First, thanks for testing the app.
Well, your Ricoh XR-S is a SLR isn't it ? With SLRs you can't measure times faster than the x-synchro speed, because faster Speeds are generated by the distance between the two curtains which has no effect on the sound.
Have you tried testing longer times like 1/60 or 1/30 ?
it's been a while since this thread started, but I have some news regarding the App
First, there will be an update very soon (it is still in review by Apple). It will fix a major problem regarding iOS 5 users (the content was displayed in wrong display orientation) and offer the possibility of measuring and saving old shutter speeds like 1/5, 1/10, 1/50 etc. as suggested in this thread.
Second, there is now a possibility of doing real light-measurements with this App !!
As discussed in the thread, the acoustic-measurement has its limits. Much better would be a light measurement via phototransistor. Unfortunately, the iPhone doesn't has such a sensor build inside. BUT, what most people don't know: The iPhone has a microphone-input inside the earphone-socket. This offers the possibility of attaching a phototransistor to the iPhone, and do light measurements.
I did some experiments, and found a very smart solution I think:
This small plug contains this very simple schematic:
It doesn't need batteries, it just uses the small voltage which the iPhone provides (for the electred microphone). The resistor is 4,7 kOhm and the fototransisitor I use is a BPX 38. The resistor is needed so that the iPhone recognizes the plug as a microphone.
Plug it into the headphone socket, and voilà, you have a mobile light-measureing shutter tester:
To use it, just take a camera, remove the back, light it with a light source from the back and position the plug to the lens:
Then you proceed as usual.
What you get is a very nice and clean signal with clear visible peaks:
Here with 1/60:
It works very nice, even at 1/500:
It is very simple to build a plug like this, the only thing which is a bit hard to get is the 4-pin phone-connector.
Would be great if someone would try this out !
Very nicely thought out and presented. I like the app and the old shutter speed levels will be a welcome addition. The light measuring phototransistor would be excellent. If one could be placed in a bellows near the front of the camera, perhaps at or near the rear of the lens, it might be possible to see and record the actual exposure for timed shots, that would be an incredible advance. Especially in the the range from one second to a few minutes.
Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand
Shutter-Speed-Tester for your iPhone
This sounds like a great app and sensor Idea. I'll check if I can find that fototransistor here and assemble one for your app. Thanks
Excellent addition to the app; this is what it really needs.
This is a good idea except that the sensor will be outside of the image area of the lens, which means you're metering the wrong thing. However if you wanted to modify an LF camera for example, you could take the Minolta approach of metering off the film - google for "OTF meter". Requires a little sensor and very simple optics inside the camera body to average the intensity of the light diffusing off the film during exposure and when there's "enough", ends the exposure. Minolta used that for TTL flash metering with no preflash and I believe another 35mm manufacturer (Olympus?) used it for metering long exposures under varying light; both were in the 1980's.
Originally Posted by Curt
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This is great stuff... I only hope that Echolot will extend his powers to an Android version so I wont have to borrow an iPhone! BTW, the BPX 38 is widely availible; Mouser, digikey and RS all have thousands in stock at 10 for 12 bucks or so.
Thanks Echolot, way to go!
Although I read somewhere that Minolta invented the technique for flash exposure but Olympus had it first in their OM-2 and it did long exposure as well like you said. Most cameras with TTL flash auto exposure used this technique until the introduction of the digital SLR then the cameras would rely only on preflash. In the 90's a number of cameras used both off the film plane and preflash.
Originally Posted by polyglot
The new Update, including old shutter-speed-values and a bug fix regarding iOS 5 users is now available for download
Fototransistor-Plugs for sale
In my last posts I told you about the fototransistor-plug, which allows you to make real light-measurements with your iPhone.
I am know able to offer those plugs for sale, if you don't want (or don't know how) to built the plug yourself.
The price is $15,50 each. Shipping to USA is $4,50, so total $20 incl. shipping.
If you are interested, just send me a short email at: firstname.lastname@example.org
Last edited by Echolot; 05-08-2013 at 07:06 AM. Click to view previous post history.
Fototransistor Plugs for sale