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Stack-n-stitch on one foot dried flowers bouquet - Advice ?

 
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KumsaJack



Joined: 13 Apr 2017
Posts: 4

PostPosted: Mon Apr 17, 2017 10:46 am    Post subject: Stack-n-stitch on one foot dried flowers bouquet - Advice ? Reply with quote

Because I’ve done lots of landscape panorama’s and a wide variety of stacked photos (macro and landscape)--I assumed a panoramic macro would be just a little bit more difficult. ha ha ha.

After burning through a weekend, I’ve learned that I don’t know nearly enough to do a stack-n-stitch correctly. The final images looked terrible.


Background:


Here’s a sample of a subject:
https://drive.google.com/file/d/0B6HsY1NkgqiicU9FQXM1XzIwc00/view?usp=sharing

The goal is to create a hi-res image that can be printed large.

My macro lens is a Tokina 100mm, and I’ve set the entrance pupil with a macro rail.

Because I use Zerene, after my failure, I reached out the Rik Littlefield. He supplied some great info, and referenced this forum.

Problem Definition:


I created five different stacked sets to be combined into five images, which could then be stitched. However, the final five images would not stitch correctly. Individually, each image looked good, but the stitching created errors and showed severe ghosting.

Recommended Next Steps ?


I’m not looking at doing microscopic macro-panoramas, just dried flowers. So, I’m not sure if I need to be working with a telecentric addition or not. I accept that I’m not likely to get a step-by-step guide, but there is so much information available that I’m not sure which area is appropriate to investigate, and which is not.

If anyone can point me to the resources that would be appropriate references, that would be a big assist.

Thanks !
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elf



Joined: 18 Nov 2007
Posts: 1319

PostPosted: Mon Apr 17, 2017 11:22 am    Post subject: Reply with quote

What stitching software are you using? Microsoft ICE works well. I usually blend each boundary manually when there is an obvious seam.

Other points to consider:
    Initial stack point for each frame should be the same.
    Subject plane should be close to parallel to the sensor plane. You may want to alter this for a better perspective.
    Rotating around the entrance pupil is essential. Adjust until it's precisely aligned.
    Use bellows to change focus plane for stacking.
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KumsaJack



Joined: 13 Apr 2017
Posts: 4

PostPosted: Mon Apr 17, 2017 11:34 am    Post subject: Reply with quote

Thanks ELF,

My panoramic go-to has been Hugin. http://hugin.sourceforge.net/

"Initial stack point for each frame should be the same. " I definitely did not use the same initial stack point. I think I can do that on another try.

"Subject plane should be close to parallel to the sensor plane." Agree, and that was attempted. I'll make that orientation better defined.

"Rotating around the entrance pupil is essential" Probably thought I was better aligned than I was.

"Use bellows to change focus plane for stacking" Geez. I hope I don't have to use bellows to change focus. That's a world of complexity for my subject.

Thanks again
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Lou Jost



Joined: 04 Sep 2015
Posts: 1765
Location: Ecuador

PostPosted: Mon Apr 17, 2017 8:59 pm    Post subject: Reply with quote

It surely can't hurt to make your lens telecentric. That will give you perfect matching between frames if you move the camera in a plane perpendicular to the lens axis. See my tests with a Tokina 90mm with a Raynox to make it telecentric:

http://www.photomacrography.net/forum/viewtopic.php?t=28980&highlight=

and read Rik's many posts on telecentric lenses.
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Mon Apr 17, 2017 11:46 pm    Post subject: Reply with quote

Unless those flowers are quite small, you're not going to be able to use telecentric optics because for those the telecentric field is limited to the front lens diameter minus the entrance pupil diameter. Telecentrics are fairly simple down to a 1-inch field or so, but larger than that they get difficult and expensive.

When elf speaks of using a bellows, that's because he keeps the lens fixed and steps focus by changing the rear bellows draw. That approach provides a perfect solution to the geometry issues, but from a mechanical standpoint it's pretty challenging to pull off. He uses custom hardware.

In many cases, a quite adequate substitute is to step focus "by ring", turning the focus ring either by hand or under software control by tethering.

The key things are:
1) Make sure that you rotate around the entrance pupil (sometimes called the "nodal point"), or at least around an average position of the entrance pupil if the pupil moves when you step focus.
2) Make sure that you allow the stitching tool to correct for small differences in scale between tiles. With most optics the final image scale will change depending on focus at the start or end of the stack, and the safe assumption is that won't be the same from one tile to another.

Hugin should have plenty of capability to do what you want, but the controls may be more complicated than you'd like. See http://hugin.sourceforge.net/tutorials/multi-lens/en.shtml for a discussion of how to handle two different lenses. Because of scale changes between tiles, you may have a different "lens" for each tile.

--Rik
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Lou Jost



Joined: 04 Sep 2015
Posts: 1765
Location: Ecuador

PostPosted: Tue Apr 18, 2017 4:44 am    Post subject: Reply with quote

Rik, since he is stitching anyway, I assumed he doesn't mind the need to take lots of pictures. In the demo I linked to, yes, my field size was about an inch, the diameter of the Raynox front lens.

