How does rear tilt affect front tilt?

[GoodOldNorm]

Alan,

You're stuck in a rut about focusing here... Clear your mind of preconceptions and consider the following.

Applying tilt and swing is NOT focusing. Yes you're checking if things come into focus or not to make sure you have the plane of sharp focus where you want it, but this is a separate and different thing than finding where to place your standards for optimum depth-of-field and f-stop.

Let's focus a shot that doesn't need movements using the near/far method:

Step 1: find the nearest object you want in sharp focus. Focus on that with the main focusing knob. Note the position of the standards on the camera bed/rail.
Step 2: find the farthest object you want in sharp focus. Focus on that with the main focusing knob. Note the position of the standards on the camera bed/rail.
Step 3: position the standards halfway between the two focus points.
Step 4: choose your optimum f-stop based on the amount of distance between the two focus points. (This assumes you've figured that out, or have at least copied the table from article on How to select the f-stop the LF home page, https://www.largeformatphotography.info/fstop.html ).

I've used this method for years with excellent results. It's not at all like focusing a smaller camera, where you twist the focusing ring until what you want is in focus and then shoot. No, with this method you concern yourself with the near/far extremes. You never even have to look at focus for anything in between them. This method reliably gives you the optimum compromise between depth-of-field and image degradation due to diffraction while ensuring that what you want sharp is sharp.

Using tilt and swing movements is a separate thing from finding the overall focus for the scene.

What you call the "initial focusing process" is NOT focusing; it's applying movements.

Now, when you want to use tilt/swing, you should do so before focusing. Yes, you'll have to focus on your reference points in order to correctly apply tilt/swing. However, after you have done so, you need to look for the nearest and the farthest object not in the plane of sharp focus and use them to focus using steps 1-4 above. Yes, you'll likely be repositioning the plane of sharp focus a bit in order to get the optimum f-stop for the depth of field you desire. This is not "destroying the whole focusing process you did initially." That's the way it works.

Clear now?

Doremus

Clear as gin, thank you!

[Doremus Scudder]

Hi, Doremus, would you consider writing a primer on using asymmetrical tilts? I found your file, dealing with base tilts a great help, thank you.

I don't have a primer, per se, for asymmetrical tilts/swings, but I'll "talk" you through it here. It's really pretty simple.

Of course, you need to decide where you want to place your plane of sharp focus and then choose reference points to focus on first.

Let's consider tilts:

Choose a near and a far reference point. Ideally, one of your reference points falls on the tilt axis (let's say one does for now - the other reference point can be anywhere, but the farther the points are from each other on the ground glass, the better). Some cameras have two tilt axes usually, one high and one low, marked on the ground glass. You can tilt around either. I think some cameras only have one tilt axis.

At any rate, choose the axis you want to tilt around (easy choice if your camera only has one), but don't tilt yet. Simply bring your reference point into sharp focus using the main focusing knob. Let's say we focused on the "far," using the bottom axis on the ground glass.

Once this point is in sharp focus, tilt the back around the tilt axis (in this case, the top of the back will move backward) until your second reference point is in focus. Voilà! You're done. The far point will still be in focus, since that part of the ground glass hasn't moved. (Note: if you choose to swing around the top axis, i.e., the "near" point, then the back will tilt in at the bottom to achieve the same result.)

What if your reference point doesn't fall on your tilt axis? Well, the easiest thing is to find one that does. Next easiest is to use your rise/fall to position the reference point on the axis, apply the tilt and then re-frame using the rise/fall. If that's impossible, then find one as close to the axis as possible. You'll have to do a couple iterations to get both your reference points in focus though (like using axis tilts with reference points on either side).

Now, on to swings:

Replace "near" and "far" in the above with "right" and "left."

There's a pdf document from Ebony that describes asymmetrical movements in more detail here: http://www.mr-alvandi.com/downloads/...el-cameras.pdf

Hope that helps,

Doremus

[Heroique]

To reinforce the excellent lessons here about back tilt/front tilt on focus, AA adds an informative twist about back swing/front swing in The Camera.

In a photo of a courthouse facade with caption, he uses back swing to achieve sharp focus.

"The back was swung horizontally to assure sharp focus across the building façade," he says, "not to overcome horizontal convergence."

It's not clear if he used back swing before or after focusing, but the wording suggests he may have adjusted back swing last.

Of course, a picture is worth a thousand words, so see the book's chapter titled "View Camera Adjustments," Figure 10-7 (A), Courthouse, Bridgeport, California, detail.

A fantastic teaching-by-doing example.

[Doremus Scudder]

Heroique,

Nice to see you posting again!

If I had been AA, I'd have swung to get the plane of sharp focus across the building façade, then found near/far and focused. But, there are more than one way to skin the banana

Doremus

[GoodOldNorm]

I don't have a primer, per se, for asymmetrical tilts/swings, but I'll "talk" you through it here. It's really pretty simple.

Of course, you need to decide where you want to place your plane of sharp focus and then choose reference points to focus on first.

