Category Archives: Photography

AF Assist v5 – optics

Since I will be using off the shelf parts for the IR emitter (LED), I need to somehow focus the wide 100deg or 120deg light given off by the emitter.
The light wavelength I’m looking for is in the low 700 nm range as measured from two Canon flash units.

I’ve found an IR emitter that puts out more then enough light at 730nm (1080-1293-1-ND from Digikey).
To focus the light in a tight beam, I just ordered some parts from Newark.

The lenses are




I’m hoping one of these small lens with enclosures will do the trick.
Will post more once I get them and try them out.

The light out of the bare LED is way to wide, and these lenses should focus the light to a tight 10-16deg beam.

AF Assistant v5.0 – First look

It’s been a while since I posted an update on this project. Life gets in the way sometimes, but I’m back at it now.
The previous design enclosure that fits under the camera has been abandoned mainly because it makes holding the camera a little awkward. Especially when using some longer lenses when I need my left hand to grasp the lens itself the AF Assistant would not only get blocked (by my hand) but also make holding the lens a little weird. Continue reading

Audio offset in Sony Vegas Video

Editing some video in Sony Vegas Video I noticed that some of the footage has out of sync audio with it.
I don’t know where this sync problem initiated (as the original footage is in perfect sync) but it’s there. I usually convert the MOV file to an AVI and then run it through a video stabilization software before using the footage, so anywhere along that path the probem could have arisen.

Anyway, the solution in Vegas is to ungroup the video and audio tracks, and shift the audio track to the right by 3 frames. With most video footage this is not noticeable, but when viewing a musical performance, the slight shift is very noticeable (at least to me). The vocalist’s mouth movement seen slightly off and the drummer looks not in sync.

When the final movie is rendered, there is no delay (using original footage) problem only seems to occur when previewing within Vegas Video

AF Assistant IR 1.0

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.


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

Book printing out of china.

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.


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.

AF Assistant v3.2 development

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.


Recovery of images from camera memory card

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.

Choosing a flash

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. Continue reading