Building A Professional Grade Shutter Tester

[aconbere]

2.9.0 has done it! We have a working tester! (Bonus points the camera's shutter is accurate as well).

 

[aconbere]

The journey continues!

Rotary dial doesn't work when the LED is plugged in · srozum/film_camera_tester · Discussion #42

[Edit - Initial I thought I had disconnected the LED but it wasn't fully loose - edited the body to show that] When I have the light source connector plugged into the control board AND the LED conn...

github.com

Summary: When I plug in the light source with the LED connected the rotary dial doesn't work. Unplugged the rotary dial works great. When plugged in the light source and all other features work great. The fan and LED turn on and turn off when a test starts, etc.

Based on the previous issue I've double checked that not only are all the connections good, but that they connect to the correct pins on the arduino (I believe they do).

Any thoughts on next steps? (sorry for hogging so much of this thread)

 

[ic-racer]

Yes with respect to "Sensor #2", A goes to pin #3 not #2. Whereas with "Sensor #1" A goes to pin #2.

Not sure about the rotary switch issue. Are you sure the push portion of the rotary switch is normally open and only closes when it is pushed in.

 

[aconbere]

I took it all apart, resoldered the connectors and put it back together and it’s happy for now. Yeesh

 

[vandergus]

All right, I managed to finish my very first version of the "Tuner" before my vacation. And here comes the solution.

The hardware modification is simple, just grab another Nano (maybe the one you used as programmer), connect Vin and GND of the added Nano to the one on the shield board. And then cut the Light PWM wire connecting shield board and the light unit board in the middle. Reconnect the wire on the shield board side to D2 on the added Nano and the light unit side to D12 as shown bellow:


Now your are all setup for the hardware mod. Just download the attached ZIP file, unzip it and open the .ino file with you Arduino IDE. Look for the following section:

View attachment 349928

These are the parameters corresponding to each EV level you'd like to control.

Column 1 controls the clock divider. The larger the number the slower the control signal frequency goes. Just leave it untouched.

Column 2 controls the output frequency of the control signal. It's the comparator number in a timer. Once the number is reached, the counter will trigger a pulse output. So with the same pulse width, smaller number in column 2 means faster output pulse train and higher output power(brighter light).

Column 3 and 4 controls the pulse width. A larger number provides a longer pulse which leads to brighter light.

Try to play with column 2,3 and 4. Tune them and upload the code to your added Nano with Arduino IDE. Check the result, change the parameters, upload and check again. Repeat the process until you're satisfied with the output accuracy and linearity. You will have to tune the whole table for each EV but it shouldn't be a a big deal.

Last but not least, play at your own risk! I will absolutely take NO responsibility to any potential lost done by my code.

I tried this mod but was unsuccessful. It seemed to roughly work until I got to EV16, then the LED went very dim. Maybe it was going into a protect mode? I backed off the 3rd and 4th column from 140 to 139 but it still went dim. Should I just keep backing it off until it stays on?

The nano board I'm using is a little different from the one you have pictured. It is an official Arduino board, not a knock-off, but the PCB is green and the micro is in a different package. Looks like a QFN rather than a QFP. But it's still labeled as an ATMEL M328P. Not sure if that has anything to do with it.

Also, the code only seemed to work with the calibration setting of 12.50. Using 14.03 the emitted light was all over the place, but that makes sense because there is probably a different table for the other calibration constant.

Edit: Running firmware v2.6

 

[billywei]

I tried this mod but was unsuccessful. It seemed to roughly work until I got to EV16, then the LED went very dim. Maybe it was going into a protect mode? I backed off the 3rd and 4th column from 140 to 139 but it still went dim. Should I just keep backing it off until it stays on?

The nano board I'm using is a little different from the one you have pictured. It is an official Arduino board, not a knock-off, but the PCB is green and the micro is in a different package. Looks like a QFN rather than a QFP. But it's still labeled as an ATMEL M328P. Not sure if that has anything to do with it.

Also, the code only seemed to work with the calibration setting of 12.50. Using 14.03 the emitted light was all over the place, but that makes sense because there is probably a different table for the other calibration constant.

Edit: Running firmware v2.6

My test was done with firmware v2.9, so it is possible that v2.6 had a different table. The senario behind it is that the origianl firmware actually outputs a PWM with variable frequency as well as duty cycle, because of the limited timer resource. In order to get which EV is selected, the added Nano use a timer to measure the pulse width of the original PWM signal, and YES the margin is not quite enough between some EVs. I guess that's where the error happens and it can also be different for 14.03. You might have to measure the pulse width of v2.6 and mod my table or maybe try upgrade to v2.9 and give it a shoot? Anyway, since my code is attached, you can modify it as you like until it fits your case. And I don't think different version of Nano will be a great different as long as it uses a M328P and the chip's package should also makes no difference.

 

[rortiz35]

Hello all! I know I'm coming to this game late! I've acquired all the parts for this project. I know this sounds crazy, but I cannot for the life of me find the sketch to program the Nano. Was it removed from the github site or am I not looking in the right place? Any help would be appreciated!!!!

