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Re: [OM] Paphiopedilum Orchid focus stack

Subject: Re: [OM] Paphiopedilum Orchid focus stack
From: Michael Gordon via olympus <olympus@xxxxxxxxxxxxxxxxx>
Date: Tue, 23 Dec 2014 22:10:29 -0500
Good points made by both the good doctors.  I have seem the results and images 
of the gear used.  I should track down the links but have to get up at 3 am to 
catch a Flt.  It seems the stack requires a bunch of clean up but as the oof 
focus stuff is ignored, somehow all gets lined up,  at least according to the 
stacking software engineer Dr. Lou Segusi.

Regards to Dr.  Feelduvyou, Mike

On Dec 23, 2014, at 7:44 PM, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> 
wrote:

> Hmm.  My good friend, Dr. Feelduvyou says he doesn't understand how this 
> would be possible.  When a 28mm full-frame lens is at 1:1 the horizontal 
> field of view is 36mm.  But at 10 times the distance the magnification is 
> 0.03X and the field of view is about 1.37 meters.  Let alone going to 
> infinity how are you going to reconcile just these 2 images???
> 
> Dr. Dunnohow
> 
> On 12/22/2014 11:25 PM, Mike Gordon via olympus wrote:
>> Thanks Dr. Focus.  I knew you would have an answer.
>> 
>> Perhaps this also explains how in an extreme stacking case going from
>> 1:1  to infinity it seems optimal to keep the entrance pupil stationary
>> and move the cam on a bellows back to get more mag.  The lens must
>> perform well at higher mag which may not be the case for  many wide
>> angles to  produce these "macro landscapes."  The Zuiko 28 seems to work
>> quite well by report though the only rig I have seen using it required
>> mount surgery and putting it on a Minolta bellows.  I am not sure how
>> else to accomplish this feat.  Perhaps a T2 mount or Mamiya Wide angle
>> could be mounted on an OM bellows as long as the registration distances
>> and minimum extension on the bellows allow for this.  I think  there is
>> a cheap T2 mount vivitar 28mm that might work but no clue as how it
>> would perform.
>> 
>> Contemplating an extreme stack, Mike
>> 
>> 
>> Dr. Focus writes:
>> 
>> If you will refer to the diagram and formulas on this page
>> <http://www.mhohner.de/formulas.php>
>> Note on the diagram that the value g is the distance from the object
>> (that's being photographed) to the optical center of the lens.  The
>> value b is the distance from the optical center of the lens to the image
>> plane.  Next note that magnification is given by g/b
>> 
>> If, when taking images for stacking, you leave the camera stationary and
>> refocus by moving just the focusing ring forward you are moving the
>> optical center of the lens away from the image plane and increasing the
>> value of distance b.  Distance g is presumably staying the same.  If you
>> move the focusing ring forward by 2mm the distance g can stay the same
>> by virtue of moving the focus point forward by 2mm as well. But since
>> the camera and focal plane didn't move the distance b is increased by
>> 2mm.  Since magnification is given by g/b and b is now larger the
>> magnification will be decreased slightly.
>> 
>> On the other hand, if you move the camera and lens together on a slide
>> as a unit the distances g and b never change.  The focus point is moving
>> along with the motion of the camera and lens but, since neither distance
>> g nor b changed the magnification didn't change.
>> 
>> Now for the kicker.  Each time you move the slide you are also
>> rephotographing an area that you already photographed,  But, since *it*
>> is now at a distance different from the prior photos its (less focused)
>> part of the image is having its magnification changed.  Hopefully, this
>> will be the part of the image that the focus stacker decides to throw
>> away.  In a nuthshell... go with the slide mechanism.
>> 
>> Dr. Focus
>> 
>> On 12/21/2014 3:42 PM, Mike Gordon via olympus wrote:
>>> The framing seems to change less with using a rail--you'd have to ask
>>> Dr. Focus as to why. (yes, I have checked both methods with the same
>> shot)
>> 
>> 
-- 
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