Neat way to test large format shutter speeds.

[tom_johnston4]

I stumbled across a way to test your large format shutter speeds without a

shutter tester. I am putting together a Podcast for large format photographers

and I decided to use the sound of a large format shutter firing as a sound

effect. After recording it, I realized that the graph produced by the audio

program I was using gave me a picture of the shutter in operation. I used

Audacity, which is a wonderful freeware audio program, but you could use any

audio program that you have. It just so happens that I had S.K. Grimes do a

CLA on one of my lenses last week. I compared the graph produced by recording

the shutter in operation with the sheet S.K. Grimes sent back with the lens and

it was clear immediately that this procedure is extremely accurate up to speeds

of 1/30th to 1/60th of a second. In fact, the graph matched the speeds that

S.K. Grimes listed perfectly for the slower shutter speeds. At higher speeds,

this procedure was no longer accurate but I rarely shoot at those speeds

anyway. Even so, the audio program should still be useful in determining if

the shutter is performing smoothly and consistently at high speeds. Using this

program, I am also going to see if the shutter speeds remain the same when the

lens is cold. I have always wondered about that and now I can tell in an

instant.

 

The attached screenshot of the Audacity page shows my results for 1 second, 1/2

second, and 1/4 second tests. These match the speeds that S.K. Grimes

reported with uncanny accuracy.<div></div>

[tom_johnston4]

BTW, you can expand the time-line in your audio program to get as much resolution as you want.

[spodzone]

Nice work. Funnily enough, I was doing the same sort of thing last week having acquired an ancient Ensign Carbine No3 with a choice of 100,50,25,B.

 

However, I notice your graphs have a convenient amount of noise going off while the shutter is open, as distinct from mine which show the shutter-release button being pushed, the shutter snapping into place at given aperture and back again, with silence in the middle. Did you play a tone through it or something?

[joshx]

Tom,<P>

I've seen this before and thought it was interesting. More interesting is using the same set up but with a photodetector. I haven't tried it, but it has been discussed on PN <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0044cW">before</a>.

[tom_johnston4]

Tim,

 

No, I didn't play with the graph or alter it in any way except to slide the graph down to the beginning of the time line. What you see is exactly what it recorded without any alterations. No effects or enhancements were applied at all. If you have a Copal shutter, give it a try and you should see the same pattern.

 

By the way, the shutter shown was a Copal 1. I am not familiar with your lens and I don't know what kind of shutter it has but, with the lens test I show here, the aperture is set before the shutter is released so the aperture has no effect on the graph at all, as you know. I always use a cable release and no sound is recorded for that since the shutter fires instantly when the release is pressed. The graph does show the shutter opening and closing sharply and Copal shutters make a whirring sound during exposure so that is why the graph records sound through the entire test. It's making noise during the exposure. But you bring up an interesting point. I am going to try this with a No. 5 Universal Synchro Shutter that I have. That shutter makes noise before and after the exposure so that should show up in the graph. Wait! Let me do it right now and attach the graph with this post since it only takes a minute.

 

This will be a 1 second exposure. This shutter is a self-cocking design so it should pick up sound before the shutter opens and after it closes.

 

OK, the test is done. This lens had a CLA about one year ago and S.K. Grimes' test sheet showed that the 1 second shutter speed was on the button at that time. But the attached graph indicates that the actual shutter speed is about 3/4 second. Either the speed is now off or the test is not as accurate with this type of shutter. But the graph does clearly show the shutter snapping open and closed so I think I can assume that this test is valid. I use 1 second exposures quite frequently so that is information to know and I will increase 1 second exposures by 1/3rd stop with this shutter now. I will test the other speeds in a minute.

 

Notice that the sound of the cable release moving the lever is recorded in this graph and also the whirring sound that this lens makes after the shutter is closed is also recorded.

 

I figured that other people have found this method of testing shutters but I thought I would post it anyway for those who haven't thought of it. I know I didn't think of it until after I had recorded the shutter to produce a sound-effect. This method can give you a good picture of how your shutters are performing. In fact, it can give you information that a regular shutter test cannot give you.

