Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 7:38 GMT
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I just bought the sigma 8mm and have only made som test shots late in my apartment yesterday and have one initial questions...
Should I have the camera in different positions if I plan to shoot 6 shoots than if I plan to shoot 4 shoots?
//Peter F
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DorinDXN
Posts: 1614
Location: Timisoara, Romania
Registered: 14 Nov 2006
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Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 9:39 GMT
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Hmmm....
Johns first reply in that thread is about rotating the panosaurus and not the tripodhead...
I'm not rotationg the tripod head, Im rotating the panosaurus...
I will try to explain myselfe...
Iv read that the entrence pupil is at different places depending on where on the lens the light enters... therfor iv heard that one sould try to find the pupil for the area where the seams will be... And the seams will be at different places if im shooting 4 or 6 shots...
So with this info I hope my initial question is easier to understand...
Should I have the camera in different positions if I plan to shoot 6 shoots than if I plan to shoot 4 shoots?
Can someone help me "read" this graph?
//Peter F
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Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 9:46 GMT
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And can someone help me read this table on the sigma 8
www.swissarmyfork.com/lens_table_1.htm
I cant find anywhere to read where these mesures are taken from, the back of the lens, the front of the lens...
The degree off axis, is it at what degree I take the pictures or is it from what angel the light enters the lens?
//Peter F
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DorinDXN
Posts: 1614
Location: Timisoara, Romania
Registered: 14 Nov 2006
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 9:48 GMT
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Peter,
there are many replies of John Houghton on that tread, at the end of those the resulting idea is to try to find no parallax for the region where you anticipate the seams, that's all
Dorin
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Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 10:37 GMT
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No I see the post that your talking about... That helps alot...
Thanx for pointing that out for me Dorin...
So, If I will take 4 shots (90degree) the seem will be at 45 degres and if I look at the picture above the right place to start is slightly behind the "golden ring" and if I take 6 shots (60 degrees) the seems will be at 30 degrees and if i look at the piture the pupil is abit futher back...
I will test that when I get home...
Thanx Dorin for the answers and John for the post in the other thread that was wery helpful...
//Peter F
Ps, Man I cant wait to get home Ds.
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John Houghton
Posts: 2130
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 11:58 GMT
updated: 28 Mar 2007 at 12:00 GMT
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Peter F said: And can someone help me read this table ...
The table has a column headed "relative to". The figures are given relative to the flange or film (sensor) plane.
The flange is the rear surface of the lens unit that mates with the mount on the camera body. The film plane is
usually marked on the camera by a plimsoll line (a small circle with a line through it).
John
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Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 14:26 GMT
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Hmmm...
As you can se on tiss 100% crop of a seam the tejp (Johns tip) isnt moving much but on the lower part and the upper part the right side is "Growin" alot... Why is that? The windows is moving uppwards ant the edge on the lower part is moving down...
How do I awoid this???
//Peter F
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John Houghton
Posts: 2130
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 15:06 GMT
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Peter, The differences at the seam are due to lens distortions that have not been corrected adequately
(if at all). This is to be expected if you are just laying the images on top of each other in Photoshop.
If you are going further and doing a quick stitch of the images to produce a psd file, then you should
apply a good set of lens parameters that are known to produce a good stitch. Probably it will be enough to
assign several well spread control points and optimize the lens parameters. But in any case, you can
see that the parallax correction is good without going to that trouble.
John
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Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 16:36 GMT
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John: Thanx for the quick answer.
This image is a stich from PTgui that I renderd in layers... I bought the lens yesterday and has only gotten to the point where I want to find the entrence pupil...
Sound good that the "sweet spot" is right.
So, on to the next question. =)
How do I find the right lens parameters?? Does anybody know a good tutorial for this??? I was just out an shoot a panorama where there sould be loads of control points in every direction including zenit. Iv read someplace that thats a good start...
Can I use the same lens parameters as someone else that have the Sigma 8mm 3.5???
//Peter F
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John Houghton
Posts: 2130
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Entrence pupil with 6 or 4 shots...
