Neurodance 2.11 – Notes

1 Reply

Equipment

I had some equipment malfunction from time to time with the wireless flash triggers. Sometimes moving a few inches one way or another or rotating the camera would solve the problem, but it was a real pain sometimes. I don’t see the flash firing when shooting, so I have to look at the screen to make sure everything worked, which becomes a hassle after a while, having to check each shot. I’d much rather the equipment worked!

The PWs had an issue where in manual mode, when the AC3 was dialed to -1 .33 EVs (which is 1/32 + 0.7EV in manual power) the flash output is nearly zero. The -1EV and -1.66EV setting on wither side of -1.33EV work as expected. Very strange. Will have to figure this one out for next time.

Lighting

I am finding the stationary flash locations to be limiting. I will see if I can coral some volunteers to hold a flash for me especially when shooting individuals dancing. I’m hoping to achieve a more directional light (rather then bathing the whole club with light) and have more control over the lighting. Idea is to set up two lights. A key light and a rim light, and have those lights move around as I move.

I’ve been doing some reading on lighting techniques, and I am really looking forward to implementing some of them in my shooting.

 

AF Assist tool v3.0 – more info

3 Replies

Light source

I just received an AF assist module out of a Canon 550EX. Bought it here on Ebay from seller procamerarepair. The ebay item title is ‘CANON SPEEDLITE 550EX AF LED ASS’Y NEW REPAIR PART OEM’

It’s the same part as the AF assist lights in my Canon 420EX flash

So I measured both the voltage and current at the LED in my 420EX flash. The voltage across the LED is 2V. The power drawn is 400mA (yes, 0.4Amps; pretty crazy, I know). The Supply voltage (with the LED disconnected) is 5.5V. That means the resistor that’s in line with the LED must be 8.5Ω.

I powered the ebay LED with 3V and with a 3.6Ω and it was drawing 0.25A and it seemed just as bright as the flash AF assist LED. I had them both going at the same time.

http://www.everlight.com/datasheets/Shuen1W_datasheet.pdf

Because of the high current draw, I am betting these are IR emitters rather then visible light LEDs. I have seen what a 30mA red LED looks like, and it’s just as bright as these LEDs. So for the extra 10x the power draw, I am betting on them being IR emitters.

I found a similar power IR emitter at Digikey. 400mA, voltage drop of 2.2v. 730nm, which should be a deep red, considering 660nm is the other LEDs I bought, and they’re pretty bright red. Will look for more, but will order this one next time I put an order in. They’re not very cheap at $4.16 a pop.

I don’t really need to buy an LED for this. It’s more for me to figure out roughly what wavelength these AF assist LEDs are in commercial flashes.

Remore trigger port characteristics

I measured the 3 pin connector on the side of the camera where the remote trigger goes. One pin is ground, one pin corresponds to 1/2 shutter press, and one pin corresponds to full shutter press. I don’t know if the full shutter press also engages the 1/2 shutter pin.

What happens on those pins? When the shutter button is not pushed, there’s 3.3v between both pins and ground. When the shutter button is pushed 1/2 or full, the respective pins go to 0V (ground). So if I’m going to use an op-amp (which I am) to pick up and use the the signal, it will have to be an inverting comparator. When there’s a voltage on the op-amp input I need 0V to be seen at the output and when there’s 0V at the op-amp input I need to see full voltage to drive the LED.

Speaking of op-amp, I will need to source an op-amp that can handle 1/2 Amp. The LM358 I have I think can handle 30mA, which is fine for the laser pointer.

Going forward

I think I will pursue both the laser pointer (line laser) as well as the AF assist emitter from ebay (the 550ex emitter)

AF Assist tool v3.0 – line laser

Leave a reply

From my last post(AF Assist tool v3.0 – more testing)I discovered that the LEDs I have found are just not cutting the mustard. Today it just happens that I receive a red cross hair laser I ordered from Deal Extreme a few weeks back. I had all but forgotten about it.

So I stuck 3 volts onto it, and put it through the paces like I did the LEDs in the last post. The laser is bright. At 40ft (in pitch black), it’s very visible. Too bright in fact. So I stuck some resistors in series with the 3v battery to see if I can dim it. At 60Ω, the laser is dim. So dim in fact that in a brightly lit room it’s hard to see at a few feet away on a white wall. Yet when I turn the light off, and point at the wall 40ft away, the camera can still focus (with the center focus point) on the flat featureless wall. (I will post some pictures soon)
Perfect!

Not having had much success so far with LEDs and this laser module arriving in the mail I think I will rebuild my tool using this cross hair laser. Really I just need one line. The perpendicular line is of not much use. I really want this line laser from DealExtreme. I just ordered a few.

