Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-22-2010, 07:52 PM   #1
New Member




Join Date: Feb 2010
Posts: 23
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
Junior Member




Join Date: Jul 2008
Posts: 32
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
New Member




Join Date: Feb 2010
Posts: 23
Original Poster
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
Senior Member




Join Date: Jan 2010
Location: Manistee, MI
Posts: 295
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
Veteran Member




Join Date: Aug 2007
Location: Madison, Wis., USA
Posts: 1,506
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
Veteran Member
lavascript's Avatar

Join Date: Jul 2009
Location: Baton Rouge
Posts: 392
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
Veteran Member
alohadave's Avatar

Join Date: Jan 2008
Location: Quincy, MA
Photos: Gallery | Albums
Posts: 2,024
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
New Member




Join Date: Feb 2010
Posts: 23
Original Poster
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
Veteran Member
noblepa's Avatar

Join Date: Sep 2007
Location: Bay Village, Ohio USA
Posts: 1,142
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
Veteran Member




Join Date: Mar 2007
Location: U.K.
Posts: 685
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
Veteran Member
StarDust's Avatar

Join Date: Apr 2008
Location: Uppsala, Sweden
Posts: 400
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
New Member




Join Date: Feb 2010
Posts: 23
Original Poster
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
Veteran Member
alohadave's Avatar

Join Date: Jan 2008
Location: Quincy, MA
Photos: Gallery | Albums
Posts: 2,024
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
Senior Member




Join Date: Jan 2010
Location: Manistee, MI
Posts: 295
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
Inactive Account




Join Date: Mar 2010
Location: Berlin
Posts: 112
This is the result with my k-x (exactly as described by justDIY)

Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
af, af assist lamp, camera, dslr, focus, hot-shoe, lamp, leds, photography, slot
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wanted - Acquired: Wein Hot Shoe to Hot Shoe Safe Sync HSHSB 990-560 excanonfd Sold Items 0 08-26-2010 10:56 AM
K-x: Using flash as AF assist lamp (only) Bulldogface Pentax DSLR Discussion 7 02-18-2010 06:14 AM
AF assist lamp alwilliams Pentax DSLR Discussion 5 02-16-2010 08:21 AM
Wein Safe-Sync Hot Shoe to Hot Shoe Iowa Tom Pentax DSLR Discussion 1 09-12-2009 09:20 PM



All times are GMT -7. The time now is 02:07 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top