I few months ago I asked if anyone had any experience of the "Photoplug" shutter speed tester. Apparently, no one had so I eventually got round to buying one myself to try out.
Photoplug is a very small device which plugs into your smartphone headphone socket and is used in conjunction with a dedicated app. It costs 29 euro plus postage.
Essentially, you shine a strong light (LED preferred) into your lens and point the Photoplug device from the rear at your shutter and you fire the shutter. This generates a waveform on the app which has a couple of spikes which represent the shutter opening and closing. You enter your selected shutter speed into the app. There are 2 movable marker points on the app. You move the first one to the start of the opening spike and you move the second one to the start of the closing spike. This gives you the recorded shutter speed and the deviation, in 1/3 stop intervals, to the selected speed on your camera. Here is a screenshot of a 1/30th shot. Note that I didn't quite line up the second marker with the start of the second spike. That was just for the screengrab. :-
So I've played with this device for about a week, trying to get the best out of it. I've found that it seems more accurate at lower shutter speeds. The device will only test up to 1/500th but the second spike on the waveform does not seem so well defined at 1/250 and 1/500. See below:-
I've got a theory that it has something to do with the two shutter curtain system being harder to read at higher shutter speeds. When I tested my Yashica 24 TLR with its leaf shutter, it seemed fine at 1/500. I did find it was important to get your light source well positioned and very important to get the Photoplug device really close to the shutter.... about 5mm or so.
You can add all your cameras into the app and it will save and display your recorded shutter speeds:-
Pentax MX
ME Super
Yashica 24
All in, I'm reasonably happy with this product although I think it is more accurate at 1/125 and below. You do need to set it up carefully for best results. I have no connection to this product, just a user. I am particularly happy with the Yashica results. Earlier this year I notice the shutter speeds were out badly at lower speeds. I did my own CLA on the Yashica, including the delicate work of stripping and cleaning the shutter blades. It was nice to see that the shutter is now reasonably accurate