Re: [Leica] how can the 75 focusthread go so bad?

[John Collier <jbcollier@home.com>]

Obviously this thread has gone on so long that the hypothetical
illustrations are now being confused with the main point.

Time for a segue....Martin? Heck, I would settle for a non-sequitur at this
point....Kyle?

John Collier :-)

> From: Mark Cohen <markc@binaryfaith.com>
> 
> 
> 
> Um.. isn't a 90mm on a 4x5 a wide angle lense whereas a 90mm on a 35 is a
> telephoto...
> 
> Not to mention that a 4x5 camera takes into account the COC and the image
> area on a 35mm doesn't.
> 
> 
> You really can't compare 4x5 to 35mm in _any_ way :)
> 
> -Mark
> 
> 
> 
> On Wed, 7 Feb 2001, John Collier wrote:
> 
> Not at the same print size. The image size on the negative is the same, as I
> already pointed out, but the final image size is different when the print
> size is the same. Which is why the DOF tables vary according to film format
> as well.
> 
> For example: 
> 
> A 4x5 camera and a 35mm camera, both with 90mm lenses, take a picture of a
> subject at the same subject distance. Now make a 4x5 print of both negatives
> using as much of the negative as possible. This is a contact print for the
> 4x5 negative and a, approximately, 4x enlargement of the 35mm negative. The
> resulting image size is "smaller" on the 4x5 contact print regardless of the
> fact that image size is exactly the same on the negative. A smaller image
> size will result, if the same relative aperture is used, in greater
> perceived ?thank you, Martin? DOF.
>
> 
>> From: "Austin Franklin" <austin@darkroom.com>
>> 
>>>> I disagree.  If you take the same lense, and use it on ANY size
>>> film, at the same distance, you will get the same DOF.  >Optics
>>> doesn't know what the film size is, and adjust it self accordingly.
>>> 3' IS 3', no matter what the film size is.
>>> 
>>> That is like saying that a 24mm lens @f8 on 35mm has the same depth of
>>> field as a 500mm lens @f8 on 35mm if you enlarge the 24mm image
>>> sufficiently.
>> 
>> No it is not what I said.  I said, quite clearly, that the same 50mm lense
>> at 3' gives the same DOF on both 35mm and 4x5 film.
>> 
>