MICRO 4/3 SHUTTER SHOCK REVISITED
OMD-EM-5 with Olympus 12-50 mm and Olympus 75-300 mm lenses
Author AndrewS
Introduction In May this year I published on this Blog an article titled "Micro Four Thirds Shutter Shake Syndrome S.S.S." This described the problem with several Panasonic and Olympus lenses on a Panasonic GH2 camera. I subsequently bought and have been testing an Olympus OMD-EM5 camera with Olympus M Zuiko 12-50 mm and Olympus M Zuiko 75-300 mm lenses. I have also had time to consider the issue, which I now prefer to call "Shutter Shock" in more detail. The problem is not specific to the Micro Four Thirds sysyem but can or might be found in any mirrorless interchangeable lens camera if certain conditions are met.
The SLR and mirror slap Single Lens Reflex (SLR) and Digital SLR cameras have a mirror which, when the operator is using the eye level viewfinder, flips up just before each exposure. So the exposure sequence is Press shutter release button >Mirror flips up >Focal plane shutter opens > Sensor is exposed > Shutter closes >Mirror drops down. The flipping up mirror sends a shock wave through the camera which can and does cause blurred pictures. My tests recently with a Canon EOS 60D camera showed that exposures using shutter speeds around 1/4 - 1/8 second are the most affected by mirror slap. These shutter speeds are rarely used in hand held photography but they are often used with the camera on a tripod. The fix for mirror slap is Mirror Lockup. The fact that mirror lockup does fix the problem tells us that the disturbance caused by the shutter opening is generally not sufficient to cause blurred results in (D)SLR cameras.
Mirrorless Interchangeable Lens Cameras and Shutter Shock MILC's have no mirror therefore no mirror slap. Unfortunately they have a potentially more troublesome problem which I call Shutter Shock. In the case of a DSLR the focal plane shutter is closed at the start of an exposure sequence. But the shutter of an ILC is open until an exposure is made. The exposure sequence for most ILC's is Press shutter release button > Shutter closes >Shutter opens >Sensor is exposed >Shutter closes > Shutter opens. The first shutter close action, prior to the sensor being exposed, sends a shock wave through the camera and lens which can cause blurred pictures sometimes with double imaging. My tests and many user reports have identified a shutter speed range from 1/20 - 1/200 second as being affected. These shutter speeds are commonly used in hand held photography which is the reason shutter shock is potentially more troublesome than mirror slap. The actual risk of shutter shock and the exact shutter speed range affected vary considerably with camera and lens makes and models. By the way, the second shutter close/open sequence also sends a shockwave through the camera but of course, this happens after the exposure has been made. The actual amount of disturbance produced by an ILC shutter is less than that of a DSLR mirror. I tried to demonstrate the shock produced in a Panasonic GH2 by sticking a thimble containing water onto the hotshoe then firing the shutter. This produced no perturbation in the water at all. But I know this camera (and others) can cause shutter shock with some lenses at some focal lengths and shutter speeds. Why ?
Fast and loose, Image Stabilisers A key feature of modern cameras is the incorporation of image stabilisers. There are two kinds. Optical Image Stabilisers (OIS), if fitted, are located in the lens and involve compensatory movements of one lens group. In Body Image Stabilisers (IBIS) require compensatory movements of the whole imaging sensor unit. Both types require that the active module, when powered up , is located by electro magnetic forces and not held in place by physical constraints. This technology allows the IS module to respond rapidly to camera movements in the service of reducing the effects of camera shake. But the flip sided is that the IS units are loose and, like AF units are susceptible to being shaken by the action of a focal plane shutter.
Shake and Rattle You can easily confirm if your camera gear contains loose elements by shaking it. When powered off, most of the ILC gear I have used will rattle when shaken. Powering on will stop the rattle. Some lenses, such as Panasonic models with OIS, rattle when shaken side to side. Presumably this is is due to the IS unit which can move side to side but not front to back. Some lenses, including the Olympus Zuiko M 12-50 mm, rattle when shaken front to back. This, presumably is due to unconstrained movement in the AF module. The Olympus EM5 body rattles when shaken side to side (IBIS unit) but not when shaken front to back. The Olympus Zuiko M 40-150 mm lens does not rattle at all but does exhibit blurring from shutter shock at shutter speeds from 1/80 - 1/200 sec when mounted on the Panasonic GH2.
Shutter Shock with Olympus EM5 I tested this camera with two lenses, the Olympus M 75-300 mm and Olympus M 12-50 mm.
Olympus M 75-300 mm I mounted the camera/lens unit on a tripod, set the focal length to 300 mm and made a sequence of exposures from 1/8 sec to 1/400 sec. Settings were IBIS off, Timer delay at 2 seconds. There was clearly apparent blur with double imaging from 1/100 - 1/200 sec. Unfortunately I did not test the effect of Olympus Antishock (A/S) with this combination before selling the lens. The implication from these results is that with A/S off, hand held shutter speeds with this combination should be faster than 1/320 sec and on tripod shutter speeds should be slower than about 1/50 sec or faster than 1/320 sec.
