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

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

From our experience of buying and selling thousands of cameras, 80% have some kind of problem that needs attention. If you buy something online from someone who only does basic checking there is a good chance it will not work in one way or another. It might under or overexpose without you realising, leading you to blame your own lack of skills instead. Perhaps the curtains aren’t in sync and you get unevenly exposed pictures. Sadly, more and more people get a bad start in film photography, not because it’s that hard, but simply because they are given a camera that doesn’t function properly – and this problem will only get worse as cameras get older.

A malfunctioning focal plane shutter can completely ruin your pictures – notice the uneven exposure on the left. This was a Leica M2.

At Kamerastore, everything is given a rating on condition. Most of the time we only list things that work perfectly, but if something minor is off we will tell you. For example, on many mechanical cameras, the top speed is slower than it should be. In these cases, we sell it cheaper and let you know so you can compensate for it when using the camera. We test the cameras to the highest level needed for that camera, all to make sure that you have a good experience. Below you can read about the levels of testing possible, from the most basic, least useful test, to the most advanced test that reveals all functional flaws. While some of it might seem unnecessary to some, the steps described below is the only way of knowing if a camera is in proper working condition.

Below you can read about the 5 levels of testing – note that these are not the same as the condition ratings on Kamerastore.com. You can read about those on the condition rating page

Level 1: The Flea Market Test

Level 1, the flea market test, can reveal some basic problems about the state of the camera. First, you can check that buttons and levers work, and for outside damage on the body, scratches on the viewfinder or mirror, or damage to the shutter curtains.

With the right batteries you can see if the meter moves. Some cameras also require batteries to test if the shutter fires at all. Next, you can listen to the slow speeds to see if they even run – often these are sticky. This is not at all an accurate method of telling if it is precise. Most people struggle to hear the difference between, for example, 0.8s and 1.4s, even though that’s almost a whole stop off!

Then you would open the back of the camera, hold it up towards the light and fire the shutter speed at the higher speed. Here you won’t be able to tell what the actual speeds are, only that, for example, 1/1000 is faster than 1/500, and again faster than 1/250. This tells you that the shutter does at least change speeds, but tells you nothing about the accuracy of exposure and therefore nothing about how the picture will turn out. The best use of this test is to see if the shutter does not work. For example, if you only see half the frame being exposed the camera has a curtain problem. Once you have completed these tests you will know if the camera isn’t totally broken, but you still won’t be able to determine if it can expose film correctly.

You hopefully think this sounds quite inaccurate and hopefully, you’re thinking that you wouldn’t want to buy a camera that has been checked like this. However, this is the kind of checking that most sellers on, for example, eBay conduct, and then claim it is fully working. The reality is that the only thing you can find out at this level is if camera clearly broken – to find out if it is working properly you need higher levels of testing. You know nothing about the accuracy of the shutter, nor do you know anything about the accuracy of the lightmeter or potential auto exposure mode found on many popular cameras, such as the Canon AE-1.

Level 2: Acoustic check with a phone

Each level includes the basic checking of external things like damage and wear, as well as the proper functioning of levers and buttons.

On level 2 you are using an app that records sound on your phone, then shows you a graph with magnitude (loudness). You can, in some cases, see when the shutter opens and closes, though the process is subjective because you have to manually read the graph. It works best on central shutters, because that is a simple opening and closing, and it works to some degree on the slower speeds on focal plane shutters. Here is an example from a Rolleiflex 2.8F that was CLAd by our professionals the same day as doing this test – it was calibrated to be as close to perfect as it could be using professional and authentic film-era machines.

On half a second it’s easy to see the peaks and identify the shutter being open.
On 1/60 finding the peaks is a bit of guessing but relatively accurate.
On 1/250 of a second, it just a guessing game. There are no cues to read the shutter speed from, even on this TLR, which should be the easiest.

However, faster speeds, even on central shutters, won’t be accurately measured, and faster speeds on focal plane shutters definitely won’t, for two reasons.

Since the focal plane shutter, on higher speeds, is in constant movement they output a constant acoustic signal. To vary the exposure time, they change the distance between the two curtains forming a narrower or wider slit moving across the film plane.

Additionally, perhaps a majority of the cameras people start with are SLRs, where the mirror will make a lot of noise, polluting the acoustic signal from the shutter. Because of this, acoustic measurements of the shutter speed is not a particularly accurate measurement – better than level 1 and definitely something you can do if you don’t have access to level 3 and up, but not something you should use to guarantee all shutter speeds of a camera with, when selling.

Finally, even though this method measures some shutters at some speeds decently, it does not measure actual light coming through, only approximate how long it is between the shutter moves, and then moves again. It should mostly be seen as an upgrade to the flea market check and not a test equivalent to using professional equipment. The test also does not determine anything about the light meter or the automatic exposure found on many popular cameras, such as the Canon AE-1. Therefore, this level is better than nothing, but should not instil confidence in the overall condition of the camera.

Level 3: 1-probe shutter test

On this level, you, of course, check the same things you do in the flea market test. It is the shutter and light meter testing that improves as we go up the levels.

