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02-17-2014, 07:41 AM   #1
Perry Perera

F-- with tokina lens

I can fit the 50-250mm Tokina lens to thye camera, but the shutter does not work as the focus (F) has to be set manually and the camera has to be focused manually.
How do do maunally set the Focus in the Pentax K-x camera.

02-17-2014, 07:52 AM   #2
Na Horuk's Avatar

Join Date: Feb 2012
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Hey, welcome! Here is what you do. Go to Menu and the very rightmost tab. Now you need to Enable the Aperture ring use.
Now on your camera body, next to the lens, you need to push the AF/MF button to MF. But if the lens has no AF capability at all, you can also leave it in AF, it shouldn't make a difference. I think the aperture ring option was the cause.
I assume the lens is pre-digital, so you might want to follow some of the advice here:
The threads I linked are for all types of manual lenses, so some of the info might not apply to your specific lens, but its a good place to learn about manual lenses on Pentax cameras

Oh, also, two other things. When you power the camera on, it might ask you for a number. That is the focal length. You probably want to input either the focal length you use the most, or just 50mm (the widest that you will use). This is only for Exif and SR functions. If you turn SR off, it will have no effect.
Secondly, on the camera display, it might say F--. This is not Focus, this is Aperture. This happens because the lens doesn't communicate its aperture value to the camera.
If your lens has an A on the aperture ring (next to the numbers), you should switch into that option. You might need to hold down a button to be able to switch it to A. But not all lenses have this feature. Just remember, F-- means "F stop unknown" and you have to select the aperture (f-stop) on the lens itself. Focus is the AF/MF button, but the camera won't try to run the focus if the lens doesn't have the focus terminal.
If you follow this advice and still can't get it to work, you might have to switch off "Focus priority" in the menu, turning it to Shutter priority or something like that.
Finally, there is a function that Pentax cameras have that is very useful for manual focus lenses. Its called Catch in focus (also known as focus trapping). There are many threads about this, it is a slightly advanced technique, but it allows you to get something close to autofocus for some of your manual focus lenses.

Last edited by Na Horuk; 02-17-2014 at 07:59 AM.

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