wilber_lacy Posted April 6, 2007 Share Posted April 6, 2007 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. Link to comment Share on other sites More sharing options...
bill a. Posted April 6, 2007 Share Posted April 6, 2007 What are you focusing on? Link to comment Share on other sites More sharing options...
User_276104 Posted April 6, 2007 Share Posted April 6, 2007 Someone had a similar problem a few weeks ago. The F4s has some sort of sensor to know when it is in the vertical position, and it would seem that this can go haywire and interfere with AF operation. Link to comment Share on other sites More sharing options...
alex_lofquist Posted April 6, 2007 Share Posted April 6, 2007 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. Link to comment Share on other sites More sharing options...
richard_meyers Posted April 6, 2007 Share Posted April 6, 2007 The autofocus sensors are positioned diagonally in the F4 so that the orientation of the body should not be an issue. Have you tried single servo vs. continuous? Just a thought. Link to comment Share on other sites More sharing options...
alex_lofquist Posted April 6, 2007 Share Posted April 6, 2007 My F4s AF module is horizontal. Perhaps you are thinking of the left and right cross modules of the F5 which are slightly tilted? Link to comment Share on other sites More sharing options...
ShunCheung Posted April 6, 2007 Share Posted April 6, 2007 The F4 has exactly one AF sensor/point, right in the center. Among Nikons, the 1996 F5 was the first body with multiple AF points. Anything before 1996 had only one AF point. Link to comment Share on other sites More sharing options...
aaron_ng Posted April 7, 2007 Share Posted April 7, 2007 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. Link to comment Share on other sites More sharing options...
richard_meyers Posted April 7, 2007 Share Posted April 7, 2007 "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. Link to comment Share on other sites More sharing options...
alex_lofquist Posted April 7, 2007 Share Posted April 7, 2007 It's too bad that Nikon doesn't release these documents to its customers. How did you get ahold of it? Link to comment Share on other sites More sharing options...
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