Archived posting to the Leica Users Group, 2010/03/20

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Subject: [Leica] Image circle
From: philippe.amard at sfr.fr (philippe.amard)
Date: Sat, 20 Mar 2010 22:41:04 +0100
References: <C7C97426.5FADD%mark@rabinergroup.com> <C5C098E7-DF99-4079-9389-44B26C35F8B7@sfr.fr> <36172e5a1003191635x72e31c41s32522640472d0dc1@mail.gmail.com>

a circle is a circle , how comes it has to be corrected?

ph


Le 20 mars 10 ? 00:35, Geoff Hopkinson a ?crit :

> Yes! It is just a better corrected circle. ;-)
> FWIW all of the M lenses produce an image circle sufficient to cover  
> all of
> the 24x36 mm rectangle and Peter Karbe (Optics department head at  
> Solms)
> recently said that the S system lenses provide an image circle  
> sufficient
> for that camera's 30x45 mm sensor (but no larger)
>
> Cheers
> Geoff
> http://www.pbase.com/hoppyman
>
>
> On 20 March 2010 08:40, philippe.amard <philippe.amard at sfr.fr> wrote:
>
>> Is the circle really a circle when using ASPH lenses?
>>
>> Sure?
>>
>> Phx
>>
>>
>>
>> Le 19 mars 10 ? 23:34, Mark Rabiner a ?crit :
>>
>>
>>> Richard,
>>>>
>>>> The size of a lens image circle is not absolute but depends on your
>>>> criteria. Most lenses are sharp and relatively distortionless in  
>>>> the
>>>> center of the image. Quality and illumination fall off as you move
>>>> away from the axis. You have reached the edge of the lens image  
>>>> circle
>>>> when the image quality no longer meets your photographic  
>>>> requirements.
>>>> That being said, the easiest way to determine the approximate  
>>>> size of
>>>> the image circle is to hold the lens in front of a ground glass.  
>>>> Adjust
>>>> it so that it focuses a distant scene and simply measure the
>>>> illuminated circle on the ground glass. Most normal lenses have a
>>>> reasonable quality of image in a circle with a diameter  
>>>> approximating
>>>> their focal
>>>> length. Symmetrical lens designs tend to have a bigger image  
>>>> circle and
>>>> are frequently used for wide angle lenses.
>>>> Larry Z
>>>>
>>>>
>>>
>>> And your image circle gets better when you work closer.
>>> That you learn from view camera work.
>>>
>>> [Rabs]
>>> Mark William Rabiner
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Leica Users Group.
>>> See http://leica-users.org/mailman/listinfo/lug for more information
>>>
>>>
>>
>>
>> _______________________________________________
>> Leica Users Group.
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>>
>
> _______________________________________________
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Replies: Reply from red735i at earthlink.net (Frank Filippone) ([Leica] Image circle)
Reply from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] Image circle)
Reply from mark at rabinergroup.com (Mark Rabiner) ([Leica] Image circle)
In reply to: Message from mark at rabinergroup.com (Mark Rabiner) ([Leica] Image circle)
Message from philippe.amard at sfr.fr (philippe.amard) ([Leica] Image circle)
Message from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] Image circle)