Using it for astrophotography will moot the M*/A* 300mm f4.0's main
weakness, in my opinion, it's relatively long close focus distance. For
quite some time now I've been looking for an extension tube set with A
contacts. I figure that a 12-13mm extension ring would bring the
minimum focusing distance down to somewhere between 3-6 feet and give a
long focusing distance of somewhere between 20-25 feet, just perfect for
taking viewfinder filling images of smallish but skittish creatures.
On 10/1/2013 9:26 AM, Darren Addy wrote:
While doing a little research on the M* 300mm I purchased from CollinB
I tripped across this amazingly abused A* 300mm (same optical
configuration). Don't look if you are squeamish about the condition of
your lens optics:
http://forums.steves-digicams.com/attachments/pentax-lenses/147886d1264764384-test-shots-300-scratchedlens.jpeg
Here is the amazing part: Check out the images it still produced in
this condition:
http://forums.steves-digicams.com/pentax-lenses/165305-test-shots-300-a.html
The main reason I decided to try the M* 300mm is for astrophotography.
You can get away with a lot of imperfections in daylight photography,
but pinpoint star images highlight every defect. The M* and A* 300mm
f4 featured 3 of the front 4 lens elements made of ED glass (although
marketing departments had not yet seized on the use of "ED" in the
lens nomenclature). Other elements are made of high refractive glass.
In fact, only two of the 8 elements are "normal" glass lens elements.
For a film era lens, it is pretty highly corrected for chromatic
aberration.
300mm is pushing the limit for use with the O-GPS1, and I'm not even
going to attempt it until I get the Arca-Swiss p0 purchased. It may
even have to wait for the purchase of a "real" equatorial mount that
can respond to auto-guidance (the purchase of which is a loooong way
off yet). But I couldn't resist snagging the lens when Collin offered
last Friday. It should be in my hot little hands on Thursday.
--
A newspaper is a device for making the ignorant more ignorant, and the crazy,
crazier.
- H.L.Mencken
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