Archived posting to the Leica Users Group, 2002/05/10

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Subject: Re: [Leica] Noctlilux and filters
From: John Collier <>
Date: Fri, 10 May 2002 13:46:34 -0600

The answer is yes and no.

If you use a filter to alter the tone of a small part of your image, 
then the meter should average the whole scene and the tone will shift as 
desired. If, however, the tone you want to alter occupies a large part 
of your image then the meter will suggest an exposure that will render 
the tone as middle grey regardless of what filter you put on.

For example if you have the sky as a large portion of your image, your 
meter will suggest a reading that will give you a middle grey sky. If 
you want to darken the sky in relation to other tones, you could put on 
a deep (red, yellow, green or orange) filter which will reduce the 
amount of the sky's blue light that reaches your film. If you then meter 
the sky with the filter in place, then you will still get a middle grey 
sky and the other tones will be overexposed. So if you meter on the sky 
with the filter in place you need to reduce the exposure to make the sky 
darker (maybe two stops? It depends on the B+W film you are using). You 
also can meter without the filter and apply the filter factor manually. 
That way the sky will be darker and the other tones will not be 
overexposed. As always, you have to think about what you want the image 
to look like and meter accordingly. The hard part is not the metering; 
that is easy, the hard part is imagining the image...

John Collier

PS: Yes I have left out the more complicated bits on the colour 
sensitivity of the meter and the film.

On Friday, May 10, 2002, at 11:07 AM, wrote:

> Question:  Will the TTL metering system automatically adjust with the 
> filter
> on, or does one need to make the calc and then manually make the 
> adjustment?
> Dante

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Replies: Reply from Mark Rabiner <> (Re: [Leica] Noctlilux and filters)