Bare Port for Nexus Housings

Why does the Bare T1017M5 port give such great results? 

First, you have to forget some of what you have heard about optics and dome port design.  There are lots of websites and books that explain the virtual image.  The virtual image is at a distance away from the dome port that is approximately 2 times the diameter of the outer dome port.  What most people don't explain is that the virtual image is NOT flat, but covers the whole angle of view of the lens.  If you don't believe me then try on a Hydro-Optix mask.  The image in the mask comes from all around the view of your eye, not in a flat plane.

FACT:

1.  The water/air interface of a dome becomes the first element of the lens.

2.  For an image to be the sharpest it can be, the center of the dome radius must be at the nodal point of your particular lens.

 Therefore, the front and sides of your dome must be equidistant away from the nodal point of the lens.

3.  The nodal point of a lens is the point within the lens where all the angles of light converge.  People that shoot panoramas know about the nodal point, so it is easy to search the internet to find more information on nodal points.  For more information on nodal points go HERE.

In the image above, the red, green and blue lines mark the convergence to the lens' nodal point.  When the distances are not equal, the lens may have trouble keeping all angles in focus.

Many people purchase very large diameter domes that are not suited well for extreme wide angle lenses.  These wide ports usually have the center of the dome closer than the sides, which means the corners of the image can be blurred or out of focus.

The above image shows what happens when a dome that is too wide for the lens. The center of the dome radius is too far to the rear of the nodal point of the lens, possibly making the corners of the image blurred.

Having a dome that is too small can have the same affect as having too large a diameter dome.  The difference being the too small port doesn't place the focal plane as far back as a dome that is too large.

The Bare dome port assembly is optimized for the Tokina 10-17 mm and the Nikon 16 mm F2.8 AF lenses.  The center of the dome radius is positioned exactly at the nodal point of the lens assuring sharp corners.

Look at the images on our website to see how sharp your images can be from corner to corner.

To purchase go HERE