lightmeter question

[blushark]

hi,

hopefully this question won't be too offtopic.

i recently acquired a used Gossen Lunasix lightmeter, and have had no previous experience with handheld lightmeters. it's advertised to measure from faintest moonlight to strongest sunlight (EV -4 to 18 if i recall correctly).

the problem i have is following: when measuring incident light on sunny days, if sun falls directly on the lightmeter's diffuser, the reading is almost always 'off-the-chart'. the meter suggests exposures that would produce a few stops underexposure.

EXAMPLE: i want to shoot a portrait. subject is on direct sunlight, sun is behind photographer's back. i take the meter near model's face, point it at where camera will be and measure. sun of course falls on the diffuser. meter indicates either maximum EV show on the scale, or even beyond that.
the reading is not correct as a quick check with a digital camera shows.

my old AE-1 camera, which's lightmeter is also rated at EV 18 has no problems obtaining the correct exposure.

what's the problem? is the lightmeter broken (too old)? is it working fine and for some reason lightmeters can't cope with direct sunlight? am i doing something wrong?

if i can only meter in shadows, that's seriously limiting the meter's usefulness.... and i need the meter since i'm shooting film, often slide, and can't see the histogram right away.

i was hoping incident light metering would solve exposure troubles of a film photographer with an old camera.

 

[Peter Berressem]

It's clearly a faulty / defective meter. I'd contact Gossen by mail for an estimated repair quote. Though...it's not overly pessimistic to expect a charge that exceeds it's actual value.

--
cheers, Peter

Germany

 

[jean bernier]

Clean battery contacts and battery compartment. I have a lunasix wich haven't seen a battery for maybe 20 years. That was a nice meter at the times, long ago. There is a calibration screw at the rear. Maybe some ill-advised person did play with it. Start with sunny 16 rule: 1/100 @ f:16 for ISO 100 for full sunlight. Or borrow a friend's lightmeter for a few hours in order to compare and calibrate.
--
Jean Bernier

All photographs are only more or less credible illusions

 

[cicchettis]

I had a Luna-Pro (the name the Luna-Six was sold under in the US) back in the 1970's. I was never impressed by it's accuracy for incident light readings. Be aware that there is a 10 stop neutral density filter in the meter that is slid out of the way when taking readings on the low range. If this filter is stuck in the out of the way position you will get the same meter deflection on Low or High range. I would suggest getting a more modern meter like a newr Gossen or a Sekonic.

 

[dipics]

Ok, one quick question. I'm not familiar with the Lunasix but every meter that I have used that measures both incident and reflective has used a sliding white dome that you are supposed to slide over the receptor for measuring incident light. Are you using it?

DIPics

hi,

hopefully this question won't be too offtopic.

i recently acquired a used Gossen Lunasix lightmeter, and have had
no previous experience with handheld lightmeters. it's advertised
to measure from faintest moonlight to strongest sunlight (EV -4 to
18 if i recall correctly).
the problem i have is following: when measuring incident light on
sunny days, if sun falls directly on the lightmeter's diffuser, the
reading is almost always 'off-the-chart'. the meter suggests
exposures that would produce a few stops underexposure.

EXAMPLE: i want to shoot a portrait. subject is on direct sunlight,
sun is behind photographer's back. i take the meter near model's
face, point it at where camera will be and measure. sun of course
falls on the diffuser. meter indicates either maximum EV show on
the scale, or even beyond that.
the reading is not correct as a quick check with a digital camera
shows.
my old AE-1 camera, which's lightmeter is also rated at EV 18 has
no problems obtaining the correct exposure.

what's the problem? is the lightmeter broken (too old)? is it
working fine and for some reason lightmeters can't cope with direct
sunlight? am i doing something wrong?
if i can only meter in shadows, that's seriously limiting the
meter's usefulness.... and i need the meter since i'm shooting
film, often slide, and can't see the histogram right away.

i was hoping incident light metering would solve exposure troubles
of a film photographer with an old camera.

