For a couple of reasons it can be very useful to position your camera in a slanted position when using a lens ring and a fisheye lens.
The slanted position is when you rotate your lens in the ring in such a position that the camera is not straight up (the portrait position) and neither is set horizontal (the landscape position) but set at a position in between those two at an angle of 60 degree.
Depending on the camera and lens combination it can be needed to combine the slanted position with a little tilt of the lens to fully cover zenith, the tilt that is needed can vary from zero to 2.5, 5 or 7.5 degree.
For almost all(*) combinations of fisheye lenses and cameras the slanted position has at least one or more advantages:
1) The slanted position makes the overlap of the images at the horizon(**) of the pano larger, this has several advantages:
- it will be easier for the auto control point generator of PTGui to set the control points (CP's) with a good spread, therefore the quality of the aligning of the images will be better,
- with a larger overlap the blenders of PTGui will get more play room to make a good seem in the area of the horizon, especially when using Smartblend it will be easier for the blender to remove ghosting caused by moving people in the scene.
- when the overlap is large enough it is possible to shoot a pano with fewer images, f.e. with a EOS 5D + shaved Tokina 10-17@12mm it is possible to shoot a full spherical with only 3 slanted images instead of 4 in portrait position.
2) The slanted position will enlarge the vertical field of view (VFOV) for all panos that are created with circular fisheye images that are cut off at the top and down side of the image but has curved edges in the corners of the images(***).
The slanted position is using these curved parts of the image to enlarge the VFOV to a full 180 degree, the advantages:
- it is possible to get a full spherical pano instead of a limited one, this is ideal for example when shooting from a pole or in all those situations where it is not so easy (or not wanted) to shoot a nadir patch image.
- because there are no black holes in zenith and nadir in such situations there is also no need to limit the vertical view of the pano in the player to block the black holes so the viewing experience will be often much better.
3) The slanted position can enlarge the resolution of the pano when a zoom lens is used and a full spherical pano is needed.
The gain can be up to 30% more pixels. For example, when the portrait position is used the maximum zoom of the shaved Tokina 10-17 when used on a full frame sensor camera is approx.12mm. With the slanted position the zoom can be set to 14mm. With a zoom setting of 12 mm the pano resolution is approx. 8400x4200 px (on EOS 5D) but with 14mm the resolution is approx. 9600x4800 px, resulting in a gain of 30% more pixels.
(*) In all situations where the image is full circular (f.e. Sigma 8 on a full frame sensor camera or a Sigma 4.5 on a cropped size sensor camera) there is no advantage to set the camera in a slanted position.
(**) While the overlap at the horizon is larger the overlap in the areas around zenith and nadir will be smaller. PTGui seldom places CP's in those areas so the fact that the overlap is smaller has no impact on the placing of CP's in those areas. The spread of CP's in the area around the horizon however is better and hence the total spread of CP's is better.
(***) When using a full frame fisheye image the advantage of a larger VFOV is very little, the holes in nadir and zenith in the pano will look like a ninja warp star and to reduce the size of the stars you a larger number of images. To have the stars out of view you have to limit the player, after blocking the view the gain of VFOV of the pano is limited.
There are not only advantages when using a slanted camera position, there are also some dis-advantages. Without going to deep into the "why" I will name a few:
- the image quality of the pano can be less. This issue can be a theoretical or a practical one, it all depends on the used combination of camera and lens and your personal standards about quality.
- special care is needed to reduce CA and color fringing and to sharpen the source images close to the edges.
To make it possible to judge the quality for yourself here is a link to a couple of panos that are created from 6 images shot with a EOS 5D + Nodal Ninja R-D4 rotator + R1 lens ring + Tokina 10-17@14mm in a 60 degree slanted position with 5 degree tilt:
And here is a link to an example of my PanoWalk&Drive tours, all panos are created from 3 images shot with a EOS 5D + Seitz VR motor drive + R10 lens ring + Tokina 10-17@10mm in a 60 degree slanted position with zero tilt:
When you have a lens ring and the quality of the panos suits your need then I hope this posting will inspire you to give the slanted position a try.
All Nodal Ninja lens rings are suited for slanted shooting, especially the R1, this model has an option to quickly set the tilt to one of its preset tilt positions.
Happy slanted shooting,