Thanks to both of you for the answers. I'm afraid I'm still a bit confused.
I get that with a 50mm lens the spot is roughly just a bit bigger than the
split image but not as big as the micro prism collar of a 2-13 screen.
I know I'm being a bit thick, but I can't tell if what you (Chuck) are saying
backs up what Winsor said, adds to it, or refutes it.
Are you saying that if I use a 100mm lens, the spot will still be the same
size relative to the focusing aid or not? I thought it would change but now I'm
not sure.
Of course I guess I could always just play around with a white circle on a
black background, move the camera around and see where the meter jumps, but I'd
love to understand it too.
Thanks again.
Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
And there is no direct relationship with the lens other than the fixed
2% of the image area is reading a larger or smaller angle depending on
the lens focal length. The spot area at 2% of the frame should be
approx. 4.7mm diameter and the diagonal of the film frame is 43mm so the
linear coverage of the field of view is 4.7/43 = 10.9%. You should be
able to figure out the angular coverage of the meter given the angular
coverage of the lens using that percentage. A 50mm sees a field of 47
degrees so the meter should see 5.1 degrees.
Chuck Norcutt
Winsor Crosby wrote:
> It is a true spot meter reading only 2% of the image area. It reads a
> circle slightly smaller than the focusing aid on the 2-13 screen. I
> always used the inside split image circle as the best approximation.
> That is probably not accurate, but close enough. You can seen the
> sensitive area in the 1-4n screen on this page:
>
> http://olympus.dementia.org/eSIF/om-sif/findergroup/focusingscreens.htm
>
>
>
> Winsor
> Long Beach, California, USA
>
>
>
>
> On May 19, 2007, at 10:37 AM, OM4 Land wrote:
>
>> Hi all:
>>
>> It seems everywhere I look I find different information regarding
>> the size of the metered zone of the spot meter. Can someone set the
>> record straight?
>>
>> What is the relationship between the spot and the focus aid of a
>> 2-13 focusing screen with a Zuiko 50mm f-1.8?
>>
>> How about 28mm f-2.8 and 100mm 2.8?
>>
>> Thanks
>
>
>
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