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Long Exposure Camcorder

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#1 ccs_hello

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Posted 13 January 2008 - 10:20 PM

In another thread, I need to get the answer so I dug out my old (DV25 compression Digital8) camcorders. They are NightShot capable models. Here are some observations:

1) older model (type-1/4" SuperHAD CCD '089AK PAL* resolution 724*582 sensor). (Set the NightShoot LED illuminator off.) Nightshoot mode took out the UV/IR-cut filter, gain-up (minor sensitivity gain). NightShoot 1" mode, 1 second Long Exposure, quite nice sensitivity gain. NightShoot 2" mode, 2 seconds Long Exposure, very nice sensitivity gain, noise control is not too bad.

*PAL mode due to steadyshoot


2) slightly newer model (type-1/6" SuperHAD CCD icx096/097AK (any one know their spec?? wanted may be 752*582 "PAL mode"). (Set the NightShoot LED illuminator off.) Nightshoot mode took out the UV/IR-cut filter, a bit more gain-up (minor sensitivity gain but noisy). Super-NightShoot mode, I think it's slightly less than 1 second Long Exposure, some sensitivity gain.

Looks like the older one is better (type-1/4" and 2" Long Exposure). May be I'll yank out it's optical lens assembly and use it as prime focus imager :).

P.S. 2" Long Exposure is about the same as some dedicated special VideoCam models. Sure can't compete with 56 second LE, TEC active cooling, Amp-off, and type-1/2" CCD sensor. But I got my (1) camcorder cheap :) :).

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#2 b1gred

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Posted 13 January 2008 - 10:44 PM

Hmmm, how to adapt my Sony "NightShot" camera to my scope...???

#3 ccs_hello

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Posted 13 January 2008 - 11:46 PM

Randy,

I found both of my camcorders' DV out (to PC) and analog video out (to a video monitor) are "live" during shooting.

RE: CCD coupling to OTA
I have not yet worked out a design. I think just leave everything in the camcorder still attached (thus not upset the CPU) but take the optical system out of the light path.
Then I have to glue a 1.25" barrel to the CCD chamber.

Just imagine that poor camcorder just had a front collision :rainbow: ...
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#4 b1gred

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Posted 13 January 2008 - 11:52 PM

Ya, same on mine w/r/t the DV and Analog out.

I hadn't thought of removing the lens system from the CamCorder, however that might be the best option. I wonder if there is a way to 'temporarily' remove the optics from my Sony cam... It's also the camera I use for ATV (Amateur TeleVision), so I don't want to "trash" it for that purpose...

#5 ccs_hello

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Posted 14 January 2008 - 01:43 AM

Randy,

Looks like two options:

1) Use a 16-conductor flex cable extender to extract the CCD board out of the camcorder body

or

2) Unscrew the lens module (a 24-conductor flex cable attached to the main board; do not detach or will make CPU unhappy) and make it out of the way (light path)

P.S. lens module has zoom, focus, and iris (motors + position sensors) and nightshot IR filter removal mechanism


Either way quite destructive :( :p.

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#6 b1gred

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Posted 14 January 2008 - 11:05 AM

Grrr, rats!

I suppose Eyepiece projection is a bit too lossy...? (Not to mention the weight of the holder for the camera.

#7 Alicatt

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Posted 14 January 2008 - 12:28 PM

My Sony has a 37mm threaded ring on the lens, there are eyepiece adaptors to fit that.
Used the Sony to record my CCTV cam last night so hope it came out ok

#8 b1gred

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Posted 14 January 2008 - 12:34 PM

Hmmmm....

#9 rshassell

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Posted 14 January 2008 - 12:49 PM

I have a Sony TRV50 MiniDV and a DCS-SR300 HDD camcorder. I never tried long exposures, but I have attempted to image the ISS with them. They both have 37mm filter threads, and I used an adapter ring to attach them to a 40mm EP. The images weren't as clear as I'd hoped, and there was some vignetting, but it did basically work. I got much better results with my Mallincam, as is evident from my avatar.

#10 ccs_hello

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Posted 15 January 2008 - 12:42 AM

These camcorders are designed for general consumers so I wouldn't put too high hope on lenses quality (I know some elements are molded plastic).

I think prime focus imaging is the way.

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#11 ccs_hello

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Posted 15 January 2008 - 12:57 AM

Update:

Use the 2" Nightshot (or Super NightShot mode) to shoot a LED in the dark in the back-n-forth as in a pendulum swing manner, I observe:

The LED light looks like a continuous (i.e., not jumpy) trail, almost like a slinky shifting position from one end point to the other. The continuous flow gives a pleasant viewing experience.

This indicates that the photon integration is done in both methods:

(1) on-CCD chip photon integration (i.e., the tradition long exposure) method upto a rate, e.g., 1/4 second per frame.

- This provide the apparent smooth optical flow, i.e., not too jumpy
- This method is (probably) needed since completely depend on method 2 would mean a large* size of memory is needed

*NTSC is about 30 frames/sec.


(2) off-CCD chip digital memory integration with sliding window method. E.g., for 1/4 second per frame feed, a 2" long sliding window will require a 9-frame** buffer.

** Two-second has eight 1/4 frames, but one extra frame is needed to fulfill sliding window integration calculation


Please comment on my reasoning. :grin:

BTW, what's SCII or MCHC's long exposure visual exprience/behavior?

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