Ideally it would be nice to have several lines (close together) to allow for a little misalignment of the laser line and the focusing points be projected out of the same laser, but I haven’t yet found a diffraction lens that will do that.

Since contract is really what makes the difference in helping the AF sensor focus (as opposed to more light), the laser line is perfect since the light it produces remains sharp (distinct edges) up to a very long distance. And the line gives the enter focus point something to focus on regardless of the subject distance, whereas with projecting a spot, the will be some distances where the center focus point will not line up with spot of light.

As a start, I will add a potentiometer in series with the battery to adjust the brightness (a 100Ω pot should do it). Eventually I want to go with full PWM dimming control, so I don’t needlessly drain the battery.

Now if I can only find a laser of a higher wavelength, so that the light is nearer IR. The current laser is 650nm. Something in the 750nm range would be interesting to experiment with. If anyone knows of a source of inexpensive, low power (under 5mW) near IR laser modules (700nm – 800 nm), please let me know.

UPDATE:

So you can get any pattern projected… Frankfurt Laser does a variety of patterns that may work very well. The Concentric circles I think would be awesome since it could cover most/all AF points very nicely

Additional power for Strobes

Leave a reply

The 4 AA batteries that all flashes take is enough for most uses, but if the flash is not easily accessible, or batteries die too quickly then AA batteries are not a good option any more. I’ve been thinking about how to extend the power supply of flashes.

My solution is to use Li-Ion batteries, with a DC-DC converter. I’ve identified several DC-DC converters that may work.

The big question is how much power does the flash draw when recycling after a flash? On 1/4 power, a SB800 will get about 1500 shots on a 2000mAh battery set. (source) It took 30min for the batteries to reach 1400 shots (and dies at just shy of 1600 shots), so that averages out to about 1 Amp continuous draw out of the batteries for 1/2 hour.

At full power, on a Canon 430EX II, the power draw peaks at 9Amps, then 6Amps after 1 sec, and 3Amps after 2 sec. (source post #15)

For a reasonable price ($12ish) a 5V, 5A DC-DC converter like this one or this one would probably work. The max input voltage is only 14V, so realistically only a 3S Li-Ion battery would work. That’s already twice the voltage of 4 AA batteries.

A bit more power to 10A at 5v can be had for about $18 in this module, or this one.

For higher input voltage range (9-28V) something like this can be used with the limitation that only 2A can be drawn. This one also costs about $24.

Of course there is an option for high input voltage (18-36v) and high output current (40W, so at 5A, that’s 8A) but it also costs $87 in this module. Out of my price range.

I think the best option is to have the max available current any time I need it, even though I may not shoot at full power very often. It also means the re-charge rate is maintained at the same level for a much longer period of time.

A 5000mAh 11.1v (3s) Li-Ion battery from HobbyKing costs about $25. This battery should have more then four times the capacity of 4 AA at 2000mAh.

Is it worth it for the extra complexity? I don’t know.

UPDATE:

Found a DC-DC converter (LMZ12008TZ) for a reasonable price that can handle 6A at anywhere from 0.8V to 6V output. The input voltage is 6V to 20V so a 5s battery would work. The digikey price is $22 ish and it requires very few external parts.

AF Assist tool v3.0 – more testing

1 Reply

I tried out the 540ez lens with both the LED that came with the assembly as well as the LED I bought from digikey. The digikey LED was brighter then the led that came with the 540ez lens. Brightness was judged with the LED installed in the housing, and the projected pattern was the object of judgment.

However, when it came to what the camera saw, it was a different story. At 40ft (the length of my basement; can’t go any longer indoors) the camera was pointed at a blank wall, and all the lights were turned off. The LED that came with the 540ez lens assembly was able to get a focus confirmation out of my 40D whereas installing the Digikey LED in the same lens assembly, did not provide AF confirmation. This was very interesting because the same contrast producing pattern was projected, and even though to the human eye (my eye) the digikey LED seemed brighter, the camera saw something else. At 40ft, I was could not visually  see the pattern projected by the 540ez led (yet focus was confirmed by the camera). With the Digikey LED, I could see the projected pattern (just barely) but the camera was not able to use that information to focus.

The Digikey LED is of 66onm wavelength. I can only guess that the led that came with the 540ez flash is higher then that (nearer to infrared).

I also tested a few other flashes to see if I could achieve AF confirmation on the same blank wall in total darkness, 40ft away.

Canon 420ex – AF confirmation achieved (pattern just visible 40ft away)
Nissin Di622 mark II – AF confirmation achieved (pattern not visible 40ft away)
Younguo ST-E2 – AF confirmation achieved (pattern clearly visible 40ft away)

Looking at the flash quoted AF assist distance I compiled for a few flashes seems to be understated?

