Speed tests results

So, you know that I wired up an Oscilloscope with a photodiode to read shutter speeds … thought I would mention some results.

I wrote up a spread sheet to make some simple calculations for me after I type in the number of ms that I figured out the DSO screen (too bad this one did not calculate the pulse width in normal/single mode).

First is the shutter speed setting on the camera/shutter … then I enter the ms in the green zone.

The spreadsheet converts that to a 1/x speed … and the last column is the % the speed is slow or fast.

Looks like my OM-2 shutter is still accurate (rates over 1/500s are still not that easy to measure with this setup).

Lets take a look at at a 75 year old Compur shutter after I made some positional adjustments to the escapement retard.

Also not so bad … unless you hit the high-speed spring.

The Compur shutter uses a combination of an escapement for the slow speeds, a main spring for the middle speeds and a high tension spring just for the highest speed … and it looks like that one has lost its spring !!!

I did also run through a number of combinations of the Speed Graphic focal plane shutter … what it shows that as the spring roller ages it becomes harder to calibrate evenly throughout all the tension settings.

It just keeps advancing …

I was just testing out the Olympus OM-2 shutter when I notices that the multi-stroke advance lever sometimes slipped. Now I have read online that many Olympus users do have to advance the lever a couple of times to charge the shutter, but this one sometimes free flows.

So lets take a look.

I took the top off … again … to get a closer look at the gearing.

Ok, so what do we see here … ignore that dark gear on the bottom, we are interested in the brass one just above it. If you look carefully you will see that the teeth are worn.

This is a pawl mechanism, as you push the advance lever a pawl engages a tooth in the ratchet gear and turns it. With the OM-2 the pawl revolves, with the advance lever, to turn the ratcheted gear. If it does not engage the first tooth, the advance lever will return, and then you will need to advance further, engaging the ratcheted gear again to get to the end of the cycle.

If the advance lever is really forced it will cause the pawl to slip out of the tooth … which will cause wear on both edges that are engaging … eventually over time you can wear both down so that they no longer have a grip.

I pulled out the component to see if I could get a better look … just remove the three screws on top … sadly I took a picture of the wrong side for you all.

You can see the dark gear on the bottom … and the pawl mechanism above it.

This camera has dual pawls that are not spring loaded. They appear to engage the ratchet by some light pushing force when the advance is turned.

Without taking everything apart, I just used a fine file to put more of an edge on one side of the pawls tooth … this did help a bit … the real solution is to replace both ratchet gear and both pawls … or possibly take it apart and use a Dremel to reshape the tooth?

Well, just have to live with a really multi-stroke advance.

… and remember, if you cannot advance the the winding lever using the Force to get to the end is not the solution. Winding levers don’t tend to get stuck for no reason !!!

I got a Time machine

Recently I have restarted a search of a device to test shutter speeds … always good to know if you have done it right. There are a number of devices out there that can do this:

  • Kyoritsu
  • ZTS
  • photoplug
  • phochron XA
  • alvandi
  • vmfoto
  • DIY Arduino

The first two were made for specifically for camera tech’s which are either no longer manufactured, or are extremely expensive. The photoplug uses a computers microphone jack and audio app to record the electrical output wave. The others are self contained devices that detect the light source but display the info as speeds.

I already had a photoplug-like device from vmfoto, but found that using the microphone input a crude method. Using the Shutter-Speed App was almost impossible to read (lots of noise), and it did not work any better on my Macbook using Audicity. I needed something that works … I was intrigued by the Arduino concept with a build/code your own device … but I am lazy … the Phochron XA is one of the best new designed product, but I am too cheap to pay for it.

Long, long ago I was introduced to the time machine. This was when I started High School and took an Electronics course. Our Teacher showed it to us … but we could not touch it. Ever since then I have always wanted one.

An oscilloscope can plot one or more signals as a function of time … it can show the signal of a circuit that changes over time … thus, a time machine.

I found many examples of using a light sensor that can be read by an oscilloscope to read the opening and closing of a shutter.

