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03-22-2010, 07:52 PM   #1
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af assist lamp in hot-shoe slot

Can i mount af assist lamp in hot-shoe slot? Would that work? Could I use say, couple of strong LEDs, instead of flash to help the camera focus? What I;m asking is, could the camera turn the LEDs on automatically when it needs extra light to focus?

03-22-2010, 08:21 PM   #2
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if someone was willing to experiment, they could dismantle an old pentax flash with AF and mount just the af lamp on to see if it works.

obviously, its not exactly practical nor sane to do that.
03-22-2010, 08:48 PM   #3
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QuoteOriginally posted by chaos83 Quote
if someone was willing to experiment, they could dismantle an old pentax flash with AF and mount just the af lamp on to see if it works.

obviously, its not exactly practical nor sane to do that.
No need to dismantle anything, one could use an old shoe an hook up couple of LEDs to it. Though one would have to know some electronics, in order to get the voltages and amps just right.

Well I just thought that maybe someone makes something like that.
03-22-2010, 08:52 PM   #4
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Andrzej,

The sell self-powered hot shoe "video light" gizmos, some led, some hotwire. I'm sure they're cheap on a popular online auction site.

alternately, you could get an inexpensive led one, remove the white leds and replace with near-infrared (sometimes called "deep red" or "cherry red" leds ... then your camera can focus in the dark, without the light affecting exposure.

03-23-2010, 07:45 AM   #5
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But I thought the trick was to create a very crisp pattern of thin linkes that allows the AF to find a good target even in poor light. Would a blanket of light, regardless of wavelength, allow for enough AF points without affecting exposure??
03-23-2010, 08:22 AM   #6
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QuoteOriginally posted by glanglois Quote
But I thought the trick was to create a very crisp pattern of thin linkes that allows the AF to find a good target even in poor light. Would a blanket of light, regardless of wavelength, allow for enough AF points without affecting exposure??
Have you seen the AF-assist lamps on P&S cams? There's no pattern there, just light. I think a swath of infrared light would work great, but it would take some work.
03-23-2010, 09:37 AM   #7
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QuoteOriginally posted by glanglois Quote
But I thought the trick was to create a very crisp pattern of thin linkes that allows the AF to find a good target even in poor light. Would a blanket of light, regardless of wavelength, allow for enough AF points without affecting exposure??
All you need to do is provide enough light to allow the AF sensors to work. It doesn't need to be a grid of red lines.
03-23-2010, 10:06 AM   #8
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QuoteOriginally posted by justDIY Quote
Andrzej,

The sell self-powered hot shoe "video light" gizmos, some led, some hotwire. I'm sure they're cheap on a popular online auction site.

alternately, you could get an inexpensive led one, remove the white leds and replace with near-infrared (sometimes called "deep red" or "cherry red" leds ... then your camera can focus in the dark, without the light affecting exposure.
Using the near infrared LED is a good idea. I'll give that a try when I find some time.

03-24-2010, 11:41 AM   #9
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A while back, I saw a thread where someone had rigged up a DIY focus-assist lamp, using a cheap, keychain LED flashlight. It was small enough and they just epoxied it to a shoe.

It didn't work automatically, the way the K-7's built-in one, or the ones on hotshoe flashes do, but it apparently worked rather well.
03-26-2010, 01:11 PM   #10
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I did measure voltages on my K100D 's hotshoe a couple of years back. There was one pin that changed logic level when the shutter was half-pressed and it stayed on for about 20 seconds I think. If you used that to switch on a bright light then it would still be lit when the shutter fired, so a real flashgun would have to interpret other pins' signals to turn off the light before exposure takes place, but if you were using infra-red LEDs then there would be no need to turn them off before exposure and it would make for a very simple circuit.

At a guess, one transistor a resistor and an LED would do it, but of course you need a power source as well, I don't think there's anything substantial available on the hotshoe pins, so an external battery would be needed for the LED power.
03-26-2010, 04:18 PM   #11
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Flashes can be used as SB's only and that means with some simple code the flash sends info or something like that saying "hi I'm only an AF assist right now". That could be done.
Also IR assist??? There IR filters in front of the sensors. What we see is red light, nothing else.
03-26-2010, 07:24 PM   #12
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QuoteOriginally posted by SteveB Quote
I did measure voltages on my K100D 's hotshoe a couple of years back. There was one pin that changed logic level when the shutter was half-pressed and it stayed on for about 20 seconds I think. If you used that to switch on a bright light then it would still be lit when the shutter fired, so a real flashgun would have to interpret other pins' signals to turn off the light before exposure takes place, but if you were using infra-red LEDs then there would be no need to turn them off before exposure and it would make for a very simple circuit.

At a guess, one transistor a resistor and an LED would do it, but of course you need a power source as well, I don't think there's anything substantial available on the hotshoe pins, so an external battery would be needed for the LED power.
Power source would not be a problem if I use an LED all I'll need is one or couple of CR2032 batteries, which would not take much space at all. One could start a business making this thing.

QuoteOriginally posted by StarDust Quote
Flashes can be used as SB's only and that means with some simple code the flash sends info or something like that saying "hi I'm only an AF assist right now". That could be done.
Also IR assist??? There IR filters in front of the sensors. What we see is red light, nothing else.
my point and shoot sony cybershot does not have an IR filter, do DSLRs have them?
03-26-2010, 08:21 PM   #13
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QuoteOriginally posted by Andrzej Quote
my point and shoot sony cybershot does not have an IR filter, do DSLRs have them?
Yes, they do. Your Cybershot most likely does too, but with a mode to move it out of the way for night vision shots.
03-27-2010, 08:01 AM   #14
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no filter is 100% effective, my unmodified K-x can see the pure infrared leds used by television remotes just fine, in live view it shows up as a purplish color.
03-27-2010, 08:43 AM   #15
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This is the result with my k-x (exactly as described by justDIY)

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