The simple steps outlined below are sufficient for finding the optical center (aka No-Parallax Point or NPP) for most shooting situations. But some shooting situations are more demanding, and may require a method that delivers a higher degree of precision. For example, No-Parallax Point positioning is absolutely critical anytime you're shooting a scene that has diverging/converging lines (roads, paths, fence lines, windows, etc), especially when these elements are in the foreground and close to the camera. In that case, skip to the bottom of this tutorial for further recommendations. Once you've found the No-Parallax Point for your lens, make a note of it so that you can easily repeat your setup the next time.
Level Your Equipment
One Step Leveling
If you use our PCL-1 panning clamp, this step is a snap. Loosen the ball and shift the clamp until the spirit level indicates its level, and in one step, you've leveled both the camera (the lateral axis) and the panning base (the axis of rotation).
Alternatively, level your tripod and camera separately. When you level the tripod, what you're really trying to get level is the panning base of your ballhead. For leveling the tripod, a leveling base or a leveling center column makes the first step quick and easy. And to level the camera? Use the spirit level built into one of our clamps, or use a double-bubble level mounted in the camera's hot shoe.
Place the No-Parallax Point Over the Axis of Rotation
the No-Parallax Point? The physical location of the optical center is unique for each lens. For prime lenses, the No-Parallax Point (with focus at infinity) is stationary. For zoom lenses, however, the No-Parallax Point typically shifts for each focal length. The location of the No-Parallax Point is commonly expressed as its distance, in millimeters, forward of the film plane/digital sensor.
The No-Parallax Point is best determined by experimentation: Use a "nodal slide," such as our 7.4-inch long MPR-CL II. The objective is to slide the camera along its lateral axis until the No-Parallax Point is positioned over the axis of rotation. Precise positioning is critical if your subject matter is close, but much less important if you're shooting distant landscape shots.
- Find two vertical objects; one near, one far. Position your equipment so that these objects line up in the viewfinder.
- Level your equipment.
- Mount and center your camera on the MPR-CL II.
- Start out by positioning the approximate center of your lens over the axis of rotation.
- Now pan left.
- If the rear object appears to shift to the left, then you are ahead of the No-Parallax Point. Slide the MPR-CL II forward and try again.
- If the rear object appears to shift to the right, you are behind the No-Parallax Point. Slide the MPR-CL II back and try again.
- When the optical center of the lens is directly over the axis of rotation, the rear object will not appear to move relative to the front object.
- Record your results so that your setup can be re-created.
What Image Settings Should I Use?
- Decide how much depth of field you want across the entire scene and choose an appropriate aperture. Since most panoramas are of places and not people, you can set maximum crispness and depth of field out to infinity by focusing on the hyperfocal distance.
- Set the camera's exposure mode to Manual; exposure across the scene needs to be consistent. If you're not comfortable with manual exposure settings, take a few shots in Aperture Priority at your chosen aperture, note the shutter speed, and use that setting for manual exposure.
- If you're shooting digital, don't use Auto White Balance. Set your White Balance manually.
- Decide how much overlap you need. A rule of thumb is 30-50%, but the actual amount of overlap is not that important and the amount of overlap can vary from image to image.
Need Higher Precision?
To intuitively understand the No-Parallax Point (the NPP), stick your arm forward and point your thumb up. If you look at your thumb with first one eye closed, and then the other, youâ€™ll notice that the background behind your thumb shifts. Thatâ€™s because your perspective shifts depending upon which eye youâ€™re viewing your thumb with. This apparent shift is what is known as parallax. If both eyes were in the middle of your face, the background would look exactly the same.
Set Your Gear UP to Find the NPP
Mark, a Really Right Stuff Customer Service Rep, is setting up his Nikon D7000 to find the NPP of his 16-35mm zoom lens. He aligned two vertical objects inline with his lens; Mark used two TA-3-FS tripod foot spikes mounted upside down, but any similar item works well. To his standard support gear (TVC-33 tripod, BH-55 LR ballhead, and L-plate) he added our Pano Elements Package and PCL-DVTL.
When youâ€™re shooting a pano, you donâ€™t want the background to shift in relation to the foreground from frame to frame. So that means you need to shoot from the same perspective for all shots. To do this, you must find the lensâ€™ center of perspectiveâ€”the NPPâ€”and rotate your gear about that point. Hereâ€™s how to do that using our Pano Elements Package.
Start with the lens pointed straight ahead and objects are aligned. Level the PCL, center your camera, select focal length, and start with the middle of your lens roughly over the middle of the PCL. This is what you should see in the viewfinder.
If you pan camera to the left and rear object shifts left:
If the background object appears to move to the left, pull the nodal slide back (because youâ€™re in front of the NPP). Continue until objects stay aligned when you pan left and right.
If you pan camera to the left and rear object shifts right:
If the background object appears to move to the right, push the nodal slide forward (because youâ€™re behind the NPP). Continue until objects stay aligned when you pan left and right.
The key to high precision No-Parallax Point determination is to align multiple vertical objects that are fine and narrow. Also, the vertical objects that you choose must be perfectly vertical to ensure that the objects are perfectly parallel. A great tutorial on this subject is available from Dave Watts.