Shutter-Speed-Tester for your iPhone

[Filmomat]

Hello,

I'm a 19 year old student from germany and I wrote a small application for the iPhone wich might be interesting to some of you !
It is called "Shutter-Speed" and it allows you to measure the shutter speed of your camera by analyzing the shutter-release-sound.



After you recorded the shutter-release-sound, the app will display the waveform of this sound. Opening and Closing of the shutter produces two peaks, as you can see in the picture. From the distance between those peaks, the app calculates the shutter-speed and also tells you the deviation from the target value. Afterwards you can save your measurement.
More information here: http://www.echolot-online.de/Shutter-Speed.html

Best results can be obtained from cameras with diaphragm shutter (like TLRs). SLRs or cameras with focal-plane shutter do also work, but they produce a more complex waveform, wich makes it difficult to measure shorter times than 1/60.

I compared the results from this app with an optical measurement and the values are much more exact than you might think, at least for times longer than 1/500.

I would be very happy if some of you try out this app

Link: http://itunes.apple.com/us/app/shutter-speed/id560154244?l=de&ls=1&mt=8

Best,
Lukas

 

[PeterB]

Lukas, what a great idea for an app !! I was literally about to test the shutter in my newly acquired Mamiya Sekor 55mm TLR lens using my analog CRO when I read this post. One problem is that I am an Android devotee perhaps I'll borrow an iPhone for this , in fact I think I might....

Well done.

 

[deisenlord]

Just a great idea.

 

[munz6869]

Downloading now

Marc!

 

[nhemann]

just grabbed it - pretty sweet!

thanks for developing

 

[M.A.Longmore]

.
Finally, an excellent reason to get an iPhone 4 !

Ron
.

 

[alohakeith]

I downloaded it too. I'm busy this morning, but I'll test it out later today.
Aloha, Keith

 

[E. von Hoegh]

Unfortunately, it isn't measuring the amount of time light passes through the shutter. At slow speeds, it will be sort of accurate.High speeds, less so. On an SLR, there's no knowing what it might be measuring. Good luck, you'll need it.

I've compared results from contraptions like this to a proper test of shutter speeds using a phototransistor and a scope with calibrated time base, these give an approximation at best. Useless for my purposes, which involve measuring how long the shutter actually passes light.

Edit - There are lightmeter apps. Why not write a shutter speed measuring app. that uses the light sensitive element of the cellphone to actually measure the shutter speed, not the sounds the shutter makes, i.e. doing it properly??

 

[Richard S. (rich815)]

I cannot figure out how to use it.

 

[Filmomat]

Thanks for the positive feedback, I'm looking forward to your test results

@rich815: well, what exactly is your problem ? you might have a look on the app-website I linked in my post: http://www.echolot-online.de/Shutter-Speed.html

Of course it is only an approximation. But in most cases, it's a quite good one. I compared the values from this app with an optical measurement (photoresistor + audacity) and till the 1/250 the results are quite accurate, the deviation is not more than 1/3 f-stops. Of course this also depends on the camera you are using.

This app isn't designed to measure the shutter speeds at microsecond-level. You won't be able to tell if the 1/250 is more likely a 1/220, but this isn't really necessary as you don't see the difference in your final image anyway. What you can detect, are larger deviations, wich really affect your image. For example if your 1/125 is rather a 1/80.

I had the same idea with the light-sensor, but unfortunately you can't read this sensor without the use of private APIs (forbidden commands). What you could do, is attaching an phototransistor to the mic-input of the iPhone, but I haven't tested this yet.

 

[Chan Tran]

Thanks for the positive feedback, I'm looking forward to your test results

@rich815: well, what exactly is your problem ? you might have a look on the app-website I linked in my post: http://www.echolot-online.de/Shutter-Speed.html

Of course it is only an approximation. But in most cases, it's a quite good one. I compared the values from this app with an optical measurement (photoresistor + audacity) and till the 1/250 the results are quite accurate, the deviation is not more than 1/3 f-stops. Of course this also depends on the camera you are using.

This app isn't designed to measure the shutter speeds at microsecond-level. You won't be able to tell if the 1/250 is more likely a 1/220, but this isn't really necessary as you don't see the difference in your final image anyway. What you can detect, are larger deviations, wich really affect your image. For example if your 1/125 is rather a 1/80.

I had the same idea with the light-sensor, but unfortunately you can't read this sensor without the use of private APIs (forbidden commands). What you could do, is attaching an phototransistor to the mic-input of the iPhone, but I haven't tested this yet.

So the people who wrote the lighmeter app could get access to the private APIs? 1/3 of a stop is too large an error for the measurement instrument while it's kind of acceptable if the shutter is within 1/3 stop. Using a photocell is the same as people have been doing uisng sound recorder app on the pc. I personally use an opposed sensing fiber optic, modulated red light sensor and make the measurement with an oscilloscope. The sensor has a 50micro second response time so it's reasonably accurate up to 1/2000.

 

[Filmomat]

All those lightmeter-apps use the built in camera for the measurement. The light-sensor is on the front of the iPhone, right next to the speaker.

Of course you can measure a camera without my app using your computer and a microphone/photocell. But with the app you can do it a lot easier and faster, it displays the time already in parts of a second, the deviation in thirds of an f-stop and you can save all this data in a neat table, allowing you to see all values at a look without calculating or writing down anything. And the greatest advantage: You can put all that in your pocket and check a camera in less than 5 minutes, wheather you are at home, in a camera store or on a flee market

 

[MattKing]

I think it is a great idea - android please .

