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Author Topic: Auto-step-focus-stacking  (Read 7579 times)

Dick Roadnight

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Auto-step-focus-stacking
« on: August 29, 2010, 05:35:24 AM »

What is the biggest problem with MDF? …DOF

They give us auto bracketing for HDR, so why not autofocus stacking for Focus Merge?
It would be even more useful if this was available remote tethered… we have power remote auto-focus but not manual remote focus (specifying a distance, or without having to re-compose to auto-focus).

Being able to tilt the Plane Of Sharpest Focus is the main argument for a view camera or a T/S adapter… but auto-focus-stacking would largely eliminate the requirement.

For Focus Merge to work well, you need to be able to re-focus in precise steps without touching the camera, and I do not know of any easy way of doing this without using a Medium Format Digital View Camera, or moving the subject on a precision positioning micrometer table like Doug did, see Doug's Article.

I am contemplating using a Velmex programmable linear actuator for auto-focus-stacking, and it would be nice (and lucrative) to be the only fotog that could do it, so, perhaps, I would be happier if they do provide this as a standard function on the H4D-60.

Is it complicated David Grover Hasselblad? …can this be a software upgrade?
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bdp

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Re: Auto-step-focus-stacking
« Reply #1 on: August 29, 2010, 06:02:21 AM »

I think the Sinar Hy6 camera has focus bracketing. I remember the Sydney dealer telling me of one his clients who benefited from it. I don't know any more information, but I assume it does 3 shots using user definable focus distances.

Ben

PS. And BTW some would say the shallow DOF and focus 'roll off' is one of the biggest advantages of MF - I know that's why I use it  - chip size, not just megapixels. We don't all shoot landscapes and interiors :)
« Last Edit: August 29, 2010, 08:07:28 AM by bdp »
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pchong

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Re: Auto-step-focus-stacking
« Reply #2 on: August 29, 2010, 06:35:56 AM »

A commercial solution exists...interestingly it is not too expensive...the whole system including the macro rail driven by a step motor and control electronics is about the price of an RRS macro rail.

http://www.cognisys-inc.com/stackshot/stackshot.php

Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #3 on: August 29, 2010, 08:59:39 AM »

A commercial solution exists...interestingly it is not too expensive...the whole system including the macro rail driven by a step motor and control electronics is about the price of an RRS macro rail.

http://www.cognisys-inc.com/stackshot/stackshot.php
Thank you...

This is very interesting... but I think I would need .001mm

One could mount the rear standard of a view camera on one of these for interiors where DOF would be a problem.

I was thinking of a Velmex three or five axis system for remote multi-row stitching and possibly tilt/yaw on a view camera... but I would want stitching on the rear standard and tilt on the front.

Don't tell anyone, or everyone will be able to do it!
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nad54

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Re: Auto-step-focus-stacking
« Reply #4 on: August 29, 2010, 10:51:24 AM »

I use focus stacking alot in the field with my H3D-50 (now H4D-50) and 50-110mm. There really is no need for automation (though it would be nice). THe beauty of the H camera is the mirror stays locked up. All I have to do is gently tweak the focus ring. Before I start I have noted where the near and far points are. I can work quickly and have done a 10 step stack. The biggest issue is part of the frame moving. I found the camera doesn't move at all as long as it is on a stable tripod. The other big plus with the H system is the leaf shutter doesn't create any vibrations.
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cunim

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Re: Auto-step-focus-stacking
« Reply #5 on: August 29, 2010, 10:59:42 AM »

We used to build a system that did this on microscopes.  It would move the stage in X,Y, and Z  using motors and rotary encoders.  The software needed about 10% overlap to do a seamless job in XY stitching.  The depth dimension (Z) had two options.

1.  Convolve - This is what programs like Helicon do.  They combine the best focal data from multiple planes into a single plane.
2.  Deconvolve - This extracts a single very thin plane of focus - an optical slice - from a series of images each of which has a greater depth of focus.

These systems include things like automated corrections for color casts and for light falloff.  Set it up, go have lunch and come back to an image that might be 50 XY fields of view by 10 planes deep.  OK, I'm lying, it's not quite that easy but the results can really be quite beautiful if you are into the biospecimen type of thing.  Pretty widespread these days.  Too bad it only works well on microscopes.

