Author Topic: Shutter tester review  (Read 4170 times)

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PeterR

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Shutter tester review
« on: November 09, 2015, 09:23:20 PM »
I thought I'd post a review of a shutter speed tester I bought a few weeks back. I had expected to have done it by now but it hasn't exactly worked straight out of the box and it's taken me longer than expected to get a system in place that produces consistent, reliable results. It’s also taken me a long time to write this.

The tester was made by Florin Vasile who lives in Romania. He sells a number of variants via ebay. He goes by the name of vfmoto and can be found at http://www.ebay.co.uk/usr/vfmoto.  The one I bought was this one http://www.ebay.co.uk/itm/161779795995 which does shutter speed, curtain speed and EV. It costs $129.99 which includes worldwide shipping.

The tester is built into a small box about 70x60x25mm with its own LCD which displays the menus and the test results. It has a connection for the sensor and one for a light source.  There is an on/off switch and a single push switch which is used to navigate the menus using a combination of short, medium and long presses. This button is actually like a small joystick and can not only be pressed, it can also be pushed or pulled in any one of four directions, all of which have the same effect. I've found it easier to push down on it rather than trying to press it in like a normal push button. The tester uses either a 9V battery which fits inside, or an external power supply for which it has a socket. The power supply isn't supplied and, unhelpfully, no information is given as to what type of power supply is required. Florin recommends using the power supply rather than batteries, presumably because the light source takes a lot of power, but, at the very least, a voltage and power rating for the power supply is required if the user is to source their own. Personally, I've been using the tester with a battery.


tester 1 by Peter Robinson, on Flickr

The tester comes with a sensor box for use with focal plane shutters. It should be held against the film rails in the back of the camera. It has five sensors. A central one for measuring shutter speed and two placed vertically and two horizontally to measure the curtain speeds for vertical and horizontal shutters. There is a small switch to switch between the vertical and horizontal sensors. Unfortunately, there is no information to tell you which way the switch should be for either of the two possibilities. Given the difficulty of getting the curtain sensors to work (more of that later) it took a long time to work out which way the switch needed to be for the vertical shutter I was testing.

Also supplied is a single sensor, for use with other shutter types, and a light source. The single sensor and the light source look almost identical though they do have different connectors so it's not possible to get them mixed up. I've marked my light source with a piece of tape to save me peering closely at the connector to tell them apart.

The instructions that are emailed to you separately by Florin are brief. They deal mainly with the menus and how to navigate them and what results will be displayed. There are some omissions, as noted above, and some information about the general use of the tester and especially of light sources, would be useful. Florin does suggest the supplied light source may not be suitable for curtain speed testing and suggests that, ideally, you should use three LED light sources, one for the shutter speed sensor and one each for the two curtain sensors, with no overlap between them. But there is no information about how this might be achieved. When I pressed him, he suggested using an incandescent lamp but said he uses a LED flashlight. More information on this issue is definitely required.

The menu system is simple. The first page asks if you want to do just a shutter test or a shutter and curtain test. The tester doesn't detect which sensor is plugged in so you always get this option even if you don't have the sensor box plugged in, which is required for the curtain test. Selecting items from the menu is done with a 'medium' press while scrolling is done with a 'short' press. At any time you can press and hold the navigate button for a 'long' press which will get you into the backlight menu where you can set the LCD backlight to be always on, always off or on for a fixed time. I chose always on. Whichever option you choose from the first menu page, the second gives you the option of turning on the EV function (more of that later). If you selected the shutter and curtain test then the screen goes straight to the 'Ready!' screen which means it's waiting to detect the shutter. If you choose the shutter only test, you will get an extra screen where you can choose the type of shutter you're testing. The options are Focal plane, Leaf, Diaphragm and Other. I would have thought there was only a need for two options, Focal plane or Leaf. I don't see what the difference is between Leaf and Diaphragm and I don't see the need for Other as FP or Leaf would cover everything. There's no explanation of the different choices in the manual.

So far, I've only used the tester on cameras with focal plane shutters. I'll add to this review when I get around to testing it with leaf shutters.

Shutter speed testing.

Measuring the shutter 'speed' of a focal plane shutter isn't easy. I previously experienced the difficulties when I built my own tester. It was just a simple counter that measured the time the shutter was open for and not as sophisticated as Florin's but it taught me that trying to accurately measure a gap between two shutter blades, that could be less than 2mm apart and might be travelling as fast as 5m/sec, was not easy. What I found was, it is necessary have a sensor considerably smaller than the size of the gap you are trying to measure. I achieved that by masking a light sensor so that only a small section was exposed to light, then using a laser as a light source.

The single sensor supplied is about 3mm diameter and the sensors on the sensor box are about 2.5mm diameter. I had my doubts about whether the tester could accurately measure up to the 1/8000th second specified because of this. I started with a camera that had a top speed of 1/1000. Using the supplied light source just hand held in front of the camera and with the sensor box taped to the back, I got believable results. However, what I found was the distance the light source was held from the camera affected the results. I could get a variation in shutter time of around +/- 10% by holding the sensor nearer or further away from the camera.


tester 3 by Peter Robinson, on Flickr

I don't have a camera with 1/8000 on it but I do have one with 1/4000 on it and I next used that. With the camera set to 1/4000 I found the variation due to the light source position to be much larger and too large to be acceptable. When I asked Florin about this he said the distance should be 5cm. That was based on the error I had with the first camera and probably would have given good results with it. But the optimum distance seemed different with the second camera. There's no information in the instructions about what distance to have the light source from the shutter and at this point I was about to decide the tester was unusable and send it back.

