Michael Owen
Posts: 68
Location: Colwyn Bay, United Kingdom
Registered: 1 Apr 2007
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Nodal points==Help please
Posted: 26 Feb 2008 at 19:35 GMT
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I made a good resolution today. I would settle once and for all the nodal points on my cameras. So I went to work, I know the nodal point is where the light gets down to infinity like an hourglass centre. But to my question. I have heard that the zoom on certain lenses alters the nodal point. Is this true? I cannot see how it affects something inside the camera. I am particulary concerned because I have a fisheye, a Peleng 3.5/8a. and some of my results using this lens are poor to say the least. Is it anything to do with the fact that my main camera, a canon 300D, I set up the nodal point using a kit lens 18-55. Ive tried testing the fisheye for nodal point tests, but I.m not sure Mike Owen
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DorinDXN
Posts: 1614
Location: Timisoara, Romania
Registered: 14 Nov 2006
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Re: Nodal points==Help please
Posted: 26 Feb 2008 at 19:42 GMT
updated: 26 Feb 2008 at 19:42 GMT
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Hi Michael, Nodal point, or better, no parallax point is lens speciffic not camera speciffic, so if you change the lens you need to consider a very possibile different no parallax point and so a different seting for panohead, for fisheyes may be even different no parallax point if you take 6 around or 5 around.
hope this helps,
Dorin
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Michael Owen
Posts: 68
Location: Colwyn Bay, United Kingdom
Registered: 1 Apr 2007
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Re: Nodal points==Help please
Posted: 26 Feb 2008 at 19:51 GMT
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Thanks Dorin for your quick reply. Your last sentence---"Hope this helps." Yes it does in the sense that I now know where I am, but No it doesent in the sense that I now know even the number of shots affects it. I never, evr dreamed anything like that, so its back to the drawing board. Mike
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gus
Posts: 373
Location: United Kingdom
Registered: 19 Jun 2007
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Re: Nodal points==Help please
Posted: 26 Feb 2008 at 19:54 GMT
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HI
On the peleng, make sure to lock the aperture (best at f/8) by turning the 2nd ring from the front to the lock position.
I used to tape mine with a bit of cellotape to stop it from moving. And set the zoom ring to infinity.
As you probably know,the lend is manual, so remember to turn your camera to manual focus, and adjust the shutterspeed by looking at the display when you take testshots.
The setting on the upper arm of your panobracket will be different to the setting for the kit lens. They have different parralax points. The lower arm setting will be the same, assuming it was correct to begin with.
Not sure what you meant by "I know the nodal point is where the light gets down to infinity like an hourglass centre.", but the only sure way to get find your parralax point is by following this (or similar) tutorial:
www.rosaurophotography.com/html/technical7.html
It only takes 40-60 minutes, and well worth the effort.
gus
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Michael Owen
Posts: 68
Location: Colwyn Bay, United Kingdom
Registered: 1 Apr 2007
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Re: Nodal points==Help please
Posted: 26 Feb 2008 at 20:55 GMT
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Thanks Gus. You've given me a lot to think about. Firstly, you say turn the ring to "lock." I don't know where I read it recently, but someone or some firm said the opposite, turn it to unlock. I spent a whole day experimenting with different positions of the rings, then compared the results. I came to the conclusion that "unlock" produced the best results. Please don't think I am argueing against your advice, far from it. I also tried f/8 and, again, decided 5,6 was better!!! Perhaps some other factor was influencing my results. As to the panobracket, I uise a Panosaurus, and it doesent have any settings at all. I'm not at all sure what the upper and lower arms are, I don't think its got them. Now I'm off to look at the tutorial you mention. Please don't think I am ungrateful and argumentative===I appreciate you have spent time on trying to help me. Mike
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ebig
Posts: 114
Location: Haiku, Maui, Hawaii, United States
Registered: 21 May 2007
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Re: Nodal points==Help please
Posted: 26 Feb 2008 at 22:33 GMT
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A couple thoughts...a fact is that when turned clockwise (from rear of camera,) with "lock" moved to the right, the Peleng is stopped down. When turned anti-clockwise, with "unlock" moved to the left, the lens is opened up. If "unlock" gives the "best" results, you might just need more exposure.
The Peleng can do pretty well at f/5.6, especially if enough images are used so that edge sharpness is not a significant factor. But at f/8 the edges are sharper and you can use fewer images.
Test your lens by shooting an image at each f-stop and compare those with a program such as Faststone which allows multi-image comparisons, at a size of 100% or more. If you get contrary results, you might post them.
Regards,
Ed
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Michael Owen
Posts: 68
Location: Colwyn Bay, United Kingdom
Registered: 1 Apr 2007
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Re: Nodal points==Help please
Posted: 27 Feb 2008 at 20:30 GMT
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Thanks Ed. I'm learning something every day. Now I'm off to download Faststone, a new one to me. Mike
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Tom Vogel
Posts: 23
Location: Cambridge, Ontario, Canada
Registered: 5 Mar 2007
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Re: Nodal points==Help please
Posted: 27 Feb 2008 at 23:44 GMT
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Hi Michael,
I use the Peleng as well on my Canon 400 XTi. I'm able to capture wonderful images thanks to an old-school approach to manual lens focusing called - Hyperfocal.
It's quite simple. Set your Peleng to F8 as suggested. (Trust me ... it's the best setting of the lot).
Then set your Unlock/Lock ring to LOCK.
You'll notice a very small number '8' just below the LOCK when it's been fully turned into position.
You'll also notice a small infinity symbol on the focus ring (closest to the camera body). Position that symbol directly under the small '8'.
There you go - you've achieved Hyperfocal focusing. The illusion this technigue creates is a deep focus that keeps images crisp from less than a foot away from your lens to "infinity". Try it - the results should mess with your head rather nicely. Regarding finding the nodal point - that's a delightful challenge that keeps us all up at night.
Here's an example of what my lens can do:
www.ispace-tours.com/spec-ispace/
Regards,
Tom
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Michael Owen
Posts: 68
Location: Colwyn Bay, United Kingdom
Registered: 1 Apr 2007
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Re: Nodal points==Help please
Posted: 28 Feb 2008 at 0:45 GMT
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Hello Tom, I've just checked on the forum and read your reply. I've been up for around 18 hours with work (not panos!!!) and its now 01.00 in the middle of the night---so I am off to bed---wacked. But I cannot wait to put your recommendations into practice. If I can produceanything half as good as what I've just seen in ispace-tours.com/spec-ispace/ I will be VERY happy. I'll let you know how I go on in a few days. Mike
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EmEss
Posts: 8
Location: Germany
Registered: 19 Nov 2007
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Re: Nodal points==Help please
Posted: 29 Feb 2008 at 21:44 GMT
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Michael,
if you set up your Peleng like this, you should get clear and sharp pictures:
The Witten - Hammerteich panorama was shot with my
Peleng (4+1+1) - one of my early experiments:
www.oldie-werkstatt.de/panorama
By the way, what camera do you use with your Peleng? There are adapters for Petax cameras available which are unable to make it focus at infinity.
Regards,
Martin
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Michael Owen
Posts: 68
Location: Colwyn Bay, United Kingdom
Registered: 1 Apr 2007
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Re: Nodal points==Help please
Posted: 29 Feb 2008 at 23:38 GMT
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Hello Martin and thanks for your help----In answer to your query I've been using a Canon 300D. Mike
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