Work on the new AF Assistant has gotten to a point where I thought I would post some progress.

First off, the name is slightly changing. I am calling this one the AF Assistant IR. This will be version 1.x
As the name implies I am working on using an IR lightsource (well, near IR) from a Canon 550ex. I have mounted the LED module in a case which sits under the camera. It mounts to the 1/4-20 threaded hole on the bottom of the camera. The unit is still triggered by the remote shutter release port on the side of the camera just like the AF Assistant v3.1

Fig 1. Pattern at 3 ft.

I have chosen to align the light so that the projected pattern of the module is horizontal (as opposed to the vertical line the laser  AF Assistant put out). Due to the fact that the pattern is not just a line, and that the module is closer to the lens axis then a hotshoe mounted device, parallax errors in alignments are quite small. It seems that (in the first alignment of the LED module), the center focus point can pick up  on the projected pattern from 3ft to infinity. That’s more then enough for me. I can probably tweak it to get a closer distance, but I’ll play with that later.

Fig 2. Pattern at 30ft.

Several advantages are already apparent by using the LED module.

- The pattern that this puts out is quite wide. So wide in fact that with a 50mm lens on a full frame sensor (of a 5d mk2) the side (left or right) focusing points are able to use the pattern.
- The light the LED module puts out is quite dim. Figure 1 (at 3tf) was taken at ISO6400 , 1/30, f1.4. Figure 2 (at nearly 30ft) was taken at ISO25600, 1/13, f1.4. In a totally dark room, at 30ft, I can just barely see (with the naked eye) the pattern on the wall 30 ft away.

For both the 3ft test, and 30ft test I was focusing on a flat wall with no features (in full light, the camera can not focus on the wall, since there’s nothing there to focus on) and with the AF Assistant IR light, I can focus on the blank wall at 30ft away even with the side focusing points. Quite impressive.

Some internal details

Fig 3. LTC3490 LED driver in action

I have moved away from the 1 battery setup of the previous version. The LED is drawing up about 250mA (which is 10 times what the laser was using) so I figured I’d move up to 2 x AA cells.
I have also moved away from thru hole for most components. Surface mount technology is what I’ll be focusing on from now on.

The LED driver IC is a LTC3490. It can drive up to 350mA though  I cannot drive this LED that high. The LED module heats up too much for my comfort. At about 230-250mA it still gets warm but I can keep my finger on it indeterminately. Anything above that current and I can’t keep my finger on it for too long. There is a trimmer pot on the board so I can adjust the current to the LED but I may take it out in the production version.

So far all the tests are looking very positive. The other surface mount IC is a MAX4289 op-amp. It’s able to run on low voltage (down to 0.7V). Most other op-amps need at least 3 volts to run, which I may not have if I’m running two NiMH batteries at 1.2V a piece.

Fig 4. Fully populated board

I’ve only been playing with this setup for a couple of days, and will be testing it at music festival next weekend.

UPDATE:

I took some measurements of the wavelength of light from a couple of AF assist lights form Canon flashes. Read about them here.

Book printing out of china.

http://www.diyausa.com/

Got a quote for a 100 page book (same paper as Blurb basic paper), hard cover, bound for $13, based on order quantity of 300. In quantities of $100, the cost is $33 per book.

And speaking ob making books, I’d be needing other software to design books other then blurbs Book Smart software.

Scribus is a free open source package. To insert folders full of images into the layout, read this.

UPDATE:

Doing some number crunching, and even though the individual book cost is pretty cheap (at 300 pieces), at the end of the day the the offer is not that much more attractive then the cost that Blurb charges per book.

Work has been progressing on a newer version of the AF Assistant. The next incremental version (v3.2) will be made using surface mount components, and extra safety precautions have been added to protect the camera from any unwanted electrical signals.
Both inputs from the camera are isolated using buffers, and the ground is protected against reverse voltage.

Testing on this new design should start soon, and once complete all new AF Assistants will be built using this process.