However, I decided instead to go back to my method and masked the central sensor with some foil with a pin hole punched in it and used a laser as a light source. The results I then got were more consistent, were not dependant on the distance between light source and shutter and seemed appropriate. This is now the way I use the tester.


tester 2 by Peter Robinson, on Flickr

Curtain speed testing.

For the curtain speed test I used the supplied light source. It took a bit of playing around with the light source position but I found that it would work despite Florin suggesting it probably wouldn't. I did, initially, have the switch on the sensor box in the wrong position which meant that much of the time I would get 'Read Manual' appear on the screen. Once I'd figured out the switch position I could get results most of the time but still not always and I've not worked out why. Probably just the light source position is critical. I've only tried the curtain test with a vertical running shutter and the sensors for vertical shutters are closer together than the ones for horizontal shutters. I suspect the light source would not cover both of the horizontal sensors and an alternative light source would be needed. I tried some other light sources but nothing else I had available would work. It seems it needs a very bright light, which the supplied source is, and I don't have anything else that's bright enough. It also needs to be diffuse enough to cover both curtain sensors (unless you find a way of implementing Florin's suggestion of three separate light sources). Florin does mention that using a diffuse light source will cause inaccuracies in the shutter speed measurement so it's maybe better to do the two tests separately. I suspect a diffuse light source will also give errors in the curtain speed measurement but, as the difference is probably the most important and the errors would be equal for both I don't think it would be an issue.

After I modified the sensor box by masking the central sensor, I found I couldn't get the curtain test to work at all. It seems the tester needs an output from all three sensors to work. But with the central sensor masked, there was no way the supplied light source was bright enough to trigger it. So, now it's necessary for me to use the laser pointed at the central sensor and the supplied light source very close to it to illuminate the curtain sensors. This works but it's very intermittent. So I'm currently looking at ways of combing a diffuse source with the laser.

EV testing.

I couldn’t, initially, work out what this did. An email to Florin got no response (maybe he just thinks I’m stupid). But I think all it does is to give you the shutter speed as a set of EV values using a range of apertures. I don’t see the point of this or how it could be useful. It’s a pain to have to deselect this option every time you use the tester and it would be nice to be able to permanently deselect it.

My setup.

To make things a bit easier, I came up with a method of supporting the camera and the laser with an adjustable mount for the laser so it could be accurately aimed at the sensor. I used a cheap, straight, flash bar and a couple of double ball mounts from Smallrig which gives enough flexibility to accommodate different cameras. The laser I use is intended as a gunsight.


tester 4 by Peter Robinson, on Flickr

Overall, the tester is a good bit of kit. The electronics and the programming that must have been involved appear very well done. I just don’t think it’s capable of accurately measuring fast shutter speeds of focal plane shutters with the sensors and light source supplied. Unless there is some method of use which hasn’t been detailed in the instructions and I haven’t discovered, but I don’t think so.

The tester only gives the actual speed measured and not an error amount so I put the results into a spreadsheet, calculate the error and graph the result.


FX3-v-139-v-K100 by Peter Robinson, on Flickr

More to come as and when...
« Last Edit: November 09, 2015, 09:29:09 PM by Peter R »
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Francois

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Re: Shutter tester review
« Reply #1 on: November 09, 2015, 11:24:52 PM »
For some reason, I have the feeling that there is something flawed with the design...
I'm surprised that diffusion light can make such an error. But on the other hand, it does make light rays completely non parallel.
Maybe shooting some light directly in the camera using a slide projector would give more accurate results using every sensor?
Any light that can create a hard shadow should work.

Also, the old floppy disk drives used sensors with a slit aperture on them. You might look into such a mod as it allows more light in than a pinhole yet increases the precision just as much..
« Last Edit: November 09, 2015, 11:26:43 PM by Francois »
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PeterR

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Re: Shutter tester review
« Reply #2 on: November 10, 2015, 08:33:44 AM »
I'm surprised that diffusion light can make such an error. But on the other hand, it does make light rays completely non parallel.
That's the problem. So you don't get a fast cutoff of the light as the curtain passes.

Quote
Also, the old floppy disk drives used sensors with a slit aperture on them. You might look into such a mod as it allows more light in than a pinhole yet increases the precision just as much..
When I built my own tester I used a slit but went for a pinhole here as it will work for both horizontal and vertical modes.
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Nigel

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Re: Shutter tester review
« Reply #3 on: February 03, 2016, 08:46:16 PM »
Wow.

I take my hat off to you Peter, this is the sort of thing I wish I had the patience (and the skills) to do. Rightly or wrongly, although I've always liked the idea of a shutter tester, my takeaway is 'don't buy one'.
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PeterR

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Re: Shutter tester review
« Reply #4 on: February 04, 2016, 08:45:04 AM »
Wow.

I take my hat off to you Peter, this is the sort of thing I wish I had the patience (and the skills) to do. Rightly or wrongly, although I've always liked the idea of a shutter tester, my takeaway is 'don't buy one'.

They're a double edged sword for sure. On one hand it's good to know if your shutter is inaccurate but, on the other, most people wouldn't notice quite large errors in the shutter in normal use and ingnorance is bliss sometimes. I wanted one to test the cameras I sell to make sure they're within spec.
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charles binns

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Re: Shutter tester review
« Reply #5 on: February 04, 2016, 01:22:50 PM »
ingnorance is bliss sometimes.

ignorance is bliss always  :)

I have to say if I tried to this at home I'd probably end up sticking a screwdriver in my eye.