Maximize Image Quality with Shot Discipline, Part 3: Eliminating Camera Vibration, Handheld Shooting (January 2019)
Related: digital sensor, Electronic First Curtain shutter, exposure, Fujifilm medium format, Live View, medium format, MTF and Micro Contrast, shot discipline, shutter, technique
Parts 1 and 2 of these series covered several of the key areas in making a technically optimal image. This third part discusses the sources of vibration along with mitigations for both tripod-based and handheld shooting.
Shutter and/or mirror vibration
The physical way the exposure is made has an impact on image sharpness. It can be no effect at all, or a subtle loss of micro contrast, or pronounced blur. A fractional pixel movement (a few microns!) will look sharp and motion blur will seem absent, but the image will be oddly low on micro contrast—it will seem dull and not fully sharp. Large movements create obvious motion blur but “large” as used here usually means “invisible to the naked eye” in the range of 10 microns or so.
Some medium format DSLRs have big mirrors of relatively high mass. When the mirror goes up, the camera’s world is an earthquake. At certain shutter speeds, even fairly fast ones, sharpness is quickly lost. While results will vary, the dangerous speeds are typically 1/2 second to as much as 1/125 second (or even 1/1000 second with a long telephoto on a lens foot). If the camera has an option for mirror lockup, use it along with self-timer delay and your results will dramatically improve at some shutter speeds.
Medium format mirrorless cameras such as the Hasselblad X1D and Fujifilm GFX solve the mirror-vibration issue by having no mirror. But there is still the issue of how the exposure is initiated and the type of exposure The Hasselblad X1D has a leaf shutter in each lens and I have not been able to detect any vibration effects from the leaf shutters. Focal plane shutters can damage sharpness, so it’s important to use the electronic first curtain (EFC) shutter option if there is one, since the shutter starts already open. The Fujifilm GFX has several different options for shutter; that’s the one to use: the shutter is already open when exposure starts, finishing the exposure by closing.
If the means of initiating the exposure is pressing the shutter, that is also an “earthquake” requiring a multi-second delay, e.g., self timer or exposure delay mode. That applies to tripod use of course, but it also a useful tool for slow shutter speeds when shooting handheld.
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Unstable 'rig' from lens tripod foot
The lens tripod foot on most modern telephoto lenses is almost always terrible in terms of stability, leaving me scratching my head as to how a lens can be so poorly designed—top optical performance and terrible stability. That this is so is easily seen at 100% Live View, where a puff of air will make the magnified image gyrate wildly. The core issue is the “teeter totter” effect of a small pivot point with a long lens poised above it.
Working with a teeter-totter lens tripod foot is frustrating at best, and hopeless in even mild wind. Occassionally there is a more stable 3rd-party foot that helps, such as from Really Right Stuff. If the lens can lie on top of a sandbag or similar fully-supportive platform that also helps. But it’s a knotty problem when shooting in the field—take particular care as per the suggestions in this article.
Beware of an all-electronic shutter
Using an all-electronic shutter sounds good, but the sensor scan time is usually quite slow (e.g. 1/4000 might take 1/4 second for the whole sensor), so it can result in the “jello” effect so disliked by videographers, except that the damage is more subtle for still photos, like distorted shapes—I saw this repeatedly in the field with the Fujifilm GFX-50$, before I corrected my error in using all-electronic—strange deformations. The shutter speed may indeed be 1/5400 second, but it still takes 1/4 second to scan all lines of the sensor! That is not a typo: one fourth of a second transit time with the Fujifilm GFX. See Blur and Image Deformation with Fully Electronic Shutter at diglloyd.com.
The persimmon tree image shows a case of severe image deformation (towards bottom of frame); the camera was inadvertently moved towards the end of the 1/5400 second exposure. While each group of rows of the sensor gets 1/5400 second exposure, the transit time is 1/4 second for the whole sensor so any change to the subject during that time deforms the image (camera movement and/or subject movement). I’ve seen this effect with wind flapping a slightly loose board even with very high shutter speeds.
Best practices for initiating exposure
Under casual inspection, many shooters are not likely to notice the subtle loss of micro contrast caused by fractional pixel movement (a few microns!)—motion blur will appear to be absent, but the image will be oddly dull —sharp and yet not quite sharp—lacking the snap that the lens actually delivers. Larger movements begin to create obvious motion blur.
