Although I have a good way to make sure my front and rear standards are parallel with each other I would hate to have to make a field calibration using levels. It can be done but kind of a pita.
Another way that I have found to be very accurate and accomplished quickly just involves finding a good target and panning the camera (with shift) and matching the edges with your eyes.
This can also be a quick way to set up the front and rear standards before going out for a shoot without the need for levels.
The distance to the target isn't as important as the target itself. The target should be something that you could easily distinguish with your eyes if either in or out of focus - even slight focus. At best maybe something with print which could be a white balance card set at a distance where it can be clearly seen at 100% pixels - maybe 10 to 20 feet. A tree trunk also could be used especially if something distinguishable can be used for repeatability.... anything that can be reliably repeated.
Once you have determined a good target adjust your camera [Actus] to 10mm of horizontal shift either left or right and pan the camera until the target is at the very edge of the frame. Go to 100% pixels and focus until as sharp as possible. Next shift the opposite direction with the same amount of 'MM' and pan the camera to the opposite direction until the target as at the edge of the frame (other side). If it isn't in the same focus then 'slightly' - 'very slightly' adjust the swing until focus matches. This shouldn't be much of an adjustment but with the Actus you will be adjusting while in the 'more freely' movement detent area so you can go a little back and forth until you find focus acceptable. Then...... go back and check the other side. You should be 'almost' if not already there. Maybe you will have to do that one more time but with a little practice you will have this alignment procedure done in no time. This has nothing to do with focusing in the center as the concern is with the edges to make sure that 'swing' is neutral - 'zeroed'.
Bottom line is this really works. Swing is the most important parallel adjustment to be made. If you shift for stitching and that camera movement isn't parallel there will be skew in the image.
I have also found that the tilt adjustment can easily be adjusted in the field if necessary. I have two front standards and they both have a noticeable hard stop detent that is really close to perfect. Close enough that I trust it. But if you have to adjust the tilt movement you have to then find a wall of any kind - brick would work well - and assuming the wall is pretty close to plumb set your camera up to it so that you can have full rise and fall movements while still seeing a brick or whatever. Just follow the same procedures as above except now working with rise and fall instead of shift. My results with both of my front standards have me trusting the stop but I suggest you practice maybe a couple of times to determine this for yourself.
What I have learned from all of this is that the criticism regarding the front standard movements as being 'sloppy' are not warranted. I appreciate the fact that I can actually perfectly 'Zero' my standards in the field - just took a little time to figure out.
Cheers.....
Victor
Another way that I have found to be very accurate and accomplished quickly just involves finding a good target and panning the camera (with shift) and matching the edges with your eyes.
This can also be a quick way to set up the front and rear standards before going out for a shoot without the need for levels.
The distance to the target isn't as important as the target itself. The target should be something that you could easily distinguish with your eyes if either in or out of focus - even slight focus. At best maybe something with print which could be a white balance card set at a distance where it can be clearly seen at 100% pixels - maybe 10 to 20 feet. A tree trunk also could be used especially if something distinguishable can be used for repeatability.... anything that can be reliably repeated.
Once you have determined a good target adjust your camera [Actus] to 10mm of horizontal shift either left or right and pan the camera until the target is at the very edge of the frame. Go to 100% pixels and focus until as sharp as possible. Next shift the opposite direction with the same amount of 'MM' and pan the camera to the opposite direction until the target as at the edge of the frame (other side). If it isn't in the same focus then 'slightly' - 'very slightly' adjust the swing until focus matches. This shouldn't be much of an adjustment but with the Actus you will be adjusting while in the 'more freely' movement detent area so you can go a little back and forth until you find focus acceptable. Then...... go back and check the other side. You should be 'almost' if not already there. Maybe you will have to do that one more time but with a little practice you will have this alignment procedure done in no time. This has nothing to do with focusing in the center as the concern is with the edges to make sure that 'swing' is neutral - 'zeroed'.
Bottom line is this really works. Swing is the most important parallel adjustment to be made. If you shift for stitching and that camera movement isn't parallel there will be skew in the image.
I have also found that the tilt adjustment can easily be adjusted in the field if necessary. I have two front standards and they both have a noticeable hard stop detent that is really close to perfect. Close enough that I trust it. But if you have to adjust the tilt movement you have to then find a wall of any kind - brick would work well - and assuming the wall is pretty close to plumb set your camera up to it so that you can have full rise and fall movements while still seeing a brick or whatever. Just follow the same procedures as above except now working with rise and fall instead of shift. My results with both of my front standards have me trusting the stop but I suggest you practice maybe a couple of times to determine this for yourself.
What I have learned from all of this is that the criticism regarding the front standard movements as being 'sloppy' are not warranted. I appreciate the fact that I can actually perfectly 'Zero' my standards in the field - just took a little time to figure out.
Cheers.....
Victor