Mirrors slapping around cause vibrations, and vibrations make for less sharp images. Less sharp images make for less of a good photograph. I do like to see creatively blurry shots, but soft is something entirely else. Rangefinders do not use a mirror, and can be shot at very low shutter speeds hand held while maintaining good sharpness. It’s one of the advantages rangefinder and mirrorless cameras have over their SLR younger brothers. Another advantage is since there is no mirror, the rear element of the lens can mount close to the film/sensor plane making retrofocus lens design not needed. This allows for better edge to edge sharpness. Seems like it all comes down to sharpness, but actually it allows for great versatility in shooting in the neighborhood of low shutter speeds (below 1/10 of a second and the vaunted 1/4 of a second ) where you can catch moving subjects and sharp static elements.
There are a few tricks you can do to increase stability, but first lets talk about what shutter speed you have to start paying attention. There are image stabilizers in many lenses and camera bodies nowadays. Olympus, Sony and Pentax integrate them into their digital bodies, while Canon’s IS (image stabilization) and Nikon’s VR (vibration reduction) are built into the lens. The rules with an SLR is that you need your shutter speed to be what your focal length is. Thus a 210 mm lens needs a 200th of a second shutter speed. A stabilizer lets you cheat that by 3 stops, thus 200th to 125th to 60th (hello 50mm lens) to a 30th of a second. Pretty darn good when shooting with a Telephoto lenses that can really benefit from stabilizer tech. Most people can hand hold a 3oth of second as a matter of fact, It’s pretty safe to hand held at 1/15 of second with an SLR. Lower than that, the mirror can cause vibrations as stated earlier. 1/8, 1/4, even half a second are very difficult are difficult or impossible to capture an image sharply.
Being able to shoot at low shutter speeds hand held can be an art all to itself. You really do have to achieve a stillness akin to zen. Inhale slowly, have the camera strap wrapped about you so that the camera is taunt, slowly release the shutter with out jerking the camera, hold your breath, utter a word to the diety of your choice, and make the expososure.
You may have had 2 tall lattes and are now quite jittery or perhaps just really excited about what your photographing (yea, I have been on a few Suspect shoots back in the 90’s where I was shaking like a hound dog passing peach pits during the studio session). In this case, bump the ISO up two stops to be sure. The Fuji X Pro 1 is exceptional at high ISO shooting. If all that fails, then find a hood of car, mailbox, pole, or something suitable to prop the camera on just to give you a steady edge. The best of the best can handhold a rangefinder for 2 seconds and still achieve super sharpness. Me, I’m good for a second. But then again, it depends on how many espresso’s I had at dinner.
Shoot well, shoot sharp, and shoot stable fellow Suspects,