Image of e. diadema made as above.  Slide is almost 200 yrs old (hence the dirt).  About 20 fields of view.  Can't remember how many planes.  Looks like the mounter tore a leg off during the capture.
« Last Edit: August 29, 2010, 11:09:31 AM by cunim »
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BJNY

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Re: Auto-step-focus-stacking
« Reply #6 on: August 29, 2010, 11:08:13 AM »

I use focus stacking alot in the field with my H3D-50 (now H4D-50) and 50-110mm. There really is no need for automation (though it would be nice). THe beauty of the H camera is the mirror stays locked up. All I have to do is gently tweak the focus ring. Before I start I have noted where the near and far points are. I can work quickly and have done a 10 step stack. The biggest issue is part of the frame moving. I found the camera doesn't move at all as long as it is on a stable tripod. The other big plus with the H system is the leaf shutter doesn't create any vibrations.

When tethered into Phocus,

you wouldn't need to physically touch the focusing ring

as there are left and right arrows in the software which changes the focus.
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Guillermo

Joe Behar

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Re: Auto-step-focus-stacking
« Reply #7 on: August 29, 2010, 11:24:28 AM »

Thank you...

This is very interesting... but I think I would need .001mm



Really?

You're serious about getting 0.001mm accuracy in a rail that moves a complete camera system with tolerances probably an order of magnitude bigger than that?

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Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #8 on: August 29, 2010, 12:18:49 PM »

I use focus stacking alot in the field with my H3D-50 (now H4D-50) and 50-110mm. There really is no need for automation (though it would be nice). THe beauty of the H camera is the mirror stays locked up. All I have to do is gently tweak the focus ring. Before I start I have noted where the near and far points are. I can work quickly and have done a 10 step stack. The biggest issue is part of the frame moving. I found the camera doesn't move at all as long as it is on a stable tripod. The other big plus with the H system is the leaf shutter doesn't create any vibrations.
A 10Kg tripod always helps...
I had contemplated a cable system...
Do you remember the levers they used to supply for focusing Hasselblads?
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Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #9 on: August 29, 2010, 12:23:07 PM »

We used to build a system that did this on microscopes.  It would move the stage in X,Y, and Z  using motors and rotary encoders.
I had thought that it would be routine for photo microscopy... can you configure a digitally optomised photo-microscope to get near 1:1, so that there is not a yawning gap in magnification ratio between photo-microscopy and an apo-digitar macro?
« Last Edit: August 29, 2010, 01:50:00 PM by Dick Roadnight »
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Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #10 on: August 29, 2010, 12:25:36 PM »

When tethered into Phocus,

you wouldn't need to physically touch the focusing ring

as there are left and right arrows in the software which changes the focus.
I had not found that in Phocus - it would be nice to have it automated so that you could take several photos in a few seconds of a live specimen.
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Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #11 on: August 29, 2010, 12:35:10 PM »

Really?

You're serious about getting 0.001mm accuracy in a rail that moves a complete camera system with tolerances probably an order of magnitude bigger than that?

You would only need .001 for very small subjects, and you would tend to move the subject, not the camera.

A precision system would not just have a stepper motor driving through one set of loose gears, but a double drive system so you could tension one against the other to eliminate slop.

...and/or you have a separate measuring system measuring directly on the moved end of the system.

If you have a system with .001 resolution you can move in steps of .003, 4 or 5 which would give you flexibility to make the most of your DOF, and would be very useful even if you never need to use .001 steps.
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Joe Behar

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Re: Auto-step-focus-stacking
« Reply #12 on: August 29, 2010, 12:56:58 PM »

You would only need .001 for very small subjects, and you would tend to move the subject, not the camera.

A precision system would not just have a stepper motor driving through one set of loose gears, but a double drive system so you could tension one against the other to eliminate slop.

...and/or you have a separate measuring system measuring directly on the moved end of the system.

If you have a system with .001 resolution you can move in steps of .003, 4 or 5 which would give you flexibility to make the most of your DOF, and would be very useful even if you never need to use .001 steps.

Dick,

Seriously....the entire system expands and contracts more than 0.001mm with slight temperature and humidity changes.

0.001mm equals  0.00004 inches...are you really suggesting that moving the subject by even 5 times that amount will make a visible difference to anything?

We are talking photography of objects bigger than say, 0.1 inches, right?





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cunim

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Re: Auto-step-focus-stacking
« Reply #13 on: August 29, 2010, 01:12:25 PM »

I had thought that it would be routine for photo microscopy... can you configure a digitally decustomised photo-microscope to get near 1:1, so that there is not a yawning gap in magnification ratio between photo-microscopy and an apo-digitar macro?

