Well, Part 2 generated some very lively discussion (which is a great thing).
This is the third and final installment in preparation to the February NFMAS meeting...
Shutter Speed controls the amount of time that light reaches the film or image sensor. A faster (shorter) shutter speed allows light to reach the film or sensor for less time. A slower (longer) shutter speed allows light to reach the film or sensor for more time. This is about as basic an explanation as there is. Outside of shooting marine aquaria, shutter speed can and is used to achieve very dramatic results. We have all seen the images; running water caught frozen in time (fast exposure); the mystical mist like appearance of that same water flow caught with a slow exposure. The creative possibilities are seemingly endless!
F4 - 1/60 - ISO 400 - 100mm
In marine aquaria we typically are trying to freeze time, especially in the endeavor of photographing our fish. Coral photography is a completely other discussion due to it being relatively stationary. We will touch on that in a bit. I don't know about you, but my fish do not typically pose for a snapshot. It would be oh so easy if the fish would simply sit still.
Capturing most fish with a camera requires a faster shutter speed (relatively speaking) to allow us to freeze time and space. Of course there are always those fish such as a Midas Blenny or Hawk fish which simply love to perch themselves on their favorite spot and sit perfectly still. These guys are mainly the exception. More often we are trying to photograph our Sailfin Tang, Royal Gramma, Gold Stripe Maroon Clown, etc. They rarely sit still. There is not a straight answer on the "correct" shutter speed to photograph a fish in motion. The faster the fish is moving, the faster your shutter speed will need to be in order to mitigate against motion blur. Hand in hand, the faster the shutter speed used may necessitate a wider aperture. From the previous presentation on ISO and Aperture, keep in mind that the all of these variables come together to help create a great image.
Hand-holding vs. using a Tripod
Hand-holding
When hand-holding for something like a still piece of coral or a fish, you will want to use a shutter speed that is at least as fast as your focal length (i.e. If you are using a 100 mm Macro lens, you would want to shoot with a shutter speed of at least 1/100 of a second). Can you shoot with a slower shutter speed and achieve great results? Certainly! A couple of tips you can try while hand-holding are:
1. Try bracing yourself against a wall or very stable object. This can help reduce camera movement while using a slower shutter speed.
2. As you line up the shot, hold your breath for a moment while you take the shot. This can help you to be as still as possible. This would definitely not be recommended for a 30 second exposure.
3. Got cash to burn? Buy a lens with built in image stabilization. Keep in mind that even an IS lens will not correct really bad camera shake. Even with the best equipment, it helps to have a steady hand.
F8 - 1/20 - ISO 100 - 100mm
Tripod
This is the by far best and in some opinions the only way to take longer exposures. To take the tripod approach a step further I would recommend using your camera's timer setting or to use a remote shutter release. This way you can eliminate the potential for camera shake caused by pressing the shutter release located on the camera body. For coral shots this is a best practice. A slower shutter speed combined with a wide depth of field will allow for a correctly exposed image unless of course you are trying to isolate your photographic subject.
F5.6 - 1/125 - ISO 100 - 100mm
F2.8 - 1/60 - ISO 100 - 100mm
F5.6 - 1/10 - ISO 100 - 100mm
F4 - 1/60 - ISO 100 - 100mm
F32 - 1/200 - ISO 100 - 100mm
F9.5 - 1/125 - ISO 100 - 100mm
