front tilt question

[DrPablo]

How do you figure out how much front tilt is needed for a sharp foreground? I find myself really winging it, and it takes a long time to find a degree of tilt that keeps both foreground and background in focus. Is there a system?

Thanks.

[Bob Gentile]

I focus on the farthest thing that I want to be in sharp focus. Then, I tilt the front until the nearest thing I want comes into sharp focus. Then I stop way down and trip the shutter.

In my (limited) experience, not a lot of tilt is needed.

[DrPablo]

Thanks, Bob, I've discovered that too -- usually just a millimeter or two.

But the farthest object goes out of focus once I tilt, so I end up having to laboriously go stepwise, looking at the near and far objects with my loupe, focusing, looking again, and then readjusting tilt.

[Bob Gentile]

I might go through a couple of iterations, but then I generally "call it a day" and simply stop way down. I've never had much of a problem, but some other things to consider: You may be more demanding than I... you may be shooting more demanding subjects...

Do you notice the out-of-focus areas on your negs... or just on the GG?

[DrPablo]

Well, I never leave it out of focus when I take the picture. It just takes me a long time to get it in focus. I also will stop way down when feasible for the subject. Today I was shooting over a harbor, though, and I wanted as fast an exposure as possible to prevent the moored boats from blurring. But when possible I'm sure clamping down to f/45 will atone for any errors.

[Hiro]

As far as I understand, the reiteration is the norm unless you have a sextant, deep understanding of trigonometry, a laser device on a surveyor's tripod, an HP calculator, and whatever else you need in addition :-)

Adding to the original question...
The tilt angle of the front standard determines where the hinge line is. Moving the rear standard swivels the plane of sharp focus around the hinge line according to the Scheimpflug Rule (see this link: http://www.trenholm.org/hmmerk/HMbook18.html). It seems to me that once you establish a "rough" front tilt angle (the hinge line at an appropriate position), moving the rear standard, rather than the front standard, would be a better way to reach the optimum focus. Or am I drunk...well, I know I am, but am I too drunk? Just do it?

[Capocheny]

Hi Paul,

Bob is correct in that you don't need to tilt a lot. For landscape types of shots... you'll only need a few degrees of tilt and you're home. However, there are times when a few iterations are needed.

The best way to avoid "winging it" is to scrutinize the ground glass. It'll show you what's in sharp focus and what isn't.

Cheers

[Ole Tjugen]

As far as I understand, the reiteration is the norm unless you have a sextant, deep understanding of trigonometry, a laser device on a surveyor's tripod, an HP calculator, and whatever else you need in addition :-)

Not quite as bad - if you can manage to get the tilt axis through the entrance pupil (?) of the lens you will keep focus in that line. Unfortunately few cameras have the option to adjust the longitudinal position of the tilt axis relative to the lens board, the only one I know of is the Carbon Infinity. From my own experience this works really, really well and makes tilt and focus far easier.

[Doremus Scudder]

I'm assuming you have base tilts (if not, see below...). For me, with base tilts, the easiest way to get things into focus fast with the lens stage is to

1. focus on the far (this is usually, but not always at the top of the GG).

2. tilt (moving the lens plane toward the plane of focus) slightly until both top and bottom of the ground-glass image are equally out of focus.

3. refocus the far again (since usually you tilt the lens forward, you are lengthening the bellows, so you'll have to "focus farther" i.e. make the bellows shorter). If you are lucky, you have everything in focus, but probably not, so...

4. This is the critical step! While watching the out-of-focus part of the scene through the magnifier, tweak the focusing knob slightly in the direction you think it should go (i.e. longer or shorter bellows). If the out of focus area gets better, you know you have to tilt a bit more in the same direction, i.e. if you lengthened the bellows to improve focus, you need to tilt forward with the lens stage (which lengthens the bellows). If the image gets worse, you have to tilt the other way. But, don't tilt yet! Just determine the direction you need to go.

5. Begin again with step 1 and repeat through step 4. That is, refocus on the far, tilt till both top and bottom of the GG are equally out of focus and then refocus the far and check the near. After a couple of iterations, you should have everything in focus.

As usual with things of this nature, it is much easier to do this than to explain it (just try telling someone over the phone how to put on a shirt...). With a little practice, the whole process becomes second nature.

As you probably have guessed, the same process works for the back if it has a base tilt, only the directions are reversed.

For center tilts and swings, one simply focuses on the center of the GG (assuming it is in the plane of focus that you want) and swing or tilt till the near and far are in focus. In reality, most subjects don't fall neatly into "planes of focus" and some compromise/stopping down is necessary.

Hope this helps a bit,

Doremus Scudder

[Leonard Metcalf]

If you have base tilt you need to wiggle. If you have centre tilt (on the axis) then choose something on the plane of sharp focus that is on the centre axis, focus on it then do your tilts. For me this is exactly why I chose a camera with axis tilts and swings on the front standard (and asymmetrical swings and tilts on the rear). To make like easy.