[ptx] Re: Extended focus macro work (was "waveblend 0.1.0")

[Glenn Barry]

Good poit abot the increase in magnification changing exposure, have you got
a bellows that can be mounted on a macro foucsing stage, that would allow
you to move the whole assembly?
----- Original Message -----
From: "Rik Littlefield" <rj.littlefield at computer.org>
To: "Glenn Barry" <glennrbarry at optusnet.com.au>
Cc: "Sebastian Nowozin" <nowozin at cs.tu-berlin.de>; <ptx at email-lists.org>
Sent: Tuesday, July 13, 2004 1:28 AM
Subject: Extended focus macro work (was "waveblend 0.1.0")


> Yes, I have gotten good results by adjusting back focus with bellows.
> It is the only method I know to maintain nodal point, at least with the
> lenses that I have.  But the approach has some complications.  Because
> bellows have certain minimum/maximum lengths, they impose strict limits
> on the range of subject focus.  Because the effective f/stop changes a
> lot with bellows length, you cannot just lock the exposure and get
> uniform brightness.  And because magnification changes a lot too, you
> have to rescale and register the images anyway, same as if you moved the
> whole lens/camera assembly.
>
> One important factor in choosing which approach to use is whether the
> subject has parts that hide other parts, so that what's visible would
> change if you moved the lens.  If it does, then locking the lens in
> place and adjusting back focus solves a lot of problems.  If it doesn't,
> then moving the lens/camera assembly may be equally or more effective as
> well as much simpler.
>
> --Rik
>
> Glenn Barry wrote:
>
> >For close up stuff in the big magnification ranges if you had belllows,
you
> >could maintain the nodal point by using the rear camera movement to
focus, I
> >think...
> >----- Original Message -----
> >From: "Rik Littlefield" <rj.littlefield at computer.org>
> >To: "Sebastian Nowozin" <nowozin at cs.tu-berlin.de>
> >Cc: <ptx at email-lists.org>
> >Sent: Monday, July 12, 2004 5:08 PM
> >Subject: Re: [ptx] Release: waveblend 0.1.0 - focus enhancing image
fusion
> >tool
> >
> >
> >
> >
> >>Sebastian,
> >>
> >>Great job!
> >>
> >>I ran the same images through the visibility mask algorithm available at
> >>http://www.janrik.net/ptools/ExtendedFocusPano12/ .  Results are posted
> >>there -- pretty much the same as yours.
> >>
> >>I am not sure how to compare the two approaches.  Both the beaded deer
> >>and the microscope images seem to be fairly simple cases.  I suppose
> >>it's time to haul out the macro lenses and try to work a harder
> >>problem.  (I play with insects in the 1-10X magnification range.  It's
> >>difficult maintaining fixed nodal point in that range, which makes
> >>perfect alignment problematic.  I always end up having to edit the
> >>masks.  But perhaps there are other ways.)
> >>
> >>--Rik
> >>
> >>
> >>
> >
> >
>
>