I'm having a brain fart ----

I checked all the shutter speeds on my LF lenses today and got the results in milliseconds. I want to convert it back to 1/X, . So if I got a result like 280 what is that in the usual shutter speed format? I know this should be simple but the grey matter just isn't firing on all cylinders today.

Divide 1000 by the number of milliseconds and you get the number you're looking for.

1/1000=.001
1/500=.002
1/250=.004
1/125=.008
1/60=.016
1/30=.033
1/15=.073
1/8=.125
1/4=.250
1/2=.500
1=1.00

280/1000 = 0.28 or just over 1/4 sec.

That may not help much... I like to work to the closest 1/3 stop, so I made a chart with shutter speeds in milliseconds and the 1/3-stop equivalents.
Here's a link to the tolerance chart from Carol Flutot's site: https://www.flutotscamerarepair.com/Shutterspeed.htm

Best,

Doremus

(Edited to correct my error in arithmetic... hope I didn't cause any confusion)

hi eric

i just used a calculator to divide out the fractional seconds ... your .28 is around 1/4s

I've got the chart from 1 sec to 1/1000, I was just wanting to work out exactly what my shutters are doing. My Ektar Graflex shutter is REALLY off.

I use the tolerance chart from Flutot's and this one: http://www.photographyuncapped.com/articles/photography/iso-shutter-speeds-f-stops/
The Graphex/Rapax shutter is not difficult to service. http://www.southbristolviews.com/pics/Graphic/manual-pdf/GraphexShutterService.pdf
The assembly steps for the #1 are out of sequence so use the steps for the #2/#3 shutter and skip the steps for parts not used in a #1.
I've done several of them.

Thx. I will give it a try.

You don't need to worry about tolerances since you know the exact speeds. Use those speeds in your meter if you have one that can set shutter speed in 1/3 or 1/10 increments.

Doesn’t it feel better after?

I have an old spreadsheet that helped me visualize my shutter behaviors. It assumes 3 entries of each shutter setting, slow to fast, fast to slow and then slow to fast again. This was for my personal use and a quick snapshot so it wasn't ready for prime time but it may be handy for some folks and at least, a good start.

Sometimes a basic comprehension is better than memorizing some rote conversion 'formula!

• 1000 milliseconds = 1000 milliseconds / 1000 milliseconds per second = 1 second
• 500 milliseconds = 500 milliseconds / 1000 milliseconds per second = 1/2 second or 0.5 sec
• 250 milliseconds = 250 milliseconds / 1000 milliseconds per second = 1/4 second or 0.25 sec
• 100 milliseconds = 100 milliseconds / 1000 milliseconds per second = 1/10 second or 0.1 sec

so 280 milliseconds = 280 milliseconds / 1000 milliseconds per second = 0.28 second -- or between 1/4 and 1/3 sec.

I'd be more concerned about consistency than precise speed. That's why I test each speed multiple times to see if there's any significant deviance. But if it's more than a sixth stop high or low from the dial speed, then I post a little note on the lensboard. That's for fussy work like chrome film. With black and white film I don't care unless its more than a third of an EV off.

Eric Rose said:

I've got the chart from 1 sec to 1/1000, I was just wanting to work out exactly what my shutters are doing. My Ektar Graflex shutter is REALLY off.

Click to expand...

The problem (or trick) is that if you fire the shutter once you will get one speed, fire it ten times and the lubricant will loosen up a little and the speeds will be faster, take it outside and the shutter speeds will drag. Don't chase yourself.

I did multiple firings and averaged the speeds. They didn't vary by much anyway.

How do you check shutter speeds? I have a medium format camera Mamiya RB67. The Mamiya lenses have built in shutters that I can activate when the lens is not mounted in the camera.

