Archived posting to the Leica Users Group, 2001/05/04

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Subject: Re: [Leica] Which Ultra-Wide, Heliar 15mm or Heliar 12mm
From: Henning Wulff <henningw@archiphoto.com>
Date: Fri, 4 May 2001 17:07:02 -0700
References: <45EDA71CFF25D411A2E400508B6FC52A031E0741@orportexch1.internal.nextlink.ne t> <3AF31EE6.A6D9C572@visi.net>

At 5:28 PM -0400 5/4/01, Isaac Crawford wrote:

>  > Off line I've received several very interesting replies regarding the
>>  Heliar. Including some very technical and interesting points about
>>  vignetting, light fall off and other issues at various apertures. These
>>  might cause metering issues.
>
>	That's some serious light falloff if its affecting a center weighted
>metering system!:-)
>
>They also me to understand the lens. Superwides
>>  are attractive little creatures, because they're unusual. But they do have
>>  their foibles.
>
>True enough...
>>
>>  Dave

In my experience super wides need a little more exposure, partly due 
to the fact that since such a large solid angle is imaged and both 
near and far are often important components of the image, the 
contrast range tends to be greater than with longer lenses. Combine 
this with the larger amount of light falloff to the corners, and you 
then need even a bit more exposure overall. I usually give 1/3 to 1/2 
stop more exposure with slide film and another 1/3 with negative film 
when using the 15 or 12, compared with metering the same surface with 
a 50. The 21's generally need an additional 1/3 stop at most.

In reply to: Message from Isaac Crawford <isaac@visi.net> (Re: [Leica] Which Ultra-Wide, Heliar 15mm or Heliar 12mm)