First I needed to understand how to use one, so I know what kind of scope I need … Martin Lorton has some great videos on understanding and using an oscillosope

So I started searching for an oscilloscope … well, they aren’t cheap either (I kinda knew that already). I did find a blog post about shutter speed testing and they were using a cheap DIY build DSO (digital storage oscilloscope) kit. Looking around on Amazon, I found that there are a large number of these being advertised … now they are not as sensitive, accurate, (or built as well) they can do the simple job that I need it to do.

I decided to get a $50 Kuman Q15001 DSO (JYE Tech DSO150 board) that was pre-assembled (you can get a DIY kit for as little as $21 CAD).

I had a couple of the vmfoto light sensors so I figured I could take it apart and reuse the components to wire up a simple circuit using a photodiode, resistor, and power source … I found the above circuit example on the web … though I am not sure if the vmfoto device used a photodiode or a phototransistor (there is a difference). I did have an breadboard kit that came in handy, so time to experiment.

My circuit ended up with the photo-sensor from the vmfoto (removed the internal resistor) before putting it back in the case (note there is a lot of glue in there) with the mic jack plug cut off, a 1M ohm resistor, and 5VDC power from the USB port on my MacBook. The external light source is a USB LED light.

The photosensor (diode/transistor) acts like an on/off switch … when light hits it, current can flow through it. When the shutter is closed, no light is acting on the photosensor so no voltage is displayed by the DSO. While the shutter is open, the photosensor allows current to flow, so the DSO reads 5+ volts. The DSO is set to trigger (to stop the output display) when the voltage drops to almost 0.

The above shows a test of the Prontor-S shutter that I cleaned up … the shutter was fired at 1/10s. You can see the waveform on the DSO screen of the shutter opening and closing.

The DSO is set so that each vertical grid line is 2V value, while the horizontal is 10ms time. The above wave shows a height of 2.5 grids … 2.5x2v=5V with a width of approximately 8 grids … 8x10ms=80ms … as a fraction that is 80/1000 = 8/100 = about 1/12s. So now I know the shutter is running a bit fast.

Note: this DSO does not offer cursors to measure delta, though there is an rewrite of the opensource firmware that adds this.

I did test the circuit+DSO on a Nikon FE2 focal plane shutter and the mechanical 1/90s was reading about right … one thing you will notice using this method is that at higher shutter speeds the waveform is not as square, which is caused by the photosensors rise/fall time, directional characteristics plus the slight leaking of light before/after the shutter curtain (and the rise/fall timing of the cheap DSO). Below is the Nikon shutter at 1/500s (2ms). The DSO shows 4 grids x 0.5ms + the rise and fall time … so some will read this at the toe when the shutter opens, to the top of the shoulder when the shutter starts to close. The rise delay looks like 0.2ms … so the shutter time is 2.2/1000 = 1/454s if the DSO is accurate.

With a leaf shutter the wave has a more pronounced curvy slope due to how the iris opens/closes.

In the end … it gives a clean enough output that I can actually figure out the shutter speed … eventually I will solder it all together and get rid of the breadboard.

… also an oscilloscope can be used just to simply measure voltage output of a source.

I feel the need … the need for speed!

When I got the National Graflex I did write up some stuff about the Graflex company … well I am adding a bit more historical information.

Graflex, not a common name that many of today’s photographers will recognize, but their cameras made some of the most iconic images of all times. They made or rebranded many 35mm, SLR, TLR, and large format film cameras, but their most prominent cameras were in large format.

One particular aspect they embraced the focal plane shutter very early on (single curtain with varying slits, you use a combination of tension and slit size settings to get the shutter exposure) … for those that think SLR’s with focal plane shutters came out in the 50’s, well it really started in the 1880’s, and Graflex started using it in 1898. The focal plane shutter gave the advantage of higher shutter speeds than the leaf shutters produced at that time … so they decided to use both in the same camera.

Many photographers used Graflex cameras, especially sports and press photographers … many iconic images that you may have seen were taken with one:

  • Graflex SLR and other – Lewis W. Hine (you really should look at his body of work)
  • Graflex SLR – Dorothea Lange, FSA dirty thirties
  • 4×5 Graflex super D…. Weegee, the press photographer
  • Arthur Fellig Speed Graphic … 1937 Hindenburg photo
  • WWII signal corps

The last camera Graflex designed was in 1965, so now it has become “vintage” … and Star Wars wouldn’t have been the same without that flash.

