Sigma 15 fisheye, least parallax point anyone?

Does anyone have a good measurement for the least parallax point for the Sigma 15mm fisheye (Nikon mount)? From the lens mount surface preferably. (It's not a "no parallax point" because it varies with angle of incidence, or something like that.)

I am making up a 6" dome port and would like to put the center of curvature of the dome on the least parallax point.

Rough measurement made a while ago, about 38mm from the mount surface with the lens focused at 300mm

S

I asked, because I wanted to avoid the imperfect hassle of measuring it myself using lined-up pins and projecting those lines back into the lens. But I did it anyway...I prefocussed at 22cm since that should be about the virtual image of infinity with a 6" dome. I got a measurement of about 26mm in front of the mount surface. (The position varies with focus, but not that much.)

The apparent position of the iris as seen through the front element should also be about the "no" parallax point. I estimated it's position this way as 24.5mm in front of the mount.

I think the most accurate way to get the least parallax point is with a pano head, and the pano sites have data on many lenses, but not this one.

Anyone out there with a pano head to measure this?

Simon, how was your measurement done?

Put the /lens on a big sheet of graph paper. set up a vertical screen (white cardboard box) behind it and them used a laser level to project a vertical line into the lens and onto a line drawn on the screen, drew lines on the paper to match the laser line then looked for where they converged. it was all a bit rough.

Hello PeteAtkinson,

I do 360 panoramas with a Nikon D810 and I use the Sigma 15mm. I measured where my 'No-Parallax_Point' is on my lens and it is 37.5mm from the rear of the lens. (where the lens mates flat against the camera body) I have attached a photo with the spot marked in red. To be clear, this is the point around which the camera/lens pivots to eliminate parallax. I hope this helps.

This helps a lot! And it shows why I need to ask, as my measurements are so bad, and yours, and Simon K's are virtually the same!

Many thanks to both of you. If you have NPP measurements for other lenses used underwater Randall it would be great if you could post them on Wetpixel where they should be pinned. Thanks again!

www.peteatkinson.com