In article <4fnkse$177@nntpb.cb.att.com>, gang@mtdcr.mt.att.com1239MT says...

>In article <4fl5mj$15i@newsstand.cit.cornell.edu>,
>Bob Neuman wrote:
>>In article <4fjf97$dt3@nntpb.cb.att.com>, gang@mtdcr.mt.att.com1239MT
>>says...
>>>Mirror lenses also have a shallower depth of field compared to the
>>>conventional lenses of the same aperture. The usual DOF formula >>>doesn't apply to mirror lenses. Therefore, they demand more precise >>>focus.

>>I D O N' T T H I N K S O . . . . . ! ! !
>>Actually, the older Nikkor 500mm f8 seems to have greater DOF, due to
>>the high contrast sharp edges of the "doughnuts of confusion" in out
>>of focus areas. So, what brings you to the conclusion above???
>>Hope This Helps

>Here is how I arrived to my conclusion. By the way, next time, don't
>shout. It is rude.
---Sorry! I meant it as a joke - guess the funny faces are always
---needed.... Your explanation is quite logical, and, I think, correct.
---Thanks for providing it!
---My evaluations of how things perform comes from the experience
---rather than the theoretical end of things - and sometimes the
---two appear to disagree, as here with the apparent DOF of the 500mm
---Nikkor mirror vs. a conventional tele. (Even photos shot at sharp ---angles down building sides with the 500mm mirror appear to have ---near-universal DOF, so I took your pronouncement in the spirit of
---many others that appear groundless and, uh, odd.... [like audio
---interconnect cables having a direction - sorry, Nick! ;-) ]).
>First of all, a mirror lens allows the same amount of light to go >through its optical pupil as a conventional lens of the same aperture.
(rest of excellent explanation deleted, alas - read the post above)
Hope This Helps