By the way, if you have a Mac computer than the easiest way is simply to use GarageBand for this. You can check at least 1 second and 1/2 second with this programm. Works pretty well. Just checked my Rolleiflex T and the SL66. Rolleiflex T: 1 sec is 1,5 sec in reality, 1/2 sec is 0,75 sec :-(
Okay, I already knew that the shutter didn´t work properly...
SL66 however works fine. Hey, but she had just been serviced last year ;-)
Best Regards, Benjamin
When you,'ve tested your shutter speeds and assumint your test is accurate how do you know what margin of error is acceptable and still be within tolerance ?, because no shutter is absolutely accurate,.
Last edited by benjiboy; 08-18-2010 at 07:57 AM. Click to view previous post history.
A couple points....
- You can also use this procedure to check the effect of high shutter speeds whit small apertures in central shutter or to check if the diaphragm is properly closing before the shutter.
This method only compares your shutter to the digital camera shutter. Its usefulness depends on the digital camera's shutter being accurate. I assume digital cameras have electronic shutters that are very accurate, but who knows. I know digital camera ISO ratings don't match what you will get with a good handheld meter; I wouldn't put it past camera manufacturers to have offset shutter speeds for some reason.
Second, you might be tempted to use a similar method to check or adjust lens aperture scales. Keep in mind if you do this, you will be correcting for lens absorbtion, haze, and filter factor, and you will really be getting something like T-stops rather than F/stops. Depending on how much you value accurate DOF calculations compared to accurate exposure calculations, and how diverse your lens collection is, this could be a good or bad thing.
Sure, but a shutter that's 1% off won't affect image brightness in any appreciable way, whereas 50% is already half a stop. If you know how inaccurate your shutter is and you can verify that its offset is reproducible (i.e. not random), you can even compensate while shooting.
Originally Posted by benjiboy
Thanks for the tip, very useful indeed! I've used several cameras where I knew (only from seeing the end results) that the shutter speeds were off but now I'll know how far off
I'm going to be buying a new MF setup sometime soon now that I've moved my base to China and chances are I'll be buying used...maybe I'll bring my laptop along for the ride!
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50% SLOW is half a stop. 50% FAST is one whole stop.
whereas 50% is already half a stop.
Sorry for the silly question, but I don't follow this??
Originally Posted by BetterSense
For my Rolleiflex and Hasselblad I used a digicam in video mode at 30 fps, then I just count frames right on the digicam. Works for the slower speeds up to ~1/30s. Open up the aperture of lens being tested, aim at bright object, press record, fire shutter, count frames in slow-mo playback. Super easy to do, but may not be stringent enough of a test, but then if the slower speeds are good, the faster ones are probably OK too.
That's the trouble with percentages.
Originally Posted by bobwysiwyg
It's better to think in the usual terms of duration, and factors thereof.
And then too to say what you mean, more, or less.
50% slow means 50% longer, i.e. half as long again, than it should be.
Twice as long, i.e. 1 stop, is 100% longer, or if you wish 100% slower.
(50% slow however isn't half a stop, but 0.4 stop)
50% fast means 50% shorter than it should be, i.e. 2x faster. And that's one stop.
So just saying that "50% is already half a stop" isn't enough. Nor is it correct.
That's a great method, and I have used it many times. I also have a Calumet Shutter Tester, which is unfortunately not available anymore, and used right, the audacity method in combination with the right detection hardware is more accurate, because it can records more cycles per second. Attached is a test of the 1/500s setting on a Nikon.