Measuring shutter speeds on Minox cameras

[tjwspm]

DIY device for Minox Shutter Speed measurements

When offering used Minox cameras, the seller often states that the camera works because “plausible” noises can be heard at different times when the shutter is released. Aside from the fact that these noises can occur without the shutter even opening, the times can be significantly incorrect. The only way to tell by ear is whether longer shutter speeds produce longer sounds.

If you actually want to use the camera to take photos, you need to know how precisely the shutter really works. There are various methods, devices and apps for measuring shutter speeds, such as Shutter-Speed. Most methods are based on positioning a light source in front of the camera and using a light sensor to measure the opening time of the shutter. From the opened back panel one measures the opening time of the shutter using a light sensor. In addition Shutter-Speed also offers the possibility of estimating the opening time based on the shutter sound. No additional hardware is then required.

All of these procedures cannot be used with Minox cameras because the back of the camera is not accessible and the shutter noise on the Minox does not allow any estimation.
However, with a modification of the “Photoplug” light sensor, which can be purchased for the free Shutter-Speed app, measuring Minox shutter speeds is very convenient. The sensor is plugged into the headphone port of the smartphone.

The idea is to use the reflections from the highly reflective surface of the Minox shutter and to place the light sensor and light source next to each other in front of the lens. As soon as the shutter opens, there are hardly any reflections. The Shutter Speed app can use this difference in brightness for measurement. In addition to the light sensor, I modified the sensor to contain two LEDs as a light source in a plexiglass housing. The front is matted to create a diffused light:

To measure, simply place the Minox with the lens in front of the sensor and release the shutter. The app then shows the measured brightness progression:

The opening time of the shutter is obtained by marking the dark phase (here: set 1/2 s, measured 1/2.6 s):

Measurements with two Minox A IIIs cameras will follow.

 

[tjwspm]

The following measurements were taken using a professionally refurbished (CLA) Minox A IIIs:

1/2 s / 1/20 s

1/100 s / 1/500 s

1/1000 s

Please note that the f-stop deviations are not necessarily displayed correctly. To do this, you would have to select the times set on the camera in the app. However, not all values are selectable. However, this has no influence on the measurements.

 

[beemermark]

A simpler method is to use a roll of film and shoot at1 sec, 1/2, 1/4, etc using a ND filter as needed. Develop roll of film and inspect the negative.

 

[tjwspm]

You're right, easier in the sense that you don't need any hardware. However, the electronic measurement is faster and, above all, more objective. The assessment of the negatives depends on many parameters, such as the type of film, developer and development method. If you always have the same workflow and rarely have to do it, it might be an option.

With my setup it takes me about 1 minute for 4 measurements. With the Minox's 9 shutter speeds, that's 3 minutes including setup to completely and objectively test the camera's shutter speeds.

 

[ic-racer]

Very nice. I'm not familiar with the 'Photoplug.' Where is the light coming from?

 

[tjwspm]

Very nice. I'm not familiar with the 'Photoplug.' Where is the light coming from?

In the original Photoplug there is no light. I added 2 LEDs with an external power supply simply by a battery.

 

[jclup]

Bonjour
Pourriez vous nous faire une vidéo à ce sujet, je n ai pas tout compris
merci

 

[tjwspm]

In the meantime, I have written a complete article about it on my website. You can find it here:

Checking shutter speeds of Minox 8x11 cameras

So let’s measure the shutter speeds of our Minox. But how? Read my simple method to accurately measure Minox shutter speeds here.

moments-of-now.com

 

[jclup]

Merci pour les explications très precises

 

[tjwspm]

Si vous souhaitez consulter le site en français, il vous suffit d'utiliser Google Translator:

Vous recevrez alors la page suivante :

 

[ChrisGalway]

In the meantime, I have written a complete article about it on my website. You can find it here:

Checking shutter speeds of Minox 8x11 cameras

So let’s measure the shutter speeds of our Minox. But how? Read my simple method to accurately measure Minox shutter speeds here.

moments-of-now.com

Thank you! I'll try this ... I already have the Photoplug.

 

[tjwspm]

Merci pour les explications très precises

Vous pouvez également sélectionner le français comme langue en haut de la page web. La page sera alors automatiquement traduite:

This website in your own language

You can now switch this website to your own language. Simply select the desired language from the floating menu at the top. The original language of the

moments-of-now.com

 

[xkaes]

A simpler method is to use a roll of film and shoot at1 sec, 1/2, 1/4, etc using a ND filter as needed. Develop roll of film and inspect the negative.

K.I.S.S. works for me too.

 

[ic-racer]

A simpler method is to use a roll of film and shoot at1 sec, 1/2, 1/4, etc using a ND filter as needed. Develop roll of film and inspect the negative.

Where did you get the 12 ND filters? Can you show the roll of film?

 

[ChrisGalway]

A simpler method is to use a roll of film and shoot at1 sec, 1/2, 1/4, etc using a ND filter as needed. Develop roll of film and inspect the negative.

That's not measuring the shutter speed! As Kelvin put it:

"When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be."

Lord Kelvin

"Lord Kelvin" published on by Oxford University Press.

www.oxfordreference.com

As an aside, the Photoplug is a great little device, I use it to measure the shutter speeds on all the old cameras I buy. On older cameras, the speeds are invariably slower than marked.

 

[tjwspm]

That's not measuring the shutter speed! As Kelvin put it:

"When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be."

Thank you!

 

[xkaes]

..when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind:

To you it is, but everyone gets to decide what standards they want to use. I've tested lots of film density with an analyzer, but I know that the old eyeball does a pretty good job too. Most people I know simply use their baby blues to determine maximum black in their prints, not a densitometer.

