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Printing Nikkor vs Schneider Macro Varon?
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nathanm



Joined: 02 Jun 2016
Posts: 222
Location: Bellevue, WA

PostPosted: Fri Jun 02, 2017 4:03 pm    Post subject: Reply with quote

I think it is actually NEMA 11. I didn't want to have direction change (more gears, more backlash) so I wanted to go directly from the stepper shaft to a gear that engages the beta ring. We made it work, but to do that we had to cut into the lens board a bit to accommodate the back end of the stepper.

The stepper you pictured either has a shaft in a different direction, or has a little gearbox to turn it by 90 degrees. Maybe that is what you mean by the worm gear.

SK gave us the gear parameters for the beta ring. It is a spur gear which has a face width of 5mm, and is a metric gear with a 0.5mm pitch (also called 0.5 module) and 95 teeth.

As I recall, our first attempt was with a plastic stock gear, but it wasn't great and I replaced that with a metal gear. We might have made that in our shop - we have enough CNC machine tools that it is faster to make one than to hunt through web sites.

I think my current gear has 64 teeth. Of course the smaller the number of teeth, the more torque you'll have. But the smaller the number of teeth and the closer your motor shaft must sit to the lens.

Here is a stock gear that I think would work, but there are MANY others

https://www.khkgears.us/catalog/product/BSS0.5-50B

Nathan
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ray_parkhurst



Joined: 20 Nov 2010
Posts: 1752
Location: Santa Clara, CA, USA

PostPosted: Fri Jun 02, 2017 5:04 pm    Post subject: Reply with quote

nathanm wrote:
I think it is actually NEMA 11. I didn't want to have direction change (more gears, more backlash) so I wanted to go directly from the stepper shaft to a gear that engages the beta ring. We made it work, but to do that we had to cut into the lens board a bit to accommodate the back end of the stepper.

The stepper you pictured either has a shaft in a different direction, or has a little gearbox to turn it by 90 degrees. Maybe that is what you mean by the worm gear.

SK gave us the gear parameters for the beta ring. It is a spur gear which has a face width of 5mm, and is a metric gear with a 0.5mm pitch (also called 0.5 module) and 95 teeth.

As I recall, our first attempt was with a plastic stock gear, but it wasn't great and I replaced that with a metal gear. We might have made that in our shop - we have enough CNC machine tools that it is faster to make one than to hunt through web sites.

I think my current gear has 64 teeth. Of course the smaller the number of teeth, the more torque you'll have. But the smaller the number of teeth and the closer your motor shaft must sit to the lens.

Here is a stock gear that I think would work, but there are MANY others

https://www.khkgears.us/catalog/product/BSS0.5-50B

Nathan


Nathan...I'm still not clear why the beta / CAS ring would need adjusting during a stack, even a deep one. I assume the magnification is not changing through the stack, and you certainly would want to optimize the CAS for the in-focus areas. Please explain why the ring would need adjustment.
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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Fri Jun 02, 2017 5:26 pm    Post subject: Reply with quote

Ray, he's moving just the sensor, so magnification decreases linearly with respect to distance from subject.
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ray_parkhurst



Joined: 20 Nov 2010
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Location: Santa Clara, CA, USA

PostPosted: Fri Jun 02, 2017 6:00 pm    Post subject: Reply with quote

Lou Jost wrote:
Ray, he's moving just the sensor, so magnification decreases linearly with respect to distance from subject.


Ahh, that makes more sense, thanks.
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nathanm



Joined: 02 Jun 2016
Posts: 222
Location: Bellevue, WA

PostPosted: Fri Jun 02, 2017 6:11 pm    Post subject: Reply with quote

hmmm.... I have a reply but the system is not letting me post it
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nathanm



Joined: 02 Jun 2016
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Location: Bellevue, WA

PostPosted: Fri Jun 02, 2017 6:12 pm    Post subject: Reply with quote

Magnification IS changing in the stacking method I use. Here is an explanation.

In a conventional single photo with deep depth of field (for example a wide angle shot), the objects closest to the lens have a different magnification than those farther away. This is called wide angle distortion, or perspective distortion, but in the terms of interest to us in macro, the cause is having a range different magnification.

So you could call it "magnification range distortion". When the magnification gradient is strong across a subject you will see it as distortion.

By the way this happens with the human eye as well. Our eyes see something much closer to us as bigger. Eyes even "focus stack" to some degree in the sense that the high res part of your retina is the fovea and it scans across the field of view, remembering the resolution of the best focus.

As a result, some magnification gradient is also what gives us depth cues. That is why perspective drawing has vanishing points - things far from the viewer shrink (vanish) the further away they are.