 

This method is not a perfect substitute for a shutter tester but it is clearly very useful. It is extremely accurate for speeds up to about 1/60th of a second with my Copal shutters. And it can obviously also be used to test for smooth or erratic shutter operation. You can easily compare repeated shutter graphs with great detail to see if they are consistent.

[tom_johnston4]

Rick,

 

That's neat! Thanks for posting the link. That would be useful for the high speeds. But the nice thing about using the audio program is that it costs nothing and no extra equipment is necessary. And, for me anyway, I almost never use fast shutter speeds in LF anyway and I rarely shoot in small formats so the limitation with this method really is no problem for me at all. However, the method you mentioned would be very useful for testing small format shutters. Thanks much!

[spodzone]

<p>OK, I get it. The Ensign Carbine has a radically different shutter from the Copal 1 - the Copal has the sound of the spring unwinding during the shot.</p>

 

<p>Have replicated it with my shutter here at f/6.8:

<a href="http://pig.sty.nu/Pictures/misc/copal-1-shutter-speeds.jpg">copal-1 shutter speeds</a>, where it seems to be about 15% out at 1/2s.</p>

 

<p>You can even see that it runs *slightly* <a href="http://pig.sty.nu/Pictures/misc/copal-1-shutter-speeds-f22.jpg">quicker</a> at f/22.</p>

 

<p>Thanks for reminding me to play with the proper shutter! :)</p>

[tom_johnston4]

And thank you for sharing your tests, Tim. I'm going to test my other shutter speeds with the No. 5 shutter now. I'm almost afraid to see the results but it's better to know what's really going on. The Universal Synchro shutters are known to be pretty inaccurate and even S.K. Grimes couldn't get the fastest speed (1/50th second) to within one stop of it's rated speed. But I don't like it that the 1 second speed is off as much as it is because I use it a lot. Also, when I need, say, a 4 second shutter speed, I often give four 1 second exposures and if it's off by as much as the graph indicates, that error would accumulate. On the other hand slow shutter are more efficient than fast shutter speeds. Combine that with small f/stops which are more efficient than large f/stops and which are are generally used with long LF lenses and the effective exposure may be accurate. (I'm just thinking out loud.) If anyone knows if that may be the case, I would appreciate hearing about it.

[van_camper]

Great idea Tom, thanks for the suggestion!

[spodzone]

If I've got my calculator and head on the right way up, the 15% error I observed at 1s on my copal shutter is about 1/5th stop. I also *think* the 1/8ths is only 1% out.

 

Don't forget, above 1-2s exposures you're probably into reciprocity failure territory, just to add to the entertainment.

[tom_johnston4]

Tim,

 

Oh no, I never forget reciprocity. After decades of shooting LF, it's second nature to me. Well, actually I can pretty much forget it with Tmax 100 (100 Tmax now) which has been my standard b&w film since the original version came out. But I always had to compensate for reciprocity with my standard color film which was Velvia 50 for many years. But now that I have switched to Velvia 100, I hardly ever have to figure it in even for color which is very nice. However, I do use other films that do require compensation. Most of my exposures are in the 1/8 to 30 second range. In 8x10", about 1 to 2 seconds is probably about average for me. That's why I'm glad I found out that my 1 second shutter speed is running fast running fast for my 360 Commercial Ektar lens. All my other useful shutter speeds with all my lenses are well within tolerances which is nice to know.

 

I have just finished testing all of my LF lenses and I am happy to report that the tests were very good and almost perfectly consistent. In fact, they pretty much agree almost exactly with test charts that I received the last time each lens had a CLA. The only real exception I found was the 1 second shutter speed for the No. 5 shutter mentioned above. Based on how consistent the tests were (I repeated them several times) I am now confident that they are accurate. In fact, the fast shutter speed tests may be accurate too because most fast shutter speeds are off on LF lenses anyway and, in fact, my tests pretty much agree with S.K. Grimes tests for each lens at the fast shutter speeds. The fastest shutter speeds are off with all my lenses which is pretty much to be expected but I never use those speeds anyway and if I ever did need them for some reason, I know how much to compensate so that's no problem.

