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dvmorris
Joined: 25 Dec 2005
Posts: 2
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 Posted: Fri Dec 30, 2005 9:22 am Post subject: |
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I am new to this whole panoramic photography idea, and I just received a nodal ninja for Christmas.
After extensive research, I have discovered that no one has taken it upon themselves to publish any kind of useful chart that would display the precise nodal points for all these lens/camera combinations.
I emailed Canon tech support last night about getting a chart with nodal point numbers for my lenses and my camera, and got this response:
| Quote: |
Thank you for writing to us. We value you as a Canon customer and appreciate the opportunity to assist you.
Unfortunately, this information is not tested or published by Canon.
We do not have this information to offer you. We apologize for any inconvenience this may cause. |
So I asked if it would ever be published in the future and got this response:
| Quote: |
Thank you for your inquiry. We value you as a Canon customer and
appreciate the opportunity to assist you.
The Principal point or Nodal point is defined below.
The focal length of a thin, double-convex, single-element lens is the
distance along the optical axis from the center of the lens to its focal
point. This center point of the lens is called the principal point.
However, since actual photographic lenses consist of combinations of
several convex and concave lens elements, it is not visually apparent
where the center of the lens might be. The principal point of a
multi-element lens is therefore defined as the point on the optical axis
at a distance equal to the focal length measured back toward the lens
from the focal point. The principal point measured from the front focal
point is called the front principal point, and the principal point
measured from the rear focal point is called the rear principal point.
The distance between these two principal points is called the principal
point interval.
We hope this information is helpful to you. Please feel free to contact
us again if you have any other questions or concerns. |
Anyways, to be more specific, I have an eos 300d, a canon ef 28/f1.8, and the basic 18-55, and I am wondering if someone already knows the settings I could use on the nodal ninja, or if I really just need to test it out using one of those methods.
Also, I understand the nodal point (or entrance pupil, whichever one you're really supposed to use) changes based on the focal length at the time, but does it really change also based on the aperture of a particular shot as well? I have tried a few pano shots of interior scenes, and I am getting some decent results, but they could certainly be better if I found the exact points.
Thanks for your help,
Dave |
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ATucker
Joined: 27 Dec 2004
Posts: 88
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| Posted: Fri Dec 30, 2005 3:44 pm Post subject: |
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| dvmorris wrote: |
Anyways, to be more specific, I have an eos 300d, a canon ef 28/f1.8, and the basic 18-55, and I am wondering if someone already knows the settings I could use on the nodal ninja, or if I really just need to test it out using one of those methods. Dave |
Dave: Look at this thread:
http://www.tawbaware.com/forum2/viewtopic.php?t=2213
Then go to this site:
http://www.panotools.info/mediawiki/index.php?title=Entrance_Pupil_Database
I do not see the ef 28/f1.8 listed there so maybe you can contribute. Regardless, I would still test out the values supplied before you shoot your masterpiece. |
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dvmorris
Joined: 25 Dec 2005
Posts: 2
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| Posted: Fri Dec 30, 2005 4:55 pm Post subject: |
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| wow, that's great, I wish that site could be more google friendly so more people could find it. Thanks so much for your help. |
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nputtick
Joined: 20 Dec 2005
Posts: 26
Location: North Yorkshire, UK
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| Posted: Fri Jan 06, 2006 4:53 am Post subject: |
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JohnH writes:
"The EP position for the Canon 70-200mm f/4L is well behind the lens mount"
I am curious as to how you are measuring this, John. Max Lyons clearly shows in his review of the KingPano that he cannot move the camera body far enough back along the axis to place the "nodal point" over the axis of rotation for this lens. However with the Panosaurus, which has a longer arm, he can achieve this, and his results suggest he is correct! See http://www.tawbaware.com/kingpano_review.htm
I also have this lens and have been unable to measure the "EP" as yet for precisely the same reason - because the rearward extension of my homebrew head is insufficient to reach the no-parallax point. I will soon have a Kaidan Spherical and will hopefully be able to measure the correct position for the 70-200 f/4L, which I believe is about 2cm inside the front element, and not behind the plane of the lens mount.
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dvmorris writes:
"I have discovered that no one has taken it upon themselves to publish any kind of useful chart that would display the precise nodal points for all these lens/camera combinations"
Well, there is a start (at least) here:
http://www.panotools.info/mediawiki/index.php?title=Entrance_Pupil_Database
and the KingPano website has some data on positioning for camera/len combinations which has to be reverse-calculated from the arm dimensions, so is less useful.
Nigel |
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johnh
Joined: 20 Jul 2003
Posts: 2062
Location: UK
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| Posted: Fri Jan 06, 2006 9:24 am Post subject: |
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| nputtick wrote: |
JohnH writes:
"The EP position for the Canon 70-200mm f/4L is well behind the lens mount"
I am curious as to how you are measuring this, John. Max Lyons clearly shows in his review of the KingPano that he cannot move the camera body far enough back along the axis to place the "nodal point" over the axis of rotation for this lens. |
The position of the entrance pupil that Max indicates in his photograph is for a zoom setting of 70mm. The entrance pupil moves much further back at longer zoom settings. I investigated (rather than measured!) the entrance pupil position by viewing the entrance pupil through the front of the lens and checking for lateral motion as I rotated the lens about various points along the lens axis. My comment referred to the 200mm setting. Actually, I think "well beyond" was overstating it, but I was making the point that the entrance pupil was not necessarily inside the lens. A better example is in this table which suggests that the Nikon 80-200mm at 200mm zoom has the entrance pupil 29.8mm behind the film plane.