When we stack macro pictures there are three cases.

1. Keep sensor fixed, and focus with the lens - Rik calls this "by ring".

2. Keep sensor and lens fixed and focus by moving the sensor and lens as a unit. Rik calls this "by rail".

3. Keep lens fixed and move the sensor. This is what I do, and what elf does. I will call this "by sensor", because I don't have a good word starting with an r to called, and saying it is "by rear" just doesn't sound right :-).

Each of these has plusses and minuses. By ring and by rail mess with the perspective in different ways. Rik has a good discussion on his site of ring and rail on the Zerene site

Using a motorized macro rail like Stackshot generally means you are doing it "by rail". Because the sensor to lens distance is constant, this puts everything at the same magnification. The result is something like orthographic projection or parallel projection

there are NO vanishing points - things further from the camera are not rendered at a different magnification, because when each part of the image is in focus, it is the same distance from the lens.

In conventional scale photography this occurs with a telephoto lens - it flattens perspective and depth.

There are two big problems with "by rail" - if you have a deep subject then you must move the camera by the same distance. To take a picture of something 10mm deep, that is not a problem, but if it was 10m deep that is a ridiculously long rail.

But that is what cinematographers do for a dolly shot - they lay a long track and move the camera along it (often sitting on the same platform as the camera).

They don't stack of course, but in principle you could take a dolly shot and stack the frames.

Also, if you really did the 10m movement, you would get a funny looking orthographic drawing look rather than conventional perspective.

By rail works for high mag, and for thin subjects.

By ring works generally better when you can do it - that is Rik's assessment on the Zerene site - because you have less change of perspective issues.

However, you still are changing the perspective because (for a simple lens anyway) the position of the entrance pupil (or "no parallax point") changes while you focus the lens. Floating element lenses can be a different story - they focus by moving elements inside the lens rather than moving the distance from lens to sensor, but mostly the entrance pupil changes for them too.

So, if you want to absolutely minimize perspective changes during a stack, and most closely approximate the perspective of the idealized deep DOF single shot, you must do the 3rd method - keep the lens fixed and move the sensor.

This is like "by ring" in the case that you have a lens with a tripod collar.

It is also what most studio view cameras do to focus - you tend to focus by racking the rear standard with the film holder. Most field view cameras rack the front standard because it is easier to make a folding camera that way.

So this is what I do for "low" mag - i.e. < 5X.

Once I am at 5X, I use Mitutoyo objectives which are pretty close to being telecentric. A telecentric lens effectively does the orthographic projection thing in the optics. Things that are out of focus are the same size they will be if in focus.

Elf is the only other person that I know who does this, maybe he can chime in, although Sager has said in some posts that he does it.

I choose this in part because I thought it would lead to fewer stacking artifacts, and less trouble in doing stitched panoramas. Elf has in the past confirmed that is his experience, and that helped push me this way.

However, I will admit that it also just seemed like a cool way to do it.

It has the advantage that for a large and heavy lens you are only moving the sensor/camera body.

Assuming I like the Rayfact 2-5x, then I will be doing it by sensor up to 5X, and will switch only for higher than 5X.

Nathan
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nathanm
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nathanm



Joined: 02 Jun 2016
Posts: 222
Location: Bellevue, WA

PostPosted: Fri Jun 02, 2017 6:13 pm    Post subject: Reply with quote

I had URL links in the reply I just posted, but the forum software would not let me post - it kept giving a blank post.

When I deleted the URL links it allowed it to go through.

Sorry....
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nathanm
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nathanm



Joined: 02 Jun 2016
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Location: Bellevue, WA

PostPosted: Fri Jun 02, 2017 6:14 pm    Post subject: Reply with quote

Here is the most important link - Rik's discussion of by ring or by rail

http://zerenesystems.com/cms/stacker/docs/troubleshooting/ringversusrail
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19412
Location: Richland, Washington State, USA

PostPosted: Fri Jun 02, 2017 7:17 pm    Post subject: Reply with quote

nathanm wrote:
I had URL links in the reply I just posted, but the forum software would not let me post - it kept giving a blank post.

When I deleted the URL links it allowed it to go through.

The forum software often produces a blank post when the thing inside the URL tags does not look like a legal URL. I'm not sure exactly what the rules are, but it happens to me frequently enough that I consider it routine. Debug strategy when a post goes blank in preview is to look very closely at the URL tags and try to guess what it doesn't like. Sometimes I have to run the URL through something like https://www.urlencoder.org/ in order to make it acceptable.