Contacting the the camera in any way causes movement/vibration—remember that the context is microns (millionths of inch). Use a remote wireless release if available (wired releases can exert a force via the cable), otherwise self timer mode. I almost always use self timer, releasing the shutter with my finger, which works perfectly every time, so long as the delay is sufficient for the stability of the 'rig'. Two seconds of delay is sufficient with most cameras and lenses *if* the shutter release is pressed very gently. Use 3 seconds if there is a risk of less than perfect pressing of the shutter release.
Below, some designs limit the self timer to either 2 or 10 seconds, which is baffling—do the camera engineers not consider actually making pictures with the camera in the field?
The use of a shutter release cable can be sub-optimal since the cable can exert a force on the camera—plus wind can transmit vibration. I recommend eliminating any solution involving physical contact except in cases where use of the self timer is itself an unacceptable delay, e.g., when the exposure must happen at the instant the release is pressed.
- Use electronic first curtain shutter preferentially to all other shutter modes excepting extremely high shutter speeds (1/2000 and faster).
- When using the self timer, press the release gently. Ensure that at least two seconds pass, more for telephoto lenses and/or unstable situations (e.g. tripod on spongy ground).
- For cameras with a mirror (DSLR), always configure the camera so that mirror lockup is immediate, followed by the self timer delay.
- If wind is an issue, enter magnified Live View and expose only when vibration has visibly ceased (any vibration will be obvious at 100% magnification Live View). In this case, a remote release is ideal so that the exposure can be made at just the right instant.
External factors, e.g., wind
The #1 challenge for making sharp images that I run into out in the field is wind. Wind induces vibration/resonance into many tripods. The *real* reason to use a larger tripod is not because it supports more weight (irrelevant for any reasonable load using proper technique), but because larger tripods have larger-diameter tubes, and these tend to vibrate less in the wind. That said, some larger tripods vibrate more than smaller ones due to design, number of legs, etc—know your gear.
Strong wind means a very high risk of at least slightly degradation of micro contrast. Here are various practice I employ:
- Block wind from hitting the tripod directly by standing upwind of it.
- Time the exposure for a lull. In this case it might be useful to use a remote release so that the shutter can be released at just the right time, since gusts can be unpredictable and lulls can be frustratingly sporadic.
- Shoot behind a rock or vehicle so that the brunt of the wind is broken.
- Increase shutter speed by raising the ISO a stop or two. The image will be noisier but chances of blur are greatly reduced. Alternately, increase shutter speed by giving up a stop or two of depth of field.
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Handheld shooting has its own shot discipline: the manner in which the camera is held and the shutter released while exposing contribute to sharpness. Worst possible technique: holding the camera out in front to view the rear LCD—the iPhone technique. Doing it right means another shutter speed or three of shooting envelope vs the unstable iPhone technique.
Shoot handheld using what I term mass coupling. The camera should be pressed firmly against the face or forehead or eye area, thus tying the camera to the body. The result is eliminating high frequency shaking with the only motion being relatively slow low-frequency overall body motion. Sharp images can be made at surprisingly low shutter speeds. For example, with image stabilization on the new Nikon Z7, I had many tack sharp successes at 1/6 second and some at 1/3 second and I can reliably get tack sharp images at 1/25 second (35mm focal length). On medium format I can almost always get a tack sharp image at 1/15 second with a 90mm lens, though it might take me 3 or 4 frames.
It takes a conscious effort to develop the habit and it might mean hunching up a shoulder or other minor contortions to create a fully stable shooting 'body rig'. Nearly everyone I see does it poorly, having little contact between the eyepiece and the face area.
Below is an image showing the technique plus a few more points:
- Mass coupling—camera firmly against head area.
- Both hands grasp the camera.
- Also press the camera against the shoulder (large cameras make this easier).
- Pin elbow to side (when feasible).
- Take advantage of any nearby object to steady the whole body.
By adopting these best practices for actually making the exposure, your hit rate for optimally sharp images should rise. Next month I’ll wrap up with how to make the best possible exposure, which is often not what the camera auto-exposure suggests.
Lloyd’s photography blog is found at diglloyd.com; it covers many brands, lenses, cameras including diglloyd Medium Format. To get the most out of any format requires perfect execution; see diglloyd Making Sharp Images. By subscription. Other areas Lloyd covers are cycling at WindInMyFace.com and computers at MacPerformanceGuide.com.