ACL light-meter calibration

[Patricia Dauder]

Hi all,

I'm trying to calibrate my ACL II, LED7 built in light meter, following the procedure described here:

https://eclaircameras.wordpress.com/acl-meter-calibration/

I follow all 6 steps but when I rotate all the way the potentiometer knob to set the proper exposure, I never only get the central diode (zero) lit, the -0,5 stop diode is always lit , regardless of the rotation.

Does that mean that the light meter is not working?

I'm trying to calibrate my Sekonic reflected meter to the ACL meter, to get proper exposure and be able to decide about sub/overexposure for creative reasons

Thanks,

 

Patricia

[Mark Dunn]

Hopefully you will get a better answer than this, but it's possible that the electronics are out of spec due to age. Capacitors are particularly prone to deterioration after 40 or 50 years.

[Patricia Dauder]

Thanks Mark. Will test different exposures to see if I can find a way to figure out the inner meter failure

[Duncan Brown]

If you only ever get the one LED lit it does sound like your meter is broken, but just because this is a good spot to mention it, let me explain what that meter really is....  It's basically an "offset from ideal exposure meter"  First you use an ACTUAL light meter to set your camera properly for the scene it's looking at.  Then you spin the dial on the ACL to normalize the meter to that amount of light coming through the lens, by getting only the center LED lit.  Then, if while shooting the camera with those settings, the light changes, additional LEDs will come on in the viewfinder to let you know that.  Then you change your lens aperture until only the center LED is lit again, and you know you have changed the lens to match the changed light.

So all of this assumes the lens is set so that the amount of light coming in is more or less in the range of something that would be proper for the camera.  If you don't start off with the the camera set right for the light based on another meter, you might be fighting a losing battle to even get just the center LED lit, much less the fact that it won't be giving you information you can use.

Duncan

[Patricia Dauder]

Thanks for the explanation Duncan.

I use first a Sekonic meter L-478D, measuring both incident and reflected light, to get the right exposure and set the camera meter accordingly. But since I can never get the center LED lit alone in my ACL because the next LED after the center one, below, (- 0,5 f)  is always lit, no matter which aperture I'm using , that makes me think the LED7 meter is not working.

In that case, I guess I can only trust the Sekonic readings and forget about the ACL light meter calibration. Correct?

Thanks again

 

[Mark Dunn]

Back in the day when 16mm. was used for news where the light was unpredictable, a built-in meter made some sense. But if you have some control over when and how you shoot, and the system needed an exposure meter anyway, unless you really need the feature as you say, forget it. If you need to move between areas with different light levels, rehearse the shot and change the aperture manually.. You would have had to do that with the ACL anyway.

[Duncan Brown]

6 hours ago, Patricia Dauder said:

In that case, I guess I can only trust the Sekonic readings and forget about the ACL light meter calibration. Correct?

Yes, as Mark said, you were always going to need the real meter anyway, for your initial setting.  If the built in meter is broken, I wouldn't spend any time or money getting it fixed, just meter again if the light changes.

Duncan

[Patricia Dauder]

Thanks for the tips. They've been very valuable to me

 I realize that exposure is quite a thing. I've used film for some time but not that regularly and now I want to learn more about exposure and lighting.  I'm trying to implement Ansel Adams Zone System process to film tests I'm doing.

Will keep on practicing

 

Thanks both!

[Duncan Brown]

I've done still film photography since I was a wee lad (which was a very long time ago!)   I may even be pretty good at it.  This exposure thing is a whole different ball of wax when you can't change the shutter speed, only the aperture and the light.  And you have to look through the lens stopped-down.  Practice, practice, practice.

Duncan

[Boris Belay]

Patricia, if you are still reading this thread (sorry for the delay) : if I understand your point, the led below the middle one is always on ? If that is the case, it's obviously stuck as it should come off when the exposure is correct and especially when over-exposing.

There is a procedure to calibrate the light-meter properly so that it covers all the expected ISO settings, it was meant for installing a new lightmeter in a camera.  But I don't think this is what you are describing.

If I misunderstand your question, let me know.

Boris