 

I'm pretty excited about this because now I can quickly test my lenses any time I feel like it and note any changes over time. In the past, I was not always confident that the shutter speeds had not drifted and, for that reason, I just sent my lenses in for a CLA every couple years. Now, unless they really need a cleaning, I won't have to send them in unless the tests indicate it's time. In the meantime, I can track their speeds with simple tests that only take a minute to do. It's a warm and fuzzy feeling to know how the shutters are performing. I hope anyone who has not thought of this or heard about this before will give this a try. Of course, you can always buy a basic shutter speed tester but this method works fine for my purposes.

[michael_p6]

By linking an optical sensor to a couple of resistor and an audio jack, you can get a tester that doesn't rely on sound but rely on the light passing thru the shutter instead. There are several models, some of them are even "stereo" ie they allow you to time the two curtains if you have a curtain shutter.

 

One such description is there: http://www.open.hr/~dpleic/photo/Shutter.html

 

Remember that the shutter takes time to open and close, so the efficiency at high speed needs to factor the time of the blades opening and closing.

[tom_johnston4]

Thanks Michael. Yes, I know about shutter efficiency as I mentioned in a previous post. Efficiency is, of course, higher at slow shutter speeds. Efficiency is even greater when using a slow shutter speed in combination with a small aperture as is usual when shooting in large format. I'm not sure if any shutter tester takes that into account.

 

Thanks for the link. You can also simply buy a relatively inexpensive shutter tester. However, the big advantage of the method I described above is that you don't need to buy or make anything at all, assuming you have a PC or Mac with a sound card, and the results I got using this method are almost precisely the same as S.K. Grimes got with their testers which, I assume, are very accurate. You can clearly see the shutter snapping open and closed in the graph produced. The results I got match S.K. Grimes test results with incredible accuracy.

 

Thanks much.

[tom_johnston4]

Michael,

 

Thanks again for sharing those plans. Thats neat! I think I'll make one. The nice thing about it is that you can test focal plane shutters with it as well. As far as accuracy goes, it looks like either will produce excellent accuracy with leaf shutters.

[jschlach]

where will your podcast be when it's available?

[johndc]

This method occured to me years ago when I was trying to record the sound of my dial-set compur. Unfortunately it didn't help much. Slow shutter speeds I'm able to judge by ear, and fast shutter speeds require the use of the photoresistor/diode circuit. But it's fun none the less.

[tom_johnston4]

Jason,

 

I just began work on the Podcast. In fact, I was sitting down to do some more work on the first episode right now when your message showed up. I haven't produced a Podcast before so I am not sure how the uploading and listing part works yet although I have information on how to do it. LOL! But, seriously, she has an outstanding Podcast that has already won awards and she has been invited to do a presentation at a major symposium in Chicago about it!) I will have to learn how to get it listed in various places which should be no problem but one place I definitely want it to be listed is in iTunes. I will post something when it is up and running. Thanks for your interest.

[tom_johnston4]

John,

 

I knew when I stumbled onto this method that others probably knew about it since it is so easy. I don't have any Compur shutters so I don't know how they record but the results I am getting are incredibly accurate when compared to test data that S.K. Grimes sent back with a lens last week - far greater accuracy, in fact, that I need for practical purposes but which provides me with a wide margin of confidence in the method. But you are right about the fast shutter speeds. I don't have the confidence in the results I am getting with fast shutter speeds that I am getting with slow speeds. It's difficult to judge the high speed graphs. However, I am seeing extremely good accuracy up to 1/60th of a second and, even at the fastest speeds, the results I'm getting does seem to correlate with the data S.K. Grimes has sent out recently with two lenses including the one I just got back last week. I am going to inspect the high speed graphs more carefully today, crunch some numbers, and see how it works out. But I am not concerned about those speeds anyway. I cannot remember when I last used a high shutter speed in LF. It would have been years ago in the studio with electronic flash and, in that situation, shutter speed is not important anyway, unless you are adjusting ambient/flash ratios, as you know.