Let's consider tilts:

Choose a near and a far reference point. Ideally, one of your reference points falls on the tilt axis (let's say one does for now - the other reference point can be anywhere, but the farther the points are from each other on the ground glass, the better). Some cameras have two tilt axes usually, one high and one low, marked on the ground glass. You can tilt around either. I think some cameras only have one tilt axis.

At any rate, choose the axis you want to tilt around (easy choice if your camera only has one), but don't tilt yet. Simply bring your reference point into sharp focus using the main focusing knob. Let's say we focused on the "far," using the bottom axis on the ground glass.

Once this point is in sharp focus, tilt the back around the tilt axis (in this case, the top of the back will move backward) until your second reference point is in focus. Voilà! You're done. The far point will still be in focus, since that part of the ground glass hasn't moved. (Note: if you choose to swing around the top axis, i.e., the "near" point, then the back will tilt in at the bottom to achieve the same result.)

What if your reference point doesn't fall on your tilt axis? Well, the easiest thing is to find one that does. Next easiest is to use your rise/fall to position the reference point on the axis, apply the tilt and then re-frame using the rise/fall. If that's impossible, then find one as close to the axis as possible. You'll have to do a couple iterations to get both your reference points in focus though (like using axis tilts with reference points on either side).

Now, on to swings:

Replace "near" and "far" in the above with "right" and "left."

There's a pdf document from Ebony that describes asymmetrical movements in more detail here: http://www.mr-alvandi.com/downloads/...el-cameras.pdf

Hope that helps,

Doremus

Thank you again Doremus that is a well written set of instructions.

[Alan Klein]

Alan,

You're stuck in a rut about focusing here... Clear your mind of preconceptions and consider the following.

Applying tilt and swing is NOT focusing. Yes you're checking if things come into focus or not to make sure you have the plane of sharp focus where you want it, but this is a separate and different thing than finding where to place your standards for optimum depth-of-field and f-stop.

Let's focus a shot that doesn't need movements using the near/far method:

Step 1: find the nearest object you want in sharp focus. Focus on that with the main focusing knob. Note the position of the standards on the camera bed/rail.
Step 2: find the farthest object you want in sharp focus. Focus on that with the main focusing knob. Note the position of the standards on the camera bed/rail.
Step 3: position the standards halfway between the two focus points.
Step 4: choose your optimum f-stop based on the amount of distance between the two focus points. (This assumes you've figured that out, or have at least copied the table from article on How to select the f-stop the LF home page, https://www.largeformatphotography.info/fstop.html ).

I've used this method for years with excellent results. It's not at all like focusing a smaller camera, where you twist the focusing ring until what you want is in focus and then shoot. No, with this method you concern yourself with the near/far extremes. You never even have to look at focus for anything in between them. This method reliably gives you the optimum compromise between depth-of-field and image degradation due to diffraction while ensuring that what you want sharp is sharp.

Using tilt and swing movements is a separate thing from finding the overall focus for the scene.

What you call the "initial focusing process" is NOT focusing; it's applying movements.

Now, when you want to use tilt/swing, you should do so before focusing. Yes, you'll have to focus on your reference points in order to correctly apply tilt/swing. However, after you have done so, you need to look for the nearest and the farthest object not in the plane of sharp focus and use them to focus using steps 1-4 above. Yes, you'll likely be repositioning the plane of sharp focus a bit in order to get the optimum f-stop for the depth of field you desire. This is not "destroying the whole focusing process you did initially." That's the way it works.

Clear now?

Doremus

Wow. That's totally different than what I thought focusing was. A couple of questions. How do you know what near and far points to pick for the intilal far focus and near tilt? How do you know what the near and far points are not in the plane of sharp focus? Use my above picture of the barn with water pump in the foreground to explain how you would do it.

Another question. When you set the middle of the standards distance between far and near focus point, does that give you the typical 1/3 near and 2/3 far distances you would typically use in a fix camera when calculating the DOF?

[Doremus Scudder]

Wow. That's totally different than what I thought focusing was. A couple of questions. How do you know what near and far points to pick for the initial far focus and near tilt? How do you know what the near and far points are not in the plane of sharp focus? Use my above picture of the barn with water pump in the foreground to explain how you would do it.

Another question. When you set the middle of the standards distance between far and near focus point, does that give you the typical 1/3 near and 2/3 far distances you would typically use in a fix camera when calculating the DOF?

Alan,

I described how I'd set up, apply movements and focus for your image in post #49 already, so I won't repeat all that here.

About choosing reference points for applying tilts and swings: It really helps me to visualize where I want the plane of sharp focus to lie in the scene. With a simple scene, say a sandy beach with a piece of seaweed in the foreground and the sea and a distant sea stack in the back ground, you'd likely want to have the plane of sharp focus lie along the foreground and hit the distant rock at about the halfway point. Since you have asymmetrical tilt that moves around an axis at the bottom of your ground glass (the far, in this scene), you'd want to pick point that fell on that axis. Let's say the halfway point on the distant rock does. So you'd bring that point into sharp focus using the main focusing knob and then tilt to bring the foreground objects into sharp focus. Now you tighten down your tilt knob and leave it there.

