Nodal Point calibration with high focal length  

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Leonardo
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Nodal Point calibration with high focal length

by Leonardo » Wed Feb 26, 2014 1:00 pm

Hi all,
I have to make a panorama of a ceiling vault of a church and I will use a 200mm lens. The problem is that I can't make a perfect nodal point calibration because when I point on the zenith the sliding bar with the camera body would beat against the head structure. My question is: do you think I can avoid the calibration of the nodal point and use the "multiple visual" option in the creation of the pano? Do you think it could be possible to reach in this way a good metrical result (i.e. no deformation in one or more axis)?
Thanks for you attention
Leonardo

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mediavets
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Re: Nodal Point calibration with high focal length

by mediavets » Wed Feb 26, 2014 1:13 pm

Leonardo wrote:Hi all,
I have to make a panorama of a ceiling vault of a church and I will use a 200mm lens. The problem is that I can't make a perfect nodal point calibration because when I point on the zenith the sliding bar with the camera body would beat against the head structure. My question is: do you think I can avoid the calibration of the nodal point and use the "multiple visual" option in the creation of the pano? Do you think it could be possible to reach in this way a good metrical result (i.e. no deformation in one or more axis)?
Thanks for you attention
Leonardo


When I shot a pano of (just) the roof/ceiling of my local church - built in 1485 - using a Merlin robotic pan head I turned the pano head on it's side and shot a regular matrix of images which stitched fine using the XML file created by Papywizard.

In other words rather as one might shoot a landscape partial pano but with the pano head on its side.

http://www.three60views.org.uk/roof-pan ... of-02.html (my pano)

http://www.druidic.org/camchurch/churches/isleham.htm (the context)

This was my first attempt - and white balance was badly affected by light pouting in through clerestory below ceiling...it's far from perfect but proved the concept.

I used 50mm rectilinear lens on a Nikon DX body.

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Leonardo
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Re: Nodal Point calibration with high focal length

by Leonardo » Wed Feb 26, 2014 1:26 pm

Thanks for your reply!
That was my first idea but I work with a Clauss HD and technicians told me it could damage the engines of the head. So the second idea (if mutiple point doesn't work properly, but I really hope it will!) could be to take two partiale panos and stitching them as one: where can I find some information about the stitching of two or more panoramas?
thank you
Leo

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klausesser
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Re: Nodal Point calibration with high focal length

by klausesser » Wed Feb 26, 2014 1:40 pm

Leonardo wrote:Hi all,
I have to make a panorama of a ceiling vault of a church and I will use a 200mm lens. The problem is that I can't make a perfect nodal point calibration because when I point on the zenith the sliding bar with the camera body would beat against the head structure. My question is: do you think I can avoid the calibration of the nodal point and use the "multiple visual" option in the creation of the pano? Do you think it could be possible to reach in this way a good metrical result (i.e. no deformation in one or more axis)?
Thanks for you attention
Leonardo



Which head do you use? From what you say i guess it´s a Merlin?

Regarding Andrew´s suggestion: tilting the head to 90° and have it rotate vertically basically WOULD be a good advise - but the Merlin´s motors most likely arent´t strong enough to do that with a 200mm lens at all.

You definitely need a precise NPP alignment using a 200mm indoors if you want to avoid heavy editing the images manually. How much is the difference with your setup? Try the multiple viewpoints anyway!

best, Klaus

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Leonardo
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Re: Nodal Point calibration with high focal length

by Leonardo » Wed Feb 26, 2014 1:52 pm

Hi Klaus,
my head is this one:
http://www.dr-clauss.de/en/foto-studiot ... s/item/187
The difference with the "perfect" calibration, I think is about 10cm along focal axis, so I don't know if multiple point could work. Another idea: I make a perfect calibration to take all the ceiling vault but the zenith area for the problem of disturbance of the head structure; then I take the zenith are without calibration using the multiple viewpoints; finally I stitch the two panos.
What do you think? Do you have samples about the stitching of two panoramas?
Leo

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klausesser
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Re: Nodal Point calibration with high focal length

by klausesser » Wed Feb 26, 2014 1:54 pm

Leonardo wrote:Thanks for your reply!
That was my first idea but I work with a Clauss HD and technicians told me it could damage the engines of the head. So the second idea (if mutiple point doesn't work properly, but I really hope it will!) could be to take two partiale panos and stitching them as one: where can I find some information about the stitching of two or more panoramas?
thank you
Leo



Oops - messages crossed . . :cool:

Honestly: a Dr. Clauss RODEON should be able to do it!. What lens is your 200mm? Which camera? What´s the weight of camera/lens?

