Last september (2010) I wrote a blog entry about hooking up a laser pointer as an Auto Focus assist light for a camera. The need came up because I wanted AF assist in AI Servo focusing mode of my DSLR. Currently to my knowledge all Nikon and Canon DSLRs will only put out the flash AF assist beam until focus is achieved. After that if the (if the camera is in AI-Servo focus mode) if the subject moves and the focus changes, you’re out of luck in dark situations because the AF assist beam will not continually come on to keep assisting the focus.

The previous look at using a laser pointer as an AF assist tool,  I had very little success with that projects. Last week I came across the laser pointer again and new thoughts/ideas came to mind.

So I rigged a laser pointer to a bunch of batteries and a push button to act as an Auto Focus assist to my Canon 40D. The results are spectacular.

I’ve already started working/thinking about the next version of this. Updates on the AS Assist Tool V2.x will be here.

This is what I did, and how it worked.

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The need to control an off camera flash came about a while back. I purchases an hotshoe extension cable (YONGNUO FC-681) which allowed me to handhold and aim the flash by hand. In itself the cable worked great, however I needed the AF assist feature that the flash provides and aligning the AF assist beam of the flash by hand is next to impossible while looking through the camera’s viewfinder.

So I bought a YONGNUO ST-E2 wireless controller for its AF assist light and in itself works great, but doesn’t control my flash very well in E-TTL mode. Further to that, since the ST-E2 control is done by optical communication, I am afraid that even if a new flash will be able to be controlled by the ST-E2, outside or otherwise dark environments with black walls there may not be much/enough light reflected to be able to trigger and communicate with flashes that are placed behind the camera.

So I decided to combine the E-TTL hotshoe extension cable with the ST-E2 controller. With this setup I get the AF assist beam of the ST-E2 and am able to E-TTL command the flash where ever it may be pointing.

Brief description of the project: I chopped off the hotshoe connector cable at one and, and soldered the wires into the ST-E2 right as they come off the hotshoe.

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None of the Canon cameras turn on the AF assist light (the red light) on external flashes continuously after focus has been achieved.

I’d like to stick a laser pointer (one that projects a pattern) in the flash slot and paint the subject with some sort of laser light pattern to give the AF sensor something to easily focus on. This way, if the laser light is on continuously, then I can use the AI Servo mode to continuously track the subject in low light situations.

In order to turn on/off the laser pointer, I will use the top left most small pin off the flash hot shoe (not the big round one). See diagram in this thread.

Canon hotshoe pinout description here.

I may have to tweak the diagram shown in the link to turn on the laser pointer, but it should be doable.

The beauty of using the signal off the hot shoe connector is that it comes on only when the camera needs to focus, and stays on only for 7 seconds after it’s done focusing, or 3 sec after the shutter is fired.

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Update: 20 Sept 2010

I went to Club neutral last night and shot some pictures there. (Description of results from that night’s shooting at this post) I took the laser pointer with me, but I could not reliably use it. I had no mount for it other then the velcro I brought with me, which couldn’t keep it in one place especially when having to push the button all the time to trigger it.

When leaving the club noticed a red led bike light, and thought it may work for me too. Tried the red led bike light I have, to see how well it would assist the camera in focusing. Compared to the AF assist light from the Sigma EF500 DG super flash, it took almost twice as long to focus, and at times the bike light didn’t even acquire focus. So much for a simple solution.

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UPDATE: 24 Sept 2010

Came across a few forum posts where people are discussing AF assist lights. This chinese site has an interesting idea.

Also this forum and this forum have discussions on AF Assist lights.

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UPDATE: 02 May 2011

I have progressed this project further.  Check out this post for a working laser AF assist tool.