soundcard shutter tester works great!

[65Galaxie]

Just made a shutter tester out of a $1.50 infrared photocell from RadioShack and my computer's sound card. Tested my Speed Graphic lenses. My 90 Optar measures too fast in most settings (.736 at 1 sec. and 1/50th right on). My 135 Optar measure slow (1.3 in 1 second and pretty accurate for the other speeds. My newly purchased 210 Rodenstock in Copal was very accurate at .905. I couldn't accurately measure the top 1/400th speeds of the shutter as they showed the same speeds as the 1/200th settings. Now for the fun part. I measured my focal plane shutter which i have never ussed. The 1/30th was off almost a stop slow but the rest of the speeds were more accurate than the leaf shutters and It seems I could accurately measure the 1/500 speed but not the 1/1000 speed. The test revealed why some of my Velvia film came back underexposed with the 90 lens. The 1/25th was especially fast and that would be the speed used in full brightness situations.

[Peter Lewin]

Could you share how you did this?

[JW Dewdney]

my suspicion is that he recorded the sound of the shutter opening and closing on the computer and identified the peaks and troughs of 'which actions registered where' and then just read the time off the display with graphical waveform editing software.

[Marko]

I'm getting ready to make one too. It's a real simple schematics - one phototransistor, one resistor, a single 1.5 V AA battery and a switch, all in a serial connection with a mic input on the PC sound card. Total cost = approx. $5.00. OK, $10.00 if you want to get fancy.

When the light is shone through the lens and the shutter fires, the phototransistor generates a pulse very similar to that of the microphone. The sound card records it as a function signal. The duration of the signal as measured in a sound-recording program - i.e. the length of the signal wave - represents the shutter speed.

It actually sounds much more complicated than it really is...

[Ron Marshall]

I'm getting ready to make one too. It's a real simple schematics - one phototransistor, one resistor, a single 1.5 V AA battery and a switch, all in a serial connection with a mic input on the PC sound card. Total cost = approx. $5.00. OK, $10.00 if you want to get fancy.

Would you post a part number for the phototransistor and a supplier, and the resistance for the resistor.

[Bill L.]

I've found that you don't need the battery. I took a phototransistor and resistor from radioshack (sorry, not sure the part no.), soldered them onto a small piece of breadboard and used an old computer microphone jack. There is a public domain wave analyzer called audacity which you can use to time the peaks between opening and closing. The waveform is small but readable.

Bill

[Marko]

One more thing - if you want to really test the focal plane shutter, you can use two phototransistors appropriately spaced and connect them to the sound card using a stereo cable. A PC sound card IS stereo, after all. That way, first and second curtain can be pretty accurately measured, as there would be two peaks for opening and closing.

[65Galaxie]

The phototransistor I used was the only one Radio Shack had in stock. They call it an infrared phototransistor. I used a 4.7kohm resistor and a 1.5 volt battery that was probably getting weak. Plugged it into my soundcard mic input and recored the sound with SoundForge. Maybe one could get by without the battery. I do know that most sound card mic inputs aren't stereo but use one of the legs to supply power to a microphone. I just plugged an 1/8th inch mono plug into it and it worked ok. Probably shorted out the mic power supply part but it's probably protected with an internal resistor in the sound card. Just do a search on google and you'll come up with plenty of schematics. Some use a capacitor to tame things a bit I suppose but I tried it without and it worked ok. Maybe with the capacitor the pattern would be easier to read. I wonder whether one could get by without the reisistor and plug it into the line level input of the sound card instead of mic input. I just cut out a 4x5 foam core and put the phototransistor in the middle of the board through a hole. Used a flashlight shining through the lens with aperature wide open. The 90 6.8 lens showed a very small spike in the soundwave so it was harder to read. Had to really zoom in on the wave with the zoom features of the program.

[Marko]

Would you post a part number for the phototransistor and a supplier, and the resistance for the resistor.

The phototransistor I used was the only one Radio Shack had in stock. They call it an infrared phototransistor. I used a 4.7kohm resistor and a 1.5 volt battery

Yes, it is the only one they carry, but most Radio Shack sales associates just gave me a blank look when I asked for a phototransistor. Most of them had no clue what it was, and one guy had a vague idea, but not enough to know where to look for it (in his words). Radio Shack website was of no help either - the search would work only by catalog number. Radio Shack catalog number, that is. No, no way to find out the catalog number without the actual catalog.

But once I found out the catalog number - 276-145 - there was no problem, the local guy just looked the number up, went to the rack and started looking through capacitors and resistors drawers. When I told him that he was looking in the wrong places, he replied that "things just get thrown in here and the best place to start was resistors because that's what people buy the most". Go figure.

Some use a capacitor to tame things a bit I suppose but I tried it without and it worked ok. Maybe with the capacitor the pattern would be easier to read. I wonder whether one could get by without the reisistor and plug it into the line level input of the sound card instead of mic input.

I think the resistor provides to load for the current and the capacitor, if used, smoothes the curve. You could definitely use a more sophisticated circuit with a pre-amp and signal stabilization connected to the line input, but the point is to have it cheap and simple.

[John Hannon]

Yes, it is the only one they carry, but most Radio Shack sales associates just gave me a blank look when I asked for a phototransistor. Most of them had no clue what it was, and one guy had a vague idea, but not enough to know where to look for it (in his words). Radio Shack website was of no help either - the search would work only by catalog number. Radio Shack catalog number, that is. No, no way to find out the catalog number without the actual catalog.

So much for their motto "You have questions.... we have answers"

That soundcard tester works well. I used one for a while until I was lucky to find a Calumet tester at a flea market.

Here is another shutter tester link that may be of interest http://www.geocities.com/Yosemite/2131/shspeed.html

--John