To comply with Rik's point #1, you could try focus-stacking with the lens fixed, using a lens whose entrance pupil is fixed during focusing. Then rotate this lens around its entrance pupil for the to-be-stitching shots. The only lens I've seen myself that has this property is the one built into the Panasonic FZ200 or 300, at its widest setting (which will introduce an unusual and in this case probably unwanted perspective and defeat his purpose...). But forum members probably know others. Maybe some internal-focusing zoom? Maybe a coupled pair of lenses with the rear lens doing the focusing?
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KumsaJack



Joined: 13 Apr 2017
Posts: 4

PostPosted: Tue Apr 18, 2017 3:20 pm    Post subject: Reply with quote

rjlittlefield wrote:

2) Make sure that you allow the stitching tool to correct for small differences in scale between tiles. With most optics the final image scale will change depending on focus at the start or end of the stack, and the safe assumption is that won't be the same from one tile to another.

Hugin should have plenty of capability to do what you want, but the controls may be more complicated than you'd like. See http://hugin.sourceforge.net/tutorials/multi-lens/en.shtml for a discussion of how to handle two different lenses. Because of scale changes between tiles, you may have a different "lens" for each tile.

--Rik



There's that great quote that in theory there is no difference between theory and practice. In this case, I have a hazy concept of the lens parameter being a little different for each tile in a focus stack. But .... I'm not sure how to define what it would be.

I'm using a prime 100mm macro, so in my little brain, I have no idea of what else to put in for Hugin, other than 100. In fact, it sometimes reads the EXIF and suggests something else, and I overwrite it. If I can get some time in the next few days, I'll do a simpler test macro/pano and capture the settings, etc.
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Tue Apr 18, 2017 7:13 pm    Post subject: Reply with quote

KumsaJack wrote:
There's that great quote that in theory there is no difference between theory and practice.

Even worse, practice changes from time to time. I downloaded hugin to take a look, and discovered that its current user interface is a lot different from what is shown in the tutorial.

Of course this is exactly as documented. "Note: This tutorial is based on the 0.8.0 version of Hugin. Although your version may differ, the underlying principle will remain the same." Sigh...

Quote:
I'm using a prime 100mm macro, so in my little brain, I have no idea of what else to put in for Hugin, other than 100.

No problem, go ahead and do that. Get the panorama looking as good as you can. Save the project, just in case something goes wrong. (What could possibly go wrong?)

Then proceed as follows...

1. In Hugin's menu system, go to Interface > Advanced. At the Photos tab, you will see a list of your images, all showing "Lens no. 0". If you select one of the images and look down under "Lens type", it will say Focal length: 100. The same value will show for all of the images.

2. At the bottom of the Photos tab, in the Optimize section, select "Geometric: Positions, View and Barrel (y,p,r,v,b).", then click Calculate. For reference, record the numbers that turn up in the "Optimizer run finished" popup. Apply those changes.

3. Probably the Focal length is still showing as 100 mm. But if not, then at least it is still showing the same value for all images. (We'll fix that next.)

4. For each of images 1-N (that is, excluding image 0), select the image, then right-click and in the popup menu do Lens > New Lens. When you're done with all images, they will now show "Lens no. 0", "Lens no. 1", "Lens no. 2", and so on, with each image having a matching lens number.

5. Now repeat step 2, pressing Calculate to optimize (y,p,r,v,b). Again record the numbers and apply the changes.

6. Finally, step through the list of images again, selecting each image and looking again at what is shown for "Focal length:" in the Lens type area. In the test that I'm running as I write this, I am now seeing focal lengths of 99.699, 99.918, 99.886, 100.075, 100.352, and 100.074, and the average control point distance (reported in the optimizer results) dropped significantly.

There are other methods to do this that are more "theoretically correct", but they also require more twiddling that can go wrong, so I think it's best to start with what I've written here.

Let us know how you get along, please.

--Rik
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ChrisR
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PostPosted: Wed Apr 19, 2017 2:04 am    Post subject: Reply with quote

If the lens is one where the FL reduces as you focus close, to say 70mm, would that make a difference? I'm aware some alter quite a lot.
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rjlittlefield
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PostPosted: Wed Apr 19, 2017 8:33 am    Post subject: Reply with quote

ChrisR wrote:
If the lens is one where the FL reduces as you focus close, to say 70mm, would that make a difference? I'm aware some alter quite a lot.

Offhand, I think what matters should be how much focus breathing the lens exhibits. (Focus breathing = change in angle-of-view with focus.)

Lenses that reduce FL when focusing closer are actually better in this regard. See http://www.photomacrography.net/forum/viewtopic.php?t=20981 for discussion.

--Rik
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KumsaJack



Joined: 13 Apr 2017
Posts: 4

PostPosted: Wed Apr 19, 2017 10:43 am    Post subject: Rik, those steps are incredibly helpful Reply with quote

Thanks Rik, I can't believe you took the time to break it down. It's very appreciated, and I will report back on my findings (probably a week).

I'm anxious for a rematch !
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