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I'm looking at an old film recorder from 1985, the Polaroid Freeze Frame, the back of the machine pictured here:
enter image description here

From here: https://www.radiomuseum.org/r/polaroidco_freezeframe_video_recorder.html

I believe the output to 35mm film was 640 x 480, but I'm not sure. I can't find any info online confirming this.

Can a digital signal can be fed into this machine, increasing the resolution?

I know there are converters for everything these days. HDMI to RGB maybe?

Can someone explain the connections available on the back in detail to me, from the time (1985) and if this is possible?

This is the CRT in the machine: http://oddmix.com/tubes/e2787pdw.html

Got this info from the Freeze Frame teardown video on youtube.

Basically I'm wondering what the maximum theoretical resolution is that can be recorded to film using this machine.

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  • The resolution likely supported by that CRT and the video inputs is probably 240p and 480i. The horizontal resolution is not really specified. Some systems (e.g. Amiga ECS) could generate 1280 horizontal pixels in 480i in the 1980s.
    – Brian H
    Sep 11 at 1:39
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    So what does this have to do with computing?
    – pipe
    Sep 11 at 1:46
  • There is most likely NO digital resolution, since this is not only analogue output, but most likely as well analogue input. There might be cut of bandwidth, but that is as well analogue issue. So the only 'digitized' part here will be the number of horizontal lines.
    – Raffzahn
    Sep 11 at 1:57
  • Isn’t the ECS from 1990?
    – Tommy
    Sep 11 at 3:56
  • If you want to try and hack the device: be aware that CRT based equipment from this era did not always protect the CRT circuitry very well from catastrophic failure due to being driven with far out of specification timings.... Sep 16 at 20:30
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I've never used one of these devices, but I can see from the photo that the device has the typical inputs you'd find on studio equipment at the time, and for many years after.

It appears to accept NTSC composite video, TTL RGB, and Analog RGB with a composite sync, or RGBS (using EXT. SYNC input). NTSC composite input would work with consumer VCR's and camcorders, and also found as an output from computers and consoles of the time. TTL RGB is for "CGA" inputs from PCs and other computers with that type of output. The RGBS (Analog RGB) signal would work with high-end "pro-sumer" equipment or slightly later computers and consoles that had that kind of output.

All of these inputs and the internal CRT suggest compatibility with a 15.7kHz horizontal scan. That means it is capable of displaying/recording 240p and 480i resolutions. Indeed, that is what most video devices of that time generated. Note that this does not specify the horizontal resolution. That would be highly variable and determined by the input device. For example, an Apple ][ would give you as low as 140 pixels horizontal in 240p, while an Amiga (ECS chipset) could do 1280 pixels horizontal in 480i.

I doubt the device can handle 480p video signals because I'd expect it to include a suitable/commononplace input if it did. That would be a VGA input, and the device is a few years too early for VGA.

As far as using it with a high-resolution, modern, digital signal, you would need to downscale the input to 15.7kHz. For example, you might use a common studio device like the Sony DSC-1024HD to convert 1280x1024 or 1024x768 down to RGBS. Combined with a simple, modern HDMI-to-VGA converter to supply the hi-res analog to the Sony DSC, you could hope to record a modern HDMI signal.

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    Thanks very much for the explanation. What I was trying to figure out was what the maximum pixels were that could be recorded to the film. The successors of this device were 2k and 4k digital film recorders that were hooked up via SCSI, but it sounds like this Freeze Frame wouldn't get close to that even with a HDMI to RGBs converter. Sep 11 at 2:21
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Basically I'm wondering what the maximum theoretical resolution is that can be recorded to film using this machine.

There is no resolution defined by dedicated pixels as picture generation (the tube) as well as picture storage (the film) is analogue. Any description in terms of modern digital imaging will miss the capabilities.

Quantisation in vertical is done by lines, which are distinct, but variable in size and distance. Considering that its made for TV signals a vertical resolution between 500 and 600 such lines can be assumed.

In Horizontal there are literally NO pixels at all. Changes in grey level, as well in colour can happen at any level and incline - the later being defined by signal bandwidth.

If you must, you may imagined a line consisting of a Bazillion pixels. A black to white change over a line can reach all values possible by quantum mechanics :) The caveat is that a hard change from black to white does take a certain time - defined by the signal bandwidth, something measured in the analogue world by 'lines', the maximum number of alternating black and white lines that can still be seen as full white and full black. A TV does anywhere between 150 and 300(*1), studio equipment can do up to ~500 lines (remember, that's vertical).

Now, being TV, this bandwidth is different for colour (*2). Bandwidth on colour is usually less than 1/3rd that of B&W, so less then 100 'hard' colour changes over a scanline (*3). This is another point where TV is made to fit human perception, as colour is just a bonus information in rough resolution overlayed to more detailed B&W basic data.

And finally there is of course the film's 'resolution' it is again measured in lines. A cheap ASA 100 colour film will deliver anywhere between 60 to 150 lines/mm. Depending on how the 35 mm film is used, the image area 18 x 24 mm (motion picture) or 24 x 36 mm (still/Leica) thus as worst case good for at least 1000 x 1500 lines (~2000 x 3000 pixel), but usually more like 4000 x 6000 (~8000 x 12000 pixel).

So that's what signal path and media can do. What of that can be reached with this device may be kinda blow.


*1 - If one must compare, double the number is what a digital picture format has to cover (as minimum) to create a picture of the same quality by putting up alternating black and white pixel.

*2 - At least when feed a non RGB signal.

*3 - Kinda like Amiga's HAM mode - in fact due the vary same reason: limited Bandwidth.

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  • Fantastic answer, thankyou. So if the machine is somewhere between 500 - 600 lines, how can I compare it to say, a 4k(pixel) film recorder, lpmm to pixels? I had originally posted to electronics.stackexchange.com/a/586241/136260, and a user says it would be 320 x 200 pixels? Is that about right? I do realize the output between an analog and digital recorder are very different things. Sep 11 at 17:40
  • @Curiousmarble It's simply not comparable. Vertical it will have the number of 'pixels' depending on the horizontal lines of the video signal. Horizontal resolution is pure analogue. Depending on the picture captured it may be as bad as 320 or better than 4k - if the picture is composed of slow changes. That's the beauty of analogue (Results may be incredible detailed or useless fuzzy, all depending on content) vs. the reliability of digital (results are always the same. Never better but also never worse).
    – Raffzahn
    Sep 11 at 17:54
  • Ah ok! That is very interesting. So if I'm wanting to feed in a still digital image (like other film recorders that succeeded this one), from my laptop, that consists of no slow changes (I'm assuming you mean motion?) that is say, 4k resolution pixel-wise, would the 4k in pixels make it to the film, or would there be considerable loss? Depending on the connection between the laptop and this recorder, and if that is possible or not. Sep 11 at 18:07
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    @Curiousmarble No, it's not about motion. The device should not care for that, as motion is between frames. The slow change is about changing colours or brightness over a screen line. From full black to full white. A somewhat related modern issue id the grey to grey time of LCDs :)
    – Raffzahn
    Sep 11 at 18:18
  • @Curiousmarble see this testcard: upload.wikimedia.org/wikipedia/commons/1/1c/… The red or blue area in the lower left will have a horizontal 'resolution' way past 4k (unlike the digital picture shows), while the resolution of alternating vertical B&W lines will be way lower (see middle of card).
    – Raffzahn
    Sep 11 at 18:24

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