Posted: 28 Mar 2007 at 19:26 GMT
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Peter, To evaluate the lens parameters, you could just chuck your images at PTGui and let it get on with it
automatically. But I suggest you take a bit of trouble to do everything manually and hopefully get a better
result. Here goes:
I hope you shot RAW images. Convert them with chromatic aberration corrected, rotating them all into portrait
orientation. Be careful with the zenith image: make sure all the images are showing the same orientation:
-90. (It's all too easy to have the zenith image upside down). If using Photoshop CS, the orientation value is
available in the exif properties for the camera data.
Add the images to PTGui. Set the crop circle to just inside the blue border and apply to all images. Check
the placement of the crop circle in the zenith image to be sure it's exactly in the same position as for the
horizontal shots). Be careful to disregard a false image circle edge that can be caused by an intrusive arm
of the pano head.
In Advanced mode, select the Image Parameters tab and select the yaw settings of the 4 horizontal images. Then
click on Fill Yaw - accept defaults and click ok.
For the zenith image, set pitch=90. (-90 if you have a nadir too)
Assign control points for the horizontal images manually - 6 points per seam, well spread out vertically. When
placing points, hold down ctrl/alt as you drag points into exact position required. Avoid putting points on anything likely to move between shots (like clouds).
Lens parameters: set fov to 180, b= -0.03
Set the ouput image projection to Equirectangular, 360x180.
On the Create Panorama tab, set the output size to maximum.
Optimize tab: Select advanced mode.
Check fov, d, e.
Check y,p,r for all the horizontal images except image 0.
In the "Use control points of", check only the horizontal images.
Click on Optimize.
Check lens parameter a and Optimize again.
Check the control points table for any bad points (large distance). Check the placement and correct if necessary.
Uncheck parameter a and check b
Optimize. Repeat for a and again for b.
You should now be getting a very good optimization report with an average error of around 1 and a maximum
of 2 or 3.
Add some control points between the zenith and the horizontal images.
Optimizer: uncheck all lens parameters.
uncheck y,p,r for the horizontal images.
Check y,p,r for the zenith.
Check the zenith image in the "Use control points of" table (in addition to the horizontal images already checked).
Optimize.
Do likewise for the nadir if it was taken on the pano head.
Finish by optimizing lens parameters fov,a,d,e; y,p,r on all images except 0, with all images checked in the "use
control points of" table.
Repeat with lens parameter b checked instead of a.
You should now have a very good optimization if all has gone well! Save the project file.
I just did exactly this myself and got an average distance of 0.9 and a maximum of 2.4, so that's something
to aim for. My lens parameters (Sigma 8mm f/3.5) ended up as fov=180.3, a=-0.082, b=-0.03, c=0.
Let us know how you get on.
John
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Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Re: Entrence pupil with 6 or 4 shots...
Posted: 29 Mar 2007 at 7:09 GMT
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Im at work now but will test that as soon as I get home...
John, cant thank you enough...
//Peter F
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Peter F
Posts: 68
Location: Uppsala, Sweden
Registered: 29 Jan 2007
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Re: Entrence pupil with 6 or 4 shots...
Posted: 29 Mar 2007 at 7:16 GMT
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Wait! Question! =)
Do you optimize with PanoTools or PtGui??? I always get a lower value with Panotools but i guess that because they use different kind of values???
So my question pano tools or ptgui?
Does PtGUi optimizer support Vertical control points???
//Peter F
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John Houghton
Posts: 2130
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Entrence pupil with 6 or 4 shots...
Posted: 29 Mar 2007 at 7:47 GMT
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Sorry, that was a vital bit of information I omitted. You must use PTOptimizer. PTGui's optimizer does not
support t1,t2,tn points.
John
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Hans Nyberg
Posts: 713
Location: Denmark
Registered: 28 Aug 2005
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Re: Entrence pupil with 6 or 4 shots...
Posted: 29 Mar 2007 at 7:49 GMT
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Exellent description John.
I would use panotools optimizer. The reason why you get a lower value is that panotools calculate it after the selected output size in your create panorama tab.
If you select maximum size you get the same values as ptgui optimizer which calculates it after the source images.
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