On my Panoneed-head i can set the torque from 1 Nm to 4 Nm when i tilt the head to 90° for having it rotate vertically. It´s slower then of course - but it takes a D800 with a heavy 1,4/85mm lens. I´m pretty shure it would also take a 200mm . . . but here are very heavy 200mm lenses out there . . . =D

Do you really NEED 200mm? I realized 85mm on a D800 already gives you very hires spheres of around 6 GPix . . .

best, Klaus

Ok - i oversaw you mean the "station" model . . that´s definitely very heavy stuff for tilting it to 90° . . . :cool:
Last edited by klausesser on Wed Feb 26, 2014 2:04 pm, edited 2 times in total.

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klausesser
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Re: Nodal Point calibration with high focal length

by klausesser » Wed Feb 26, 2014 2:01 pm

Leonardo wrote:Hi Klaus,
my head is this one:
http://www.dr-clauss.de/en/foto-studiot ... s/item/187
The difference with the "perfect" calibration, I think is about 10cm along focal axis, so I don't know if multiple point could work. Another idea: I make a perfect calibration to take all the ceiling vault but the zenith area for the problem of disturbance of the head structure; then I take the zenith are without calibration using the multiple viewpoints; finally I stitch the two panos.
What do you think? Do you have samples about the stitching of two panoramas?
Leo



So you´re gonna shoot a full sphere?

I used an 85mm lens to shoot with a Canon 5D2 on my Panoneed head: about 3,5 - 4 GPx: http://www.klausesser.de/Stadthalle/

Doing it with a D800 would result in about 5-6 GPx with the same lens.

If you NEED to use the 200mm i would try it with the Rodeon @90° - it´s the most sturdy head i know.

Guess you need to run a test using multiple viewpoint!

best, Klaus

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Re: Nodal Point calibration with high focal length

by Leonardo » Wed Feb 26, 2014 4:49 pm

Hi Klaus,
first of all congratulations for your image: it is great! Is it an HDR image? How did you do for focus issue: manual, af assistant ...?
In my work I will do just the panorama of the ceiling vault (not the full sphere) with my D800E with Nikon AF Micro-Nikkor 200mm f/4D ED-IF, so (for the total weight) I am not sure to rotate the Clauss!
What do you think?
best, Leo

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klausesser
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Re: Nodal Point calibration with high focal length

by klausesser » Wed Feb 26, 2014 7:27 pm

Leonardo wrote:Hi Klaus,
first of all congratulations for your image: it is great! Is it an HDR image? How did you do for focus issue: manual, af assistant ...?
In my work I will do just the panorama of the ceiling vault (not the full sphere) with my D800E with Nikon AF Micro-Nikkor 200mm f/4D ED-IF, so (for the total weight) I am not sure to rotate the Clauss!
What do you think?
best, Leo



I mean you have a problem using the Rodeon STATION here - guess the guys are right saying it´s too heavy for being tiltet @90°.
Two suggestions:
1) try to find a shorter 200mm lens.
2) use a manual 180mm lens instead. It´s rather short and it´s very good. http://www.kenrockwell.com/nikon/180f28.htm

The problem is that afaik with the "Station" model you cannot shift the camera-fixing on the vertical arm upwards. If teh vertical arm would be longer your 200mm lens
would be able to look straight upwards.
Ask the Dr. Clauss guys for an option. They are very helpful and polite!

Here you can see how Panoneed - i accompanied the development - has solved the issue: a 300mm lens can look 90° up (we even slided the camera too much backwards for showing how much space it has for setting the NPP - that´s because the vertical arm is high enough).
www.panoneed.com (see the movie down on the frontpage)

best, Klaus
Last edited by klausesser on Mon Mar 03, 2014 3:39 pm, edited 1 time in total.