The Plan:

Near-infrared is starts at 780nm and goes up from there. So I’ll have to find some LEDs that are between high 600nm and 800nm
OR
Find some brighter deep red LEDs.

UPDATE:

For the next version of the autofocus tool I’m currently working on I need to test several wavelengths of IR light .
3 x IR LED 770nm (p/n: 15P2280)
3 x IR LED 830nm (p/n: 93K0966)
3 x IR LED 850nm (p/n: 97M1058)

Sizing LED resistors

Leave a reply

For LED 2X2.5MM SUPER RED CLEAR 1.7V forward voltage, 25mA max current draw

@ 9v, need 330 Ohm resistor
@ 6v, need 180 Ohm resistor
@ 3v, need 56 Ohms resistor,

For LED 2X2.5MM SUPER YELLOW CLEAR, 2V forward voltage, 30mA max current draw

@ 9v, need 270 Ohm resistor
@ 6v, need 150 Ohm resistor
@ 3v, need 39 Ohms resistor,

For IR EMITTER 1.9MM 950NM DOME SMD,

@ 9v, need xx Ohm resistor
@ 6v, need xx Ohm resistor
@ 3v, need xx Ohms resistor,

AF assist tool v3.0 – testing

1 Reply

So I got some parts from DigiKey today; enough to  do some more testing. Took out the ebay purchase I’ve had for a few weeks, and got to work.
I picked up this AF assist lens from a Canon 540EZ flash, complete with LEDs.

CANON AF LED UNIT SPEEDLITE 540EZ FLASH NEW

I hooked up an LED to the 540EZ AF lens along with a resistor (200 ohm) and a 9v battery.

This is what I got in terms of a pattern. Shot on the left was from 7.5ft, then 15ft, then 30ft. At 30ft, I could barely, just barely make out the pattern on the flat white door onto which I was projecting the pattern.

The camera exposure was:  ISO:3200, aparture: f1.4, exposure: 1/40

Again I must stress, there was VERY little light on that door from 30ft away, however the AF sensor on the camera locked in an instant. Maybe took a fraction of a second longer then from the 15ft distance, but it was hard to say.

I can hardly believe that such little amount of light can produce such a focus lock on a flat color (white) door in total darkness.

I took out my 420EX flash and fired the AF assist light (was not able to capture it since the flash was on the camera, and the light goes off once AF is achieved) and the light is much brighter. Maybe 1-2 stops brighter from 30ft. Maybe I need to use a lower value resistor to get more power out of the LED that came with the 540ez lens, or just replace it with a brighter LED.

Either way, it looks like adding contrast is MUCH more effective then just adding light to help the AF sensor focus and the idea of using a flash AF assist lens is looking much more promising then the laser pointer idea.

The 540ez lens module is kind of bulky. I would prefer it to be a little slimmer. The AF assist lights in my 420ex is made of 2 side by side lenses which are a better size. Will need to scope out some of those lenses.

Pocket Wizard Flex system : now works with more flashes

1 Reply

I had purchased a PW Flex TT1, 2 flex TT5s and an AC3 a while back and could not get my Sigma EF-500 DG Super or the Nissin Di622 MkII to adjust their power. The Canon 430EX I owned would work beautifully (Of course, it was on Pocket Wizard’s compatibility list).
The Sigma and Nissin flashes fire, but they always fire at full power, no matter what setting I chose on the AC3 or the camera FEC.

I had installed version 6 .00 of the Flex firmware a while back when it came out (a month ago or so) but never re-tested the Sigma and Nissis flashes. The compatibility list on the Pocket Wizard website had not changed.

I was preparing for a photo shoot and was testing all my gear, and I accidentally put the Nissis flash on a Flex TT5 unit. To my amazement, the flash power was adjusted! I was amazed!
I then quickly tested the Sigma flash, and it too worked. The power was adjusted as per the setting on the AC3 contreller. All of a sudden I have 2 more flashes that I can use on the TT5 units!

Horray!

If you have a Flex TT5 unit, and own either the Nissin or Sigma flashes I mentioned above, please test them and let me know if they work for you.
Just to mention it again this change has been in effect only since the firware 6.00 has been released for the Flex TT5/TT1 units.

UPDATE:
The Nissin works great; rock solid especially in manual mode. No HSS though, but they have their time and place.

As for the Sigma, I have some reservations. The shots fired are hit and miss. Some are proper exposure, some are not. There’s the occasional firing of the flash by itself. And the biggest gripe is that the pocket wizards fail to communicate with each other way too often. The dreaded red blinking light. I have not found a pattern as to why/how this happens. Maybe to much interference from the flash?
It’s too bad though, since these flashes are quite powerful and inexpensive.