So I think my sensor is glowing...

[xpiotiavos]

<p>Hey everybody.</p>

<p>In preparation for an upcoming two-month trip to Swaziland, I picked up a couple off-brand batteries for my K10D labeled at 1800 mAh. The Pentax label battery is listed at 1650 mAh, so I figured I'd give them a try. My main interest on the battery front is in relation to star trail photography, so I was hoping the 1800mAh batteries would give me an extra hour or two of exposure time.</p>

<p>I'm getting a bit off track, but the Pentax labeled battery is still the champ, keeping my shutter open for an average of 2.85 hours verses the new-fangled 1800s which keep it open around 2.4 hours. (with dark frame subtraction turned off)</p>

<p>Anyway, back to the point: On my first long-exposure test exposure, I had my camera sitting on my desk with the lens cap on, but forgot to put the eyepiece cover on, so I figured I was just dealing with light leaking through the viewfinder when the first frame came out looking like this:</p>

<p>( K10D + FA35/2 @ f/8, ISO100, 2.97 hrs )<br>

<a title="20090430-IMGP0757 by adamwilson.photo, on Flickr" href=" src="http://farm4.static.flickr.com/3591/3492501138_6cf03bb6c2_o.jpg" alt="20090430-IMGP0757" width="900" height="602" /></a></p>

<p>So on the next few runs, I made sure the lens cap was on correctly, swapped the eyecup for the viewfinder cap, and hid my camera under a towel in my closet with the lights off just to make sure. However, the odd purple area didn't go away, and all of my exposures still look like this:</p>

<p>( K10D + FA35/2 @ f/8, ISO 100, 2.83 hrs )</p>

<p><a title="20090501-IMGP0757-1 by adamwilson.photo, on Flickr" href=" src="http://farm4.static.flickr.com/3376/3495244436_87e9d0278e_o.jpg" alt="20090501-IMGP0757-1" width="900" height="602" /></a></p>

<p>Anyone have any idea what this could be? I've never tried exposures this long in the real world, but the fact that the purple area shows up even when my camera was isolated from all light worries me, as it makes me think it's a flaw in my sensor.</p>

<p>Has anyone else ever heard of this? Or ever encountered it themselves?</p>

 

[john_shriver]

<p>More likely an area where other electronic devices in the camera are making the sensor warmer.</p>

 

[carina_z]

<p>Sensor heat build up, possibly <a href=" glow</a> .<br /> Your options:<br /> - pick a colder night to do the exposure<br /> - turn back on NR<br /> - wrap the camera in gel cold packs if you dare (it's an established pro trick, but I sure wouldn't try this on a humid night -- imagine condensation forming inside the electronics)<br /> - shoot as a series of short exposures instead, and stack 'em into one after the fact</p>

[jaophotography]

<p>I had this with the k200d and the k10d, except mine started showing up at around 10 minutes. Come to think of it, I always shot star trails with the dark frame subtraction turned off, so I don't know if it's still there if I turn on the noise reduction. I never could get rid of it in photoshop without being able to see it, so now if I ever do star trails, I do them on film.<br>

About the batteries though, I don't know about that high of mAh's. Nothing might happen, but then I'd rather have to change batteries more often than to risk burning out something. If you shot one, one hour exposure, than changed batteries and did another one hour exposure, then another on the last battery, when you put the pictures together, you would have a 3 hour exposure. Although, if you have the NR turned on, there would be a large delay in the star trails where the camera was reducing noise. If there was a way to remove that purple spot, you wouldn't have to use NR, and the star trails would line up with practically no gap between them.<br>

-Jon</p>

[andrewg_ny]

<p>I don't present myself as an expert on this topic but I'm not under the impression that there's any difference to the camera with longer or shorter mAh ratings. It's pretty much like having a smaller or larger gas tank. The same current and voltage, just for a longer period of time.</p>

<p>Adam, have you considered finding an external power source for the camera?</p>

[mc2imaging]

<p>Fresh batteries can certainly make a difference in noise. </p>

<p>btw: you are not the first to notice something similar: http://vagabondphoto.blogspot.com/2007/10/dslr-and-star-trails-part-3.html</p>

 

[miserere_mei]

<blockquote>

<p>btw: you are not the first to notice something similar:</p>

</blockquote>

<p>Very interesting, the glow is in <em>exactly</em> the same spot!</p>

<p>I imagine this is the type of stuff dark frame subtraction was intended for :-)</p>

[xpiotiavos]

<p>Hi. Thank you everybody for the responces. You guys are right: it's the so-called "amp glow." I realized after looking over my exif data that for both of those frames, my SR was on. Woops!! So I took an exposure with SR turned off and got the same glow (and, incidentally, LESS exposure time out of my fully charged battery as with SR turned on, which makes absolutely no sense whatsoever).</p>

<p>I threw on my battery grip and turned on the dark-frame subtraction to 1) see how long the batteries last and 2) see if the glow goes away.</p>

<p>I'll report back when I wake up in the morning ;).</p>

[miserere_mei]

<p>OK Adam, it's time for you to have woken up already. Don't be lazy! :-D</p>

[xpiotiavos]

<p>HA! Mis. You're funny. Do you see the time stamp on my last message?? Viva la college vida, baby.</p>

<p>Anyway, my pentax battery in camera and off-brand battery in the grip w/ NR turned on kept my shutter open for a humble 2424 seconds (~40 minutes) last night. There was no amp glow in the frame, but upon boosting it +4.00 stops in light room, it become obvious that the problem is still there, it just wasn't exposed for long enough to become obvious in the frame.</p><div></div>

[xpiotiavos]

<p>and the edited version:</p><div></div>

[miserere_mei]

<p>Notice the timestamp on THIS message, Adam? It's my bedtime! Adam, don't be a fool—stay in school :-)</p>

<p>I look forward to a proper 3hr exposure with noise reduction. Just for the hell of it.</p>

[mc2imaging]

<blockquote>

<p>Very interesting, the glow is in <em>exactly</em> the same spot!</p>

</blockquote>

<p>yep, it makes me wonder what might be down in the bottom of the camera that could be inducting that...</p>

<p>Who's going to take one for the team and volunteer to tear apart their K10D to find out?</p>

[carina_z]

<p>Disassembly not required. The fixed location, consistent across shots on this and other K10Ds, makes it almost certainly the CCD amplifier (thus, "amp glow") that's the responsible component.</p>

[henkc]

<blockquote>

<p>In preparation for an upcoming two-month trip to Swaziland</p>

</blockquote>

<p>Where are you going to be in Swaziland?</p>

[xpiotiavos]

<p>I'll be in Manzini mostly, working with an organization called Adventures in Missions.</p>

<p>You're in SA, right?</p>