Tutorial: How To Find Your Lens Nodal Point

[Andy]

David_S85 made up this awesome tutorial on how to find your lens' nodal point, for perfectly stitchable panoramas. I just did it, and it works perfectly!

TIP: If you have no Pez dispensers, two candlesticks in candleholders will do nicely

thanks David!

[DoctorIt]

Mmmm, Pez! nice work Dave

[wxwax]

Nodals?

I thought this was a family site?

[David_S85]

Thanks guys. I had lots of other PEZ at my disposal -- many with much pointier heads, but Homer and Marge just seemed so right for this.

For those replicating this test with your own lenses, cams and pano heads, you should note that you don't even need to take any pictures to perform these calibrations (with a dSLR). Just look through your viewfinder and pivot your rig left and right. Manually focus somewhere between the targets and stop down the lens a bit (use depth of field preview to get a clearer view if necessary).

I did this tute in portrait orientation (since that's the only way I shoot pano's), and the # of shots and swing degrees markings on the slide reflect portrait only (in case you shoot with identical gear).

If you shoot your pano's in landscape orientation, your same front-to-back settings will work, but the number of shots will be very different from any you do in portrait.

As for why in the world would one need to calibrate a slide for lenses anyway when you're shooting objects at near infinity away... well, you wouldn't really need to. But out in the field you might want to include a foreground object. Remember, there's always grass, leaves, stones and stuff on the ground in front of you. If you have ever attempted to eliminate stitch ghosting in post-processing then you know why calibration is so important. Also, if you shoot indoor pano's (real estate stuff), then its an absolute must-do excercise.

Originally Posted by wxwax

Nodals? I thought this was a family site?

Sid.

[01af]

Nice tutorial! Except it won't find the lens' nodal point ... and neither the lens' optical center. It will find the lens' entry pupil (or, to be precise, the point where the optical axis and the entry pupil intersect).

-- Olaf

[Andy]

Originally Posted by 01af

Nice tutorial! Except it won't find the lens' nodal point ... and neither the lens' optical center. It will find the lens' entry pupil (or, to be precise, the point where the optical axis and the entry pupil intersect).

-- Olaf

There you go ruining things, with Optical Science

[ziggy53]

Originally Posted by 01af

Nice tutorial! Except it won't find the lens' nodal point ... and neither the lens' optical center. It will find the lens' entry pupil (or, to be precise, the point where the optical axis and the entry pupil intersect).

-- Olaf

Would you be so kind as to explain the difference between the nodal point and the "point where the optical axis and the entry pupil intersect"?

Is it still an appropriate method for calibrating a system for stitched panoramas?

If not, what is an appropriate method and why?

Thanks,

ziggy53

[TOF guy]

Thank you to Dave for writing the tutorial, and for Andy for posting the info .

Happy Hanukah to all!

Thierry

[David_S85]

OK, why don't we just call it the pivot point? And no matter what it's called, you just keep sliding the thing forward or backward to the place where nothing in the viewfinder/picture shifts when you're swinging the rig.

[DavidTO]

K, so I'm going through this process, and all i have to say is NO FAIR!!!!

My L bracket has no marking for the center of the camera. So's I'm guessing!

Nice tute, Dave!

[David_S85]

Thanks, David.

Easy enough to find the middle and mark it with a line, no?

[DavidTO]

Originally Posted by David_S85

Thanks, David.

Easy enough to find the middle and mark it with a line, no?

[phuong]

ziggy53, the "entrance pupil" is often incorrectly refererred to by panorama photographers as the "nodal point". it is not a serious mistake, though. just some optical science stuffs, as Andy pointed out. so you dont really have to worry about it.

i think you can look it up on wikipedia too.

[David_S85]

And whatever the heck one calls it, it is only important that things get adjusted enough that they line up.

[Nikolai]

Now, can somebody honestly tell me, what difference all this precision gadgetry makes on the outcome?

Most of my panos were shot handheld, and I have yet to see the particular problem. I'm not talking about sky banding or similar issues. My point is: the stitching s/w is pretty smart these days, and while perfect original shots would make its life easier, it seems to handle even some rather complicated cases just fine.

I do understand that this precision was vital in the days of yore, when the best you could hope for was to blend several shots together in the chemically stenched dark room. But today, with CS3, Panorama Factory and other nice stitching tools, how big is the real difference?

Can anybody who onws this gear showcase this?
Like, make a pano with the rail and dialed in pivot/modal point, and then make another one just handheld, and then run them both through the same tool?

In fact, I can run it for you, I just don't have to panning gear

Just to be clear: I'm not saying it's not needed, I'm simply wondering about ROI and quality improvement factor..

[Andy]

Originally Posted by Nikolai

Now, can somebody honestly tell me, what difference all this precision gadgetry makes on the outcome?

Sure. I can shoot any number of combinations with my gear, and when I bring the files into photoshop, they stitch together instantly, no waste, and no distortion. I have set nodal points for my 24 TS-E, my 16-35L (at 16, 21, and 35).

[Nikolai]

Originally Posted by Andy

Sure. I can shoot any number of combinations with my gear, and when I bring the files into photoshop, they stitch together instantly, no waste, and no distortion. I have set nodal points for my 24 TS-E, my 16-35L (at 16, 21, and 35).

And can you make comparisons with the handheld with the same settings? That would be awesome!

[DavidTO]

Originally Posted by Nikolai

And can you make comparisons with the handheld with the same settings? That would be awesome!

Nik, you're welcome to borrow mine if you want to run that test for yourself...

[Nikolai]

Originally Posted by DavidTO

Nik, you're welcome to borrow mine if you want to run that test for yourself...

Oh, really? Sweet, I'd love to! Thanks, man!

[pathfinder]

Nick, my take is if you are only shooting objects at effective infinity, nodal points do not matter very mugh at all, as when you are hand holding.

But if your shot has objects in the forground that are much closer to the lens, then the nodal point rotation axis matters quite a bit more.