 

[jeff.blackwell]

I agree with MattKing, how about some love for Android users. Actually, its no problem. My wife has a iPhone, and she may find it "missing" for a little while.

 

[Richard S. (rich815)]

I downloaded it before work and quickly gave it a try (winged it!) with my Contax G2 without reading your website. Not extremely intutive on the fly but I think after reading your website I can figure it out. Will try again tonight.

 

[bobwysiwyg]

I think it is a great idea - android please .

+1

 

[Diapositivo]

May I suggest to specify in the web site that the tool is useful for all speed that can be used with a normal electronic flash. That means up to 1/60 with some cameras, or 1/90, 1/125, 1/250 with some other cameras. 1/30 with some Zenit cameras IIRC. It can give no indication for speeds that cannot be used with a normal electronic flash.

Leaf shutters (i.e. central shutters) can be used with flash on all their speed range (normally never faster than 1/500).

 

[Newt_on_Swings]

Couldn't you use the default camera instead of the light sensor in the front? Say have it record in movie mode, at a very low resolution only recording the presence of light and not an image, and measure the shutter speed using a flash light or other bright light source. Then pretty much use the same analysis, the first peak, is when it open, and when it again records no light is the end of the shutter duration.

 

[munz6869]

I tried it last night with an old Wollensak shutter on a miniature Busch Pressman and it works very well - can I suggest that in your comparative speeds table, you include speeds for older shutters like 1/10th, 1/25th, 1/50th etc. as well as the modern ones? I am far more likely to be suspicious of older shutter speeds and want to test/keep a note of them...

Marc!

 

[polyglot]

The frame rate of the camera is much too low to make such timing measurements. Audio is the best approach for decent timing on a phone unless you want external hardware like a photosensor on the microphone... in which case this app is just as applicable. Since the app is flexible enough to allow you to select endpoints, you could make a more-accurate timer by using a photosensor to modulate a 15kHz tone and feed it into the phone's mic-input.

I'll give it a bash on my LF lenses tonight.

 

[Michael W]

I tried it last night with an old Wollensak shutter on a miniature Busch Pressman and it works very well - can I suggest that in your comparative speeds table, you include speeds for older shutters like 1/10th, 1/25th, 1/50th etc. as well as the modern ones? I am far more likely to be suspicious of older shutter speeds and want to test/keep a note of them...

Marc!

I agree on adding the older shutter speeds. If i get this app it will be to check old LF shutters.

 

[Filmomat]

Thanks for testing, I'm glad it worked. Including the speeds for older shutters is a good idea, will be part of the next update !
Unfortunately there will be no Android version, as I have no idea how to develop for that (it's very different from iOS).

@Diapositivo: I don't quite see your point, what has flash synchronization to do with the app ?

 

[Diapositivo]

@Diapositivo: I don't quite see your point, what has flash synchronization to do with the app ?

When you use a focal plane shutter, the flash synchro speed as indicated on the shutter speed dial is the fastest speed that leaves a moment when the first curtain ended its trip but the second curtain did not begin moving yet. That is the moment when the flash can flash and its light will hit the entire frame.

With shutter speeds faster than the X-synchro, as you know, the second curtain begins its trip before the first curtain ended its one, there never is a moment when the entire frame is exposed to light, the film is lighted by a "slit" of light moving along its length.

You seem to be aware of the problem but not of the fact that the last measurable speed with your app is the X-synchro speed.

<<
Please consider that satisfying results from most SLR‘s as well as from cameras with focal-plane shutter can only be obtained up to the 1/125sec. Thereafter, the time is regulated by the distance of the slit between the two curtains, wich doesn‘t affect the shutter release sound very much and therefore can‘t be recognized in the waveform !
>>

Could become, for the sake of clarity, and as a mere suggestion:

Please consider that satisfying results from most SLR‘s as well as from cameras with focal-plane shutter can only be obtained up to the the X-synchro shutter speed and including it, that is often 1/60 or 1/125sec but can be as low as 1/30th or as high as 1/250. Thereafter, the exposure time is regulated by the distance of the slit between the two curtains, which doesn‘t affect the shutter release sound very much and therefore can‘t be recognized in the waveform! The X-synchro speed can normally be recognised easily as it is marked by a "lightning" symbol or is painted with a different colour on the shutter speed dial. Some cameras have an X-synchro speed which is different from the normal sequence, e.g. 1/90. Refer to the instruction manual..

Central shutters (leaf shutters) can be used with flash on all speeds and can be used with your app on all speeds, I suppose.

X-synchro refers to electronic flashes. Some bulb flashes have a slow-combustion emission which allows the photographer to use faster speeds without side effects because the flash lasts long enough to hit the film during the entire "slit" travel. IIRC there are now some electronic flashes who work the same way and allow the use of a shutter speed faster than the X-synchro albeit with a lesser flash power.

 

[theoria]

I think it is a great idea - android please .

+2

 

[Filmomat]

Ah ok, now I understood what you mean, thanks for explaining.
You're right, this is a simple and elegant method to judge, up to which maximum speed the app can provide accurate results for a given camera. Haven't thought about this yet, I will add this to the website soon.