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Old 17-03-2012, 01:42 PM
apaulo (Paul)
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Turning off Dark Frame Substraction with the Pentax K x

Hello Everyone,

One of the main problems using the Pentax K x with astro photography is the inability to turn off the Automatic Dark Frame Substraction (DFS).If your sub is over 30 seconds the camera will utilise this function, regardless how you set the Noise Reduction options.

This is frustrating when it takes roughly 110 minutes to collect an hours worth of data. Battery life is seriously reduced and the thermo noise is constantly rising.
The firmware has attempted to remove the hot pixels and thermo-noise but the results are rather disappointing.
As a result the dark frames you take are useless and you are left with severe limitations when processing due to the gouging out the dark, flat, bias and light frames.

After looking at my pentax camera and wondering "If there isnt an better excuse to buy and CCD now there never will be". My wife suggested to seek a possible answer via the internet.

To my surprise and disappointment there is a whole page full of websites dealing with this exact issue. The best ones being:



The modest.492 and sysparam.txt files are here (attached file) or you can obtain them from the above listed websites.

Your pentax needs to have the latest firmware installed. Firmware 1.00 will not work. To check what firmware you have simply press the menu button while turning on the camera. After 5 seconds it will return to normal operating mode.
I have just installed 1.03 and the debugging now works and I have managed to easily turn off the DFS.

The firmware update can be found at pentax.

Now I can image more data without the wait and have to look for another excuse to be allowed to purchase an CCD.

Please note the ONUS is on you for the above mentioned alterations.

Regards Paul.

Last edited by apaulo; 17-03-2012 at 02:40 PM.
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Old 17-03-2012, 04:39 PM
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Big Dave (Dave)
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Nice write up.
Note: This does not happen on the K7 or K5. A few people may think Kx, where x represents any number. Silly model number sequence from Pentax!
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Old 18-03-2012, 09:37 AM
stevous67 (Steve M)
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That's good news Paul! Can't wait to see what happens next to your future images.

Good luck.

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Old 18-03-2012, 02:52 PM
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Satchmo (Mark)
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I have a Kx also so I look forward to seeing your results , Paul.
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Old 18-03-2012, 04:18 PM
apaulo (Paul)
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Thanks Steve

You started the whole thing rolling Steve! I am surprised the internet provided the answers I needed.
Mark its a easy process upgrading and running the debug program.
The program is not permanent Mark, you can easily turn it off in two ways.
One via the menu option and two via the debug program itself.
The proof will be in the pudding though weather pending I will be going to Snake Valley and will get a good idea then.

Regards Paul.
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Old 18-03-2012, 11:28 PM
Poita (Peter)
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The k-r does not have this issue either.
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Old 11-06-2012, 09:10 AM
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cometcatcher (Kevin)
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This worked for me and my K-x. Many thanks!
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