Autofocus problems

[Brewski]

I took my new D300 out diving last weekend. I was having a great time at first, then after 30 minutes or so I noticed the 60mm Macro lens having problems locking focus.
It would focus as near as possible then not respond to the shutter button to refocus.
This also happened the next day almost immediately when I tried to focus onto a metridium. Some have suggested that I need to add a focus light. Has anyone else experienced this happening?

I did discover that when this happens I can coax it out of this mode by moving very close to something and focusing on it then move backward and work myself back to a normal distance.

 

[jcclink]

Might be lack of focus light, but I've shot the D300 w/60mm in fairly dim light w/o focus light. If its the old 60 with AF/M ring on lens, make sure that's it locked in AF. One time I accidently rotated this ring a couple of mm while attaching the lens & had focus problems similar to what you suggest. Just a guess.

 

[Brewski]

This is the new 60. It has a switch on the left side for
Af/m.

 

[MarineResearch]

Check your focus settings. I think you might want to use Focus Mode Continuous-servo AF, and possibly change your AF-Area Mode to Single-point AF, or Dynamic Area AF as long as you are careful regarding your Custom Settings a3 configuration (see manual pages 61-71; 269). As mentioned, a focus light might help as the problems I have had were all related to low light and/or poor visibility.

 

[danclem]

Actually, I think you want to use single focus mode. If you choose continuous when there is ditritus or other material in the water (very common in Seattle), the lens has a lot of trouble focusing.

Another tip is to be sure you use a single spot focus in the middle of the screen (mentioned above). Nikon has a wide variety of focus options, and if you select too wide an area material in the water will keep you from being able to focus.

I have a super focus light, and rarely need to use it, even in dark Puget Sound waters.

Have Fun Shooting!

Dan

 

[Chuck Tribolet]

Focus light for sure. I use Ikelite Mini-C lights. Cheap (about $25 as LeisurePro) and Ultralight has
HW to mount them (since your are a Monterey diver, see Backscatter for the HW).

Start with single point AF just eliminate a variable. Be sure to move the focus point around
to the eye of the critter (or whatever). The camera setup mantra is:

- Visualize
- Strobe angle
- Focus point
- Aperture
- Shutter speed

I use continuous AF as it refocuses as the surge moves me around.

When things start screwing up, try focusing on a nice contrasty area. That will separate out the
two source of the problem (camera not telling lens to focus, AF not locking on).

Also, when it's screwing up try using the focus botton on the back of the camera. I use a
D300 on the surface, and I've set it up (via the menus) so it doesn't focus on the shutter button
at all, just the back focus button. This is really handy for wildlife photography, but does have
long finger retraining curve.

 

[Nocturnal Lights]

A majority of the time the camera simply cannot focus since there's simply not enough light for the censors to pick up where the subject is.

We have the SLX 800i focus light/video light. It's got a 90 degree wide beam and a light that's powerful enough to get a wide area of coverage w/o any signs of hot spots. If you're interested let us know what kind of setup you have and we can direct you to the right setup/accessories that will work with your housing.

Nocturnal Lights Underwater Focus Video Lights

 

[danclem]

Hi:

With all due respect, I have not found focus lights to be the issue with my Nikon DSLR's. For a focus light I use a Hartenberger nano compact, which I love, and two Ikelite 125's with modeling lights for strobes, and have had focus issues when there is backscatter in the water. The solution for me has been to narrow the focus to center, and make sure to be on single, rather than continuous focus.

With respect to continuous focus, we did a test in one of Stephen Frink's sessions two years ago (Key Largo), and it worked fine in really clear water, but caused focus issues when there was material in the water and we were shooting up close. If you are shooting wide angle, probably not an issue. It is a pretty significant issue when shooting macro or "portraits" in places like Puget Sound, Northern California, or BC. Lots of nutrients in the water.

Hope you find a solution that works for you!

Dan

 

[Mariozi]

What housing/port are you using?

 

[Chuck Tribolet]

With respect to continuous focus, we did a test in one of Stephen Frink's sessions two years ago (Key Largo), and it worked fine in really clear water, but caused focus issues when there was material in the water and we were shooting up close. If you are shooting wide angle, probably not an issue. It is a pretty significant issue when shooting macro or "portraits" in places like Puget Sound, Northern California, or BC. Lots of nutrients in the water.

I shoot continuous autofocus for macro in Northern California
about 130 dives a year. It works just fine.