soundcard shutter tester works great!

[Ron Marshall]

Thanks for the info. I'm off to the local Radio Shack.

[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

[Marko]

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

Well, as they say, formulating a question is more than half the way toward finding the answer...

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

That's the one I'm using, although I still haven't decided on the software yet. I might even have my son write a custom app for me...

[Mark Kapono]

Aloha:--The photo LED at Radio Shack will work fine, which is actually the description for the p/n above. It is tuned to the near IR, and comes with the transmit LED. In those same drawers try to locate the silvered, dished LED holder, which mounts in the project box cover. Wire it up with an old headphone cable to your mic jack and shazam. I put a piece of thin black foam on the top of the project box with the LED poking through which makes for resting the shutter on a soft surface. Remove cells-->Open Audacity-->R-->fire shutter five times-->SPACE (stops R (record)). Zoom and determine highlighted waveform for the time (milliseconds) and input data into S-Plus for the general statistical analysis...mean, variance, &c. I just focus a desk lamp down through the shutter barrel. My question to folks who have done this longer than I have is what sort of service life have folks been getting from this LED. I have found a decrement in performance of the LED with time and usage, with a weaker and less defined waveform.--A hui hou!--Mark

[Brian Ellis]

Going the opposite, and more expensive route (as I usually do), the Metrolux II compensating timer also works well as a shutter speed tester. Of course it costs a little more than the Radio Shack version - about $350 as I recall.

[Oren Grad]

This is all very cool. Bear in mind that the measurement of effective leaf-shutter speeds is not straightforward and is aperture-dependent, because the action of the shutter blades is akin to an iris diaphragm opening and closing. I'm not sure what the technical conventions are for dealing with this.

[Mike Davis]

This is all very cool. Bear in mind that the measurement of effective leaf-shutter speeds is not straightforward and is aperture-dependent, because the action of the shutter blades is akin to an iris diaphragm opening and closing. I'm not sure what the technical conventions are for dealing with this.

I tested this yesterday with my 14" commercial ektar and a sound card tester I built yesterday afternoon. Previously I had tested the slow speeds by simply recording the sounds so I had an idea about the shutter.

What I found with regard to the shutter speed and aperture was not much difference between f16 and f6.3. By "not much" we are talking .001-.005 seconds, in my tests.

A problem with using the sound card tester with LF (8x10) and larger is getting it centered in the bellows. My next mod will be to mount the tester box on a paint stirrer. But, I found that f16 was about the most closed that I could set the lens and still get discernible readings using a flashlight shining directly in the lens. I attribute this to the sensitivity (or lack thereof) of the IR photo-transistor and the placement of the box in the bellows. I did not test the shutter without the lens elements.

Some Results from the ektar in Ilex 5 shutter.

1 second- .635 average
half second- .445 average
fifth second- .282 average
tenth second- .132 average

Since according to Steve Grimes the Ilex is designed to be accurate within 1 full stop, all of these fall within that spec. I still plan to send it up to Frank Marshman for a CLA as soon as I get the proper board for my 240-w Germinar on the Wehman.

Having a much newer Copal 1 shutter, the Germinar tests much closer to speed for all speeds.

Mike

[scrichton]

measure it wide open. As this is when the shutter is at it's least effective point due to the full movement. smaller the aperture the more efficient it will be due to less are of movement.

[Oren Grad]

I should have said not just aperture-dependent, but also speed-dependent, because in principle the opening-closing action constitutes a larger portion of the overall exposure time as the speeds get faster. But just how fast the mechanical action is and where it starts to be an issue, I don't know.