 

[blushark]

every meter that I have used that measures both incident and
reflective has used a sliding white dome that you are supposed to
slide over the receptor for measuring incident light. Are you
using it?

yes, i'm using it for incident measuring.

 

[blushark]

It's clearly a faulty / defective meter.

what puzzles me, why i don't understand how it could be defective, is that reflected light metering is pretty accurate (compared to canon AE-1 and EOS 300D). that should mean the sensor is okay and accurate. it's just as if the white dome that slides over picks up too much sun or something.

how do you guys measure incident light when sun is involved?

 

[blushark]

Clean battery contacts and battery compartment. I have a lunasix
wich haven't seen a battery for maybe 20 years. That was a nice
meter at the times, long ago. There is a calibration screw at the
rear. Maybe some ill-advised person did play with it.

yeah, i checked everything, even installed a fresh battery today. i did the calibration too...

 

[jean bernier]

yeah, i checked everything, even installed a fresh battery today. i
did the calibration too...

What do you mean " I did the calibration" ??? You aligned the needle with the very last line, left of display, I suppose. ? That is correct.
Is the needle freely moving, is it ever "sticky"?

With incident metering, the dome should not be pointed at the source. It should be pointed at the camera . The dome represents a three dimentional subject. It's the best designers were able to come with. If the sun is shining at 90 degrees to the subject, only half the dome would be illuminated, therefore the reading won't be the same as if the dome was facing the sun. It should indicate around 1,3 stops less light than when it's pointed at the sun.
Summing up:

camera and sun facing the subject: f:16 1/100 ISO100

camera facing subject, sun at 90°: f: 11,3 1/100 ISO100

In both cases, meter dome is directed at camera.

--
Jean Bernier

All photographs are only more or less credible illusions

 

[blushark]

What do you mean " I did the calibration" ??? You aligned the
needle with the very last line, left of display, I suppose.? That
is correct.

yes, i did precisely that.

Is the needle freely moving, is it ever "sticky"?

yes, it's freely moving.

With incident metering, the dome should not be pointed at the
source. It should be pointed at the camera.

i understand that. i point it at the camera of course, not the light source, but even if only half of the dome is illuminated by the sun, it's already too much for the meter. 1/4 dome illuminated is about maximum meter can measure, and less than that is within coupling range.

but regardless of whether it's in the range or not, sun makes the meter read far more light than there actually is, resulting in underexposure.

for example, if sun falls on only 1/4 of the dome, lunasix will give 1/1000s at f/16 at ISO 100. that's more than 3 stops less then what you stated.

so now i can't figure out whether there's something wrong with the meter, or it's normal for it to go crazy when dealing with direct sunlight?

thanks for the reply!

--
photo: blushark.deviantart.com/gallery/
design: bushidocat.deviantart.com/gallery/

 

[jean bernier]

so now i can't figure out whether there's something wrong with the
meter, or it's normal for it to go crazy when dealing with direct
sunlight?

One thing for sure, there has been nothing wrong with the sun lately. Are you using the yellow pointer? The red and green symbols relate to the spot attachement.

If the meter is properly assembled, the yellow pointer on yellow scale, Number 20 , ISO 100, speed/fStop scale should indicate f:16 1/125th.
This is EV 15 on the lower EV scale.

My meter is labeled Gossen Lunasix 3.

If problem persists, do not see a doctor. Get a digital meter, much cheaper to build accurate.

thanks for the reply!

--
photo: blushark.deviantart.com/gallery/
design: bushidocat.deviantart.com/gallery/

--
Jean Bernier

All photographs are only more or less credible illusions

 

[Peter Berressem]

how do you guys measure incident light when sun is involved?

Exactly as you described.

Hmm.., my tech theory: for whatever reason, the meter can't cope with high light intensity anymore. This may happen but is not common. Most meters work for decades.

There are lots of good meters at about € 50 to 70 on ebay Germany. Snipe a new one and forget about the faulty ;-)

--
cheers, Peter

Germany