Solved! Pentax K-x Fatal Filmmaking Flaw

Update : the shifting exposure issue is solved thanks to YouTube! The AE-L button on the K-x is set to be ‘Auto Focus’ by default – even in Movie Mode. Go to Menu and change it’ to AE-L and now you can can lock exposure.

I made a new video to explain this.

A DSLR that shoots HD video for under $650? That’s what the Pentax K-x promised. I ordered mine right away, thinking about yummy depth of field, cool focus effects and creating some gorgeous visual imagery.

Oh, sometimes it’s a bad idea to be an early adopter.

I got my K-x yesterday. It’s a well built, solid 12 Megpixel DSLR with some great features. Easy to use. As a still camera.

As a video camera, it had two serious problems. First one – my editing software (Sony Vegas) couldn’t find the footage files. I spent hours and hours trying to solve that problem. The Motion-JPEG or MJPEG format simply wouldn’t worked. The clips showed up as black. Eventually I found this codec and it worked – the Morgan M-JPEG Codec V3.

The other problem is brightness shifting. I first, I thought it was just me. And maybe I’m still missing somewthing but after reading Pentax’s manual for the K-x, I don’t think so.

And it ALWAYS happens. I made this video to explain better.


  1. Interesting – so I see aperture can be manually set, what about shutter speed?

    That’s a bit of a shame that there is essentially no manual exposure mode for video, though I don’t think you should take it as a specific knock against Pentax. If you look at the Nikon and Canon cameras in the range (D5000, Canon Rebel T1i), I don’t believe that they have ISO control either, or even aperture control!

    That’s basically what these cameras are, consumer DSLRs with consumer video functionality for anyone who wants to point and shoot, but not for anyone trying to do real cinematography.

    If Pentax were to release a firmware for this (and like you said, all it would take is a firmware upgrade, like Canon did with the 5D Mark II), that would be great, and would make the K-x a killer videocamera for the price it’s selling at.

  2. I think it’s even problematic as a point and shoot. It’s too bad, really.

  3. Nathan, D5000 and Rebel T1i both provide the possibilty to lock exposure (ISO) by pressing a certain button, so shifts in brightness won’t happen.

    There’s no problem whatsoever in providing at least that!

    I was about to get a K-x but without being able to lock exposure, video mode is absolutely useless to me.

    And I guess majority of people who had been waitong for K-x for it’s video mode might feel the same.

    Thx for the warning anyway Lee!

  4. I just checked some images of K-x.

    There IS an AE-L button! Press it or keep it pressed during video recording and ISO will stay at the value it was the moment you pressed it.

  5. The Problem with Exposure that others is experiencing primarily is , User-Error. And when somebody got the right answer to his/her problem is , all they can is “thank you, i missed that part” BUT THE BASHING ON PENTAX HAS ALREADY BEEN THAN, MORON”
    Let say, okay you’ve use nikon and canon and the fun part you’re expecting did not come out as expected. Good question is , Do you really know how to use pentax ? if not then dig more on the manuals and see what’s going on in this (as-if) unpopular dslr .
    *** brightness shifting *** READ AND UNDERSTAND THE MANUAL, this is similar to different language, some term are different from others but the function is the same, dont expect the terminology use by other manufacturer are exactly the same, LEARN

    Bojjern Landicho

  6. I’ve read where people are having problems with the batteries. Did you experience this?

  7. Thanks so much for taking the time Lee to update your YouTube on the Kx. I was about to cancel my order when I found your follow up.

  8. I have a big problem with my new Pentax K-x. It’s turned off and I changed the batteries and it’s still off. I guess that the button on/off doesn’t work or is burned. I’ve used only 24 hours (bought new from e-bay from prodgital co. ontario). The camera does not want to turn ON!
    I don’t what to do?…. before I used a Pentax MZ-50 without problem.
    Thank for help.


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