An improved version of the old trick - using computer sound card and an electronic shutter tester.
This one offers the following improvements:
no battery required (uses computer USB port for powering the electronics)
uses its own light source
provides somewhat more accurate measurement (i.e. more readable on higher speeds)
This was actually made by a friend (who knows more about electronics than I do), just as a proof of concept, i.e. a prototype, and I'll be the first one to admit that it looks rather ugly :)
Here's the new gadget:
Parts:
1) Light source, mounted in a
largish board, which serves as a platform on which you place the
camera (lens down)
2) Light sensor, placed behind the shutter,
does the actual measuring
3) Light source controls (555 chip and
some resistors in a housing made from old film canister)
4)
Microphone jack
5) USB connector
The large board with the light source is used like this:
Actually, you can take the lens off if the camera is too unstable on this "platform". It doesn't really matter as regards the actual measurements.
This is how the "platform" with the light source looks from behind:
For large format cameras, you can even place it or attach it (rubber band comes to mind) to the front of the lens...
Otherwise, you can measure the speeds of your LF shuttered lenses like this:
This is how it looks like "in action":
- Look, Ma, no batteries!
The mic jack goes into the microphone input of
your computer, and the USB connector is plugged into a free USB port.
It's not advisable to look directly into the light source LED when
plugging in the USB connector - the light is bright, and pulses on
high frequency...
Here's what I got in the way of technicalities,
i.e. the parts required to make this, if you are the "DIY
type"...
The light source schematic:
The chip is 555, as described here.
The resistors R1 and R2 should be chosen so that the frequency of light for the LED is about 15 Khz. The R3 resistor is 1K Ohm. The transistor is any of the N type, and the LED used is a white one, ("Ultra Bright"), with light beam between 4 and 6 degrees, from 1000 to 1200 mcd. The unmarked resistor should be chosen according to this LED.
The sensor schematic:
Photo transistors: any available NPN type...
(Don't ask me more
about the technicalities, I just wrote what the actual author told
me....)
The rest is easy: once the tester is assembled,
the USB connector is plugged into the computer USB port, mic jack is
plugged into the microphone input of your computer sound card, and
any sound recording software is used (again, I use the freeware
"Audacity").
Place the camera (or LF lens in shutter) on
the light source platform, cock the shutter, start recording in the
program (press the red recording button), fire the shutter, stop
recording, and take a look at the resulting waveform:
There are actually two measurements ("audio tracks") in the above screenshot: the top one shows half a second (1/2), and the bottom one (selected) shows one fifth of a second (1/5), as measured on my old Kiev. The length of the selected portion of the bottom wave is 0.206 seconds, which translates to approximately 1/4.9, which isn't bad at all (only about 3% deviation from the nominal speed, which is 0,2 seconds for the speed of 1/5).
I've also prepared a small Excel sheet with some numbers and formulas: you only need to enter the measured duration in the appropriate row in the "Measured" column, and the actual speed and difference from the nominal (in %) are immediately shown, like here:
You can download the sheet here.
BTW, if you don't feel too confident about building this yourself, you can contact the original author at:
I guess he could be persuaded to make one for you :)