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Thread: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm

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GlamourBomb

Posts: 70
Location: United States
Registered: 27 Dec 2010
Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 2 Jul 2013 at 6:21 GMT
Hi, all.

I've been having a heck of a time locking in my lower rail setting. At first it seemed easy enough to do it visually but when I used the AF focus points on my camera and peered through the lens, it just seemed ever so slightly off the bullseye of the Nodal Ninja logo.

So I referred to the Entrance Pupil Data base at PanoTools and determined the lower rail setting (by H of the database) to be 38.5 for a Canon T1i and added 14mm for NN3 to this data making the LRS to 52.5.

When I made that numerical adjustment and looked through the viewfinder, it was completely and totally off.

So I went back to doing this visually and arrived at 51 with the "1" being covered.

But still it looked off to me.

So I made 8 shots at 45° around and looking straight down. Then I layered the images in Photoshop with guides to check. The results are that the center is somewhat within the bullseye but some images are slightly off by a few hairs.

Can somebody please please please download and check my Photoshop file and advise?

The file can be found here: bit.ly/14nlfxv

Note: The file size is about 47mb.
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John Houghton

Posts: 3934
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 2 Jul 2013 at 7:05 GMT
Using the focus points to align the centre of the image frame with the centre of the panohead rotator knob is not an accurate way of aligning the entrance pupil with the vertical axis of rotation. In theory, this should work perfectly well. In practice, tolerances in various settings combine to produce an alignment offset that can be quite large in some cases. For example, the optical axis of the lens is rarely exactly centred on the camera sensor. It is for this reason that PTGui has the optimization parameters d & e to apply a correction for this. So use the focus points method as a quick and easy way of setting up the head. Then fine tune the adjustments using other methods that enable the misalignment of the entrance pupil to be more directly checked.

John
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hindenhaag

Posts: 901
Location: Netherlands
Registered: 7 Mar 2010
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 2 Jul 2013 at 7:55 GMT
Hi, please upload a full set of single pics with www.ge.tt.

Heinz
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GlamourBomb

Posts: 70
Location: United States
Registered: 27 Dec 2010
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 2 Jul 2013 at 8:16 GMT
John: So the plumb line recommended on your site is meant to actually cross the surface of the lens and applied with tape? I'm a little squeamish to have the glass touch anything but will do so if need be.

Heinz: What a nifty little site. Will use that one more often. Here's the link: ge.tt/64AmClk/v/0?c

It's 1:13am PDT. I'll take your reply in the morning. Cheers and thanks.
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burake

Posts: 336
Location: Antalya, Turkey
Registered: 7 Jun 2012
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 2 Jul 2013 at 10:27 GMT
updated: 2 Jul 2013 at 10:28 GMT
You can also have a look at these tutorials of Smooth for finding out your exact settings:


www.easypano.com/forum/display_topic_threads.asp?...

Regards
Burak
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John Houghton

Posts: 3934
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 2 Jul 2013 at 11:49 GMT
updated: 2 Jul 2013 at 11:49 GMT

GlamourBomb said:

John: So the plumb line recommended on your site is meant to actually cross the surface of the lens and applied with tape? I'm a little squeamish to have the glass touch anything but will do so if need be.

There's no need to use tape at all. Hold the plumb line in your fingers just in front of the lens. I only used sticky tape to take the photo as my fingers were otherwise engaged in operating the second camera.

John
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GlamourBomb

Posts: 70
Location: United States
Registered: 27 Dec 2010
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 3 Jul 2013 at 3:18 GMT
Thanks, Burak!

I quickly tried this method using 8 shots around and um, I, uh, forgot to tilt down. blush All I can say is that I'm still getting used to my new tools and this ain't my Sigma 8mm!

Here's the result: ge.tt/6eNkppk/v/0

I'll try it again tomorrow and update accordingly.

And John, makes sense and will try your method in combination with the EasyPano discussion thread.
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GlamourBomb

Posts: 70
Location: United States
Registered: 27 Dec 2010
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 4 Jul 2013 at 0:32 GMT
updated: 4 Jul 2013 at 0:40 GMT
Hey guys,

So based on the method that Burak linked to, I fiddled with it until I got this close:







While I don't have a sawtooth, it looks like the lower part of the head (the silver part) is thicker than the upper part but maybe that's a stitching/warping thing that happened in PTGui?
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Smooth

Posts: 4310
Location: Mount Panorama, Australia
Registered: 21 Jul 2004
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 4 Jul 2013 at 5:13 GMT
While your left to right position (lower rail) is fairly accurate your fore and aft (top rail) It appears you have the camera too far forward.

