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Thread: Focus Correction on Pentax K-x

  1. #1

    Post Focus Correction on Pentax K-x

    I just saw a K20 by default have the af correction menu on the camera while the Pentax K-x dont have. Ive been searching until i found this one, so i just post it here for K-x users (including me) This thread is to fine tune your focusing front and back focusing.

    Using Pentax Kx debug mode to do a focus adjustment
    Create a plain text/ascii file named "MODSET.492" with just one text line in a root folder of your SD flash card:

    [OPEN_DEBUG_MENU]

    the line must end with CR/LF (as it is a customary w/ "MS Windows" text files).
    Turn on the camera while holding <+/-(Av)> button pressed.
    Enable the mode through the first menu item "DEBUG MODE" (press "ISO" arrow-button to change "DIS" to "EN").

    Press "OK" button, the LCD screen will switch itself off.

    Press "MENU" button.

    Scroll to the "TEST MODE" tab that will be visible now (it was hidden before).


    Scroll down to "AF TEST" menu item in the "TEST MODE" tab and select it.


    Do the necessary corrections with "FocusCorr" slider.



    Save the adjustments by pressing "OK" button, the LCD screen will switch itself off.

    Press "MENU" button again.


    Again scroll to the "TEST MODE" tab that will be visible now (it was hidden before).


    Scroll down to "DEBUG MODE DISABLE" menu item in the "TEST MODE" tab and select it to return back to the normal camera operation.




    Switch the camera OFF and ON again.


    Some things to remember - any changes that you will do using "FocusCorr" slider are cumulative - so if you will change it to "-50" once and then to "-30" next time - it will be "-80", not "-30". You need to change it to "+20" to make the correction equal to "-30" if that was the absolute value that you want. Also you do need to log out (disable) from debug mode to do the testing, while you can make test shots immediately after doing the adjustment I think that AF adjustments are not effective w/o powercycling the camera. Make all the changes with a freshly charged set of batteries if not using DC power. Making negative ("-") adjustments to "FocusCorr" slider will move the focus point away from you (camera) - to correct FF/front focus situation (when originally the camera focuses before the target) and making positive ("+") adjustments to "FocusCorr" slider will move the focus point closer to you (camera) - to correct BF/back focus situation (when originally the camera focuses behind the target). You can keep the "MODSET.492" file all the time on your flash cards - just do not forget to remove the flash card if you will neeed to send your camera to the service for whatever reason.

  2. #2

    Default Re: Focus Correction on Pentax K-x

    That's cool! good piece of info if need arises
    Thanks for sharing.

  3. #3

    Default Re: Focus Correction on Pentax K-x

    Hi

    Thank you for sharing. However, I don't know how this work. When do I need to adjust the focus? Is there anything wrong with standard setting? Sorry, I am very noob

  4. #4

    Default Re: Focus Correction on Pentax K-x

    only do it if you are sure.. anyways can undo i think.

    i used to do that for my modified k100d.

  5. #5

    Default Re: Focus Correction on Pentax K-x

    Quote Originally Posted by wazzupku View Post
    Hi

    Thank you for sharing. However, I don't know how this work. When do I need to adjust the focus? Is there anything wrong with standard setting? Sorry, I am very noob
    you only need to do correction when you are CERTAIN that the AF is not working fine.

    if you have been getting sharp pictures with the focus just where it should be, and there is no other reason for the blur-ness (e.g. handshake, subject movement).. then it could be back focusing.

  6. #6

    Default Re: Focus Correction on Pentax K-x

    Quote Originally Posted by night86mare View Post
    you only need to do correction when you are CERTAIN that the AF is not working fine.

    if you have been getting sharp pictures with the focus just where it should be, and there is no other reason for the blur-ness (e.g. handshake, subject movement).. then it could be back focusing.
    Thank you nightmare.

    So when I took a photo of my fish tank, I wanted to focus on the fish but the auto focus seems lost and trying hard to focus on the tank instead, then I need to adjust right?

  7. #7

    Default Re: Focus Correction on Pentax K-x

    Quote Originally Posted by wazzupku View Post
    Thank you nightmare.

    So when I took a photo of my fish tank, I wanted to focus on the fish but the auto focus seems lost and trying hard to focus on the tank instead, then I need to adjust right?
    not necessarily.

    in the case of your fish tank there are factors such as reflections on the tank, so the af might be acquiring focus on something with HIGHER CONTRAST. af works by detecting contrast, which is why when you take a picture of a white smooth wall you will kill yourself trying to attain focus.

    in this case, the water will diffuse the contrast somewhat, hence it is easier for the af to obtain focus on whatever is reflected on the tank, probably.

  8. #8

    Default Re: Focus Correction on Pentax K-x

    Quote Originally Posted by night86mare View Post
    not necessarily.

    in the case of your fish tank there are factors such as reflections on the tank, so the af might be acquiring focus on something with HIGHER CONTRAST. af works by detecting contrast, which is why when you take a picture of a white smooth wall you will kill yourself trying to attain focus.

    in this case, the water will diffuse the contrast somewhat, hence it is easier for the af to obtain focus on whatever is reflected on the tank, probably.
    Thanks again nightmare. Awesome knowledge

  9. #9

    Default Re: Focus Correction on Pentax K-x

    You can try using manual focus in live view. You can magnify the display in live view by pressing info to make it even easier.

    I tend to use autofocus in live view when I want to be very sure that what I want is in focus.

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