Scheimpflug in Practice

[Bob Salomon]

Vaughn's point here is right on. It's really important to mentally determine the where you want the plane of sharp focus to be; only then can you really decide what movements you need.

So, if the plane you want to focus on is not parallel to the back, but displaced top-to-bottom (e.g., like a near/far landscape of flat ground), you need tilts. If the plane you want to focus on is displaced right-to-left (e.g., a wall is close on one side and stretches into the distance), you need swings. If the displacement is oblique, you'll need both swing and tilt.

Once I've determined where I want the plane of sharp focus to be, I choose focus points: top and bottom of the ground glass for scenario 1, right and left of the ground glass for scenario 2 and both top/bottom and right/left for scenario 3.

Before applying tilts or swings remember the old adage: "The back backs away from; the lens looks at" the plane you want to have in focus. Now, unless you have asymmetrical tilts/swings, my procedure would be:

For top/bottom points, I always focus first at the bottom of the ground glass (usually the more distant point) since I use field cameras with base tilts a lot. With axis tilts it doesn't matter. Anyway, I focus on the first focus point then tilt lens stage or camera back in the proper direction (i.e., "backing" or "looking") till both my chosen points are equally out of focus. Then refocus on the first point and then focus on the second point. If you have to rack out the bellows to get point 2 in focus, you need to move back or lens stage in whatever direction is needed to make the bellows a bit shorter. Vice-versa if you have to shorten bellows extension to get point 2 in focus. A couple iterations of this and you'll have both your points in focus.

The above works for left/right focus points too, just substitute "left/right" for "top/bottom."

For an oblique plane of sharp focus, you'll have to make adjustments for both top/bottom and left/right. It doesn't matter which you start with, however your focus points need to be directly opposite each other on the ground glass (i.e., vertically and horizontally aligned for top/bottom and right/left respectively). Apply one movement (say tilt), then apply the second (swing) using the method above. Then go back and check.

It's really easier and faster to do than to explain.

The next step for me is finding the focus spread between the nearest and farthest objects I want in focus in the scene (like Mark points out, there are always pesky objects that don't lie in your chosen plane ). If you've applied tilts/swings you need to really remember that the "near" is not necessarily what is nearest to you and the camera, but what is in front and/or above the plane of sharp focus and the "far" is what is behind and/or below the plane of sharp focus. I find the focus spread and note the bellows extension for each extreme. I then position focus exactly halfway between the two extremes and use the total distance to find the optimum f-stop to keep everything acceptably sharp (as described in the article on the LF home page, "choosing the optimum f-stop").

Hope this helps,

Doremus

Or just pick your self up a Rodenstock/Linos pocket Scheimpfluf/depth of field calculator and just follow its instructions!

[minh0204]

Did you check out the guide?

http://www.largeformatphotography.in...-to-focus.html

Procedure I works very well for me, I can get the correct tilt within 2-3 iterations (after some practice).

[Keith Pitman]

If you are using a P2, you have asymmetric tilts and swings. Simply focus on one of the lines on the groundglass with the focus knob (lower line for tilt and right line for swing), then use the tilt or swing to bring the other line into focus. You should be using the fine tilt knob, not the coarse tilt lever. This effectively automates Scheimpflug. It’s covered in the Sinar manual, but it more clear in a specific publication Sinar had. It used to be on the Sinar website.

[bieber]

Thanks a bunch for the advice everyone, I've got a lot of practicing to do.

If you are using a P2, you have asymmetric tilts and swings. Simply focus on one of the lines on the groundglass with the focus knob (lower line for tilt and right line for swing), then use the tilt or swing to bring the other line into focus. You should be using the fine tilt knob, not the coarse tilt lever. This effectively automates Scheimpflug. It’s covered in the Sinar manual, but it more clear in a specific publication Sinar had. It used to be on the Sinar website.

Ohhh, so that's what those dashed lines on the ground glass are for. Thanks, now that you put it that way that part of the manual makes a lot of sense. So the way the rear tilt and swing work is that they shift about an axis such that they always keep either the right or the bottom dashed line in focus, if it was in focus before the movement began? I'm curious about this bit, though:

Direct tilting and swinging with the lens standard is not satisfactory as its optical setup always involves an overall sharpness shift

So what they're saying is that if you want to use front standard tilt or swing, you should first find the correct amount of movement with the rear standard, and then transfer the movement to the front standard, right? I can see why moving the lens around would be different from moving the standard, but won't copying the movement from the rear standard introduce the same optical effect that you would have seen if you'd just moved the front standard directly in the first place?

[Mark Sawyer]

(like Mark points out, there are always pesky objects that don't lie in your chosen plane ).

But if you apply the Scheimpflug Principle correctly, at least you'll also have vignetting from having your lens way off-axis...

[Thom Bennett]

"I was told there would be no math." Focus on the farthest point you need in focus. Tilt the lens towards the plane you want in focus until the nearest point and farthest point are equally out of focus. It's easy to see on the ground glass. Lock the tilt. Then refocus on the farthest point and everything along the plane will now pop into focus. Since you are dealing with a 3D object, stopping the lens down will now help to bring parts of the object that lay outside of the flat plane into focus. Again, watch the gg as you stop down and you will see just how far you need to go. Best to practice on something not so small. Try the top of a table and get used to the movements before moving to smaller objects. Once you get the gist of it you can tackle any subject. Same principles apply to the swing. In your case a bit of both tilt and swing would probably be ideal. Good luck!

[Peter Collins]

others have said it: Use very little tilt, and check.

[John Layton]

A really good fresnel (like a Maxwell) will allow for a decent amount of stopping down while still being viewable enough to visually evaluate DOF.

[Bob Salomon]

A really good fresnel (like a Maxwell) will allow for a decent amount of stopping down while still being viewable enough to visually evaluate DOF.

Maxwell is a fresnel? Or is it a ground glass? Or is it the same as the Linhof Super Screen or the Beattie screen?

A Fresnel is a non focusing screen with concentric grooves on one side. It is sandwiched, usually on top, with a ground glass.
A ground glass is ground on one side and that side is what the image is formed on.
A Super Screen or Beattie Screen, both were manufactured by Fresnel Optics in Rochester, NY, the parent company of Beattie, is a piece of acrylic, like a fresnel, with one side frosted to act as a focusing surface and the other side grooved like a fresnel Screen.

Which are you suggesting?

[williaty]

Maxwell is a fresnel? Or is it a ground glass? Or is it the same as the Linhof Super Screen or the Beattie screen?

A Fresnel is a non focusing screen with concentric grooves on one side. It is sandwiched, usually on top, with a ground glass.
A ground glass is ground on one side and that side is what the image is formed on.
A Super Screen or Beattie Screen, both were manufactured by Fresnel Optics in Rochester, NY, the parent company of Beattie, is a piece of acrylic, like a fresnel, with one side frosted to act as a focusing surface and the other side grooved like a fresnel Screen.

Which are you suggesting?

The answer to that is dependent on which size of ground glass you need. Depending on size, he can do anything from a simple fresnel with high transmission coatings to whatever magic pixie dust is used to make his complete ground glass replacement wonder-screens (I'm not mocking the product, the top of the line screens are stunning). The bigger stuff only gets the simple fresnel, the smaller screens can have your choice of price-and-performance.