D70 Autofocus

Hello,

I have just graduated to a new D70s and a Sea&Sea housing. I have an 8" dome and a nikon 17-35 f2.8. I am in AF-S and "single area" focus.

I just put everything together today and took it into the pool for testing. I am very excited about the quality of the pictures it takes but I have some concerns about the autofocus. With the Sea&Sea DX-D70 housing and the 17-35, the zoom gear overrides the manual focus ring - instead of focus it controls zoom.

In the pool I had a huge amount of "searching" with the AF - frequently it would simply refuse to take shots and it made me really frustrated as I missed shot after shot. Additionally I am unable to switch to manual focus to override due to the zoom ring. Finally, underwater with the smallviewfinder its hard to see what's going on and I can't see the little red flash that says its locked nor can I hear the beep.

So, I am totally excited but looking for some input. On land it seems to lock on quickly with no problem. In the pool it seemed very sensitive to lower light.

Is this issue something normal that I should work around, or does something sound wrong with my setup?

Thanks for the help!

Yep, that annoyed me at first as well. What i did was switch to AF-C. A lot of the time in AFS i would see that what i wanted was in focus but it wouldn't shoot!!! highly frustrating.

With AFC you can always shoot, it doesn't lock down like the AFS. Now i always use AFC underwater.

GIve that a shot

Sweet! Thanks for the idea...so in AFC it will attempt to lock on but still take the picture even if it doesn't? Does that mean I should expect more out of focus pictures?

I will try it right away...

Yea, you get a few more out of focus pics but i find my eye is usually pretty good at figuring it out. You shouldn't have too much of a problem, its really easy on macro and stuff. Sometimes a bit tougher in WA if what you are shooting is somewhat far away or if water is murky....but still better than AFS

Alrighty - I'm on it. Thanks for the expert advice!

Happy New Year!

HI

You might just find that this lens is bang on the limit and will be hit and miss unless you use a Dioptre.

its MFD is 28cm and that will be at its widest end i guess. so once you move away from 17mm this distance will increase , thus the lens will not focus..

you could try adding a +2 to it and see if that solves the problems.

Even though sea & sea don't list using a +2 ,you are having issues, so its worth a try.

Other UW systems might work just fine, they are all different after all.

regards

craig

The other thing to remember is that the autofocus system uses contrast to focus. So if you're trying to shoot something that has very little contrast, perhaps a reef shark, and you're aimed right on the shark's body, the autofcus system will search and search and search for contrast to lock up on, but won't find any, so it keep ssearching.

This could also be a factor if you're testing in a pool. If your camera is still seeing the sides of the pool, which will be a uniform color and offer no contrast, it's going to hunt and hunt. If you repo your focus point to an edge (&/or make your subject as big in frame as popssible), get the camera to lock focus, and then re-frame, that may solve part of the problem.

You could also try using the other auto-focus area mode choices that the D70 offers. You can choose single area, dynamic area, or closest-subject. It's all explained on page 140 of your D70 user guide.

Good luck!!

Craig, I will try the +2, sounds like a good option. I was worried about the MFD so I was shooting at 17mm for the most part and trying to keep subjects at arm length just to be sure.

Ken, I was kinda thinking about the contrast issue. It is an indoor pool and so the light was not that great. I tried to line up on contrast as much as possible. I think you are right about the uniform color and the lower light really enhanced that. I will give the other AF modes a shot and see if there is any change.

Thanks!