OK … what I have is the Miniature Speed Graphic which is a 2-1/4 x 3-1/4 format “press” camera … a smaller version of the Anniversary Speed Graphic camera. It also was the first Graflex press camera to have a front rise. Made between 1939-46, Graflex produced about 47,000 of them

It is designed specifically for sheet film camera … Ilford and Arista still make this format … there was even a Grafmatic speed loader that held 6 sheets for rapid shooting. The Miniature Speed Graphic (not to be mixed up with the Pacemaker) has the classic focal plane shutter with speeds up to 1/1000s … and also included a large variety of lens/shutter combinations (I think over thirty different ones).

When I got it the focal plane shutter was running slow. It did not need much to free up the mechanism … on the left side of the camera are two metal bushings that terminate the rollers. These can be unscrewed, cleaned, and oiled a tiny bit … then some exercise and now the shutter is a go.

The Compur leaf shutter was running good, and the Kodak lens was nice and clean (I think credit has to be given to the metal lens cap), so I did not have to touch it at all.

The only real thing that was wrong was that it was dirty. While I was examining the metal “patina” I realized that the brown “aging” of the metal was actually years of tar accumulation.

Lots of scrubbing later, the yello metal looks like metal again.

minispeedclean

Kodamatic shutter up close

Continuing on with the box of folders … the Kodak Vigilant, lets take a look at that No.1 Kodamatic shutter.

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Ok, as typical with these old folders the shutter/lens can be removed.

Unscrew the retaining ring in back using a spanner wrench through the back of the camera.

Shutter release arm coupling can be unscrewed.

Note the front cell sits with little gap when at infinity … remove the infinity stop which is hexagonal making it easier to grip than the TKS.

Unscrew the front cell.

 

 

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Ok, now flip it over.

The curved shutter release arm can be remove my taking off the two top screws.

Do not remove the bottom screws at this time.

The rear lens element just unscrews.

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OK back to the front.

In order to get deeper you have to unscrew the middle group … typically you can use a rubber tool to get a grip, but in this case it was really stuck. You should use a large flexi clamp, but I did not have one, so I ,reluctantly, cut a couple of “nice” notches with a Dremel, so I could use a spanner wrench.

Wiggle off the cover.

Remove metal shutter setting arm cover

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The black speed cam ring pulls off, along with the self timer charging arm.

Next plate, three large flat headed slot screws … one at top is shortest.

Shutter release arm … move the spring out of the way

Convince the top plate to come out …

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Map all the springs that you can see …

Unscrew the cover for the shutter arming lever.

Flip over and remove the two last screws … longer is the one on left.

Remove loose self timer springed gear (at 7 o’clock).

Next will be lifting the shutter out … note that the aperture blades will come along with it all, so be aware of the underside.

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Open the aperture wide open … cock the shutter

Slowly lift out while looking at all those springs … memorize

The escapements are not self contained, so if you remove the securing screws you will loosen the top cover plate … and then you will have a handful of gears to contend with.

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Bottom part will have the aperture ring thing

Ok, the ring thing is actually called the diaphram operating ring.

Flip over to see aperture

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If you want to get to the shutter you have to (nicely) spread out the aperture blades to get at the screws.

You will notice that the blades have no real post … they have a punched hole (burst hole) that creates its own post from the bent metal, so this makes them susceptible to being flattened if they pop out.

I decided not to go there (luckily the blades were good), so I nicely put the aperture blades back into position.

Now … putting it back you have to play around a bit to get those blades back into the slots of the operating ring. … close the aperture so it forms a perfect circle on the inside … move the aperture lever to the top … then slide back in … while partially sliding it back in, work all the springs back to where they are supposed to be.

Work the aperture lever to see if it catches all the leaf posts … keep on working it in.

The adventures of this guy who tries to restore and repair vintage photographic equipment … and wins (most of the time).

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