I had to tune the power supply voltage up to 13.5V in order to reach 16EV.
Here comes my build. I used the horizontal keypad but placed it vertically in order to fit a smaller aluminium enclosure. I also tried multiple types of acrylic boards and ended up with a 3mm PC diffuser. It performs almost the same with a 5mm thick acrylic but it is much thinner. I had to tune the power supply voltage up to 13.5V in order to reach 16EV. The linearity of the light source is pretty good and the maximum error is within ±0.2EV, which happens at both ends of the testing range. In order to fit the thinner diffuser and make the panel flat, I redrew and CNC a front plane using 3mm thick aluminum board, and it worked out great
with the enclosure.
View attachment 349075
View attachment 349076
Not sure why my LED requires a higher voltage.
Make sure your LED driver PCB is configured correctly. I think it is worth investigating: “While adjusting the voltage be carefull to not exceed 13V or you can damage componets of the Tester!”
Source (under Calibration):
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Light Source
DIY Film Camera Tester. Contribute to srozum/film_camera_tester development by creating an account on GitHub.github.com
I'm wondering if reflective material, such as tinfoil should be added to the inner surface of the reflector. I printed it with black ABS using an FDM printer. And I don't think it reflects too much light. Maybe adding tinfoil will help to improve the efficiency but will have negative impact on consistency.The Nano takes up to 20v, the LED driver takes up to 25v, the only thing I could determine that is limited to 12V is the fan, but my experience with these fans is that they can handle a few extra volts. Otherwise, I suspect, a resistor could be placed in line with the fan.
Not sure why my LED requires a higher voltage.
Btw, there was someone who I think had a similar problem to yours. The issue was a fresnel lens with a wrong focal length:
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Light Source Calibration Issue · srozum/film_camera_tester · Discussion #29
Hi Serhiy, So I started with a calibration of 12.5v as recommended from Light Source Wiki. I don't have a fancy luminance meter but I do have various camera hot shoe meters and digital cameras. At ...github.com
Ok, I guess you found the source of the issue. This does not look like the right one. The two dark squares and the thick separation lines inside the lens give it away.
Here is a link to a seller that should have the right one:
https://aliexpress.com/item/1005002137930742.html (12V, 20mm)
If you can’t ship within China, can you at least message the sellers on the platform and ask if they also have a Taobao store? Most should have one. The 3000K version should look like this:
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