Another question: Didn't John Shaw mention something about stopping
down with the reversed lens rather than the prime lens?
The 50mm reversed onto the 200mm gives 4X magnification
over life size. One drawback is that there seems to be
only a one inch working distance. I will try to sneak up
on a small insect but I think the lack of working distance
is a problem, and it's a characteristic of the reversed lens
independant of the "prime" lens.
Now I'm not "chicken" to photograph an ANT, unless ofcourse
it's a Driver Ant or an Army Ant or for that matter a real
Aunt.
It might be better to reverse the 50mm onto a doubler or
extension doubler which is how I took the Medfly pictures
on my web page at http://www.netcom.com/~flzhgn/medfly.htm
Hank
On 01/16/98 14:54:14 you wrote:
>
>At 11:31 AM 1/16/98 -0600, Ken Norton wrote:
>>Oops, do we have a magnification ratio calculation error here?
>>
>>>> I then used a 50mm f/1.4 reversed onto a 135mm f/3.5. This gives roughly
>>>> 2.7 times magnification (50/135).
>>
>>Hmm. Doesn't it go the other way? 50/135=.37 That's 1/3 magnification
>>not 2.7x. If I put a 50mm reversed on a 50mm, I get 1:1 magnification. If
>>I put the 50mm on a 100mm I get a 1:2 magnification. A 50 on a 200 would
>>give you 1:4 magnification. You will only get greater than life size by
>>reversing a longer focal length on a shorter focal length. For example, a
>>50mm reversed on a 35mm is 50/35=1.4x magnification. A 200mm reversed on a
>>50mm will give you 4x magnification (and serious vigneting too).
>>
>The magnification is defined by:
> M=Image Distance/Subject Distance.
>Since your image is formed on the film in your camera, the image distance
>is the focal length of the lens ("prime" called by John Shaw) directly
>attached to the camera and the subject distance is the focal length of the
>reversed lens.
>
>Therefore,
>M= Focal Length of the prime lens/ Focal length of reversed lens
>
>The top example: 50mm reversed onto 135mm
>M=135mm/50mm=2.7
>
>
>Tomoko Yamamoto
>Photographer, Composer, Soprano
>mailto:tomokoy@xxxxxxxxx
>http://www.charm.net/~tomokoy/
>-All the photos (except panorama) with OM's-
>http://ep.com/ep/csp.html?csp=1130
>-Olympus Equipment Classifieds-
>
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