 

[ChrisGalway]

To you it is, but everyone gets to decide what standards they want to use. I've tested lots of film density with an analyzer, but I know that the old eyeball does a pretty good job too. Most people I know simply use their baby blues to determine maximum black in their prints, not a densitometer.

Have you heard of the Cornsweet Illusion?

Cornsweet illusion - Wikipedia

en.wikipedia.org

The eye/brain is easily fooled.

 

[xkaes]

The eye/brain is easily fooled.

No foolin'. I studied under R. L. Gregory 50 years ago.

 

[MattKing]

That's not measuring the shutter speed! As Kelvin put it:

"When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be."

Lord Kelvin

"Lord Kelvin" published on by Oxford University Press.

www.oxfordreference.com

I always think of Lord Kelvin as having been kind of cold .
And probably no fun at parties.

 

[tjwspm]

To you it is, but everyone gets to decide what standards they want to use. I've tested lots of film density with an analyzer, but I know that the old eyeball does a pretty good job too. Most people I know simply use their baby blues to determine maximum black in their prints, not a densitometer.

Of course, if this is the right procedure for you, then you should proceed in this way. However, the electronic measurement is more objective. The assessment of the negatives depends on many additional parameters, such as the type of film, developer and development method.

The right method depends on the goal you are pursuing. If we want to discuss here how much the exposure times of Minox cameras can deviate or what influence deviating shutter speeds have on our photo results and how we can compensate for this, we should use objective methods, i.e. measurements.

By the way, I have now hopefully presented my method a little more clearly on my website here:

Checking shutter speeds of Minox 8x11 cameras

So let’s measure the shutter speeds of our Minox. But how? Read my simple method to accurately measure Minox shutter speeds here.

moments-of-now.com

 

[Niglyn]

That's not measuring the shutter speed! As Kelvin put it:


As an aside, the Photoplug is a great little device, I use it to measure the shutter speeds on all the old cameras I buy. On older cameras, the speeds are invariably slower than marked.

Yes, the reason it measures speeds slower than it actually is, is the fact it is measuring both slit width and sensor width. The higher the speed, the greater the error.

It also cannot measure curtain speed, which is essential for correctly calibrating a focal-plane shutter.

Look on this forum for discussion of my tester, the issue above is described in detail how my tester gives accurate results.

Kosmo photo has two interesting articles, this one, showing how to test shutters and detailing how these single sensor testers are not good.

5 Levels of Shutter Testing: How Accurate is your Film Camera?

Introduction Here at Kamerastore, we buy and sell thousands of cameras every year. With this experience, we know that the vast majority (over 80%) have some kind of issue that requires attention from our mechanics. If you buy a camera online from someone who only does basic testing, or no...

kamerastore.com

 

[ChrisGalway]

Yes, the reason it measures speeds slower than it actually is, is the fact it is measuring both slit width and sensor width. The higher the speed, the greater the error.

It also cannot measure curtain speed, which is essential for correctly calibrating a focal-plane shutter.

Look on this forum for discussion of my tester, the issue above is described in detail how my tester gives accurate results.

Kosmo photo has two interesting articles, this one, showing how to test shutters and detailing how these single sensor testers are not good.

5 Levels of Shutter Testing: How Accurate is your Film Camera?

Introduction Here at Kamerastore, we buy and sell thousands of cameras every year. With this experience, we know that the vast majority (over 80%) have some kind of issue that requires attention from our mechanics. If you buy a camera online from someone who only does basic testing, or no...

kamerastore.com

Thanks for pointing this out. Actually I'm a medium format person and the shutters are invariably leaf-shutters in the lens, so I think the single sensor PhotoPlug is accurate ... am I correct? (It is a little aperture-dependent I suspect.)

 

[Niglyn]

Thanks for pointing this out. Actually I'm a medium format person and the shutters are invariably leaf-shutters in the lens, so I think the single sensor PhotoPlug is accurate ... am I correct? (It is a little aperture-dependent I suspect.)

No, not that simple I'm afraid. It seems so simple, use a sensor to measure how long it sees light. Alas, that just does not work.

I have updated my The Shutter Tester to include leaf shutter testing, using the formula below. However, not having a leaf-shutter, I have not been able to test it against an actual shutter, just a mock-up, which seems to work perfectly.

One does not just measure the open time in the centre of the shutter, but one also measures the time for the leaves to fully open and the time for them to fully close. The only way to do this is with two sensors, but again one has to calculate the raw readings to allow for sensor width, which then gives the correct result.

(Thanks to IC Racer, for the diagram below).
The formula is time open = centre open time + (time to open + time to close)/2

 

[ChrisGalway]

No, not that simple I'm afraid. It seems so simple, use a sensor to measure how long it sees light. Alas, that just does not work.

I have updated my The Shutter Tester to include leaf shutter testing, using the formula below. However, not having a leaf-shutter, I have not been able to test it against an actual shutter, just a mock-up, which seems to work perfectly.

One does not just measure the open time in the centre of the shutter, but one also measures the time for the leaves to fully open and the time for them to fully close. The only way to do this is with two sensors, but again one has to calculate the raw readings to allow for sensor width, which then gives the correct result.

(Thanks to IC Racer, for the diagram below).
The formula is time open = centre open time + (time to open + time to close)/2


View attachment 383231

Agreed, that why I said "aperture-dependent"! But for the slower speeds (slower than 1/100?) this effect is second-order, I think, after all a measurement of the total light reaching the image plane needs only to be good to around 20%, even if exposing colour transparency film. I've used my measurements for exposing Provia 100f for several years, and the results are "perfectly" exposed (well, nothing's perfect!).

I would be really interested if you compared the single- and double-sensor methods on a leaf shutter at a couple of apertures.