Is the nominal shutter speed listed on the Calument tester correct?

[Pfsor]

The accuracy of the 555 timer is several orders of magnitude worse than a crystal.

I would never use a 555 in the design of a shutter speed tester or any similar device.
I have used thousands of 555s in designs where absolute accuracy was not needed.

- Leigh

If I remember well, the 555 runs on 0.1 MHz. Enough to measure to 1/100000 s. And yes, the 555s are used in time measuring devices (with a 4026 to count the oscillation). You can always strive for better. Besides, there is no meaning to use 16-200MHz crystals to measure times long at most 1s. Not in a device with possible errors from off centre position!

[Pfsor]

The deltas (time between adjacent speed settings) can be much more accurate than the absolute speed.

- Leigh

So what?

[Pfsor]

The accuracy of the 555 timer is several orders of magnitude worse than a crystal.

I would never use a 555 in the design of a shutter speed tester or any similar device.
I have used thousands of 555s in designs where absolute accuracy was not needed.

- Leigh

As a side note - you would be probably shocked to know that Tomahawk missiles use in their time measuring device not crystals, not any timer circuits but Swiss mechanical calibres (watch movements) proudly and promptly manufactured in La Vallée de Joux...

[Jac@stafford.net]

You guys with precision metrics are going to make my head explode!

When paying by check I often have to ask, "The date today, please?"
The answer is something like "September 16" to which I must respond,
"Yeah I know that, but what year is it?"

I kid you not.

[Alan Gales]

Really? Have you ever wondered why shutters are marked in 1/3 of stops?

Nope. It's overkill in my book.

Bracket a bunch of shots in 1/3 stop differences and see what you think.

[Pfsor]

You guys with precision metrics are going to make my head explode!

If it can be of some consolation to you, Leigh will measure (with a crystal oscillator!) the time of your explosion. I will just sadly confirm your instantaneous end.

[Pfsor]

Nope. It's overkill in my book.

Bracket a bunch of shots in 1/3 stop differences and see what you think.

In such a case we are probably talking apples and oranges. You probably take B&W - I take chromes and 1/3 of a stop is important to me. It can make a difference between a keeper or a botched picture.

[Jac@stafford.net]

If it can be of some consolation to you, Leigh will measure (with a crystal oscillator!) the time of your explosion. I will just sadly confirm your instantaneous end.

You are funny. Thanks. Did you know that nerve messaging in the human body travels at about the speed of sound? That's good enough for me. Digressing... We are so slow.

I take chromes and 1/3 of a stop is important to me. It can make a difference between a keeper or a botched picture.

An old friend of mine, in fact a former employee, went on to work for National Geographic in the Kodachrome days. He was also the 1/3 stop guy. When asked about his light meter he never, ever responded.
.

[Pfsor]

You are funny. Thanks. Did you know that nerve messaging in the human body travels at about the speed of sound?

No, I did not know. From now on I will prop my ears if I don't want to feel anything. Hope it will work in my dentist office...

[Alan Gales]

In such a case we are probably talking apples and oranges. You probably take B&W - I take chromes and 1/3 of a stop is important to me. It can make a difference between a keeper or a botched picture.

You are correct. I shoot mostly 8x10 B&W.

I cut my teeth on 25 ASA 35mm Kodachrome back in the 1980's. When learning, I used to bracket my shots 1 stop difference for the perfect exposure. What I learned was that usually I came out with 3 good shots. Sometimes my slightly over or under exposure shots were best. Sometimes I could not pick which was the best shot because all three looked great and I'm talking a one stop difference between each. Then of course you can talk about high key or low key which is popular in portraiture if we wanted to open another can of worms.

To be honest I'm surprised that 1/3 a stop makes that big of a difference on your chromes to you but to each their own. To be fair to you I have read that there are photographers who also feel as you do. As always I recommend that photographers experiment and find out on their own what looks good to them.