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Old Nov 13, 2006, 2:49 AM   #1
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I'm not sure on why some macro lenses, like the Raynox DCR-250 43m, have their magnification indicated with an "x" factor, while others, like the Panasonic DMW-LC52 52mm have a "+" number. If you check those, you'll see that the Raynox


http://www.bhphotovideo.com/bnh/cont...ughType=search


is said to have a 2.5x magnification, while the Panasonic


http://www.bhphotovideo.com/bnh/cont...goryNavigation


has simply a +3. Perhaps someone can explain the difference between both ways of measure magnification, perhaps if there's some equivalence between them and any aditional information about it... it would be appreciated.


Thank you.

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Old Nov 13, 2006, 3:50 AM   #2
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Hi José,

there is little sense in publishing magnification factors.
Do you know the real size of your sensor? ...and does it matter?

Serious authors do not deal with sensor/camera/zoom specific "magnifications" any longer.
Even the field of view (a better value) has to be calculated for each lens/camera.

We need these data:
- focal length or diopters (exact values)
we can calculate the focussing distance, field of view and depth of field with this value.
- quality,lens characteristics: single lens (1E/1G), achromatic (2E/1G or 3E/2G ..)
- inner lens diameter (vignetting?)
- thread rear
- thread front
- optimal focal length of the used camera/lens

nice:
- weight

I have not found a single manufacturer who publishes all of these data.
We had to collect these data on our own and there are still gaps:

http://people.freenet.de/seemolf/achromats.html#chart

Here is a terrible example of unpublished data:
http://www.bhphotovideo.com/bnh/cont...ughType=search
Only the price is specified and the "55" could be the rear thread to an expert eye.

By the way the +3 might be the diopters of the lens, but who cares ... It is still a single lens.
Raynox deals too much with camera specific "magnifications" and hides the diopters, this is not much help. ....somebody should tell them.


Cheers

Sven






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Old Nov 13, 2006, 4:30 PM   #3
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Thanks a lot for the information.

I had some of the data (focal length / diopters) somewhere, I should find it so I can calculate the focussing distance, field of view and depth of field.
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