--Rik
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Sager



Joined: 09 Jan 2015
Posts: 48

PostPosted: Fri Jun 02, 2017 8:14 pm    Post subject: Reply with quote

I shoot almost exclusively by moving the sensor and locking the lens. Nathan and Rik outline many of the benefits. I prefer this method chiefly for the ease of composition and the lack of physical constraints during shooting. Almost all of the work I've been doing lately uses this method.

A few thoughts on each method:

"By Sensor"
•It's much easier to compose an image by focusing on the intended foreground and then moving your sensor forward until you reach your intended far focus. For the miniature landscape work I've been doing lately it's essential to shoot this way. The only difficulty that can arise is on shorter lenses and large flange to focal distances on DSLR's impeding your far focus requirements. Mirrorless cameras, digital view camera setups with in-lens shutters and global electronic shutters largely get around this limitation. Depending on the lens, focus rail and type of camera you can often go typically go from 3X magnification to infinity.

"By Rail"
• The working distance of the lens at a given magnification limits the subject to lens distance and the depth of the stack and types of composition you can achieve. If you want to edge to edge sharpness you have to manipulate your subject in a way to not exceed the boundaries of your setup. I'm often fighting the dimensionality of the subject (or apparatus holding the subject) causing potential collisions with the lens, linear rail or other portion of the setup during movement of the rail. [/url]
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ray_parkhurst



Joined: 20 Nov 2010
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Location: Santa Clara, CA, USA

PostPosted: Fri Jun 02, 2017 9:31 pm    Post subject: Reply with quote

Good discussion on stacking/focusing methods.

I made the assumption you were focusing "by rail", in which case the change in CAS would not be needed/wanted. You probably stated otherwise but I missed it.

I have occasionally done manual focus stacking by moving the rear standard. This works reasonably well across a wide mag range. But in general I use telecentric MM objectives at 3x and above, so focusing by rail gives an excellent result that does not require any scaling from image to image.

edited to add:

My 85MV is back after Mark's measurements, and I will be checking it out again for coins. As I remember, the CAS ring changes focal length, but I don't remember which direction vs magnification. I guess there would be a good and bad direction if back focusing. You would probably want focal length to decrease as you are focusing closer to lens. Either way it would complicate the focusing algorithm, since you could not just focus by moving the sensor, then adjust the CAS ring, because the focus would change either further or the movement compensated depending on direction of focal length change. What is your planned algo for stacking with combined sensor movement and CAS adjustment?
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19412
Location: Richland, Washington State, USA

PostPosted: Sat Jun 03, 2017 10:24 am    Post subject: Reply with quote

nathanm wrote:
I had URL links in the reply I just posted, but the forum software would not let me post - it kept giving a blank post.

I just now encountered that problem with one of my own posts.

The difficulty in that case was that I had failed to turn a bracket into an equal sign, when using the [url=link]text[/url] format.

For example:
Code:
[url=https://www.google.com]This correctly links to Google.[/url]

[url]https://www.google.com]But this makes the post print as blank![/url]

--Rik
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ChrisR
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PostPosted: Sat Jun 03, 2017 2:28 pm    Post subject: Reply with quote

Cf Dolly Zoom : https://www.youtube.com/watch?v=iv41W6iyyGs
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Sager



Joined: 09 Jan 2015
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PostPosted: Wed Jun 07, 2017 12:11 pm    Post subject: Reply with quote

On the note re: gears for the MacroVaron- Nema11,14,17 all typically have 5mm shafts. I might take Nathan's suggestion and go with a smaller motor as the Nema 17 might be a bit large for most setups.

Another great source of custom machine components is Misumi Corp. https://us.misumi-ec.com/

I have ordered numerous gears, custom shafts, customized hardware etc from them over the past 10 years and the prices are competitive and the lead times short. They also have 0.5 mod 20? pressure angle gears in brass, nylon, stainless.

Comparing a brass 0.5module, 50 tooth, 5mm bore gear between KHK and Misumi there is only about a $1 difference in price (KHK = 16.62 and Misumi = $15.77). KHK has them in stock and Misumi has around a ~5 day lead time. Note, you get much better price breaks from Misumi - price drops by about $5 ea. when you buy 10 as opposed to around a $1 from KHK.
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nathanm



Joined: 02 Jun 2016
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Location: Bellevue, WA

PostPosted: Tue Jun 20, 2017 4:53 pm    Post subject: Reply with quote

My evaluation copy of the Rayfact 2x-5x variable lens is here and I am trying to assemble the new set up to use it.

In the meantime I have posted a thread on the Rayfact MJ90 f/4 lens.
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