Article and photos by Denni Raubenheimer
***Click on images for high res versions
All experienced photographers with long
lenses can attest to the challenges that low light brings to achieving sharp
images. One of the fundamental things that I teach beginner clients with
regards to shutter speed is how to know if your shutter speed is quick enough
to avoid camera shake when shooting hand-held. The guide line is simple: keep
your shutter speed faster than your focal length, or at least equal to it, when
shooting hand-held. If your camera has a cropped sensor then I advocate using
your effective focal length as the minimum. However, this isn’t always feasible in low light. This is where
Mirror-Up shutter release mode, or a delayed shutter, becomes useful.
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| Leopard at sunset. Focal length 420mm without VR at 1/400s using a bean bag with Mirror-Up. Click on image for high res version. | |
Professional Nikon D-SLRs have a shutter
release mode called Mirror-Up (M-Up). This mode is the same as activating
Mirror Lock-Up with a Canon, or other D-SLR, but it is readily accessible. It
is also effectively the same as setting a delay of at least one second between
your camera’s mirror-lift and the actuation of the shutter.
Mirror-Up isn’t always the go-to in low
light situations, one will usually compensate for low light with large
apertures, high ISOs, physical stabilization (e.g. a bean bag) and, or
vibration reduction (i.e. image stabilization). However, for relatively
stationary subjects and especially when you want to avoid excessive ISOs and
don’t have very good image stabilization (or none at all) Mirror-Up can help
you produce sharp images at shutter speeds well below those you would usually
require.
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| Reflections and ripples in water at sunset. Focal length 420mm without VR and on a beanbag at 1/320s with Mirror-Up. |
In Mirror-Up one needs to press the shutter
button twice to take a photo. The first press lifts the camera’s mirror, the
second one releases the shutter. If one waits a second or two after the mirror
lifts, before pressing the shutter button a second time the vibrations caused
by the mirror lifting will have largely faded and will not reduce image
sharpness. The effect of these vibrations are negligible at high shutter
speeds, but at low shutter speeds they will reduce image sharpness. Obviously,
their effect become redundant if the camera is not kept physically stable –
then blurring caused by the “macro” movements of the camera will far outweigh
blurring caused by the internal vibrations produced by mirror-lift. Furthermore,
different D-SLR camera models’ mirrors produce different amounts of vibration as
their sizes, weights and rotational velocities differ. Nevertheless, at shutter
speeds that are low relative to focal length when one’s camera is kept
relatively static, avoiding the vibrations generated by mirror-lift will always
improve image sharpness.
The Nikon D800 has a 36MP full-frame sensor
that can show very high levels of detail and thus easily betrays a lack of
sharpness. It’s mirror-lift (or rather -slap) causes significant vibrations and
when using good quality lenses vibrations coming from the mirror can
significantly impact image sharpness at slow shutter speeds. With the D800 I
most often shoot wildlife at 420 mm (300mm f/4 with 1.4 TC) with a Nikkor lens
that does not have VR (i.e. IS). Due to the high resolution that the
combination of the lens and sensor give, the photos quickly betray lacking
sharpness. Personally, I find that for consistently pin-sharp images (when not
panning) with this combo hand-held I need to go faster than 1/800s (i.e.
1/1000s, or faster). In low-light I have found that if I have to shoot
hand-held at 420mm I can use 1/400s when I use Mirror-Up and get consistently
acceptable sharpness, and noticeable sharper images than when not using
Mirror-Up. I would then estimate one stop improved stability for hand-held
without VR (i.e. IS) at telephoto focal lengths.
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| Burchell's zebra at sunset. Focal length 420mm without VR and hand held at 1/320s with Mirror-Up. |
Where the release mode really shines is
when I use it on a beanbag. When shooting wildlife from a vehicle and to a
lesser extent on foot I am very fond of bean bags. The are not as stable as
tripods, but give lots of maneuverability with lenses that are not excessive in
weight. With the non-VR 300mm f/4 + 1.4 TC and on a steady beanbag I can quite
comfortably shoot at 1/250s and expect sharp images (without a cable release),
whereas I would not try and avoid going below 1/400s in these conditions in
regular release modes (remember the D800 easily betrays lacking sharpness and
has significant “mirror-slap”). When I need to, I can go even slower on a bean
bag with Mirror-Up. The below image of the Giraffe was taken at 420mm and 1/100s
on a not-so steady bean bag.
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| Giraffe at sunset. Focal length 420mm without VR and using bean bag at 1/100s with Mirror-Up. |
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100% crop of above image.
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I once was forced to capture bioluminescent
waves under a starry sky on a beanbag (I cannot remember if it was with, or
without a cable release). I only had a brief few moments to grab equipment
before my “body guards” left for the beach and had decided not to add a tripod
to our flight luggage. Furthermore, my “guards” quickly became impatient on the
beach, so I just went for Mirror-Up and tried keeping the camera as static a
possible on the beanbag (mounted on a laundry basket!). In the end I used 1s
exposures at ISO-12800. Amazingly, a portion of the images were acceptably
sharp!
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| Bioluminescent ocean waves under starry sky. Focal length 24mm on bean bag at 1s shutter speed with Mirror-Up. |
The draw-back for using Mirror-Up on live
subjects and when shooting without a tripod is that after lifting the mirror
you shoot blind, i.e. your view-finder is completely black. Also, you obviously
lose continuous release. However, in situations where my subject does not
require continuous release and the light demands slower shutter speeds than the
value of my focal length Mirror-Up is often part of the solution – and
sometimes invaluable.
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| Burchell's zebra portrait. Focal length 420mm without VR and on a bean bag at 1/320s with Mirror-Up. |
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| 100% crop of above image. |
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| Black-headed Oriole. Focal length 420mm without VR and on make-shift beanbag at 1/250s with Mirror-Up. |
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| 100% crop of above image. |
