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Re: [OM] Focus Stacketing [was Re: OM-D E-M1 Mark II or?]

Subject: Re: [OM] Focus Stacketing [was Re: OM-D E-M1 Mark II or?]
From: Moose <olymoose@xxxxxxxxx>
Date: Sat, 20 Jan 2018 21:11:03 -0800
On 1/20/2018 4:45 PM, Jan Steinman wrote:
From: Moose <olymoose@xxxxxxxxx>

Then they go and use the term "Focus Stacking" particularly for the combination 
of taking a
set of focal plane slices and composting them into one all in-camera.
Cool! After they’re composted, do they grow good tomatoes?

(Gotta love auto-spelling correction… :-)

    Compatible with :
    M.Zuiko Digital ED 60mm f/2.8 Macro
    M.Zuiko Digital ED 12-40mm f/2.8 PRO
    M.Zuiko Digital ED 40-150mm f/2.8 PRO
    M.Zuiko Digital ED 30mm f/3.5 Macro
    M.Zuiko Digital ED 7-14mm f/2.8 PRO
    M.Zuiko Digital ED 8mm f/1.8 Fisheye PRO
    M.Zuiko Digital ED 300mm f/4.0 IS PRO

- Oh, goodie, I have ONE of those. Doesn't work with my 12-100/4 Pro, 12/2, 
25/1.8, 45/1.8, 75/1.8, 9-18, 12-50, 14-42,
75-300? or any of my several Panny lenses.
Yea, I found that somewhat puzzling, as if you’d ever want to focus-stack the 
8mm fisheye. But perhaps I simply lack imagination.

People say that with very short FLs, focusing is kinda optional, as DoF covers everything. Having recently been using a 7.5 mm lens, I can say that they are not telling the truth. Sure, if you are going to make an 8x10 print with no or minimal cropping, and view it at arms length, or whatever the standard is, it's probably true that hyperfocal focus is OK.

But if you view/print it large, or want to crop a lot, or want to correct linear distortion, blah, blah, blah, it does make a difference. At wider apertures, some parts are in focus, others not so much. So maybe there is a place for stacking a fishy.

Do you have any feeling for the difference between actually changing focus in 
focus-bracketing, as opposed to changing the camera position?

This is a classic and unavoidable part of the stacking process, small differences in magnification need to be corrected. The software expects it.

MikeG should chime in here, as he is more knowledgeable than I. I do know that moving the camera position has been the preferred method, apparently creating less to be corrected. I have done it manually, with limited success. I tend to forget if I have moved the camera between exposures. It is going to be subject to more fluctuation in not completely static subjects, changing natural light, etc. than the in-camera focus bracketing of your E-M1 II, which finishes the stack in a couple of seconds.

What we don't know, is how the lens is accomplishing focus. With unit focusing lenses, which were/are used for most focus stacking before the Oly in-camera innovation, it's simple to know what's happening to perspective and magnification.

You might notice that all the above lenses, and indeed all the µ4/3 AF lenses I think of off hand, focus internally, without changing length. We know that at least some early lenses that do this do so by changing the FL, and I suspect that's the dominant method in use. But we really don't know what legerdemain the designers may be using. For all I know, someone could be moving front and rear nodal points forward without moving the lens body or changing the FL by moving internal element(s).

The lenses and this process are really a black box, and all we know is that they provide slices that work in software originally designed for moving camera body.

That's good news for you, as it means your technique should work. In fact, it does, as there gadgets sold that do exactly that.

Especially for macro, I’m thinking the difference is going to be minimal.

I’ve acquired a stepper-motor slider and an Arduino. I should be able to move 
the camera in 0.005 mm increments, allowing you to choose the front, back, and number 
of steps in-between. I know this will subtly change perspective, but on most lenses, 
changing the focus *also* slightly changes perspective.

I assume you are doing this for fun?

But if anyone has a strong argument about how this is A Bad Idea, I’m prepared 
to make a stepper motor change the position of the front or rear standard of the 
bellows, instead.

I would certainly try what you propose first. It's the way it's always been done, and should work fine. Let me rephrase - I would suggest that you try what you propose first . . .  I actually would just use the camera function - and do.

Analog Movement Moose

--
What if the Hokey Pokey *IS* what it's all about?
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