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Bevanj

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Bevanj last won the day on August 7

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About Bevanj

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  1. I was using Cree C503C-WAS-CBBDB231 LEDs. I think it is of far more importance is getting good quality fibres which have low refractive losses. The TC74HC132AP is very appealing. It has low quiescent current, and a NAND can be configured as an inverter, or an AND gate. This whole thing can be made using two. 16pin DIP versions. Too bad there's not a 6ch version of this IC rather than a 4ch version - if there was, it could all be done with one IC, some resistors, and capacitors.
  2. The AND gates I was using are NC7S08M5X The SI gates I was using are NC7S14M5X I would recommend X7R ceramic capacitors. They have very low leakage. I'll have a crack at finding some through-hole equivalents, and putting the design together for a small-ish board that people can order off Oshpark, or JLCpcb, and solder at home with basic soldering skills. Bevan
  3. Hi, As some of you are aware, I was making LED trigger boards. Sadly, I've been super busy with my day job, and haven't really had much time to make them any more. Sorry to those that may have tried to contact me in regard to them. In true Wetpixel form, here is the basics of how I have been making them, and how they work. The core of the circuit involves some simple logic gates, a RC timer circuit, and a NPN transistor. Plus resistors, caps, and a diode. This design, provided the right components are picked, will work for years, and take tens of thousands of photos off a single set of button cell batteries. There are plenty of schematics out there that simply hook a hotshoe output to a transistor to drive the low side of the LEDs. However, there are some serious downsides to doing that. If you pick a shutter speed of say 1/200th of a second, the LEDs will light for 1/200th of a second - let alone if you pick an even longer shutter speed. This is incredibly wasteful of valuable battery energy. Far far shorter LED pulses are enough to trigger a fibre optic based strobe, and set it off, making for far far more efficient use of the small amount of energy in button cell batteries. Into the nitty-gritty. If you look at the drawing, there are two types of logic gates used. One is a schmitt inverter - these simply invert a signal. If the input is high, the output will be low. If the input is low, the output will be high. To note though - is the schmitt trigger on the input. This causes the detected input threshold from low to high to take place at quite a specific voltage, and the transition from high to low to take place also at quite a specific voltage. The other is an AND gate - if both inputs to this gate are high, the output will be high. In all other input scenarios (either is high, or both are low), the output will be low. Some basics... D1 provides input polarity protection for if some numpty puts the batteries in back to front. C1 and C2 provide some input voltage stability. After the hotshoe, you have R3. This is a pull down resistor. It simply makes sure that the input to R4 is pulled to ground if the hotshoe contacts are open. R4 simply provides a bit of resistance to the input to Schmitt inverter #1. It is probably not needed, given the incredibly high input impedance of the Schmitt inverter. Should the hotshoe be open, the input to SI#1 will be low, and due to how the gate works, SI#1 output (labeled as Point#1) will be low. The opposite is true. Should the hotshoe close, SI#1 input will be high, and SI#1 output (Point 1) will be low. R5 and C3 form the heart of how this circuit works. They form what is known as an "RC Timer." If the output from SI#1 goes high, it takes a while for C3 to charge through the resistance of R5. Likewise, if SI#1 output goes low, it will take a while for C3 to discharge through R5 to ground through SI#1. Thus, there is time lag between SI#1 output and what is happening at C3, and in turn the input of SI#3. This time lag is defined by the choice of values of C3 and R5, and can be finely tuned. SI#3 and SI#4 were used simply to get a non-inverting output output off the RC timer circuit. Two inverters = a non-inverter. But, in this case... with a schmitt trigger. I went this way, because I already needed to order schmitt inverters for SI#1. If you want to use a non-inverting schmitt buffer in place of SI#3, and SI#4, that will do the exact same thing. Sooo... actual operation. If the hotshoe is open, SI#1 output will be high. Provided enough time since the last shot, C3 will be fully charged. SI#3 and SI#4 will be providing HIGH to one side of the AND gate. Bam! A photo is taken. The hotshoe contacts close. SI#1 input goes high. S#1 output goes low. At the same time, the RC timer starts discharging, and SI#2 input goes low. SI#2 output goes high, and VOLIA, both inputs to the AND gate are high! The NPN transistor turns on, and the LED turns on! Once this has been in this state for long enough, C3 will have discharged enough for SI#3 input to go low, and in turn through SI#4, for the AND gate lower input to go low. This means LEDs will turn off, even before the hotshoe opens, and after an amount of time defined by the selecton of R5 and C3! When the hotshoe opens again, if you chase the logic, the upper side of the AND gate will instantly go low. The RC filter will take a while to charge (plenty before a camera is ready for another shutter actuation). The lower output to the AND gate will be HIGH, and we are ready to take another photo! How cool is that? The flash time of the LEDs can be fine tuned down to microseconds simply by the choice of resistance of R5, and the capacitance of C3. Provided you pick the right logic gates that have incredibly low quiescent current, and are 6V tolerant, along with the right type of capacitors that have low leakage, this circuit can sit dormant on a set of batteries for YEARS with no use! Hopefully this is useful to somebody! Happy photo taking, Bevan For those interested: https://en.wikipedia.org/wiki/Schmitt_trigger https://en.wikipedia.org/wiki/RC_time_constant EDIT: I'll scan the drawing when I have access to a scanner.
