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06-30-2019, 06:26 AM   #1
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Pentax KX Dark Frame Subtraction Disable Process

I have researched quite a few posts and online articles about how to turn off Pentax KX Dark Frame Subtraction.
Some of these posts and articles are correct, but none seem to describe the actual steps that work.
DFS disable is very handy to reduce the time taken for longer exposure astrophotographs.

Please read the entire post below to make sure you understand the process.
The process below seems quite safe, but I take no responsibility for camera or other hardware/software failure.

Before following the steps below, ensure your KX has the following settings:
1). Slow shutter speed noise reduction (off)
2). High ISO NR (off)
3). High ISO noise reduction starting sensitivity level (ISO 3200)

Step 1. Using your KX SD memory card, install the memory card into a card reader and connect the card to your computer.
Step 2. Probably a good idea to delete all SD memory card files (make sure you back up any important photos) so the card is blank.
Step 3. Open Notepad or similar, paste in [OPEN_DEBUG_MENU] and press Enter to add a blank line below.
Step 4. Save As... the Notepad file to your KX SD memory card as MODSET.492 not MODSET.492.txt
Make sure you remove the .txt file extension.
Step 5. Download Notepad++ and install the program to your computer.
It must be used to create our next required file called SYSPARAM.TXT
Step 6. Run or open Notepad++ program and paste in [DISABLE_BULB_ALG] 1@ and press Enter to add a blank line below.
Step 7. Save As...SYSPARAM.TXT to your KX SD memory card.
Your SD memory card should have the following files shown as:
MODSET.492
SYSPARAM.TXT
Step 8. Remove the SD memory card from your computer and install into your Pentax KX camera.Close the KX SD card door.
Step 9.Holding down the +/-Av button, turn on your camera. If things are good, you will see the Debug Mode menu and screen.
Step 10. Select the first Item for the Debug Mode from "DIS" (Disable) to "EN" (Enable) by pressing the Left or Right Arrow.
Then press the OK button, you will be in the "Debug Mode"!:- The screen will then be blank. Don't worry.
Step 11. Turn the MODE selector around until M (manual) is selected.
Step 12. Rotate the e-dial until Bulb is selected.
Step 13. Press the shutter button and take an exposure of at least 30 seconds.
If the DFS has been deactivated, you will be able to take another exposure immediately.
If the camera takes another equivalent length exposure, DFS is still active and there is an error in your SD card files.
Step 14.To re-enable DFS and return the camera to normal mode:
Turn off the camera.
Turn on the camera and Select the first Item for the Debug Mode from "EN" (Enable) to "DIS" (Disable) by pressing the Left or Right Arrow.
Then press the OK button, you will out of the "Debug Mode" and back to normal mode. Turn off the camera and remove the SD card.

NOTE: Debug mode is a temporary program edit to your camera, although the camera will stay in this mode until you return to normal mode.
It is suggested that you have two SD cards for your Pentax KX.
One SD card for normal everyday camera operation and,
a second SD card that contains the MODSET.492 and SYSPARAM.TXT files for temporary DFS deactivation and longer exposures.

06-30-2019, 06:52 AM - 1 Like   #2
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Wouldn't disabling slow shutter speed NR (step 1 above) be sufficient? What's different on the K-x that necessitates using debug mode?

Adam
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06-30-2019, 07:49 PM   #3
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QuoteOriginally posted by Adam Quote
Wouldn't disabling slow shutter speed NR (step 1 above) be sufficient? What's different on the K-x that necessitates using debug mode?
Hi Adam,
The Pentax K-x Dark Frame Subtraction cannot be disabled unless the user enters the debug mode.
The K-x default DFS setting means that for any exposure length of 30 seconds or longer, the camera will take an equal length dark frame exposure, doubling the time taken to obtain the image.
As an example, for astrophotographers, this means that if the camera is used to take a long exposure, say 20 minutes, then immediately after the initial exposure is completed, the camera will take a dark frame exposure for another 20 minutes making the total exposure time 40 minutes.
06-30-2019, 08:44 PM   #4
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Interesting! On future models, all that's needed is the one slow shutter speed NR setting.


Adam
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07-01-2019, 09:49 PM   #5
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Hi Adam,
I think the next model Pentax released was the K-r, which had the option to turn off DFS. If one Googles 'Pentax K-x DFS disable' there are many web links on the issue.
Due to the low noise level of the Exmor Sony sensor, and the lighter weight of the camera body, the K-x, when it was released, was seen as a good camera for astrophotography, but, the DFS could not be turned off unless it was used in Debug mode.
Of course there are now many DSLR cameras probably better suited to astrophotography, most having red sensitivity increased (for capture of nebulae), and higher ISO speeds, but the Sony Exmor sensor is still a very good one for astrophotography and for those K-x owners wishing to get into this area of astronomy, most would want the option to turn off DFS so the Debug mode and DFS disable procedure makes the camera viable for long exposures.
Pentax K-x - Wikipedia
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