Now, let's say there are some pieces of driftwood in the foreground that stick up a bit from the plane of sharp focus that you want sharp in the final image. The nearest part of one of those would be your "near" focus point. Focus on that, note the position of the standards to the camera body. Next find the "far," which in this case would likely be the distant horizon line. Focus on that and note it's position too. Now, to "focus," you simply place the standard halfway between the two extremes. To find the optimum f-stop, you need to consult your table (see the above post for the link to the article on the LF home page).

But, I digress...

More about choosing reference points for applying tilts/swings. Sometimes you tilt or swing to get the face of a building, a cliff wall, a long stretch of foreground (as in our example above), etc. in focus. Then it's easy to find points along that chosen plane to use as reference points.

And, as I described above (post #49 again), I'll often tilt to get two near objects in the plane of sharp focus and then rely on the repositioning that happens when I actually focus to put the plane of sharp focus in the optimum position deeper in the scene. This works well in situation where you have a stretch of flat foreground and then a tall object like a building, tree, etc. My reference points in this situation are a foreground object at the very bottom of the ground glass and the nearest part of the tall object, say the closest tree branch or the eaves of a barn. Very little tilt is needed for this, but that little bit often keeps you from having to stop down that extra stop into diffraction degradation.

It's a bit more difficult to choose reference points when there's no obvious plane in the scene and lots of irregular objects sticking up. You have to imagine the plane in the scene and where it will best go to optimize depth of field. With the camera in "zero" position (everything parallel) the depth of field is in front of and behind the plane of sharp focus (not necessarily distributed in the 1/3 in front, 2/3 behind... more about that later). Every part of the plane of sharp focus is equidistant from the film plane.

However, when you tilt or swing, the plane of sharp focus changes orientation and actually intersects the film plane (and the lens plane) somewhere (that's Scheimpflug). So, in your image, parts of the plane of sharp focus will be closer to you and parts will be farther away. When you tilt a lot, the depth of field ends up being above and below the plane of sharp focus; with lots of swing, it side-to-side, always with shallower depth of field closer to the camera and more depth of field farther away.

It helps in this case to think of your depth of field as a wedge of sharpness with the narrow part of the wedge being close to you and the gradually growing wider as it recedes. The thickness of the wedge is determined by the aperture; smaller aperture = thicker wedge. But, remember, the thin part of the wedge close to you doesn't get very thick even when you stop down a lot. So you have to be careful of foreground objects (and camera position) to make sure they are sharp if you want them to be.

Visualizing this wedge helps in placing the plane of sharp focus. For example, a common beginners mistake is to use tops of distant things for reference points for applying tilts/swings. Say you have a nice landscape with a long flat foreground and a distant tall mountain. The mistake is to use the top of the mountain for a reference point. If you place the plane of sharp focus on the mountaintop, the the whole top half of the wedge of depth of field gets wasted when you stop down to taking aperture and the base of the mountain may be out of focus since it may be beyond the depth of field. Better is to place the plane of sharp focus halfway up the mountain so that the depth of field there includes the mountaintop and base.

Finally, being able to recognize which scenes don't benefit from tilts/swings is important. Scenes with tall near objects and no appreciable stretch of foreground don't benefit from tilt (although a swing might help if that tall object is on one side only). Tall near objects on both sides? Forget tilt and swing; just stop down.

A problem with asymmetrical tilts/swings is that in order for them to work easily, you need a reference point that falls on the axis line. If your chosen reference point doesn't fall on that axis, then you need a work around. You can use rise/fall to place your point on the axis, apply the movement and the re-frame if that works, but often it won't. In that case, you need to use the same method I outlined in dealing with base tilts: focus on one reference point, tilt till both are equally unsharp, focus again on your reference point, check the other, tweak focus to find which way you need to tilt/swing, apply a tiny bit more movement, check again and repeat as needed till all your reference points are sharp.

Now, about that "1/3 to 2/3 distribution" of the depth of field. This really only holds true at the so-called hyperfocal distance. When focusing farther away (say at infinity) or focusing close up, the distribution changes. At portrait distance, the distribution is closer to 50/50. But, if you use the near/far - split the difference focusing method, none of that matters. Placing the standard halfway between the extremes of focus automatically takes care of all that.

Hope this helps,

Doremus

[Alan Klein]

Thanks Doremus. That's a lot to digest. I'm going to have to pull out my camera and just play with it on different scenes without actually shooting anything.

[Jim Noel]

Thanks Doremus. That's a lot to digest. I'm going to have to pull out my camera and just play with it on different scenes without actually shooting anything.

That is a very wise, and inexpensive thing to do.

[Alan Curtis]

Doremus

Thank you so much for your excellent description of what I often do wrong with rear tilt. There are countless negatives with sharp foreground and out of focus tops o f trees in my collection.