A 1-probe tester is where you send light through the camera, then have a sensor behind the camera, where the film would be, that measures how long the light is coming through the camera – essentially measuring exposure time, or shutter speed. It doesn’t test how much light comes through (overall exposure) and so only checks the speed of the shutter, not the light meter – we will get to that eventually.

One of the shutter testing machines at our office. Most often used for TLRs and other leaf shutter cameras.

Professional workshops have these for testing in-lens central leaf shutters, such as those found on medium format systems, like Hasselblad V (500) and TLRs like Rolleiflex. These machines will accurately tell you how long the light is allowed through the shutter. This type of shutter tester works well on these central shutters and works to some degree on focal plane shutters too. However, for a focal plane shutter to work accurately two curtains have to follow each other in perfect sync. Since we only have one point of measurement we cannot determine how fast each curtain is moving. If one is catching up with the other it will lead to an uneven exposure.

There are now 1-probe sensors you can buy and plug into your phone. Newly designed, handheld, independent shutter testers are also on the market now. Recent tests against professional equipment conducted by some camera repair community members do indicate that they are not particularly accurate. While not scientific, it’s hard to guarantee their accuracy compared to professional equipment, but for the shutter described above, they are certainly a step up from acoustic testing, in terms of accuracy – particularly on the higher speeds. Again – these still do not test the light-meter or accuracy of automatic exposure, only the manual shutter speeds on some cameras.

Level 4: 3-probe shutter test

Beyond the routine testing described above, this level allows you to properly test the focal plane shutter curtain speeds.

As discussed earlier, for most shutter plane shutters to work properly you need the two curtains to be in sync. To check if the curtains run at the correct speeds, and maintain a constant exposure slit that gives an even exposure, you need at least two, usually three light probes placed in the direction of travel. These must have a known distance between them so the machine can measure the times of each curtain. Some shutters travel in the vertical direction and some in the horizontal, so the tester needs probes to check both directions. With this test, you can check any manually controlled shutter (cameras with a shutter speed dial) and see if it exposes to factory specification. For manual cameras, this is the highest test level you need to determine proper shutter operation.

Currently, there is at least one commercially available, hand-held shutter tester, but as we discussed earlier, it seems that they do not have the same level of accuracy as the old ones. Because no new machines that we can trust completely are made for purpose, it is rare that sellers check to this level. All focal plane shutter cameras sold at Kamerastore.com are checked to this level, but many film camera stores don’t have the equipment to check to this level. This is big, because it is the only way to properly test a lot of shutters in a way that you can, with confidence, say that it works 100%.

Level 5: Automatic exposure test

This is the highest level of testing and is the level we use for all cameras that have auto-exposure.

The challenge here is to trick the camera into thinking that it is reading light from a scene. The challenge is to create a ‘scene’ (a light source) that you can control accurately to a known value so we can assess if the camera reading matches the expected output value.

This problem is many-fold. First, you need to produce a light that is an exact, specified intensity and be able to decrease or increase the intensity to other values – generally, these are measured in EVs (‘exposure value’, one EV corresponding to 1 ‘stop’ of light change, meaning a doubling or halving in intensity). You can see the buttons on the right side in the above picture corresponding to EV values. The hole in the middle emits the desired value. By testing different intensities of light you can see if the camera reads all levels of exposure well, and test that the camera chooses that correct shutter speed.

The next challenge is that the lens you are testing with has to have a calibrated aperture so that an aperture of f/5.6 actually is what it says on the tin. Therefore, you cannot use any random lens coming in but need to have one calibrated lens for every conceivable system. In the picture above you can see some of the calibrated lenses we have for this purpose. You also need to keep the lens at infinity for light-falloff not to take effect. Furthermore, you need to make sure that, if the lens does not have defined click stops for the aperture, you carefully select the right aperture. Next, you have to measure the light accurately when it comes out where the film would be. For that, you need a calibrated probe that reads the total exposure to the film plane and thus tells you that the shutter is off, or the light meter reading is off.

Of course, if you want to test the curtain speeds as well, that will be on a separate machine like we discussed on level 4, doubling the amount of work.

As you can see from the above, this is not a simple task and requires very specialist equipment and focused technicians. This sort of equipment and work ethic was pretty common in good repair shops back in the day, but many of them were scrapped when film went out of fashion and today far too few repair shops have these tools. Without this machine, you cannot test basic cameras such as the Canon AE-1, properly.


Hopefully this article has given you some insight into the challenges and requirements that go into testing. It should be said that this is not something we do for special cameras, but something we do for all cameras – expensive or cheap. Either we find that they work well, and we clean them, change the light seals and sell them, or we find that they are in various states of bad repair, and they take the appropriate route.

For cameras to last another 10, 20, 40 or 80 years we have to take care of them. Online private sellers don’t have the equipment and knowledge to, which is why we do why we do. Admittedly, it does lead to higher prices because of the extra work. That is the harsh reality of trying to keep cameras alive for as long as possible in a world with no new spare parts and knowledge of the craft dying out.

All cameras Camera Rescue buys and Kamerastore.com sells from Tampere (search location) are tested in the way described above so you can expect that the camera you buy is one that you will enjoy for a long time to come.


This article was originally published on 28.8.2020

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