Purchase a photo transistor https://www.mouser.com/ProductDetail/Vishay-Semiconductors/TEPT4400?qs=sGAEpiMZZMs50KUSuyRkpqZUFgTLpDQJco7jy2yAnhc= , twin lead hookup wire and a 1/8 mono plug.
Connect the emitter of the transistor to the center lead of the plug and the collector to the shield/outer connector of the plug. Mount the transistor centered in a piece of 1/4 foam core (black preferred) cut to fit the film plane of the camera to be tested with the side facing the lens covering all but the center half of the transistor's diameter. An alternative is to mount the transistor in one piece of wood or foam core then put a second piece with a cutout to fit the lens/leaf shutter mount placed on top so that the transistor is center of the shutter.
Download Audacity https://www.audacityteam.org/ or similar audio recording program, install it, plug the plug into the microphone jack on your computer and start the audio recording program. When light reaches the transistor the recording line will go up or down from the center line in a near straight line then continue flat until light is cut off when it will go back to the center line. The speed is in milliseconds and the time line can be expanded for easier reading of fast times. The shutter time is from when the line first deflects from the center line until it starts to return.
Start Audacity, press pause then record, place the shutter on the test pad, cock the shutter, position a light source over the shutter, turn the light on, press pause to start the recording, trip the shutter, press pause or stop, turn the light off, set the next speed and repeat the procedure. Use waveform db for the pattern (its default) and right clicking the 0 at the left of the record graph increases the height of the recorded line.

Use the site search or internet search for shutter speed tester. There are cell phone apps and more complex designs available.

The sites I used for the diagram no longer exists and the supplier (radio shack) no longer offers them. If the transistor is for IR then put a piece of deep red filter material over the transistor to use regular incandescent, fluorescent, or LED light sources.

The inherent problem with trying to determine shutter speeds of a mechanical between-the-lens shutter with this level of precision is that this type of shutter is never 100% efficient, and not as efficient as, say, a focal plane shutter. Older photo books demonstrated this issue with successive images of a between-the-lens shutter as it opens and closes--it opens starting with a small aperture, growing to fully open, then closing down to the small aperture, then closing fully--like a round window growing open from the middle to the outside, then reversing.

Thus, the shutter is only fully open for a percentage of the exposure time, and that percentage varies with the f-stop being used, and, of course, lens diameter. At a small stop, the efficiency may be 90% (I am guessing here), and at a large stop, it may only be 60%. So trying to nail in your shutter speed to within 1/3 stop may not be practical for photographic purposes.

Where shutter speed testing can help is to find really big discrepancies--like a shutter speed that reads 1/50th of a second and is really 1/4 of a second.

voceumana said:

The inherent problem with trying to determine shutter speeds of a mechanical between-the-lens shutter with this level of precision is that this type of shutter is never 100% efficient, and not as efficient as, say, a focal plane shutter. Older photo books demonstrated this issue with successive images of a between-the-lens shutter as it opens and closes--it opens starting with a small aperture, growing to fully open, then closing down to the small aperture, then closing fully--like a round window growing open from the middle to the outside, then reversing.

Click to expand...

A large format shutter working properly on release throws the shutter blades open in 0.2 to 0.4 thousands of a second. The timing delay holds the shutter blades open for the selected time then the high tension setting spring forces them closed faster than they opened.
I and most test with the aperture wide open and the sensor at shutter center, the alternative is to place the sensor at the edge of the smallest aperture opening of the shutter. Times measured at both positions will vary by 0.001 second or less.

voceumana said:

Where shutter speed testing can help is to find really big discrepancies--like a shutter speed that reads 1/50th of a second and is really 1/4 of a second.

Click to expand...

Its more like 1/60 running at 1/45, 1/50 at 1/35, 1/125 at 1/80.
1 second is the longest delay time so checking it and 1/2 second usually gives an accurate indication of the shutter's operation and can be done by watching the shutter and a clock's second hand.
Speeds above 1/125 are spring driven and no delay mechanism is engaged.

Alan Edward Klein said:

How do you check shutter speeds? I have a medium format camera Mamiya RB67. The Mamiya lenses have built in shutters that I can activate when the lens is not mounted in the camera.

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Take a look at my shutter tester: www.phochronxa.com. I've been selling them since late 2016, and was part of a very successful Kickstarter project. My website contains all of the info.