🚀 go-pugleaf

In article <1992Aug11.165800.8441@swift.cs.tcd.ie>, mahonj@swift.cs.tcd.ie
writes:
> Could anyone recommend a lens of about 50 mm focal length
> optimised for 1:1 reproduction ratio ?
> 
> This would be used with a c-mount video camera with an image
> sensor size of 8.8 x 6.6 mm so a wide angle coverage is not
> important.  What is important is the ability to resolve at
> least 10 microns (preferably much better than that).
> 
> I have already considered enlarger lenses, but I really want
> something for 1:1 which is outside their optimal range.
> 
> It should have an iris, and ideally a focus mount, but this
> is not critical.  Any fitting could be used.

I recommend the Sigma line of lenses.  They make lenses fitting
all of the popular mount types (with the exception of c-mount).
You might try the Nikon auto-focus mount since I know that 
Nikon-to-c mounting adaptors exist.  The advantage of Sigma is
that they are cheap and every bit as good as the name brands.

I just bought a 90mm f2.8 macro that goes down to 1:1 with the
included life size adaptor lens.  I believe a 55mm version
exists also.  They are about $200 - $250 depending on where you buy
them.

In any case, be sure to specify that you want 1:1 capability
since many macros only go 2:1 or 4:1.  I've even seen
supposed micro lenses that only go 2:1 (figure that out!!)

As for resolution, on an f2.8 lens, the best resolution will
be at f5.8 or f8.  For a decent lens, this is typically in the
80-100 line pairs/mm range.  If you're imaging at 1:1 your resolution
may be limited by your sensor (i.e. 8.8mm /512 = 17 microns).

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|Dick Wallingford      | Internet: dickw@iastate.edu                 |
|Center for NDE        | Packet  : wd0anb@n0an.ia.usa.na             |
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