Be careful that no control points are ever on the tripod and reduce your rotation image count to 6.

Regards, Smooth cool
www.omnipix.com.au
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klaus mayer

Posts: 147
Location: Australia
Registered: 15 Jan 2008
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 4 Jul 2013 at 11:58 GMT
updated: 4 Jul 2013 at 12:00 GMT
While I definitely use Smooth's method to get the lower rail setting right, I am using another step first because I found my upper rail position out by 4mm despite getting rid of the sawtooth when using Smooths method only with my last lens/camera combination.

Use an object very close to the lens (I use a piece of gutter guard sticky taped to a window because it gives me a nice grid) and something with straight lines much further away (light post, building etc). Then take one shot at 30 deg tilted upwards and one shot at 30 deg tilted downwards.

When you compare these 2 shots side by side, parallax will show you immediately if the camera is in the right position on the upper rail because these 2 shots are not affected by rotation or lower rail position.

Once you have the correct location on the upper rail repeat Smooth's method and you will get a much better circle once you have the correct location on the lower rail.

This first step has never failed me and it is much faster to compare 2 images side by side than stitching several images for every incremental change.
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GlamourBomb

Posts: 70
Location: United States
Registered: 27 Dec 2010
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 12 Jul 2013 at 16:04 GMT
Thanks everybody. This seems to be the best results based on my findings. Any feedback is appreciated:


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DennisS

Posts: 1787
Location: Los Anglels, United States
Registered: 1 Sep 2007
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 12 Jul 2013 at 16:20 GMT
klaus,

Then take one shot at 30 deg tilted upwards and one shot at 30 deg tilted downwards
This movement checks the calibration the camera mounted to the upper rail as you are pivoting around the upper rotator. Currenty there is no pano head on the market (that I am aware of) that allows you to adjust left/right on the upper rail. It is assumed that your camera is set plumb/ square/centered correctly on the upper rail. I am not discounting your finding or questioning your technique. Anything that helps dial in a rig is a good thing.


GlamorBomb,

You are oh so very close. You still need to move the camera back so the circle no longer has points. If the circle starts to look lumpy, you have moved too far back. You also need to move left/right just to do the final dialing in.

Your images will most likely stitch just fine with your current settings. Take some pictures and start stitching. If your results look good, then your settings are good enough.

Dennis
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GlamourBomb

Posts: 70
Location: United States
Registered: 27 Dec 2010
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 12 Jul 2013 at 16:49 GMT
Thanks DennisS.

I am having difficulty nailing it down precisely because when I turn the knob it causes movement which is very frustrating. At this point, I feel it is "good enough" for test shots.

Now at 8mm I follow VRWave's number of pictures required for a 360° panorama which is "Standard (1.3x,1.6x): N, 4 images every 90° at +10° pitch, no zenith image required".

The image came out good.

However at 12mm with "Recommended (1.6x): N, 5 images every 72° at +10° pitch, no zenith image required" there is a big hole in the sky. Am I mistaken on pitch or is a Z shot necessary?
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DennisS

Posts: 1787
Location: Los Anglels, United States
Registered: 1 Sep 2007
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 12 Jul 2013 at 17:09 GMT
GlamourBomb,

Recommendations are just that. There are no hard and fast rules in the world of Panoramas. You start with recommended settings and based on results, make adjustments and publish your findings.

Sounds like you need to either tilt up more (making a bigger Nadir hole) or shoot at 0 degrees pitch and include a Zenith shot. You could even pitch down (to make the Nadir hold smaller) since you will be taking a Zenith shot.

Dennis
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John Houghton

Posts: 3934
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
Re: Adjusting the Lower Rail Setting: NN3 + Canon T1i + Canon 8-15mm
Posted: 12 Jul 2013 at 18:39 GMT
updated: 12 Jul 2013 at 18:42 GMT
-Deleted- I didn't note that it was a T1i 1.6 crop camera.
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