Valve Sensor Tutorial
This tutorial will explain how to setup and use the valve sensor with the Camera Axe. The general premise of this sensor is you use it in a dark room with a long camera shutter expose. The photo would be black except that you use a flash to light the scene for a brief moment. The reason you use the flash to capture the picture is because a flash is much faster than a camera, and a camera shutter is just too slow to get an accurately timed and blur free droplet photo.
Here is the Camera Axe's valve menu.
Drop1 Size is the number of milliseconds (ms) that the valve is open. If this value is too small you won't get a drop. If it is too large you will get a stream of liquid instead of a drop. I usually start with a value of 50 and adjust as needed.
Drop2 Delay is the number of ms from the end of the first drop till the start of the second drop. If you want to collide drops getting is value correct is critical. More about this later.
Drop2 Size is the same as drop1 size except it is for the second drop. If you only want to work with a single drop set this size to 0 and there will be no second drop.
Flash Delay is the number of milliseconds from the end of the second drop until the flash is triggered. This is also a value you will need to play with to get a good value.
When connecting the valve sensor you want to plug it into the Sensor1 port on the Camera Axe. To trigger your camera there are two options. The first is to trigger it manually with a fairly long exposure like 5 seconds just before you activate the valve sensor. The second option (and I think this is a little easier) is to connect your camera to the Camera Axe's Camera/Flash1 port and put your camera's exposure to bulb so the Camera Axe can trigger your camera. You will need to connect one or more flashes to to the Camera/Flash2 port. I show the setup I used below. It has two flashes so I used a splitter cable to connect them. You should only use a splitter cable if you have two of the same flashes.
Now here is a video I composed from 46 shots with the Camera Axe. I had Drop1 Size=50, Drop2 Delay=0, Drop2 Size=0, and Flash Delay varied from 180ms to 410ms in 5ms increments.
That's pretty cool, but we can do better by colliding drops. You can either play around with the Camera Axe settings until you get a colliding drop or you can do a little math. I'll explain how to use a little math so you can get colliding drops.
From the sequence I used to make the video above here is the shot with a 300ms flash delay. This would be a good position for drop1 when drop2 hits it.
From the sequence I used to make the video above here is the shot with a 205ms flash delay. This would be a good position for drop2 to be when it hits drop1.
I'm going to use 50 for Drop1 Size and Drop2 Size because that gives me a good drop size with this liquid. Now if I take 300ms (from image above) - 205 ms (from image above) - 50 ms (Drop2 Size) that gives me 45ms. I will set Drop2 Delay to 45ms. Now if I take 300ms - 45ms (Drop2 Delay) - 50ms (Drop2 Size) that gives 205ms. I will set Flash Delay to 205.
Here is the picture I got with Drop1 Size=50, Drop2 Delay=45, Drop2 Size=50, and Flash Delay=205.
It looked a little early so I increase the Flash Delay to 210 and got this.
That looks good, but lets try a flash delay of 215.
And that's how you can calculate the settings for doing drop collisions. This was just a quick example. The real beauty starts to happen when you take time to place your flashes in good locations, adjust camera positions, and try different liquids. Below are a few examples taken with the Camera Axe.