Originally Posted by Don Landis
I put my bets on the optical block construction precision being far better than the ball head being plumb.
Then you have lost this bet!
Yesterday evening I spend 3 hours to measure the optical systems of both TD10s, and today additional 3 or 4 hours. I did that by plotting the position of the crosslines of both camcorders to a large piece of paper on a wall, using the cross-laser to transfer the position of the cross hair to paper. I did that for both camcorders. And did that for different zoom positions and used the rig with the ballheads, and saw again that this is precise really.
What was transfered to paper is the position of the 4 corner points of the rectangle of the cross hairs. Then you can follow how the position of the corner points changes if you change the zoom. A variance in the corner points will end up in a variance in the final video, depending how you adjust the cameras. The variance can be both vertical and horizontal. In other words: the result shows the differences of the two optical systems when you compare the two camcorders.
I did the test with two strategies for the start point:
1. I adjusted the ballheads in a perfect way, installed the camcorder and had a look to the level of adjustment both in full zoom and in full wide angel- and for a lot of positions between. This gives me an information about the quality of the mechanical system but also about the optical system.
2. I did the same as in 1., but then adjusted the camcorders in full wide angel and measured again the adjustmet both in full zoom until full wide angel - and for a lot of positions between. This test gives me an information about the behaviour of the optical system.
a. The mechanical system is really precise, if you adjust the tripod and the igus system is in balance. Its behaviour is reproducible.
b. There is a variance both in horizontal but also in vertical alignment in the optical system. If you start with an adjusted system in full wide-angel, you find a non-adjusted system in full zoom and the other way round.
c. The TD10 has 30 zoom steps. With an adjusted system in full wide angel as in 2., you can zoom in and stay adjusted for the first 5 steps in a perfect way, until 10 in an acceptable way - and then you see that you shift out of the adjustment more and more.
For the test 2 I have calculated the pixel deviation - from the 1920 pixel I see a variance of 84 pixel or 4,4%, from the 1080 pixel I see a variance of
18,8% or 203 pixel (so, measured if I adjust the both cameras in full wide angel and then zoom full in. This was measured with the displays, an overscan is not considered here). Maybe only valid for the specific setting of my measurement - but just to have a feeling.
Next I have tried to calculate the difference in the heigth, if that causes the troubles. Using the crosslaser again to measure the difference in full zoom, and using the theorem of intersecting lines (is that translation ok - dont know) I end up with a height difference of 4.1 mm that I would have to bring up the lower camcorder. I am not sure if that is right or not, the figure looks high to me - but it is worth a try. I wait for longer 1/4 inch screws, they are ordered - and I have small metall plates with that 4.1 mm here.
Overall conclusion: if I continue to use this camcorder system, I have to do the adjustment in full wide angel or at step 5 to 10 of the zoom. And can use the system from wide angle to the first 10 zoom steps. Or I exchange the camcorder system if the increase in heigth does not work out.