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Determining number of shots for a stack?
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rjlittlefield
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PostPosted: Thu Feb 11, 2010 4:03 pm    Post subject: Reply with quote

bvalente wrote:
on the diffraction side of things, if I understand microscope objectives it sounds like they have much larger relative apertures and therefore would suffer less diffraction.

Correct. A typical 10X microscope objective at NA 0.25 - 0.30 is roughly equivalent to f/1.8-1.5 in an ordinary lens.

Quote:
Getting back to my original question/post, it seems like the "basic" math and roughing things in is exactly what would be helpful, at least to me and perhaps others who are at least familiar with photography and the basics, and need a starting point. Maybe I will rough something together.

It would be very helpful to see what you write down. One reasonable approach would be to just take f/5.6 as a given, since that's pretty close to optimal for most lenses. Combine that with the simple formula for DOF that I gave above (as TDF=), and in most cases you'll be within a factor of 2X or so.

--Rik
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AndrewC



Joined: 14 Feb 2008
Posts: 1436
Location: Belgium

PostPosted: Thu Feb 11, 2010 4:06 pm    Post subject: Reply with quote

Extract from my cheat sheet shooting with a D200:

55mm micro on a PK-11 ext ring, f8, 30cm to subject - 1638um slices
50mm el-nikkor, reversed, 60mm extension, f5.6 - 208um slices
50mm el-nikkor, reversed, 200mm extension, f5.6 - 52um slices
80mm el-nikkor, reversed, 200mm extension, f8 - 104um slices
80mm el-nikkor, reversed, 150mm extension, f8 - 208um slices
10x objective at 160mm, 6um slices
20x objective, 210mm, 3um

Don't worry about the funny numbers (1638um, could just as easily be 1500um), it comes from how my controller is programmed.

Those numbers work for me, others might use something different Smile

Andrew


Last edited by AndrewC on Fri Feb 12, 2010 5:07 am; edited 3 times in total
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rjlittlefield
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PostPosted: Thu Feb 11, 2010 4:07 pm    Post subject: Reply with quote

bvalente wrote:
elf wrote:
I usually change the bellows draw to change the focus point instead of moving the subject. Each focus step length using bellows draw is different, whereas moving the subject the focus step length will be the same.
May I ask why would you take that approach vs moving the whole bellows/camera setup?

It avoids perspective changes caused by moving the lens. This is important for stitching multiple stacks together side-by-side, as in "panorama stitching".

--Rik
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bvalente



Joined: 18 Jan 2010
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Location: Los Angeles, CA

PostPosted: Thu Feb 11, 2010 4:07 pm    Post subject: Reply with quote

delightful - the picture is getting more clear - thanks everyone


I will indeed share my 'cheat sheet generator' when I can pull it together here.


Cheers

Brian
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elf



Joined: 18 Nov 2007
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PostPosted: Thu Feb 11, 2010 4:08 pm    Post subject: Reply with quote

bvalente wrote:
elf wrote:
I usually change the bellows draw to change the focus point instead of moving the subject. Each focus step length using bellows draw is different, whereas moving the subject the focus step length will be the same.


elf

May I ask why would you take that approach vs moving the whole bellows/camera setup?


Cheers

Brian


The primary reason is that it allows shooting panoramas with minimal parallax error. Here's an example: http://www.photomacrography.net/forum/viewtopic.php?t=7326
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bvalente



Joined: 18 Jan 2010
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PostPosted: Thu Feb 11, 2010 4:14 pm    Post subject: Reply with quote

Ed - that makes perfect sense. I shoot plenty of panoramas in non-micro world so I see the value of that. Brilliant silverlight rendition of the flowers

Cheers

Brian
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DQE



Joined: 08 Jul 2008
Posts: 1653
Location: near Portland, Maine, USA

PostPosted: Thu Feb 11, 2010 6:38 pm    Post subject: Reply with quote

rjlittlefield wrote:
bvalente wrote:
elf wrote:
I usually change the bellows draw to change the focus point instead of moving the subject. Each focus step length using bellows draw is different, whereas moving the subject the focus step length will be the same.
May I ask why would you take that approach vs moving the whole bellows/camera setup?

It avoids perspective changes caused by moving the lens. This is important for stitching multiple stacks together side-by-side, as in "panorama stitching".

