robirdman wrote:I was looking at this post Nikon CFI 10X Plan Achromat on Canon 100 mm macro lens, giving 5X.
Is that because that lens is only going to 1/2, not lifesize like my 200mm macro?
No. In both cases the rear lens (the 100 mm or the 200 mm) would be set to infinity focus. (See HERE
for an exception, stepping focus by internally focusing the rear lens.)
The reason for 5X versus 10X is that infinity objectives deliver actual magnification in proportion to the length of the lens they are used with. For most objectives, including Nikon and Mitutoyo, rated magnification happens when used with 200 mm. So when I use it with a 100mm, I only get half the rated magnification. However, such a setup retains the original NA (numerical aperture), which means that optically you get the same resolution on subject
. That turns a nominally 10X objective into an extremely sharp 5X.
And does tube lens just refer to such lenses as these. I hadn't seen them called that in other situations.
The term "tube lens" is borrowed from microscopes. In the beginning microscopes used "finite" objectives that worked by themselves shining light down an empty tube to form the real image that the eyepiece magnifies for viewing. Then microscope designers split up their systems into an "infinity" objective whose output consists of bundles of parallel light rays, plus a new lens that converges those parallel rays to form a real image. The new lens was positioned at the bottom of what used to be the empty tube, so it was called the "tube lens". When using an infinity objective in front of a long lens mounted on camera, the long lens serves the same optical function as the microscope's tube lens. That's why I often write something like "using an ordinary telephoto lens as a tube lens
Here is a large beetle that I took with the primitive macro setup I have been using so far.
I guess it didn't appear.
See the detailed instructions at http://www.photomacrography.net/forum/viewtopic.php?t=7
. Also it would be best to start a new thread ("topic") to show your own images. Inserting them into a FAQ thread is getting too far afield.