Copal 0 shutter speed accuracy

[Drew Wiley]

I've found modern Copal 0 shutters to be very consistent year after year, always predictably remaining within a sixth stop or so, except the very fastest stop, which is generally too far off to be worthwhile anyway. But what those exact speeds are at each setting needs to be precisely measured, and then you can just print a cheat sheet or tiny label for the lensboard itself telling you the correction factor at each speed, if any. In certain cases, I haven't found any deviation from the official one. I use a Calumet electronic shutter tester.

[Vaughn]

Much depends on how one is going to use the lens. For my work under the redwoods, all I use is B or T, depending on the length of the exposure...B if I am willing to stand there the whole time. T if I want to take a nap, or do something constructive like write my notes. Working in the sunshine is a whole different story.

The one second setting is at the far end of the range of the shutter, so perhaps not the best one to test. If your system for testing can test towards the middle of the range, that might give you a good picture of the lens' condition.

[r.e.]

Here's what I mean about a good waveform display. The first screen capture below shows iZotope RX 8 with one of my audio recordings loaded. In the second, I've zoomed in a bit on a small part of the waveform. I can zoom into it down to the pixel. The horizontal axis right below the waveform display gives extremely accurate information on time.

I'm not suggesting that anybody buy RX, although the trial version would be a nice way to do this. My best recollection is that the limit on the trial version is that you can't save sound edits, but that doesn't matter for this. All you need is a screen capture. In any event, you can do pretty much the same thing with a DAW such as GarageBand (free for Mac users) or Reaper (they like you to pay after a couple of months, but you don't have to). Audacity would work too, if you have more patience for it than I do

To me, it doesn't make sense to use a smartphone app to do this given that there are much more capable applications that can be used for free.

[abruzzi]

I was editing to include a reference to Audacity while you were posting. Audacity will work, but it would be my last choice.

As I said, there are issues with iPhone audio. I don't trust it for time measurement. I also think that it's highly unlikely that the waveform display from an iPhone app will come close to the display that one will get from a DAW or iZotope RX. I have a number of recording apps on my phone, including one from DPA Microphones, whose miniature mikes/lavalieres I use, and I would not use any of them for this purpose.

While I agree that a phone display is less that ideal, if the hardware is working at a specific sample rate, it should be very accurate up to the nyquist liimit, otherwise recording audio and playing it back would have bad audible jitter or or noticible frequency changes between recording and playback. So if an app eliminates the need to look sample to sample to find the start and end time, it should prodived relatively accurate timing. The caveat would be how well it can accurately determine what to consider the start and end time, which I think would have a much greater impact on accuracy.

Then of course throw in that even if the top speed of is 100% acurate, the shutter is spending most of its time of its time opening and closing with part of the opening occluded by the shutter blades unless it is stopped down, meaning that some of the light will be blocked. Smaller apertures do reduce the affect, but wide open you can loose a non trivial about of the total light. But that's a different discussion.

[Drew Wiley]

Regardless of the testing instrument, one should always test at either the f-stop most used, or consistently at some reasonable mid-point like f/22.

[r.e.]

While I agree that a phone display is less that ideal...

Let's just leave it at that. There are better alternatives, three of which I've identified and one of which I've included screen captures for as illustration. This being a photography forum, a debate about issues with smartphone audio is unlikely to be helpful

[Times2]

Thanks for the advice on measurement. In case those initial inaccuracies are confirmed what is my best course of action? How probable is it to find one which is in case of a speed accuracy spot-on or near that (because of previously mentioned 20-30%)? I have 30 days to decide on what to do (and no camera to test it).

[Bob Salomon]

Thanks for the advice on measurement. In case those initial inaccuracies are confirmed what is my best course of action? How probable is it to find one which is in case of a speed accuracy spot-on or near that (because of previously mentioned 20-30%)? I have 30 days to decide on what to do (and no camera to test it).

Any shutter that is +- 30% is spot on to industry specs.

[r.e.]

Links to two of the applications that could be used for this, assuming that one isn't on a Mac, which has Garageband. Both have free trials. If I recall, RX's trial is 10 days. It is used to edit the sound on just about every feature film and television show made, and it is increasingly used in music production. Reaper's trial period is 60 days. After that, they ask you to pay US$60, but they don't enforce it except through reminders when you open the app. Reaper is an unusual case. It is extremely good, very popular software that is also inexpensive for what it does.

iZotope RX

Reaper

[Leszek Vogt]

info@paepke-fototechnik.de

This place is in Dusseldorf, Germany and they may take on your shutter or perhaps point you at the right direction (you could send the shutter).