--Rik


Are the above considerations relevant for someone like myself who is seriously considering using the StackShot system with an MPE-65 over a 1-5x mag range, with a full-frame camera? I don't use a bellows with the MPE-65 and have been assuming it's OK to adjust the camera+lens distance to the subject via the StackShot. Yet it seems that compelling arguments are being made against moving the camera/lens assembly in favor of (???) resetting the lens to a different plane of focus between stack slices.

Perhaps the disconnect here is that the above discussion does not apply cleanly to the variable-magnification MPE-65 lens?

I apologize in advance for both ignorance and misunderstandings on my part.
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"Diffraction never sleeps"
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augusthouse



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PostPosted: Thu Feb 11, 2010 8:29 pm    Post subject: Reply with quote

bvalente wrote:
Quote:
At the same time I would hope there could be a way to at least get a rough estimate. Something like

- camera sensor size
- bellows extension (if any)
- lens focal length
- lens aperture



There is a table, titled 'Close-Up Depth of Field for 35mm Cameras' on page 27 of "The Manual of Close-up Photography" by Lester Lefkowitz. Starts at 1:10 and goes through to 30:1 at various apertures.
*Note at base of table (points A to E important): "Data are for symetrical lenses of any focal length and m obtained by lens extension, including "macro" lenses."

Many forum members have this book and it may be the type of reference bvalente is hoping to have on-hand, with allowances for reasonable overlap of slices.

For example on a FF sensor, magnification at 1:1 @f/8 DOF is indicated as 1/32" (0.96mm). 5:1@ f/4 DOF is indicated as 0.002" (0.058mm).

An initial glance, if my understanding is correct (please correct if I'm wrong), this indication is in the region of the increments provided with the post by Charlie regarding his MPE-65 and Velmex rail setup?

http://www.photomacrography.net/forum/viewtopic.php?t=9032


Craig
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rjlittlefield
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PostPosted: Thu Feb 11, 2010 8:59 pm    Post subject: Reply with quote

DQE wrote:
rjlittlefield wrote:
bvalente wrote:
elf wrote:
I usually change the bellows draw to change the focus point instead of moving the subject. Each focus step length using bellows draw is different, whereas moving the subject the focus step length will be the same.
May I ask why would you take that approach vs moving the whole bellows/camera setup?

It avoids perspective changes caused by moving the lens. This is important for stitching multiple stacks together side-by-side, as in "panorama stitching".

Are the above considerations relevant for someone like myself who is seriously considering using the StackShot system with an MPE-65 over a 1-5x mag range, with a full-frame camera? I don't use a bellows with the MPE-65 and have been assuming it's OK to adjust the camera+lens distance to the subject via the StackShot. Yet it seems that compelling arguments are being made against moving the camera/lens assembly in favor of (???) resetting the lens to a different plane of focus between stack slices.

Perhaps the disconnect here is that the above discussion does not apply cleanly to the variable-magnification MPE-65 lens?

I apologize in advance for both ignorance and misunderstandings on my part.

The StackShot should work fine with an MP-E 65.

The arguments against moving the lens entrance pupil sound more compelling in theory than they turn out to be in practice, unless you are trying to stack-and-stitch.

When you are just shooting ordinary single stacks, the usual alignment procedures found in all major stacking software will do a fine job of correcting for perspective changes caused by refocusing. As example, see images in the draft tutorial HERE that I'm developing for Zerene Stacker. BTW, there's nothing special about ZS in this regard. I've run the same source images through Helicon Focus and CombineZP with no problems either.

--Rik
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elf



Joined: 18 Nov 2007
Posts: 1378

PostPosted: Thu Feb 11, 2010 10:55 pm    Post subject: Reply with quote

rjlittlefield wrote:
DQE wrote:
rjlittlefield wrote:
bvalente wrote:
elf wrote:
I usually change the bellows draw to change the focus point instead of moving the subject. Each focus step length using bellows draw is different, whereas moving the subject the focus step length will be the same.
May I ask why would you take that approach vs moving the whole bellows/camera setup?

It avoids perspective changes caused by moving the lens. This is important for stitching multiple stacks together side-by-side, as in "panorama stitching".

Are the above considerations relevant for someone like myself who is seriously considering using the StackShot system with an MPE-65 over a 1-5x mag range, with a full-frame camera? I don't use a bellows with the MPE-65 and have been assuming it's OK to adjust the camera+lens distance to the subject via the StackShot. Yet it seems that compelling arguments are being made against moving the camera/lens assembly in favor of (???) resetting the lens to a different plane of focus between stack slices.

