Re: [Leica] UV filter for Noctilux-measurable light loss??

[Henry Ambrose <digphoto@telalink.net>]

>>An aside to Tina: What instrument do you use to measure darkness? ;-)
>>Nick.
>
>
>O.K., Nick.  I tried it again.  I am using a Minolta IV F Auto Meter.  I've 
>entered 3200 as the ISO and 1/125 as the time.  In room light, without the 
>UV filter in front of the meter I get an f number of 2.89.  With the UV 
>filter, I get an f number of 2.86.  Not much difference, it's true, but 
>enough to matter when you are taking pictures in the dark!  In my dark 
>hallway, with an ISO of 3200 and 1/30, I get a reading of 1.0 without the 
>filter and a reading of "under" with the UV filter.
>
>Tina
Hi Tina,
Are you  measuring it with a flat diffuser on your Minolta or the little 
dome? If the dome it'll vary from holding the filter in front of it cause 
it is gathering light from the whole hemisphere of the dome. Your hand 
and the filter's metal ring block some light. With the flat diffuser 
installed you actually have a chance of measuring "through the filter 
only"

Try it with a spotmeter mounted on a stand aimed carefully at an evenly 
ilumminated area.  
No filter - read. Then filter  - read again. Without moving the meter.

Even better burn some film!

Henry
who went through all this last year upon buying a new meter and 
rediscovering that NONE of them are very precise and that SELDOM do two 
or more match each other's readings (most all are good enough for making 
pitchers, so we're saved)

next start metering gray cards if you really want to go nuts!