John |
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nputtick
Joined: 20 Dec 2005
Posts: 26
Location: North Yorkshire, UK
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| Posted: Fri Jan 06, 2006 4:30 pm Post subject: |
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Thanks, John, I've looked at that table now. I find it intuitively difficult to imagine a no-parallax point some 30mm BEHIND the sensor (film plane), but I won't rule it out. What I will do is measure the position of the EP or no-parallax point for the 70-200 f/4L for myself, at different focal lengths, and post the results.
Such a position for the "EP" would make it very hard to use a pano head, as the camera/lens would have to be mounted IN FRONT of the axis of rotation of the spherical arm, i.e. the "wrong" way round, and the whole assembly would then move up and down by several cm when performing up/down tilt for successive rows, introducing severe parallax errors. Try visualising it.
I would be very surprised if it is correct, but as I say I do have an open mind!
I wonder what Max has measured for his 70-200 at the long focal lengths?
Cheers
Nigel |
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GaborSch
Joined: 27 Aug 2005
Posts: 765
Location: Canada, British Columbia, West Vancouver
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| Posted: Fri Jan 06, 2006 5:44 pm Post subject: |
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| nputtick wrote: |
| Such a position for the "EP" would make it very hard to use a pano head, as the camera/lens would have to be mounted IN FRONT of the axis of rotation of the spherical arm, i.e. the "wrong" way round |
Can't you mount the camera "upside down" (so that the grip is underneath), in order to get to the front of the pivoting point?
Of course, only for measuring it, not for the normal operation.
_________________
Gabor
www.panopeeper.com |
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maxlyons
Joined: 20 Jun 2003
Posts: 3345
Location: USA
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| Posted: Fri Jan 06, 2006 8:26 pm Post subject: |
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| nputtick wrote: |
| I wonder what Max has measured for his 70-200 at the long focal lengths? |
I fear that I'm going to disappoint a lot of folks who measure the magic point ("nodal", "entrance pupil", whatever...we know what it is when we see it) in mm. I'm not this precise. I know that if I slide the camera all the way to the back of my Panosaurus it gets pretty close to the right point at 70mm. If I slide it all the way forward it gets close enough (for my purposes) at 200mm. I rarely use this lens at 200mm because it is blurry on one edge (something I've written about more than once on this forum), and for points in between I usually guestimate an intermediate point between the extremes of the Panosaurus.
Max |
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johnh
Joined: 20 Jul 2003
Posts: 2062
Location: UK
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| Posted: Sun Jan 22, 2006 3:21 pm Post subject: |
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Early on in this thread, I reported that I was involved with a small group looking into the rival claims for the nodal point and entrance pupil being the "no-parallax" point. We have now finished our investigations and experiments. The results are reported in this paper by Rik Littlefield. Some of the findings will probably surprise you. However, the bottom line is that the no-parallax point is indeed the entrance pupil, and Gabor will no doubt be pleased to find there are ray diagrams to prove it!
John |
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GaborSch
Joined: 27 Aug 2005
Posts: 765
Location: Canada, British Columbia, West Vancouver
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| Posted: Sun Jan 22, 2006 8:17 pm Post subject: |
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I can not read the linked pdf file. I could read the first few pages, then nothing more, but now not even so much; Acrobat goes into an endless CPU loop.
I downloaded it separatedly as well, but my Acrobat version can't process it.
_________________
Gabor
www.panopeeper.com |
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Jim Z
Joined: 11 Oct 2005
Posts: 774
Location: Tahoma CA
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| Posted: Sun Jan 22, 2006 11:17 pm Post subject: |
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John,
Thank you and the others for the work. The external and internal aperture experiment really makes a sensible idea out of the 'abstract' optical question.
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Jim Z |
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johnh
Joined: 20 Jul 2003
Posts: 2062
Location: UK
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| Posted: Mon Jan 23, 2006 2:39 am Post subject: |
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Gabor, I have Acrobat 5.0 and Adobe Reader 7.0 installed on WinXP and both read the pdf file without any problems.
John |
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GaborSch
Joined: 27 Aug 2005
Posts: 765
Location: Canada, British Columbia, West Vancouver
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| Posted: Mon Jan 23, 2006 3:03 am Post subject: |
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That's funny. I have Acrobat 5.0 on XP and I receive
There was an error opening this document. The file is damaged and could not be repaired.
The same happens with an even older version on Win98.
I don't install V7 on XP, because there are some older documents, which become unreadable. I'm not sure if I can keep two versions, I will investigate that tomorrow.
_________________
Gabor
www.panopeeper.com |
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Wolverine@MSU
Joined: 18 Dec 2005
Posts: 116
Location: East Lansing, Michigan USA
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| Posted: Mon Jan 23, 2006 7:20 am Post subject: |
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| I have the same problem as GaborSch. Acrobat opens, the file seems to load, but then nothing. Downloading the file and trying to open it with Acrobat 5.0 also leads to hangup. |
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johnh
Joined: 20 Jul 2003
Posts: 2062
Location: UK
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| Posted: Mon Jan 23, 2006 8:34 am Post subject: |
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Odd! I have tried opening the file with Adobe Reader V6 on another machine and that had no problems. I will let Rik know that some people have these problems.
John |
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