LED module for 16mm film scanner

Hello!

I’m using an incandescent bulb for my scanner, but I’m not sure whether it’s the right approach, as it’s not as bright as I want it to be and it won’t give me much control when scanning colour negatives.

I’ve looked for LED modules online and found this one: https://www.mouser.co.uk/ProductDetail/LED-Engin/LZC-B3MD07?qs=ykpMnEfb%2BJzKA/ze773Sgg%3D%3D

I’ve got a 12v power supply 20a (approx., not entirely sure as I’m reusing an old one and I don’t remember the exact model number). Would it work if I plug the LED directly to the power supply or would I need a driver for it? If so, would this work? LM2596 Driver DC-DC Step-down Adjustable CC CV LED Power Supply Module Battery | eBay

Or is something like this better for this project? https://www.dx.com/p/mr16-1-3w-650-700ma-constant-current-regulated-led-driver-8-40v-input-2005612.html

Ideally, I’d like to be able to dim the RGBW leds with an Arduino. I’m struggling to understand how to wire LEDs, I’ve never done it before and it’s so much more complicated than incandescent!

I’m using a Nano for stepper motor control, camera trigger, and LCD screen (number of feet, frames). Do you think it might be a bit much to add LED control to it or is the Nano powerful enough? Do you recommend I use a separate Arduino nano for this?

Thank you very much for your help! This forum is amazing!

In case I don’t figure it out with a proper LED system, do you recommend any other alternatives? Are off the shelf LEDs good enough?

Thanks!

First of all I have to tell you that I am in favor of simplicity, without giving up getting good results.

I have never tried the LED you propose. I have taken a look at the technical characteristics. Apparently it is an LED that can produce light of any color of the visible spectrum.

In my opinion, such sophistication is unnecessary for film digitization work.

The power of 40 W and the resulting luminous flux seem to me to be exaggerated for this application.

In my device I am currently using a simple and cheap 2 W, 170 lm, 3300 K LED lamp, very easy to use, powered by 12 V, which is really giving me good results.

With the Raspberry Pi HQ camera, good images are obtained with 4 ms of exposure time.

I am digitizing Super8 films, I have not tried it with 16 mm films, but given the low cost (1.5 €) I think it is worth trying.

I leave you a link to my device, which includes a captured image.

Good luck and success in your project.

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I have to agree with @Manuel_Angel here. For me at least, going simple with an off-the-shelf LED bulb was absolutely the right way to go. This way you don’t have to worry about a driver and you can literally just hook it up to an adequate voltage power supply and be done with it. If your scanner is built around a projector, mounting the bulb is much easier as well, because it will probably fit right where the old bulb went.

The most important thing to look out for, I think, is colour accuracy. You probably want a CRI 90, better still 95 or even 99. Otherwise, I would recommend a warm white LED for scanning reversal film and a daylight balanced LED for colour negative film. If you are scanning in RAW and your CRI is high enough, I personally believe you can get away with either, though, and just fix the colours in post (as you do in negative conversion anyways).

For my own scanner, I ended up buying an LED that was bright enough and otherwise relying on the camera for controlling exposure as I found that easier to do than to dim the lamp. If you want to dim the lamp (LEDs in particular), you have to make sure to avoid things like PWM-related flicker etc.

To give you some pointers: I’m using this fairly cheap LED bulb. I also tried this probably higher quality one by Philips, which was great, too, but actually turned out to be too bright in my setup at the time. The MR16 form factor covers 8mm perfectly when diffused adequately and I think 16mm should be fine, too.

Especially regarding colour accuracy and negative film scanning, there is a lot to learn from this excellent video by Hashem of Pushing Film.

Hope this helps!

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Here is a posting of the machine I assembled, the last posting illustrates that the light source quality (the LED) is an important contributor to the quality of the scan.

The simple answer:

  • An incandescent bulb light is driven by the voltage (V) across the lamp. The bulb is acts as a resistor, and it has no polarity. It would work with alternating or direct voltate (AC or DC). Although for scanning it may be best to use DC.
  • The LED light is driven by the current (I), the LED is a diode and will illuminate when the current has the appropriate polarity. It also has a minimum voltage to make the diode work (Vf in the specifications). What the drivers typically do is to regulate the current, which can also be achieved by a resistor.

As part of the quality there are a couple of aspects to consider: the spectrum of the light source (AKA the CRI), and also as important, how even the light is across the film surface. Here is an article (in spanish) on the subject of making the light source even.

As previous comments suggest, intensity and color control have significant complexity and are not necessary required to start.

Hope it helps.

PS. by intensity I mean the ability to dim manually or controlled; by color the ability to mix color LEDs for color correction.

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Yes the YUJILEDs are the best white light LEDs you can get for scanning. You want the 5600K one, and then you diffuse the light using your chosen diffusion method (that can take some time and tinkering to get right).

Cine2Digits no longer sell the commercial-grade RGB light to hobbyists, and at a certain point the Film Society would be better off investing in one of the entry level commercial film scanners - in particular they could look into the Lasergraphics Archivist which they’d be able to use for paid work as well to bring in some money and pay it off.

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Sorry for the late reply!! I’m in the final week of exams and I haven’t been online that much.
Thank you so much for all of your comments, they are incredibly helpful!

I think you’re right, @Manuel_Angel, this module might be a bit overkill. It also adds many issues, such as setting up a software that controls the different colour lights too. Maybe for V2?

I’ve been going through a few modules with high CRI, such as the ones @jankaiser and @filmkeeper have linked. I also found this one Nichia NFCWL036B-V3 Optisolis COB LED, 5000K | the leading LED-shop by LUMITRONIX with CRI 97 and cheaper than the Yuji. The Yuji is 3190lm-3740lm and the Nichia is 710 lm. Do you think that the Nichia will be bright enough? It should work with a lower powered driver than the one I’d need for the module I linked a few posts back or the Yuji, right?

There’s also this one: Nichia NFCWL060B-V2 COB-LED 5000K, R95 | the leading LED-shop by LUMITRONIX that is closer in luminous flux to the Yuji with 2,080 lm.

What do you think? is it worth going for the Yuji or the Nicha 2,080 lm? Or will the cheaper Nichia be enough? This LED would be inside the bulb compartment of an Eiki projector, so I haven’t got much space for a big chip + big heatsink.

Again, thank you so much for your help!!

Hi @didacus:

Of the several lamps I have experimented with, one was a 7W, 750lm, 4000K lamp.

The result was that the lighting was so intense that it simply saturated the camera’s sensor, making it impossible to capture any images.

The lamp I currently use is 170 lm and the lighting is sufficient to achieve exposure times as short as 4 ms, with the lens at f 5.6.

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