what do pro telecine/scanners use for a backlight?

[milesandjules]

Hi guys, I'm experimenting with a 10watt led with very fine scrim to diffuse for transferring slightly under exposed neg and the brighter the light source the blacker the blacks are so I'm wondering what the pro scanners use to get it to look so good?

The led seems just as bright as a 50watt halogen …but the halogen seems to be more defused with less hotspot.

[slashmaster]

Maybe you'd want something with a higher color temperature. The halogen is about 3200k what do you think the led's are?

[carllooper]

One of the problems with many white LEDs is that they don't produce as broad a spectral response as other light sources might. Odd parts of the spectrum are excluded.

One solution is to use a combo of red, green and blue LEDs, where each makes up for inadequacies in the others. Getting them to mix evenly is an exercise. But these also make possible better control of the colour.

C

[milesandjules]

interesting about the temps and the light differences….Maybe i should just get a tungsten 100watt projector bulb…than i can get a heavier defuser?

[vintagefilm]

Spirits use a xenon lamp. To 2004 it was 300 watts and later 700 watts. Scanity has an led. Muller's later design had a 100 watt 10000 kelvin led.

[slashmaster]

Spirits use a xenon lamp. To 2004 it was 300 watts and later 700 watts. Scanity has an led. Muller's later design had a 100 watt 10000 kelvin led.

That kind of wattage for scanning? Why would you need that much to shine on a little sensor?

[vintagefilm]

More light equals less exposure time for one thing. And the big machines have the light some distance away so the distance creates losses. They also process the light based on the machine's settings. There are filter wheels in the light path that can cost some light. And there are also several diffusion lenses. Also they need enough to illuminate even very dense films.

[RCBasher]

Muller's later design had a 100 watt 10000 kelvin led.

It now uses my Cine2Digits RGB adjustable LED system. Flash power is around 450 to 600W, exposures generally in the sub 100us bracket in order to freeze the film motion as it is a continuous feed (sprocketless drive) transport system.

[doug]

I don't know if there are any similarities with how scanners work, but I'm working on using the colour head from a Durst enlarger using a 100w halogen lamp. It seems nice and bright for copying slides, and good for colour adjustment. But sofar haven't used it for cine.

[RCBasher]

I don't know if there are any similarities with how scanners work, but I'm working on using the colour head from a Durst enlarger using a 100w halogen lamp. It seems nice and bright for copying slides, and good for colour adjustment. But sofar haven't used it for cine.

All depends on your film transport system (e.g. continuous or stop motion like a projector), lens, camera and speed at which you want to transfer. It is a very long time since I made photo prints in a dark room, but I recall needing to open the lens wide for focusing a) to give minimum DoF for precision and b) so I could see the image! I also recall exposures of many seconds, often minutes! But then again, blowing up 35mm to 10"x8" would spread out the available light somewhat!

Anyway, 100W halogen through filters should be quite adequate for static film frames at a reasonable speed, depending on the filter losses. A static frame at 24fps in a projector would be available for exposure for around 30ms (allowing for pull-down), that's about 300 times longer than allowable in a continuous motion system at the same frame rate so you would only need around 1/300th the light power for all else being equal.

Frank

[vintagefilm]

Franks system is a brilliant piece of engineering and the new Mullers are better for having it. I was refering to Mullers own website description of his personal earlier version. Andreas posted a link a while ago.

[vintagefilm]

By the way one other advantage of more light is that you can stop down the lens to get more depth of field. This is valuable when scanning film with cupping or warpage within the frame.

[aj]

I don't know if there are any similarities with how scanners work, but I'm working on using the colour head from a Durst enlarger using a 100w halogen lamp. It seems nice and bright for copying slides, and good for colour adjustment. But sofar haven't used it for cine.

All depends on your film transport system (e.g. continuous or stop motion like a projector), lens, camera and speed at which you want to transfer. It is a very long time since I made photo prints in a dark room, but I recall needing to open the lens wide for focusing a) to give minimum DoF for precision and b) so I could see the image! I also recall exposures of many seconds, often minutes! But then again, blowing up 35mm to 10"x8" would spread out the available light somewhat!

Anyway, 100W halogen through filters should be quite adequate for static film frames at a reasonable speed, depending on the filter losses. A static frame at 24fps in a projector would be available for exposure for around 30ms (allowing for pull-down), that's about 300 times longer than allowable in a continuous motion system at the same frame rate so you would only need around 1/300th the light power for all else being equal.

Frank

A S8 frame is only a fraction of a 35mm frame. So it will get only light from 1/36 (estimate) of the spread out 100 watt.
One could consider using a Mamiya ENLAhead or something like that. There is a MINOX adapter with condensor from Durst too which will bring more light to the S8 frame.

[RCBasher]

One could consider using a Mamiya ENLAhead or something like that. There is a MINOX adapter with condensor from Durst too which will bring more light to the S8 frame.

Just keep in mind though that condensing light produced by a basically thermal source such as halogen will also condense the heat - so be careful to not burn the film! This is a big advantage to using LEDs, also a lot lower running costs. A flashed RGB system will consume around 2W average, compare that to a 100W bulb, or even the 700W one in the Spirit! Not a big issue for occasional transfers, but maybe a serious consideration for a scanning house.

[vintagefilm]

The diffuser I use is opal glass. You can research and see what is available at Edmund Scientific.