessary, only one edge is needed so fat lines are ok, as long as there are enough of them in a wide enough pattern.
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JR

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Re: Autofocus assist
« Reply #6 on: April 13, 2012, 03:20:02 PM »
I use the st-e2 for that purpose and it does help.  However my 580 II flash seem to do a better job at it...i guess the beam must be stronger?
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Re: Autofocus assist
« Reply #6 on: April 13, 2012, 03:20:02 PM »