  4. Bill, Many thanks for talking to the guys at i-fiberoptics! If they do it, I'll place through an order for all the guys here locally. If I can get enough fiber to make 10x cables (with original fiber optic quality) for less than the price of a single new cable, it's a no-brainer.
  5. Likewise, I've had bad luck with tosink cable. The only way I can get enough light through it to trigger my strobes is with my topside 580EXii tube-based camera strobe. There is absolutely no way I can get enough light transmission through it with an LED source to trigger my strobes. I have never had a problem with multi-core fiberoptics though. The refractive losses are significantly less.
  6. As has been pointed out, you can get the MCQ-1000 easily by the meter, but the core is 1mm diameter. The Nauticam cables use MCQ-1500 cable, which is 1.5mm diameter. Sadly, the MCQ-1500 isn't listed by the meter. I've tried emailing www.i-fiberoptics.com to ask if they would consider selling it by the meter, but didn't hear back. Perhaps someone Stateside would be willing to give them a call? If that fails, and we get enough people together to divide up a spool, is there a time-trusted Wetpixel member in the US that might be willing to divide it up? I'm guessing that most people wanting some will be Stateside. However, the main reason I suggest this, is that i-fiberotpics.com quote close to $500USD to ship a spool to NZ where I am located - it does seem a tad pointless if I'm just going to divide it up and ship most of it back.
  7. Hi all, The 613 core fiber cable used in most commercial fiber cables is actually pretty cheap per meter, but can only be bought in bulk (500M spool). New fiber can be wound around a pencil, and be immersed in boiling water to produce the slinky coils before use. I'm sure the fiber used in most Nauticam/Howshot/Sea&Sea cables is P/N MCQ-1500-22 made by Asahi Kasei in Japan. With enough interest, it may be worth the group buy of a spool, and dividing it up. As we all know, when fibers break, the connectors on the ends are still perfectly good. It is remarkably easy to put a new fiber into the old connectors. A single spool of this fiber is in the realm of $1700USD ($3.4/m). With enough people, we can save considerable money by buying a spool and reusing our old end connectors. With 20 people, at $85 each (plus a little shipping), we would each get 25m of high quality fiber cable. Even at 10 people and $170 each (plus a little shipping), it would give 50m of fiber each. Given the price of replacement standard cables, this is a no-brainer in my mind. Any takers? Bevan
  8. Ok, So who is hanging out for the Canon EOS R5? Right when I was thinking of buying an A7R4, news of this shows up... What has been released so far does look very impressive. Bevan
  9. Hi HCldiver, Sorry - I've been being slack at keeping an eye on the thread I started. Sure, I can make something that will hopefully fit your A7R2 housing and be cheap and reliable. Fire me a PM. Bevan
  10. Hi everyone, Just wondering what everyone's thoughts on this are. I'm currently shooting with a 5D MK3 in a Nauticam housing usually using a Sigma 15mm fisheye lens. Right now, I'm trying to decide which way to go - I can upgrade my camera body to something else (A7R4 tempts me), or I could buy a WACP? Right now, I'm very much tempted by the autofocus system and dynamic range of the Sony, but at the same time I know full well that putting that camera behind a dome port will have serious limitations on the quality of image it can produce. This makes me tempted to go and get myself a WACP for use on my 5DIII. I already have a mint Canon 28-80mm 3.5-5.6 MKV that I scored for <$25USD specifically for if I chose to buy one. With the WACP, I'm guessing it also follows the above water rule of that glass is more important than the camera behind it. If I was to buy a WACP, I'm guessing that the value retention is going to be far far better than a new camera and housing which seem to depreciate sharply. I gather the WACP is a brick to travel with, but I can live with that. Also, does anyone know if the front element on the WACP is replaceable if it gets scratched? Thoughts? Bevan
  11. Bugger. All the newer ports with larger port openings are expensive enough that I'd be tempted to buy a WACP rather than a new port. Still, given I paid ~500USD for the lens, it's no real loss to me. Bevan
  12. Hi All, Have any of you got the forementioned dome port handy and a set of veriners (or a ruler at a push)? I've just scored a Sigma 12-24mm F4 on the cheap in hope that it will fit. However, I don't have my port handy. Unlike most of their other ports, Nauticam don't seem to have the opening diameter listed for this port. Hopefully it'll fit. The lens is 102mm in diameter. If anyone could check the port opening diameter, it would be much appreciated. Bevan
  13. Cheers guys, Yep, very much aware of the benefits of manual flash- it is what I usually use. I was simply playing around and came across the above and thought it odd. Bevan
  14. Gah.... talk about embarrassing. Use quality fiber optic cables - not chunks of cutup toslink for ETTL. Compensation out of the dial on the Z330 is minimal though. At a stab it appears to be ~1/6 stop per click. Lesson learned.
  15. Hi Everyone, I've just been having a play around with my RX100VA, and 7d, along with my Z330 strobes (via optical connection), and have come across a puzzling problem. In STTL mode, no matter what I do, I can't get any FEC control via the EV control knob on the back of the strobe! All exposures come out identical! It would seem that in EV comp, the Z330s are cutting or adding output on the preflash pulse as well as the main pulse. So, the camera gets less return from preflash pulse, aims for +-0EV flash compensation (where the camera is set), then compensates for the Z330s diminished output - thereby nullifying the FEC set on the back of the strobe. This is confirmed if I put a sekonic light meter in front of the strobe, and hit the flash exposure lock on the 7d to produce a preflash. The Z330 EV control knob is 100% having an effect on preflash strength. I've tried the strobes with both the preflash magnet in and out. No difference. Any ideas?! I'm starting to wonder if my strobes have a bug. I've only ever used them in manual mode before now. I know they were from pretty early off the production line. Bevan
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