Using a Bell&Howell adjustable-speed film projector and Sony TRV460 Camcorder, I'm recording through Firewire to MS Windows 7 Pro using three recording software (WinDV, VirtualDubMod, AVSVideoRecorder).
The projected image is in an enclosure (dark box) at the end of which is a semi-opaque plastic film (the screen). The camcorder is open-air, recording the image from the other side of the screen. [VDM does a great job of reversing the video frames later.]
Camcorder's Focus and Exposure are fixed, manually set (about "45%", just under the HotSpot).
The recordings are .dv . FFMPEG converts the video to uncompressed AVI.
Regardless of which software I use, the recording behaves reasonably well for a while, the strobing light isn't erratic (the HotSpot Filter works reasonably well on the recording later).
But once in a while, under circumstances I can't understand, the recorded image suddenly turns grey-blue and the image inverts like a photograph negative.
Sometimes the recorded image seems to bleed like film burning but the film itself is not being damaged and it replays without trouble.
And, although I'm using a plain light grey piece of plastic (about 400microns thick; I think it's called "Mylar"), the recorded image has several thick grey horizontal lines in the image.
I don't have image examples of the 'image bleeding' or 'photograph negative' instances but here's an example of the lines:
I don't know what most of these effects are called so I can't search for them. I couldn't guess keywords.
The film with which I'm working isn't mine, it's fifty or sixty years old at least, and I'm afraid to keep running it through the projector while I fumble around trying to guess what dumb thing I'm overlooking. Change the Exposure on the camcorder? Use different recording software? Use a different Codec (FFMPEG's set at the default, "Apple JPEG")? Use different 'screen' material? Run the camcorder inside a darkened box?
I'm hoping your comments will help me narrow-down many possibilities to some few most likely problems so that I can decrease the amount of time I experiment with this old film.
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Last edited by Groami Geistalt; 8th Mar 2014 at 01:35. Reason: small matter, wrong short-hand signature
First, about the image turning grey-blue and the inversion to a negative image. Did you physically inspect the 8mm film itself? I have seen these things associated with films that were poorly processed at the film developing lab (like air bubbles in the chemical tanks, or a power outage that leaves sections of film in the chemicals for too long). If the film is fine throughout, then the grey-blue shift may be due to the auto-white balance on your camcorder.
Now, about the horizontal lines. There are 2 types of shutters you are dealing with: the mechanical shutter of the projector and the electronic shutter of your camcorder. By varying the projector speed, you solved the mechanical shutter issue (which causes flicker) to some extent, although things can drift off speed incrementally, and you need to be able to override this during the course of the film run. The lines have to do with the electronic shutter in your camcorder. You must manually tweak it until the lines disappear.
I cannot recommend shutter speeds, as you do not list your location, and I have no way of knowing if you are in a PAL or NTSC country.
Hi. Thanks for replying.
I'll try to get more information about the Camcorder's "auto-white balance". The film segments Preview and re-record properly where these anomalies have occurred.
I'll also try to learn more about the Camcorder's electronic shutter. (I bought from an online puppy mill but a reputable repair company checked and fixed things and declared the camcorder fit. Fortunately the manual was included.)
P.S. I'm in Canada. NTSC.