Light metering question

[Wayne]

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This involves an old Gossen Luna-Pro (Null/9V) meter and the 15/7.5 angle/spot meter attachment. The battery is fresh and the thing does seem to meter consistently with other, modern equipment. IOW, I do not think there is anything wrong with the meter.

 

I was playing around with the meter this morning and noticed that if I point the meter skyward, with the angle/spot metering attachment in place, the meter calls for an exposure setting two stops under what it registers if I point it at the same sky without the angle/spot metering attachment. As I understand, without the attachment, the meter evaluates a 30 degree field; with the attachment, the meter evaluates either a 15 or 7.5 degree field, depending on attachment setting.

 

My question:

 

I understand that the whole purpose of the angle/spot attachment is to give more detailed evaluation of available light in a given field, but in the instance I describe, I am evaluating the same blank sky, and getting two widely different results..........Is there some critical rule of thumb one should keep in mind when trying to perfect exposure through use of a spot meter?

 

As it stands now, if I, in my ignorance, were to try to set up an exposure with the spot meter, it seems I would be underexposing by two stops.

 

Please forgive me if I have entered this question in the wrong place. I have this thing for frustrating myself with outdated, film photography related equipment. The cameras used in conjunction with this meter are, of course, Leicas.

 

Best

 

Wayne

 

[Michael Geschlecht]

Hello Wayne,

 

Did you check to see that the spotmeter attachment & the meter both were clean?

Also: When using a Gossen Lunapro with the spotmeter attachment you do NOT use the "triangle" to determine the number to transfer but you use the large "circle" next to the triangle for reading the 15 degree setting & the small "circle" next to the large "circle" to read the 7&1/2 degree setting.

 

Best Regards,

 

Michael

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[Wayne]

Thanks for the response.

 

As near as I can determine, with naked eye, the attachment is clean and bright.

 

One of the problems associated with the 9 volt (Null) Luna-Pro SBC meter is the fact that it does not include the circles or triangle markings on the dial. I will look at the manual for the other Gossen Luna model and see if I can figure it out.

 

Best regards,

[Michael Geschlecht]

Hello Wayne,

 

The Luna Pro indicates a 1 stop correction when the meter is covering 15 degrees & a 2 stops correction for 7&1/2 degrees.

 

Was your attachment covering 7&1/2 degrees when you metered?

 

Best Regards,

 

Michael

Edited January 19, 2017 by Michael Geschlecht

[Wayne]

Thanks for the information. I was trying with both 15 and 7.5. What you write sounds correct. The 7.5 degree field was about 1 stop lower than the 15.

 

Thanks for taking the time.

 

Best regards,

 

Wayne