[biz-engineer]

A few months ago, I decided to measure and record nodal points (distance marking on arca shift rail) for a few of my lenses, noting down a rail setting for each focal length on a small card to have in my camera bag for when I take multiple exposures for panorama stitching. Yesterday I had setup the lens + rail distance according to what I wrote on the card, but to my surprise I could see parallax error from edge to edge of frame in LV mode. I moved the camera+lens on its rail to cancel the parallax, then I rotated the camera in portrait orientation and I discovered that the parallax had reappeared.

So I'd have a few questions, if someone is knowledgeable on this topic:
- Does lens nodal point change with focus distance or lens aperture?
- Why would nodal point be different if I use the camera in portrait or landscape orientation?
- Should parallax error be measured with in camera lens distortion correction enabled or disabled?

[Unregistered User 8]

Should parallax error be measured with in camera lens distortion correction enabled or disabled?

Hey biz, just reminding you that in-camera lens corrections only apply to jpegs and Pentax lenses.
RAW, and third party lenses disable in-camera corrections.

Apologies if you didn't need reminding.

[biz-engineer]

Hey biz, just reminding you that in-camera lens corrections only apply to jpegs and Pentax lenses.RAW, and third party lenses disable in-camera corrections.Apologies if you didn't need reminding.

Thanks. That's also my understanding. What I'm not sure about is how to consider lens distortion for calibration of parallax error. Maybe I shouldn't mind about it, if near and far objects are distorted the same way by the geometrical distortion of the lens.

[zapp]

Nodal point location changes with focus setting - typically not by too much though.
Rotating the camera has no effect on nodal point unless lens elements move physically, alternatively you setup has a problem.
Do not adjust distortion. The idea is to rotate around the nodal point and stitch from that position. Any adjustment to the images before stitching cabin corrupt the stitching model.

---------- Post added 14-02-21 at 01:48 PM ----------

Nodal point location changes with focus setting - typically not by too much though.
Rotating the camera has no effect on nodal point unless lens elements move physically, alternatively you setup has a problem.
Do not adjust distortion. The idea is to rotate around the nodal point and stitch from that position. Any adjustment to the images before stitching cabin corrupt the stitching model.

Near and far objects are distorted in a different way - but this is typically not visible.

[biz-engineer]

Rotating the camera has no effect on nodal point unless lens elements move physically, alternatively you setup has a problem.

Thanks a lot. I've found the reason of my "nodal" point shift. The RRS L bracket vertical and horizontal planes differ by about 11mm ! So, when I put the camera in portrait orientation, it's like having the camera moved back ~11mm!

Near and far objects are distorted in a different way - but this is typically not visible.

Thanks. Yes, now I get it.

[swanlefitte]

I tried my sigma 10-20 and 18-35 at the same fl and the 18-35 did much better. The less distorted lens works much better and the 10-20 has uneven distortion.

[AggieDad]

You've solved your nodal point issue, but may I make another suggestion? I find longer lenses (I use an 85mm and a 100mm) result in panos with almost no distortion. More images, but typically a better result. Have fun!