"Shutter-Speed" is an iPhone-App that allows you to measure the shutter speed of a camera. With this app you can check whether your camera is exposing the film correctly, or if there are any deviations. If there are, then the App tells you how to correct it !
As we are all analog photographers, we have one thing in common: We all work mostly with old, second-hand cameras. But did you ever ask yourself, whether those cameras still expose your film right, or not ?
The most critical component in every camera is the shutter, because the shutter-speed determines how much light the film gets. Most cameras provide multiple shutter-speeds like 1/30s, 1/60s, 1/125s, 1/250s etc. On most older cameras, those shutter speeds are created and regulated with complicated spring mechanisms. This can be a problem, because after several years, the springs inside the camera can lose their tension, which results in wrong shutter speeds: The camera exposes too long, and your film gets overexposed.
But how can you know if your camera is exposing correctly ? How can you know whether your 1/125 is still a 1/125 and not more likely a 1/80 ?
With this app, you will know. It allows you to measure the actual shutter-speed of your camera and gives you the deviation from the target value.
How does this work ?
The App uses an acoustic measuring method. When you release the shutter of your camera, the shutter generates the well-known shutter-release-sound. But this sound is not just a sound, it contains a lot of information about the shutter ! With the App, you can record this sound. Then, the waveform of the sound is displayed on your iPhone. In this waveform, you will recognize two Peaks:
The first peak indicates the opening of the shutter, the second the closing. You can now use the two bars on the bottom to measure the time between those peaks. This is the shutter speed of your camera !
This also works for faster speeds, here for 1/125:
Of course this way of measuring isn’t 100% exact, because you just measure the sound, not the actual light passing through the camera. But nevertheless, it gives you a very nice overview whether your camera exposes correctly or not, without wasting expensive film !
If you want a more exact measurement, then there is an “extension” to this App:
This small plug contains a phototransistor and a resistor. The resistor is 4,7 kOhm and the transistor used is a BPX 38:
It is quite easy to assemble and costs only a few bucks.
If you plug this into your iPhone, it will no longer record the shutter-release-sound, but the light, that hits the phototransistor. You can now measure the actual amount of light that passes through the camera !
To do this, remove the back of your camera and light it with a light source (lamp or simply the sun). Then point the phototransistor towards the lens of the camera:
Start recording and release the shutter. Again, you will get two peaks, the first when the shutter opens, and the second when the shutter closes. In comparison to the acoustic measurement, this signal is much more cleaner and the peaks are clearly separated:
It works easily up to the 1/500s:
After you made your measurements, you can save the measured data to a table, which displays the target value, the actual value of your camera and the deviation of each single time in thirds of an f-stop:
One important note: Both the acoustic and the light-measurement only work well for cameras with leaf-shutter, (for example Rolleiflex 2,8f). Cameras with focal-plane-shutter like SLRs only work up to the X-Sync speed (mostly this is the 1/60) !
You want more information about this App ? Click here