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Re: Nodal Point calibration with high focal length

by lumelix » Wed Feb 26, 2014 10:13 pm

Hi Leonardo
The NP of the Micro Nikkor 200mm is somewhere between 95 - 96 mm from the mount, at infinity. With the D800, you need about 65mm more for the camera. You need 160 - 170 mm space from the head base.
I can't believe it that you can't get it in the right position with this giant head.
Do you really know where the nodal point of this lens is ?
You can find some more interessting informations on this page:
http://www.pierretoscani.com/echo_short ... hortpres06
Regards
Martin

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Leonardo
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Re: Nodal Point calibration with high focal length

by Leonardo » Mon Mar 03, 2014 2:13 pm

Hi lumelix,
sorry for my late reply. I will calibrate again the NP of the Micro Nikkor 200 (checking the no parallax point using a vertical line in the foreground and one in the background) and I will check also if it is congruent with the informations made by Pierre Toscani (that web site is incredible!).
I will let you know
Thanks
Leonardo

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Re: Nodal Point calibration with high focal length

by lumelix » Mon Mar 03, 2014 2:41 pm

Hi Leonardo
See also this site:
http://wiki.panotools.org/Entrance_Pupil_Database

I use this lens also for a lot of my panoramas. If the motiv is far away, the NP isn't important.
I don't know if in your case, the ceiling is far away enough and in the same distance.
Regards
Martin

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klausesser
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Re: Nodal Point calibration with high focal length

by klausesser » Mon Mar 03, 2014 4:19 pm

Leonardo wrote:I will calibrate again the NP of the Micro Nikkor 200 (checking the no parallax point using a vertical line in the foreground and one in the background)



Preferably use a near-point and a far-point distance for your calibration which resembles the distances you will find in the church.

best, Klaus

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lumelix
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Re: Nodal Point calibration with high focal length

by lumelix » Mon Mar 03, 2014 4:35 pm

And place this two targets at an angle near the stitching zone (dependent from the overlapping).
Then you get a perfect result.
Regards
Martin

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Leonardo
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Re: Nodal Point calibration with high focal length

by Leonardo » Mon Mar 03, 2014 5:52 pm

Hi lumelix, hi klauss,
thanks a lot for your replies. It is hard to use the near point and far point of the church for NPP calibration: infact the whole range is from about 30 to 60 meters. And here is the problem: with 200mm lens the NPP varies a lot with focus distance but I can't use an aperture size which can produce a depth of field so large. Infact for example, if I use an f/11 (for having a good detail) @ 30m, I will have a near limit of 23.9m and a far limit of 40.2 for a total of 16.2m. So I was thinking to use an autofocus assistant like this one:
http://www.factum-arte.com/pag/8/Panoramic-Photography
So, what about the NPP calibration? With autofocus, it is impossible to reach the calibration?! But on the other hand, distances are so high that calibration is not so important ...
Probably I didn't tell you, but the main goal of my work is to make a Gigaphoto of the paintings on ceiling vaults, that is why I use a 200mm lens.
@lumelix: sorry for my stupid question, but in the entrance pupil database, I have three values for my 200mm: what are 1:1 and 1:2?
Thanks again
Leonardo

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klausesser
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Re: Nodal Point calibration with high focal length

by klausesser » Mon Mar 03, 2014 6:09 pm

Leonardo wrote: It is hard to use the near point and far point of the church for NPP calibration: infact the whole range is from about 30 to 60 meters.


Then optimize the NPP to 45m. DOF "grows" faster in the depth than in the foreground. But you can also have the head stopped at the end of each row and refocus manually.

That´s what i do in such situations - i didn´t do it in the historical townhall because i used an 85mm @f11.

I had Josef implement the feature of stopping at the end of each row for re-focusing manually for shooting the next row. That´s a very helpful feature for dealing with DOF.
The xml treats it as one continuous shooting - regardless how often i put the sequence on hold.

I wouldn´t leave it to the AF . . . :cool:

best, Klaus

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Re: Nodal Point calibration with high focal length

by lumelix » Mon Mar 03, 2014 6:14 pm

Hi Leonardo
This two other values are for macro fokus at 1:2 and 1:1 scale. But with this, you normaly will not shoot a pano ;)
Try to get the NP at 40m focus distance and 3/4 of the image width (25% overlapping). I guess it will be ok also for the whole range from 30-60m then.
At 40m focus distance and f/11 you have everything between 30m and 56m in focus. But this Micro Nikkor is a little bit different to normal lenses.
Regards
Martin

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Leonardo
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Re: Nodal Point calibration with high focal length

by Leonardo » Mon Mar 03, 2014 6:38 pm

Thanks for all your suggestions, I will let you know how I will proceed.
Best
Leonardo
@Martin: I've understood the values later on my question!;)


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