DIY shutter-speed tester: Informed opinions?

[Ulophot]

Hey, folks. Any of you technically inclined wizards have thoughts on the item linked below? The author says it's only good to speeds as short as 1/30 or 1/60, but that accounts for many of the ones I use in LF, at least. It's investment cost is very small, and I'm guessing that where to put the wires is indicated somehow in the code her provides--just a guess, since I have zero knowledge of electronics.

I'm wondering what prevents modest accuracy -- say, 1/4 stop -- up to 1/125 or 1/250. Photo cell? Rasberry? Could this be improved upon with another $10 or so?

https://www.youtube.com/watch?v=R1OOC43ndPs

[Graham Patterson]

It is a couple of polling loops. There is a certain unavoidable overhead in the test and recording, but that can be determined by making both while tests succeed immediately giving the minimum code execution time. The Pico is available and cheap, but runs at 133Mhz. A full Pi 4 at 1.5Ghz would be over 10x faster. But they are still victims of the chip shortages. Fine if you have one.

The iPhone app that used a photocell stored a short audio clip and used the sensor to blip the audio input. The signal processor for audio is very fast, so the recording had no polling delays. The time was then eyeballed from the waveform. Finer-grained data.

The Pico code might be good enough if the minimum time to execute the tests is short enough.

[tomwilliams]

Philip - there have been a number of shutter testers presented in the large format forums, the latest that I know about (aside from the subject of your post) is here. I used a part of the Arduino code in that link to improve the slow-speed measurements of my most recent homemade, Arduino-based tester. From which I conclude that the code can influence the accuracy of the tester. I've never used Python though, so won't comment on Mr Jackson's code. No doubt the sensor plays a role too - Mr Jackson doesn't indicate exactly which phototransistor he used. I found that using an IR sensor in my tester didn't work well at slower shutter speeds.

Mr Jackson isn't clear about his thinking on the limited range of accuracy for his tester ... its seemed at least to give expected results at 1/4, 1/2 and 1 second, without too much variance. He's certainly measuring speeds within the general manufacturer's spec of +-30%(as I understand it). In any case, without calibrated equipment/software, one can only infer accuracy and precision. From what I've gathered, and seen in my own shutters, speeds above 1/125 in large format shutters are generally not accurate, and tend to be less precise than the slower speeds. Mine tend to come in at around 1 to 1.5 stops slow at 250, 400 or 500.

If you're thinking of making the tester yourself, Mr Jackson's setup looks really simple - I imagine a person could duplicate it just by looking closely at the breadboard in the video. You'd need the photoresistor ID though - or a lead to a slicker sensor - and you'd need to be able to compose the code and download it to the Raspberry Pi Micro he shows on the breadboard. The programming interface would be free, but you might need a cable. There are a few niggly chores to handle (like downloading libraries, learning the interface....). The tester I gave a link to is better documented, giving part names and wiring illustrations, for instance.

cheers
Tom

[Doremus Scudder]

Philip,

There are a number of cell-phone app shutter testers out there. I've used Lukas Fritz' "Shutter Speed" with good success. The app is free. He has an optional photo-sensitive plug in that improves the accuracy that does cost a bit. There are others too. You might try one of them if all you need is quick information about your shutters.

And, there are shutter-speed testers for sale on eBay, etc., some pro-quality, some cobbled together things, for not all that much.

If you want to tinker, that's another thing.

Doremus

[Graham Patterson]

There's an adage in software development 'Are we building the application right? And are we building the right application?'. This is about as simple as it gets. There are a lot of issues it does not touch on - consistent sensor position, is the light source stable, and do we care about the iris effect of leaf shutters?

There are several shutter tester threads on Photrio that go into these things in depth.

I suspect most of us are less interested in accuracy, and more in consistency. Is the shutter behaving as it did yesterday and last month?

The video author admits to asking an AI for the code!

[nitroplait]

Many years ago, the guy who made the shutter speed sound testing app sent me a devise build into a TRRS jack plug to be inserted into the phone.

When exposed to light through the lens it gives a much more easy to read and precise measurement through the whole scale of speeds of a central shutter - much more so than when using the shutter speed tester with sound alone.

I don't know if these are for sale somewhere online, or if someone can decipher from enclosed photo of what parts they are made.
To my eyes it looks just like a photo resistor and maybe someone can decode the colors of the other resistor?



It are obviously very simple and only need to provide different levels of noise when exposed to different levels of light to work well with the app.

I have found it very useful.

Edit: I just looked up my old correspondence: The guys name is Lukas Fritz. He ended up calling the thing above "Photo-Plug" and had a website www.photoplug.de - a url which now forwards you to another site: https://www.filmomat.eu/shop/photoplug
They seem to charge €40 for the thing - which seems excessive.

[JefW]

Many years ago, the guy who made the shutter speed sound testing app sent me a devise build into a TRRS jack plug to be inserted into the phone.

When exposed to light through the lens it gives a much more easy to read and precise measurement through the whole scale of speeds of a central shutter - much more so than when using the shutter speed tester with sound alone.

I don't know if these are for sale somewhere online, or if someone can decipher from enclosed photo of what parts they are made.
To my eyes it looks just like a photo resistor and maybe someone can decode the colors of the other resistor?



It are obviously very simple and only need to provide different levels of noise when exposed to different levels of light to work well with the app.

I have found it very useful.

Edit: I just looked up my old correspondence: The guys name is Lukas Fritz. He ended up calling the thing above "Photo-Plug" and had a website www.photoplug.de - a url which now forwards you to another site: https://www.filmomat.eu/shop/photoplug
They seem to charge €40 for the thing - which seems excessive.

CatLABS has it also: https://www.catlabs.info/product/pho...r-speed-tester

[Tin Can]

I could but wii not

I think there is a Patent

I bought one from Fritz



My ear is now very good

[nitroplait]

Can’t be patented - nothing novel.

[reddesert]

Many years ago, the guy who made the shutter speed sound testing app sent me a devise build into a TRRS jack plug to be inserted into the phone.

When exposed to light through the lens it gives a much more easy to read and precise measurement through the whole scale of speeds of a central shutter - much more so than when using the shutter speed tester with sound alone.

I don't know if these are for sale somewhere online, or if someone can decipher from enclosed photo of what parts they are made.
To my eyes it looks just like a photo resistor and maybe someone can decode the colors of the other resistor?



It are obviously very simple and only need to provide different levels of noise when exposed to different levels of light to work well with the app.

I have found it very useful.

Edit: I just looked up my old correspondence: The guys name is Lukas Fritz. He ended up calling the thing above "Photo-Plug" and had a website www.photoplug.de - a url which now forwards you to another site: https://www.filmomat.eu/shop/photoplug
They seem to charge €40 for the thing - which seems excessive.

It's a phototransistor and a resistor. You can find details if you look around. I made one myself, and the homemade one works fine although you have to interpret the waveform that comes from it (it doesn't latch on/off, it has an sharp rise and a decay time at both open and close that may depend on the phototransistor I used, or the phone audio circuit). Anyway, there are several different options for shutter testing, and for LF leaf shuttered lenses the free audio version of the shutter speed app is typically adequate for speeds up to 1/60 or even 1/125. The audio version doesn't work as well for focal plane shutters but it will let you know if the slow speeds are off. I recommend that people with zero electronics experience attempt to build breadboard circuits only if you are willing and interested to learn about electronics.