underwater macro

The Whys of Back-Button Focus and Focus Lock

Posted on by in underwatermacro and tagged , , , , , , .

Back-button focus is a technique where you change the focus button to on of the programmable function buttons (F1, F2, F3, etc) on the camera so that it makes the camera focus instead of the usual half-press on the shutter button.  This will let you lock the focus at the same distance from the end of the lens until you use the function button to refocus.

You then:

  • Choose a subject.
  • Push the focus button to get a focus lock.
  • Move the camera back and forth until the subject is focused the way you want it.
  • Push the shutter button for an instant picture.
  • Keep taking pictures with the same focus.

“That sounds complicated just to take a picture.  Why would you do this?”

For starters, autofocus is slow.  You half-press on the shutter button, the camera picks a piece of the picture, moves the lens in and out until the blur disappears or is the smallest that it will get, then signals that it has focus.  You then push the shutter button the rest of the way.  If you lock the focus, then for the cost of a little bit of time setting up the shot, you can take all of your pictures after that very quickly.

You get more control.  You can think of focal plane as a sheet of glass perpendicular to the lens and at a fixed distance away from the end of the lens.  As long as something is inside that sheet of glass, it’s in focus.  Now you can do like I did with the skeleton shrimp below and put eyes and “hands” in focus by angling the camera so that the those pieces of the picture are inside the focal plane.

You can focus on something that’s not the subject and then reframe.  I do this a lot with subjects that are hard to focus on.  Moving things.  Things inside holes.  Things not in the center.  Point your camera at something the same distance away from the camera lens as the subject and then focus lock on it.  You can then move your camera back to the subject and move it towards and away from the subject to get it in focus.

Macro photography is almost impossible without focus lock.  You have too many variables to consider to make a shot.  Simplify your shooting by reducing the effort of using autofocus by locking your focus.

Shooting in low-light situations is hard, even if you’re using strobes.  You can’t always use a focus light.  Crabs and shrimps look the other way when you shine white light in their eyes.  Nudibranchs feel the heat and change direction.  When you turn off the focus light, you’ll see the camera “hunt” when you try to focus: the lens moves in and out trying to find the right focus but because it’s too dark it can’t see the difference in focus distances.  So turn on the focus light, focus on the sand or coral, turn the focus light off, reframe on the subject, and keep shooting.

Most compact cameras don’t have a moveable focus point.  On most DSLRs and mirrorless, you can use the direction arrows or joystick to move the focus point around inside of the frame.  With compact cameras, you can get focus in the center of the frame, lock the focus, then reframe the subject.

“Wow, Mike, that sounds like an awesome idea that I’m really sold on, how do you set it up?”

It depends on the camera, they all do it differently across brands.  For a howto specific to your camera, try google for “<model> back button focus”.  I’ll post later on how to do this for the Olympus OMD mirrorless.

On compact cameras, programmable buttons are fairly rare.  However, they sometimes have a “focus lock” feature where you can focus on an object and then lock the focus point.  I’ll post later on how to do this for the Olympus TG4 and TG5.

Sample times when I’ve used back-button focus:

  • Fast Little Blue Fish.  They move in and around the coral too fast for you to get a good focus.  So lock your focus and take a picture when they appear in the gap between coral.  I talked about this in Little Fast Blue Fish.
  • Skeleton Shrimp.  They live usually on hydroids: cousins to coral that look like little white-brown shrubberies.  These hydroids sway gently in the current.  Back and forth, back and forth.  Too fast for your auto focus.  Next time they swing by, focus on them and lock your focus then snap each time they swing by after that.
  • “Fast-Moving” Nudibranchs.  Focus on a spot in front of their direction of movement where they crest a micro-hill and lock your focus.  When they move up on top of the terrain, get a picture when they’re more silhouetted. I describe this in this post about Bornella.
  • Critters in Tunicates. You’re taking a picture where the subject is inside a tube.  The autofocus on the camera sometimes will lock on the top of the tube.  Lock focus then move the camera forward to move the focus into the middle of the tube.
  • Hairy Shrimp and Other Teeny-Tiny Things.  When using supermacro gear and taking pictures of things smaller than 3mm across, your focal plane is extremely small.  Use focus lock to lock your focus then move the camera slightly to give you the focus that you want.

 

 

See you underwater!!

–Mike

Why You Should Take Macro Pictures Underwater (Or at Least Try..)

Posted on by in philosophy, underwatermacro and tagged , , , , .

There are many reasons why you might want to try underwater macro photography while you dive. I personally got started when my wife and I attended a macro workshop with Irwin Ang and Jane Mong Lee Kian in Tulamben, Bali. We didn’t really know much other than basic photography techniques. As far as macro, we only knew that it was a type of underwater photography and we are always ready for another diving trip to Tulamben.

  1. It’s fun. Almost addictive. It’s like a miniature treasure hunt each and every time. In my usual dive site, there is almost a flavor-of-the-week feel to it. Some days it’s nudibranchs. Other days, skeleton shrimp, or even seahorses.
  2. You’ll amaze your friends. I’ve seen it time and time again: when I show friends my underwater macro photos, they don’t believe that they were taken on the same planet that we live on.  Good pictures look like they come from the mind of Dr Seuss.
  3. You can do it anywhere. Where I live now in Singapore, they call the water “milo peng”–iced chocolate drink–because the visibility on a good day is 3 meters. On a bad day, it’s 0.5 meters–1.5 feet. But when you are on a dive taking macro pictures, all you need is 20cm of visibility. You would be surprised how many sandy, silty, shallow “muck dive” sites that exist.  These sites have no interest for normal divers but for macro shooters, they are paradise.
  4. It can save a trip. Even in some of the best diving locations, the weather is beyond your control. Wind and waves can stir up sand and silt to reduce visibility and make the surface unsafe for boat activity. Current and tides can push divers out past the dive site or turn the dive into a drift dive. But no problem, just look for a shallow, flat dive site in a sheltered bay and try your skills at macro.
  5. You get better diving skills. Macro diving requires breath control, fin movement, and buoyancy skills on a microscopic level. Move too much and you can’t find your subject again. I’ve personally seen my air consumption slowly get better as I get more relaxed and efficient underwater.
  6. You find more wildlife. I’ve taken friends on macro dives, and when we go slow and deliberate and “check all the shrubberies”, we see 10x the normal amount of sea life. Part of that is the new small things we find, but the big sea life also is less afraid of you when you don’t charge right at it and stick an action camera and video light in its face.
  7. You learn more. You start to learn about ecology and habitat. You find where the animals live and what their behavior is. You learn more about photography, waterproofing, and lighting. You learn more about yourself, your skills, and how to stalk underwater subjects.
  8. It’s as uncomplicated (or complicated) as you want it to be. I’ve seen photographers with a handheld torch and an Olympus TG-4 that can take better pictures than other photographers with expensive setups. With macro modes on compact cameras, macro doesn’t require a huge investment in equipment.
  9. It makes you a better photographer. Underwater macro is sometimes demanding on your lighting and camera use. You’re using a paper-thin plane of focus and being pushed side-to-side by the surge. You have to find a stable position and not crush the coral. You’re breathing through a hose underwater. This stress-test of your skills translates into better photography skills on land and subjects like flowers that suddenly seem easier to photograph than before.
  10. Guaranteed whale shark sighting! Or mola mola. Or manta. Or something big that you can’t capture an image of with a macro rig.  Even in a group of divers, somebody has to take a “sacrificial” macro setup to make sure that you’ll see big animals.

See you underwater!

–Mike