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Very strange F4s AutoFocus Problem


wilber_lacy

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I have a very strange autofocus problem on my F4S. It will not autofocus if I

hold it in the regular horizontal way. If I turn it upside down it will

autofocus great everytime. Also if I hold it normal (horiz.)then begin

rotating it around the axis of the lens, it will autofocus at the same point

or angle of rotation every time. The point where it starts AF is always about

20-30 deg. from being fully vertical. It will always AF if it is upside down.

I have cleaned the lens connections and tried other lenses and still have the

same problem. Does this sound like an expensive repair? Color me baffled.

Thanks for any suggestions.

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Are you attempting to focus on subjects that consist primarily on contrasty vertical lines? If not, the F4S will have difficult time in reaching focus. I used to have problems when in this situation and so I would often tilt the camera slightly, then lock onto the in-focus image. If this doesn't work for you there may be a problem in the AF module which will require professional service. This is not a lens problem, if it were it wouldn't focus in any position. The internal vertical/horizontal switches are for setting the fields in matrix metering and should have no effect on AF.

The N90, F100, F5, and F6 use cross sensors and so do not exhibit this characteristic. So if it looks like an expensive repair, you might want to see if you can find an F5 in the used market. I find that my F5 focusses significantly faster than my F4S with "screwdriver" lenses.

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The F4s can ONLY focus on vertical lines. Make sure the area you are focussing on is vertically orientated. The orientation sensor only affects matrix metering and shouldn't be the cause of your AF problem. Have you tried focussing using an AF-S lens? That can eliminate whether the problem is caused by poor contact in the body's focussing motor.
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"The 200 superior-sensitivity CCD focus sensors not only enhance response speed -- their diagonal configuration enables the F4 to detect a wide variety of normally difficult-to-focus subjects, quickly and accurately."

 

From Nikon Document No. 8CE40900 Copyright 1989

 

The module is in the center of the field of view but the sensors which you can not see are arranged on the module as mentioned.

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