BebuLamar

As I said the 3 numbers are very good and in reality few film cameras came closer than that.

Longshadow Loc: Audubon, PA, United States

If I'm only <5 over on the interstate, I don't worry about speed traps as so many are doing 10+ over.
Local, most don't go much over the limit, can't really due to traffic. Some do though.
I don't worry about saving minutes either.

DirtFarmer Loc: Escaped from the NYC area, back to MA

I generally go just a bit slower than the guys in the left lane passing everyone at >15mph over the speed limit.

Longshadow Loc: Audubon, PA, United States

BebuLamar

A police woman gave me a ticket for doing 52mph in 50mph zone. I didn't fight it because I know if I don't get good lawyer she was out to get me.

scoundrel Loc: Wytheville VA

I don't know whether this technique still works with more modern technologies, but in the days of old-fashioned picture tubes, each half-frame me was scanned 60 times a second, 263 odd-numbered scan lines for the first half-frame, 262 even-numbered lines for the second half, for a total of 525 lines for each frame, each line representing 1/15,750th of a second. For Europeans, that would be 50 half-frames a second at 625 lines for each full frame, giving 15,625 lines per second.

Turn the screen's contrast down to its minimum setting. Then shoot a picture of the screen for each shutter speed to be tested. Shoot at least three shots for each shutter speed to minimize the possibility of being unable to count the lines because part of the lines were uncountable because the shutter opened or closed while the beam was outside the visible picture area.

For shutter speeds faster than a nominal 1/50 or 1/60 second, it is just a matter of counting the visible lines and dividing by 15,750 or 15,625, as the case may be, to get how long, in seconds, the shutter was actually open. This will be easier to do with old-fashioned black-and-white sets than color ones, but I think it can be done with color sets too. For a nominal 1/400-second leaf shutter, which is about as fast as you can expect a leaf shutter to go, you can expect a nominal 39 to 40 scan lines to be visible.

For a nominal 1/25 or 1/30 seconds, you can expect the majority of the screen to be scanned twice, with a strip to be scanned either once or thrice, depending on whether the shutter is faster or slower than the full-frame rate. It is then a matter of counting the number of dim or bright lines to find out how fast or slow your shutter is, compared to the television's full-frame rate. The same idea applies to 1/50 or 1/60 second shutters, except it is difficult to count scan lines that aren't there if the actual shutter speed is faster than the half-frame rate. You can get close enough by measuring the gap in the picture with a pair of drafting dividers and transferring the measurement to an adjacent part of the picture that has the necessary lines. This won't be perfect, but it should be close enough.

scoundrel Loc: Wytheville VA

I can buy the 1.41 millisecond because 1/2 stop slower than 1 millisecond is 1.414 msec, but 1.2 stop faster than 1 msec is 0.707 msec. I don't blame you but I am a little disappointed in Nikon.

BebuLamar

Well the aim point for the 1/1000 shutter speed wasn't 1 millisecond but they specified as 0.976 milisecond which I take that they meant 0.97656925 which is 1/1024 which is exactly 10 stops from 1 second.
But that would make the 1.41 mS to be further away from the aim point but the .68 mS is closer as the 1/2 stop is .69. Any way it wouldn't make any difference.

Bultaco Loc: Aiken, SC

The OP was asking about shutter speed.

foathog Loc: Greensboro, NC

I have a Ford Fusion w/2 liter Ecoboost engine. It seems to read 80mph whenever I'm on I 40.

Longshadow Loc: Audubon, PA, United States

flyboy61 Loc: The Great American Desert

DirtFarmer Loc: Escaped from the NYC area, back to MA

Well, first of all, I would expect you would have trouble finding an old CRT-based TV that still works. They're big, heavy, and inconvenient. Flat screen TVs and monitors have replaced them. And the way they work is not the same as the CRT, so I suspect using one for trying to measure the shutter speed would not work. I just took my camera, set it at 1/1000 second and took a shot of my computer monitor. The whole screen was visible. That means the pixels on the screen are emitting light all the time. If the image were scanned like an old CRT, I would only see a small fraction of the screen. (My camera does not use a leaf shutter, and the focal plane shutter would give a different result on a CRT).

Also, to complicate the situation, CRTs used various phosphors to generate the light. For a 525 line TV, the phosphor had to stop giving light after it was activated within 1/60 second so it wouldn't be still lit for the next activation. TV phosphors frequently decayed after a few milliseconds, so that wouldn't be a problem, but if your TV had a long phosphor, the bands you would see with your leaf shutter test would be more than you would expect and your measurement would indicate a slower than actual shutter. I don't know what sort of distribution there was of phosphor decay times, but that would be an important thing to know for your technique.

If you want to measure the time duration of a leaf shutter I would recommend a light-source and single point sensor attached to an oscilloscope (or modern equivalent).

User ID

Really the same thing. Wecome to UHH.

(Download)

Timmers Loc: San Antonio Texas.

It's a fools errand.

The speed of the shutter can be determined for a leaf shutter wide open, yes, but it is of no use in the practical application in photography. As you close the aperture the actual exposure is determined by the action of the shutter during the exposure duration. Because a leaf shutter is traveling while open and then closing, the part of the shutter is open and closing behind a aperture that has been altered in it's dimension. This has a name, it is call the dead travel time. In simplistic term as the aperture is blocking the shutters motion during the exposures duration and so is not part of the actual exposure, thus the idea of dead travel time that cannot and will not effect the actual exposure.

The out come is that you be aware of this part of exposure and then to get close to a correct exposure you are compelled to increase the exposure duration to compensate for this error that is occurring. So if your lens is closed down 1/3 of the way, increase the exposure duration by one speed faster. At half way, increase two shutter speeds faster and above the 1/2 way of the aperture being closed you increase by three shutter speeds.

Not, when using an electronic flash it is the duration of the flash and so the shutter speed is never the issue. This is not entirely true with flash bulbs.

Pneumatic type shutters using leaf shutters are first placed in the environment to stabilize their temperature to that of the ambient temperature. the shutter is the set for a one second duration, cocked, allow a moment of the cylinder and plunger to settle, then the shutter is released and an 'estimated' of that one second for the shutter to open and close. This is adjusted by a small screw mounted on the front of the shutter until a duration of one second is achieved. The shutter is now adjusted for humidity and temperature for the environment that the optic is to be used. These types of shutters are considered some of the most accurate of leaf style shutters.