Routine, hmmmm.  Easy to do badly.  Even today few systems do it well.  The convolution and deconvolution functions are massive coding projects with deep literatures behind them.

Mechanically and optically, no real problem getting 1X on the microscope.  You could simply order such a system off the shelf.  Things like focus slop and motor precision are not issues because position sensing is built into the hardware and software, usually using optical encoders.  You can locate a single blood cell on a 3" wide slide and come back to it just by feeding in its XY coordinates.

Optically, however, there are issues at 1X.  Low magnification optics have small numerical apertures and yield poor image quality.  Looking at the same image made with a 1X plan objective vs a 4 image stitch with a 4X planapo is instructive.  Same general thing as having a wide angle lens vs a stitched image made with a longer lens.  Horses for courses.

Anyway, this type of system is unlikely to be much use to you.  It works with relatively flat specimens that do not create issues of perspective.


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Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #14 on: August 29, 2010, 01:48:20 PM »

Seriously, I do not know what you problem is...

Dick,

Seriously....the entire system expands and contracts more than 0.001mm with slight temperature and humidity changes.
So you use an automated system to take a succession of exposures while conditions stay reasonable constant, and you mount the object on a rail attached to the monorail of your camera, to eliminate (relative) tripod movement in case of an earthquake.
Quote
0.001mm equals  0.00004 inches...are you really suggesting that moving the subject by even 5 times that amount will make a visible difference to anything?
At the limit, the relevant dimension is the wavelength of light.

For f5, magnification of 25:1 and circle of confusion of 0.01 the depth of field, (without allowance for overlap) is 0.004, according to Wikipaedia.
Quote
We are talking photography of objects bigger than say, 0.1 inches, right?
Wrong
« Last Edit: August 29, 2010, 02:06:59 PM by Dick Roadnight »
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Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #15 on: August 29, 2010, 02:04:15 PM »


Optically, however, there are issues at 1X.  Low magnification optics have small numerical apertures and yield poor image quality. 
I have a Schneider Apo-Digitar Macro for 3:1 to 1:3, and a set of Zeiss Luminar Microscope screw macro lenses for magnification from 1:1 to 25:1, but the Luminars are optomised for 5 * 4" I think, and I would like something for this range of magnification that is optomised for modern digital sensors.
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Joe Behar

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Re: Auto-step-focus-stacking
« Reply #16 on: August 29, 2010, 02:11:40 PM »


For f5, magnification of 25:1 and circle of confusion of 0.01 the depth of field, (without allowance for overlap) is 0.004, according to Wikipaedia.


Using a 25mm lens on your monorail camera would require a bellows extension of 625mm to achieve 25X magnification

Using a 50mm lens needs 1250mm of extension....that's over 4 feet of bellows.

(I hope I have the math right)

This is a nice theoretical discussion but.......

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feppe

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Re: Auto-step-focus-stacking
« Reply #17 on: August 29, 2010, 02:17:28 PM »

Seriously, I do not know what you problem is...
So you use an automated system to take a succession of exposures while conditions stay reasonable constant, and you mount the object on a rail attached to the monorail of your camera, to eliminate (relative) tripod movement in case of an earthquake.At the limit, the relevant dimension is the wavelength of light.

For f5, magnification of 25:1 and circle of confusion of 0.01 the depth of field, (without allowance for overlap) is 0.004, according to Wikipaedia.Wrong


You have taken pixel peeping and measurebating to a whole new level, even by LL standards ;D

Dick Roadnight

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Re: Auto-step-focus-stacking
« Reply #18 on: August 29, 2010, 02:40:28 PM »


For f5, magnification of 25:1 and circle of confusion of 0.01 the depth of field, (without allowance for overlap) is 0.004, according to Wikipaedia.


Using a 25mm lens on your monorail camera would require a bellows extension of 625mm to achieve 25X magnification
In real life, I have over a meter of monorail and bellows, and a support rail...

¿Any problems?
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Joe Behar

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Re: Auto-step-focus-stacking
« Reply #19 on: August 29, 2010, 02:50:37 PM »

In real life, I have over a meter of monorail and bellows, and a support rail...

¿Any problems?

Nope....

Its a beautiful day out. I think I'll go out and take some pictures.

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