 

[FM2]

Firmware

DIY Film Camera Tester. Contribute to srozum/film_camera_tester development by creating an account on GitHub.

github.com

 

[rortiz35]

Firmware

DIY Film Camera Tester. Contribute to srozum/film_camera_tester development by creating an account on GitHub.

github.com

Thank you!

 

[ic-racer]

Just wondering if everyone that started this has finished.

Technically I'm not done yet, I still need to make the flash synch cable.

 

[vandergus]

Mostly. I recently built the #6 sensor (EV sensor) but need to upgrade my firmware in order to use it. I've been putting it off because I don't want to monkey around with the weird ISP programmer business necessary to upload sketches. My arduino skills are basic, at best. But one of my upcoming projects is a Konica C35 automatic, and it would be great to have an EV sensor to confirm the auto exposure used in that camera.

 

[Gregory_Nolan]

Are there any reports on how accurate the tester is? Has someone compared it to a Kyoritsu tester for example?

 

[vandergus]

Are there any reports on how accurate the tester is? Has someone compared it to a Kyoritsu tester for example?

I remember seeing a post on the Learn Camera Repair facebook group where someone compared it with an older professional camera tester. It gave comparable results. I'm not a member anymore so I can't get a link or direct quote.

But I would caveat this with the fact that the build-it-yourself nature of the tester will add some variance.

 

[ic-racer]

Yes, one's skill at constructing the sensor will determine how accurate the device can measure.
The below image is from the ISO document on shutter speed testing. Many things will influence the measurement.

I made a shutter tester calibration device, and there are some on GitHub too. Of course the Film Camera Tester device can't be calibrated, but you can alter the distance of the camera from the screen to adjust the output. For example the sensor I built works best when the camera is about 250mm from the light source (see below).

 

[RMN]

I'm in the middle of this project and have ordered all the 3D prints and PCBs.

I just received the LEDs and I have no idea if its the correct one. Getting slightly concerned I won't be able to get the same LED as the firmware is tuned for. Does this look right?

I received the following items and they both look exactly the same with the one small dot in the top right.

LED World:

SZRZGT- LED Store:

Just in case i bought another warm white 7070.2 from SZRZGT- LED Store which they have listed at a different price and still waiting for that one to arrive.

 

[ic-racer]

I had to do some trial and error. I tested a real Cree against the fake one from AliExpress.

I tested for color temp (rough estimate based on DSLR evaluation of the output temp.)

Most importantly I tested for linearity of the pre-programmed steps on the light source firmware.

 

[ic-racer]

This real Cree XHP70B-00-0000-0D0BP250E spec'd at 5000K and was closer to 4700K referenced in ISO documentation. However, with the firmware available, it did not have a linear response.

 

[ic-racer]

This is the one I used. Unfortunately it came in the same package with two others I ordered from AliExpress. They all look similar. Not exactly sure which one it is.
Anyway, although about 2800k, it was perfectly linear in its output response through the EV range of the tester.

 

[RMN]

I've received the 3D printed parts today. What is the purpose of the flexible hood?

 

[ic-racer]

I did not print the hood. Better might be some flaps of felt that can keep stray light from affecting readings with the lens right up against the surface. I turn all the lights off when testing with the light source, but still might make something so I don't have to do that.

 

[RMN]

Ahh its for the outside. I will post some pics and probably some more questions as I put this thing together.

 

[RMN]

If I understand correctly, there isn't much securing the light unit in place. The mounting brackets are screwed onto the front panel and the reflector slides into the mounting bracket. Its really the bracket in the back that holds the light unit.

 

[bernard_L]

However, with the firmware available, it did not have a linear response.

Maybe a closed-loop control would eliminate that problem? And thermal drift as well. I presume that a photodiode in zero-bias mode has a linear response over a wide range of illuminations.

 

[ic-racer]

Maybe a closed-loop control would eliminate that problem? And thermal drift as well. I presume that a photodiode in zero-bias mode has a linear response over a wide range of illuminations.

Actually, in this thread, billywei decoded the brightness signal to the LED driver and intercepted it and altered it to provide the correct response for his LED.

Building A Professional Grade Shutter Tester

How are you measuring the output? The LEDs in the left of the picture look like the ones I wound up using.

www.photrio.com

 

[bernard_L]

Actually, in this thread, billywei decoded the brightness signal to the LED driver and intercepted it and altered it to provide the correct response for his LED.

Building A Professional Grade Shutter Tester

How are you measuring the output? The LEDs in the left of the picture look like the ones I wound up using.

www.photrio.com

Admittedly I did not read the 270+ posts before writing my suggestion.
Plus, this:

Try to play with column 2,3 and 4. Tune them and upload the code to your added Nano with Arduino IDE. Check the result, change the parameters, upload and check again. Repeat the process until you're satisfied with the output accuracy and linearity. You will have to tune the whole table for each EV but it shouldn't be a a big deal.

is not a closed-loop system. Or, if you prefer, the loop is closed in the designer's head and the response time is the interval between updates. It addresses the non-linearity of one particular LED, but not replacements, or drift due to warm-up during operation.
I had in mind a hardware closed loop. I don't think I invented this; I vaguely remember that some enlarger heads used that principle.