Interesting reads. Keeping these links for future reference:

http://www.served-up-fresh.com/easy-as-pie/

http://www.digital-photography-school.com/how-to-get-over-your-fears-and-raise-your-prices-as-a-photographer

http://www.terragalleria.com/licensing-terms.html

http://photography-on-the.net/forum/showthread.php?t=330529

http://photography-on-the.net/forum/showpost.php?p=4329570&postcount=2

http://creativecommons.org/choose/

http://andrewstott.net/license/

http://www.downtheroad.org/photo_use/photo_license_agreement.htm

http://nomm.com/licensing.htm

I recently had a memory card fail on me on a recent trip (the filesystem somehow got corrupted) and I could not access the photos on it. I put the CF memory card aside, and left it till I got home. Once home, I used PhotoRec (in linux)to scan and recover all my photos from the CF card.
The file name of the files is lost, but all I need to do is sort by date in Bibble (my RAW converter software), which uses the meta-data date to sort, so the file name is not that important.

I’ve been pondering what flashes to buy to use with my PW Flex/Mini system of wireless triggers.

Above all else, I want a flash with low RF interference with the PocketWizards TT5 system. Cost is the other quality. Prefer not to spend 580EX II money. HighSpeed Sync is the other requirement as I ‘d like to be able to shoot in bright daylight. Manual zoom head would also be nice. Read more…

UPDATE: Work has indeed started on the (near) IR version of this tool. Details on the AF Assistant IR 1.0 (in early development stages) can be found here.

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Right from the get go, i wasn’t the happiest with the v3.0 design (see v3.0 link for details of why I built this, and previous version history) of the AF assistant. The main concern i had with it was the sloppiness of the case, and the extra cables that were required (which some of you commented about on the hack-a-day post).
So I did some searching around at local electronics shops and came across a small case that has a battery compartment for one AA battery. Digikey also sells a version of the case in black, which I will grab for the next upgrade. Much sleeker then cream colored on a black camera, though more expensive then the $0.25 I paid for the cream colored cases.

About the same time, i received an order from DealExtreme for some line lasers i had ordered some time ago. So I put together a circuit based on the v3.0 design (plugs in the side of the camera in the remote trigger port) and i have added a dc-dc boost voltage regulator that takes any voltage (0.7volts and higher) and turns it into a constant 3.3volts (based on suggestions from the hack-a-day post comments). This is perfect since that means that regardless of what battery i use, (1.5v alkaline or 1.2v NiMH rechargeable battery) i can get a constant voltage to drive the line laser. Read more…

Updated version available here. Version 3.1 is complete.

It’s done!

Version 3.0 of my AF assist tool is complete.

Taking a step back, I should explain why I needed this tool.There are really 2 reasons I built this:

1. When photographing concerts or clubs, or any other venue where light is at a premium, the AF sensor in the camera can only do so much to give accurate focus. I am using off-camera flashes most of the time now so I am not relying on the ambient light to paint my scene; that’s what the flashes are for, but I still need to focus. No remote flash trigger to date has had a AF assist light built into it. I use a Pocket Wizard Mini TT1 trigger and Flex TT5 receivers to trigger my flashes, along with an AC3 zone controller (which allows power control of 3 flash groups). So with a flash trigger in the camera’s hotshoe I loose my AF assist light, which normally I would get from a regular flash.

2. DSLR cameras (that I’ve looked at) don’t do AF assist in AI-Servo mode. They don’t allow you to track a subject in the dark, by continuously adding the light from the AF assist lamp on flashes to help the AF sensor in the camera continuously maintain focus. You get One-Shot focus, and once focus has been acquired, the light goes of. But if I want to track a singer as the move on a stage, like one would track a moving person or a race car during the day, you’re stuck. You can’t. This AF assist solves that problem but allowing full control of the AF assist light to be projected as long as you’re focusing (focusing is done by 1/2 pressing the shutter). Read more…

I think I have a schematic I am happy with to drive either an LED or laser module.

The 3.3V from the camera comes from the Remote Shutter connection on the side of the camera. One of the pins puts out 3.3v continuously, and when the shutter button is 1/2 pressed, the 3.3v drops to 0v. The op-amp is a buffer to separate the camera from the circuit, and to provide no load on the camera connection.

The pnp transistor turns on when the voltage is 0Volts at the base, and turns off when the voltage starts to increase. The potentiometer injects a little voltage into the transistor allowing for some control of the brightness.

Will build this on the weekend and will comment on how well it worked out.

The op-amp is a low power op-amp (NJU7016D) which will work down to 1V. To get a constant 3V supply to the circuit I’ll use a step up DC-DC converter (893-1150-1) which will take anything from 2-6V and convert it to 3V. So I can use rechargable Ni-MH batteries without a problem. I suppose I could use Ni-MH batteries but the light output will not be as bright. Will need to test this.

Read more…