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JimK

Auto Focus - Nikon D-70

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I am using Ikelite housing with Nikon D-70, Nikon Strobe 105 - 18-70mm lens - Problem with Auto Focus UW - Have missed good pics because Auto Focus will not allow shutter to fire - Settings I use AF-S & Single area - Question is how close to target will auto focus work properly & anybody have different settings or methods to use?

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Have you tried changing to AF-C also multiple area; better for moving subjects. Also I believe AF-C allows you to take the shot even if AF is not locked on.

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I started out on AF-S, but after being frustrated by the same sitution you mention, I switched to AF-C. As loftus said you will be able to take a picture even if its not locked.

 

I also use dynamic area to be able to better compose shots.

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I use AF-S with an Ikelite housing and find that in situations where the autofocus will not lock on you can use the AF-L button to force the shutter to fire. I prefer this to AF-C which fires the shutter when you press the button down completely regardless of whether the subject is in focus.

 

I use dynamic area focus, by default I tend to use the centre area but select any of the other 4 areas if the subject needs it.

 

I assume you are using this lens behind the recommended dome port with a +4 diopter.

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I want to thank all who responded to my problem - I will try both methods suggested by Loftus, Expatdiver & Ken Byrne - Thx Jim K :unsure:

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I've found that if I fail to screw the diopter on all the way, I'll get random focus problems. Usually after the dive, I find out that I had it a thread or two loose....

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HI jim

 

you did not state if your using a dioptre on the lens, I suspect that your not.

 

this will be the source of your problems using small radius domes.

 

nothing at all to do with AFS or AFC AFCD etc etc..

 

you will need at least a +2 on this lens, i often use a +4, and never have an issue when using a 5-6" dome, it does not require one at all if using a 9" dome.

 

craig

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The D70 AF also needs quite good illumination to focus correctly. In deep&dark waters I usually need to "paint" the subject with my divelight before it will focus.

 

/Sten

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Craig (Sting Ray) - I have a +4 Diopter attached to the lens - I am inclined to believe the camera is not focusing due to poor light - I will be using a small light

to paint the target as suggested by Sten (Sea Wasp) - It's frustrating to see my wife get good photos with a point & shoot camera in situations I cannot focus - Any frther comments or suggestion? - Jim K

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Hi Jim

 

well, i'm scratching my head, i've really never had a problem at all with my D70 like this, yes when the subject in backlite you need to highlight with a focusing light.

 

i always use AF-S single shot when shooting wide.

 

i could imagine however that if that water is very turbid, they it could may well be attempting to focus on particle elements between the dome and subject.

 

make sure you have not got closest subject priorty enabled on the D70 as well jim.

 

regards

 

craig

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I use a D70 in AF-S exclusively, as AF-C resulted in too many out-of-focus fish. My only problem with any lens is illuminating the target and finding a contrasty edge for the camera to lock on to. A spotting light on the body works for wide-angle, but having just bought a macro port (I do most things backwards, but I hope that Alex Mustard is going to help me learn about fish next week, soI thought that a macro would be a useful addition) I found that in a dark quarry (British divers will appreciate my stupidity in taking a macro lens for its first outing to Dosthill in the evening!) I had to use the modelling lights from my Inon strobes aimed squarely at the subject to make AF-S work. You can see spotting lights and modelling lights on these images:

 

post-4522-1150919841_thumb.jpg post-4522-1150919872_thumb.jpg

 

 

Tim

 

B)

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I used to miss plenty of shots due to focus (I think similar issues to you) but have done some experimentation and seem to be getting great results now. I currently use AF-C for total control which I like. Additionally I read a bit about the AF sensors and practised and experimented and seem to be able to adjust to get good results. I don't really think about it too much anymore and I used to be really frustrated about it.

 

Check out: http://www.focustestchart.com/ which provides some really nice basics. It has helped me to raise my awareness of the process of focusing.

 

Good luck!

 

-- Justin

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