Infinity focus for pelagic?

I am wondering what you folks use for focus setting when shooting either pelagic or WA reef shots? I have tried both infinity and an actual focus distance with mixed results. If my camera was a little more accurate with the focus dial I think I could do a better job of setting a focus distance, but sometimes I spend so much time trying to get the focus 'just right' that my opportunity slips (swims) by.

Any tips/tricks out there?

Ryan

Hey Ryan

I find it pretty easy with my Amphibico to dial in a good manual focus as it has a "focus lock" button that will take it from auto to manual and lock it on what you are focusing on. Your LM should do the same.

You can then dial in the exact distance/focus you want.

Most of the time the magic 0.3m works a charm on stuff that is 5 feet or 20 feet away. IN crappy viz conditions i usually just set it on 0.3 right away as soon as i get in and leave it there for the remainder of the dive.

However, if you are going to macro or zooming then you will need to change the focus.

Assuming you are using a lens inside a dome port, your problem is that behind a dome, the lens focuses on a virtual image on the dome, not the actual subject.

There is a thead here about calculating the actual focus distance vs the distance the lens thinks it's focusing at .

http://wetpixel.com/forums/index.php?showt...p;hl=hyperfocal

Berkely White at Backscatter suggests auto focus on one of your fins and lock focus. Sounds like a good idea to me.

.3 Meters for L&M too. Turn to a diver that approximates the expected distance to your pelagic subject. Do one touch focus lock and the diver and leave it there.

Focus locked off on full wide here and if the fstop is up around 9.6 to 11 I will have focus from about the dome to infinity. If the fstop drops and the subject is moving in and out close to the port I will set focus to auto.

What Wagsy said is the way I do it. If you are shooting ambient, this technique is really beneficial because you tend to lose contrast due to color drop off....ROYGBIV, remember from scuba 101? Auto focus will typically hunt because there is no dicernable contrast to lock on, so the fin trick is generally recommended.

At smaller f-stops, a wide angle lens will generally give you sharp focus from 2-3 feet to infinity. That's what we used to do in film days with our Nikonos 15mm lenses. It's called hyperfocal distance. Focusing on a fin and locking it works for me in video.

I ballsed up a few shots by having my Bluefin locked on 0.3m when the action came in close or if I forgot to re-adjust for a close shot. I've gone back to auto focus and just press momentary auto focus if I'm videoing a pelagic in the blue and the water's a bit mucky. My Z1 hardly ever hunts but with auto you have to keep all surfaces of your lenses absolutely spotless.