 

As for judging slow shutter speeds by ear: Yes, I can do that to a degree too. But I would not bet you that I could tell if, say, a 1/2 second shutter speed was off by 1/3 stop, etc. The No. 5 shutter I mentioned above sounded good to me at 1 second but the test shows that it is actually running at about .75 or .80 second or about 1/3rd stop fast. That's not terribly off, of course, but with the narrow latitude E6 films that I use when shooting color, it can make a difference and it's good to know about. Also, when I need a shutter speed of several seconds, I generally simply shoot multiple one-second exposures and the error would accumulate in that case. (When my exposures get above five seconds or so, I use a stop watch or just count the time out.) I keep a little chart taped inside the lens caps of my LF lenses with compensation info for shutter speeds that are off. Now, with this method, I can check that data whenever I want to see if the shutter speeds have drifted. I see no reason not compensate when it takes no time at all. I am not an accuracy freak by any stretch of the imagination but it only makes sense to me to have reasonable control of the variables involved when it involves no real effort.

 

For moderately higher speeds like 1/15th - 1/60th, I don't think anyone could actually judge accuracy by ear.

 

But what makes me most happy about this method is that now I can keep track of how my shutters are performing without having to send them in for a CLA while not knowing if they actually need it or not. Until now, I sent in each of my lenses every year or two and considered it to be simply preventative maintenance. But two of my lenses that have gone the longest without a CLA are testing out to be beautifully calibrated - even better than the one that S.K. Grimes just adjusted. I was planning on sending them in soon but now I don't have to. I can now be confident that their shutter speeds are fine. That's a nice feeling.

 

Thanks for your post.

 

Best

[Troll]

After you've dont it for a while, you can easily recognize speeds from 1 sec up to 1/100 sec by their sound, quite accurately.

[tom_johnston4]

Bill,

 

Well, I've been listening to shutters for over 40 years and there is no way in the world I would claim that I could judge speeds from 1 second to 1/100 of a second accurately by sound, let alone easily. In fact, it would be interesting to place a bet on your ability to do so. I would give you 10 to 1 odds (at least) that you cannot do it with accuracy good enough for practical purposes, especially with faster speeds. Even the sound program cannot pick up diffences at those speeds and you cannot even judge them carefully studying the sound graph while taking your time. At those speeds, the mechanical functions vary among lenses too. Even at, say, a 1/4 second shutter speed, it would be difficult to identify a 1/3 - 1/2 stop error, let alone at fast speeds. But if you can do it, all power to you.

 

Can you catch bullets in your teeth too? LOL

 

Best

[martian bachelor]

I don't want to get too technical on everyone because I appreciate quick-and-dirty approaches which get the job done, but what we're really after is the integrated exposure amount, I * t.

 

The photo-detector methods are really good for this since one can put a capacitor in the circuit and essentially integrate the total amount of light coming through while the shutter is open. (Or you could calculate the area under the light curve if you've time resolved it.) Be sure to use a low-leakage type of capacitor, or if you wanted to get really involved you could add a sample-and-hold circuit to the getup.

 

One can then make a table for all speeds and f-stops, from which one can derive a table of f-stop corrections for any given combo, since whatever its speed is the shutter speed is essentially unvariable, at least at a given temperature. But you generally only need to go to such trouble if super high precision ( <0.1 stops) is required, or you've got some indication that such corrections are needed due to a shutter being grossly out of whack or mismarked, or maybe you're just that way, you know. :>

 

Also, in case no one else mentioned it, the reason the audio sampling technique might not be working with higher shutter speeds is because many LF shutters use different springs for the slower and higher speeds, with the switch-over speed being right around 1/50th sec for older shutters and presumably 1/60th for newer ones (though I don't know for sure). The audio sampling rate, being well up in the kilo-hz's, certainly should be sufficient to do the fastest shutters commonly available.