LX metering and timing

palindrom · 09-30-2009, 06:49 AM

So it happened. Yesterday my LX arrived. I took it to work (lab) and measured timing in the first place (2-20% off). OK, perhaps I can live with 4.4s instead of 4s.

What really worries me is metering and automatic exposure. I've put a piece of undeveloped film for proper metering and for various apertures and light intensities I compared indicated and actual exposure time for smooth surface. It looked like that:
1/2s -> 1s
4s -> 3s
2s -> 1s
1s -> 1.5s
I understand that LX measure light scattered from film, so even its color is relevant, but are such differences normal? It would mean that speed indicator is really roughly approximated value, but then will manual speed selection be accurate?

I think the best would be finding a high definition film, taking few shots of gray scale test and put it through densitometer (which I have at work). What film I could use?

Yes, It's worth the effort because CLA is close in price to LX itself

KungPOW · 09-30-2009, 10:07 AM

Remember the LX in auto exposure sets the shutter stepless.

So the camera's LEDs might indicate it is using a shutter speed of 4s, but it actually uses 3.2s.

That might account for some of the variation. How does the meter read in manual mode?

SOldBear · 09-30-2009, 11:32 AM

It's very interesting.

When I got my LX back from the CLA job (Eric), it had the same symptom as you described. I contacted Eric and he told me to test it with a roll of film. The negatives came back with perfect exposures.

Like you said, I tested the metering by photographing an 18% gray card under different lighting conditions. But I didn't use any special "high definition" film. I don't even remember what kind of film I used. All I remember is that it was ISO 100 B&W Kodak.

The cost of a CLA job from Eric is $160 + parts. I think a decent LX body cost a lot more than that.

Wheatfield · 09-30-2009, 05:15 PM

In auto, the readout is only an approximation of what the actual exposure is. The meter readout is off the leading shutter curtain, the actual exposure is metered on the fly off the film at speeds slower than sync. I believe all LX metering is off the curtain at speeds faster than sync.
As the resolution of the meter readout is in full stops, it has no way of resolving partial stops.
Go out and take some pictures and stop worrying about things that are of no importance.
Enjoy your LX.

09-30-2009, 06:49 AM	#1
palindrom Forum Member Join Date: Aug 2008 Location: Wroclaw Photos: Gallery Posts: 54	LX metering and timing So it happened. Yesterday my LX arrived. I took it to work (lab) and measured timing in the first place (2-20% off). OK, perhaps I can live with 4.4s instead of 4s. What really worries me is metering and automatic exposure. I've put a piece of undeveloped film for proper metering and for various apertures and light intensities I compared indicated and actual exposure time for smooth surface. It looked like that: 1/2s -> 1s 4s -> 3s 2s -> 1s 1s -> 1.5s I understand that LX measure light scattered from film, so even its color is relevant, but are such differences normal? It would mean that speed indicator is really roughly approximated value, but then will manual speed selection be accurate? I think the best would be finding a high definition film, taking few shots of gray scale test and put it through densitometer (which I have at work). What film I could use? Yes, It's worth the effort because CLA is close in price to LX itself

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09-30-2009, 10:07 AM	#2
KungPOW Veteran Member Join Date: Nov 2007 Location: Vancouver, Canada Photos: Gallery Posts: 1,699	Remember the LX in auto exposure sets the shutter stepless. So the camera's LEDs might indicate it is using a shutter speed of 4s, but it actually uses 3.2s. That might account for some of the variation. How does the meter read in manual mode?

09-30-2009, 11:32 AM	#3
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	It's very interesting. When I got my LX back from the CLA job (Eric), it had the same symptom as you described. I contacted Eric and he told me to test it with a roll of film. The negatives came back with perfect exposures. Like you said, I tested the metering by photographing an 18% gray card under different lighting conditions. But I didn't use any special "high definition" film. I don't even remember what kind of film I used. All I remember is that it was ISO 100 B&W Kodak. The cost of a CLA job from Eric is $160 + parts. I think a decent LX body cost a lot more than that.

09-30-2009, 05:15 PM	#4
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	In auto, the readout is only an approximation of what the actual exposure is. The meter readout is off the leading shutter curtain, the actual exposure is metered on the fly off the film at speeds slower than sync. I believe all LX metering is off the curtain at speeds faster than sync. As the resolution of the meter readout is in full stops, it has no way of resolving partial stops. Go out and take some pictures and stop worrying about things that are of no importance. Enjoy your LX.