Macro versus Process Lenses ?

[Nathan Potter]

I, likewise, have wondered about the visual differences between a process lens and a macro lens and have kinda thought that any difference may not be sufficient to cause worry. I have assumed that a process lens was designed and optimized for the copy of flat objects, thus optimized for flatness of field at a maximally large aperture so as to achieve highest resolution by minimizing diffraction. But darned if I can think of why one might yield images manifestly different from the other at a given FL and working aperture.

Nate Potter, Austin TX.

[Ken Lee]

Following the mathematics is fairly trivial. We all appreciate the clever inside joke at this point:

"The above integral can then be approximated as..."

... No, just kidding. I bow before all Physicists.

[Ken Lee]

At 1:1, we often use a lens at double its infinity extension. For example, on 4x5, a 150mm lens, or on 5x7, a 210mm lens.

Since the circle of coverage doubles in diameter, are we not likely, in such cases, to use mainly the center of the circle of coverage ?

If that is true, then it seems that what the Macro lenses offer, is extensive use of View Camera movements at close range - with confidence that even out towards the extremes of coverage, the image will be free aberrations like coma, astigmatism, etc. (As Peter explained.)

That makes sense, because they are View Camera lenses, not just Large Format lenses or Process Camera lenses. Just as modern designs improve over vintage designs - by offering greater usable image circles at high fidelity and correction - these Macro lenses do the same.

Is that a fair assessment ?

[Peter K]

It is a fair assessment.

But this lenses are not realy macro-lenses, simple microsope lenses, like the Luminar, Summar etc. but "close-up lenses".

Peter

[Mark Sawyer]

At 1:1, we often use a lens at double its infinity extension. For example, on 4x5, a 150mm lens, or on 5x7, a 210mm lens.

Since the circle of coverage doubles in diameter, are we not likely, in such cases, to use mainly the center of the circle of coverage ?

Remember that macro lenses often don't cover at infinity, so depending on the extension, you may still be using most or all of the coverage.

[Dan Fromm]

Um, Peter, back when I was chasing macro lenses I tried some shots at distance with a 100/6.3 Neupolar. It covered 6x6 +/- a little and was very sharp. Not what I expected. I mentioned this to Charlie Barringer, who told me in return that he'd shot his 100/6.3 Luminar at distance on a Contax Aria and that it was not too bad either.

Macro lenses such as the Luminar are typically better corrected and have better field flatness than simple microscope lenses. Although, come to think of it, I have a little Beck (UK) 5x objective in the drawer that does quite well on 35 mm at around 10:1.

Cheers,

Dan

[Peter K]

Macro lenses such as the Luminar are typically better corrected and have better field flatness than simple microscope lenses.

Dan, the Luminar is a simple microscope lens. Because it cannot used with an eye-piece or photo eyepiece as a compound microscope.

Peter

[mdm]

It appears to me, looking at the data on Ronars, Sironar S's and Macro Sironars, that the primary difference is in working apperature. The process lenses have a working apperture of f22, the Sironar S's f11-22, and the Macro Sironars f8-11. Coverage does not seem to be an issue with any of them.

So it seems that a macro lens is corrected at a faster working apperture. If you are stopping down to f22 or smaller for the dof (aka Kens razor sharp flowers) it is irrelevant which you use, a process lens is the rational option. If you want to use a narrow depth of field to best advantage then a macro lens is the way to go.

David

[mdm]

So perhaps by using a shorter macro lens one can have ones cake and eat it too.

David

[Ken Lee]

One other consideration is what we might call... Quality.

I'm unable to find these for Fujinon or Nikkon - perhaps they exist somewhere in Japanese - but the MTF curves for the Rodenstock and Schneider Macro lenses, are impressive.

http://www.rodenstock-photo.com/medi...7-42__8226.pdf

http://www.schneideroptics.com/pdfs/...r_56_120_2.pdf