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| Photo 1, 12-50 mm lens Antishock off |
Olympus M 12-50 mm With this lens on the EM5 and set to focal length 50 mm, I made four test runs: ( 1) Hand Held, IS1, Antishock off ( 2) Tripod mounted, IS off, Antishock off (3) Hand Held, IS 1, Antishock on [1/8 sec] ( 4) Tripod mounted, IS off, Antishock on [1/8 sec]. Shutter speeds ranged from 1/10 - 1/400 sec. In the first run there was clear evidence of blurring from 1/40 - 1/125 sec with double imaging at 1/80 and 1/100 sec. The second run, on tripod, with IS and A/S both off, produced good but not quite excellent results across the whole shutter speeed range. The most interesting set of results came from the third run, hand held with IS and A/S both on. This run produced good results right from 1/10 sec with no evidence of Shutter Shock and remarkably, no evidence of camera shake either, indicating that the EM5 IBIS is very effective at low shutter speeds. More surprising was that from 1/60 sec and faster, Run 3 results (hand held A/S on) were slightly sharper than the results from Run 2 (tripod A/S off). I should make it clear that I was pixel peeping test chart photos at 200%, thereby discovering small differences in sharpness which would probably not be noticed in general photography. Predictably, all the frames in Run 4 were sharp.
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| Photo 2, 12-50 mm lens Antishock on |
The interesting conclusion which I reached is that for all practical purposes and to avoid having to remember which shutter speeds do and which do not produce Shutter Shock, the best course of action is probably to set Antishock [1/8 sec] permanently with this body / lens combination. Antishock delivers obvious improvement with hand held use and shutter speeds in the 1/40 - 1/125 sec range. It also provides a small but useful improvement with tripod mounted use. Of course you also get the unwanted side effect that every shot has a built in 1/8 second shutter lag which does take some gloss off this camera's otherwise excellent performance.
Just for comparison I ran the same test sequence with the Panasonic 14-45 mm lens on Panasonic GH2 camera. Antishock is not available on this camera. I found no convincing evidence of Shutter Shock at all, handheld or tripod mounted, OIS on or off. The most I could say is that at 1/100 sec and 1/125 sec both handheld and tripod mounted there was a slight hint of unsharpness detectable only with obsessive pixel peeping at 200%.
How can Shutter Shock be prevented ?
Individual strategies
1. Know thy enemy. Run tests like the ones described above with your present equipment. Discover what if any combinations of camera body / lens produce Shutter Shock. You don't need a fancy test chart for the photographs, a newspaper page with large, small and fine print pinned to a board will do just fine.
2. Avoid the affected shutter speeds. For handheld use choose faster speeds. On the tripod, select either faster or slower speeds depending on the conditions.
3. Use Antishock if you happen to own an Olympus camera with this feature and don't mind the shutter lag.
4. Use e-shutter on the Panasonic G5 (No flash, static subjects preferred).
5. Avoid buying or test carefully on your camera body before keeping lenses reported on user forums to have shutter shock issues. These include the Panasonic PZ 14-42 mm and Panasonic PZ 45-175 mm.
Technology discussion It seems to me that camera designers have or might develop the following strategies to deal with the Shutter Shock problem.
1) Using a mechanical shutter If the camera has a standard ILC four action (close/open/close/open) focal plane shutter then Antishock appears to work quite well. The way Olympus Antishock works is as follows: Press shutter release button >Shutter closes >[Delay period occurs] > Shutter opens > Exposure occurs >Shutter Closes >Shutter opens.
The delay period allows vibrations caused by the first shutter closure to dissipate. Apparently the subsequent shutter opening does not produce sufficient disturbance to blur the photos. I found with the EM5 that the minimum available Antishock [1/8 sec] works just fine. I assume longer delay periods would also work but have not tested them. If you have an EM5 camera you can easily see anti shock working by firing the shutter without a lens attached.
Notes for Olympus EM5 users: To set Antishock, go to the Custom [gears] Menu E [Exp/ISO] > Scroll down to the last item > Antishock >Select a time > Press OK to confirm > exit Menus. This takes 26 button presses. Now press OK to bring up the Super Control Panel (SCP) > Find the Drive Mode sub panel. The standard panel has options for single, continuous, timer etc. Once Antishock is set the options are all duplicated so there is one set with, the other set without, a little diamond shape to the left of the drive mode icon. The little diamond shape indicates Antishock is active. This is how you switch Antishock on and off. Leave it set to "on" permanently in Custom Menu E.
Note about Mysets Make sure you have all settings including Antishock exactly as you want them before registering a Myset.
2) Using a hybrid mechanical/electronic shutter a.k.a. Electronic First Shutter Some cameras have this technology. With the shutter open, exposure is commenced electronically then terminated mechanically with the physical shutter. The Canon EOS 60D uses this shutter type in Live View Mode. My tests show it is effective in preventing Shutter Shock, at least on that camera. Other cameras also use this technology but I have not tested them.
3) Fully electronic capture systems with no mechanical shutter I am aware of two types of electronic shutter systems, progressive and global.
Progressive a.k.a. rolling The Panasonic G5 camera (which I have not personally tested) has the option of using a progressive system. If I understand it correctly the mechanical shutter is held open and data is read out from the sensor as you would read the page of a book, line by line. This should eliminate Shutter Shock and early reports from G5 users indicate that is the case. But progressive sensor readout is very much an interim technology. It cannot be used with electronic flash because the flash duration is less than the time it takes the system to scan the sensor. It is also unsuitable when there is movement of the camera relative to the subject. This situation causes bending or other distortion of straight lines or other recognisable shapes in the subject.
The "Global Shutter" This is the holy grail of electronic shutters. All the pixels on the sensor are read out simultaneously. It is silent, eliminates Shutter Shock, works with electronic flash and does not distort subject shapes with movement. I don't know of any actual camera which has this technology yet and even the soon to arrive Panasonic GH3 is rumored not to have it.
The Global Shutter appears to be the ultimate solution to the problem of Shutter Shock and it can't come too soon for me.
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