Perhaps the disconnect here is that the above discussion does not apply cleanly to the variable-magnification MPE-65 lens?

I apologize in advance for both ignorance and misunderstandings on my part.

The StackShot should work fine with an MP-E 65.

The arguments against moving the lens entrance pupil sound more compelling in theory than they turn out to be in practice, unless you are trying to stack-and-stitch.

When you are just shooting ordinary single stacks, the usual alignment procedures found in all major stacking software will do a fine job of correcting for perspective changes caused by refocusing. As example, see images in the draft tutorial HERE that I'm developing for Zerene Stacker. BTW, there's nothing special about ZS in this regard. I've run the same source images through Helicon Focus and CombineZP with no problems either.

--Rik


The functionality you lose having a fixed lens (no bellows) is easily compensated by ease of use in the field The StackShot and MP-E 65 should be a very versatile setup. If you want to do panoramas as well, then you'll likely need a different setup. I'd be very happy to have an MP-E 65 alongside my spherical pano setup.
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AndrewC



Joined: 14 Feb 2008
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PostPosted: Fri Feb 12, 2010 1:20 am    Post subject: Reply with quote

DQE wrote:


Are the above considerations relevant for someone like myself who is seriously considering using the StackShot system with an MPE-65 over a 1-5x mag range, with a full-frame camera? I don't use a bellows with the MPE-65 and have been assuming it's OK to adjust the camera+lens distance to the subject via the StackShot. Yet it seems that compelling arguments are being made against moving the camera/lens assembly in favor of (???) resetting the lens to a different plane of focus between stack slices.

Perhaps the disconnect here is that the above discussion does not apply cleanly to the variable-magnification MPE-65 lens?

I apologize in advance for both ignorance and misunderstandings on my part.


Unless you want to print images on the side of a house, creating multirow speherical macro panoramas by adjusting the draw distance and rotating around the lens nodal point does seem a rather specialised endeavour. It is much easier to adjust the camera/lens to subject distance. When you get to >10x magnification with microscope objectives they become telecentric anyway so you can just tile and stitch.

One other thing to consider is the remote control option in Helicon focus which will automatically adjust the lens focus. I haven't tried it myself as my macro camera doesn't have the requisite Liveview capability.

http://www.heliconsoft.com/heliconremote.html

Andrew
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ChrisR
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PostPosted: Fri Feb 12, 2010 2:31 am    Post subject: Reply with quote

Elf's spreadsheet shows more than the snapshot in this thread
but the latter does show how magnification ( and therefore field of view) changes more if you move the rear end (the sensor). Also the movements doing it that way have to become larger as you move away, which can make it more fiddly.

From those points of view, moving the lens is a pretty good way to do it. With an ordinary lens with just a helicoid to move the whole thing together, that means simply moving the focus ring the same amount for each step. BUT, if you use a lens which moves internal elements as you focus, everything changes.
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bvalente



Joined: 18 Jan 2010
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Location: Los Angeles, CA

PostPosted: Fri Feb 12, 2010 8:27 am    Post subject: Reply with quote

augusthouse wrote:
There is a table, titled 'Close-Up Depth of Field for 35mm Cameras' on page 27 of "The Manual of Close-up Photography" by Lester Lefkowitz.

Many forum members have this book and it may be the type of reference bvalente is hoping to have on-hand, with allowances for reasonable overlap of slices.

Craig



Cheers Craig - ordered a used copy ($2.02 at amazon) and hope to check it out soon.



Brian
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bvalente



Joined: 18 Jan 2010
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Location: Los Angeles, CA

PostPosted: Fri Feb 12, 2010 10:06 pm    Post subject: Reply with quote

Hi again everyone,

I wanted to get some feedback on this image - improvements to vibration problems. I switched to a zeiss luminar 40mm but also (and I think more importantly) I added some neoprene dampening between my setup board and the table, and between my subject and the board.




full size at http://www.thesingingearth.com/pub/aphids_on_flower2.jpg

It looks like the same thing I've seen charles post, where the aphids are used as hosts. These look quite dead and their 'visiting friends' long departed

Cheers

Brian
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ChrisR
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PostPosted: Sat Feb 13, 2010 1:52 am    Post subject: Reply with quote

It's certainly sharper, but if you change two things at once (as well as the subject!)... er... ummm...
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