I must admit that I become a bit confused by some of the treads here on this site about focusing regarding tilt and the use of a ground glass.
(It might be due to the fact that I am often, and easily confused, according to my son).
I have been using manual focusing on different system since about 2005. First on a 1Dsl and 1Dsll with Contax lenses.
But here the view finder was not optimal for that..
Then I got a RZ Proll + a D-model and focusing become some thing completely different.
Especially after I adjusted the position of the ground glass!
I modified a focus loupe for the camera and it become even more easy to do.
The I began to use a 4x5 camera and, using ground glass was even more easy. + with a loupe!
In one of my confused moments I replaced my RZ with a AFDll camera.
Not much more in focus in the studio after the shift compared to before
And I am still carrying about 15 kg around on my back out in the nature.
In this period I also got a Sinar P 8x10 camera.
And a Hartblei 45mm tilt/shift lens from this forum.
And 90% of my photos is manually focus.
But what I never really has understood is the priniple of focusing tilt after a number out of a calculation or table.
I am to easily confused of my subject in front of the camera to be able to do that.
And I almost never has my camera aligned horizontal. I mostly point it downwards when I am using tilt.
I will use the picture below o describe how I focus with tilt.
And I will use my Hartblei lens as an example.
First I mace a ruff composition in my view finder. And, the camera is pointing downwards a bit.
I focus ruffly in the middle of the picture.
Then I apply about 1-2 degrees of tilt depending on how much the camera leans forward.
Check focus in center.
Then starts the process of adjusting tilt.
I look at the foreground to my view finder and make (if necessary) small adjustment to focus.
Then with the foreground in focus I adjust my grip on the focus ring so I now have my index finger at 12 clock.
And since I use f5.6 for focusing it means that one of the small "tabs" on the aperture ring is just under my finger, also at (almost)12 clock.
Then I shift my view point to a position in the distant focus plane that is easy to see.
Now I rock the focus ring back and forward to get this distant point in optimal focus.
Then I feel where my finger are in regard to the "tab" on the aperture ring:
If it is past 12, then I must tilt a little bit more. "Under Tilt"
But, if it is before 12, then I have to much tilt "Over Tilt"
I adjust tilt accordingly to my result, many by half a degree or so, and then do the focus check again.
After 2 or 3 adjustments both close and distant focus point now lays on the same distant mark on the focus ring.
Any adjustment of the focus will now shift the plane of focus (ruffly) perpendicular to my chosen plane of focus.
The I ponder what f-stop I should use, it will decide how "thick" my focus plane will be.
Then I take the photo, move the focus out and in again, take one more photo, and if the composition feels good,
I repeat the refocus/take photo process one or two more times.
With this technique I will walk away from a scene with 40 - 60% good photos, depending on my f-stop.
And it takes much longer to describe than to actually do it.
On my Sinar P4x5 or 8x10 I have the benefit of using a loupe which increase the accuracy a lot of the process.
Yes, I use the same process described above on my large format cameras.
It is easy. But it requires one act of fait:
You just have to believe that you actually can use the ground glass for focusing