Easy-Bake Scheimpflug Recipe

[sharktooth]

234835


Easy-Bake Scheimpflug Recipe

Do you want to use tilts and swings on your large format camera to change the plane of focus? Of course you do, but you’re not a professional “chef” who’s been doing this for years.
Pro chefs don’t need instructions, since they do it all by “feel”, but that doesn’t work for the all the jr apprentices out there. Here’s some basic instructions for all yous’ jr apprentices who want to graduate from “clumsy Luigi” status. Best of all, you can do this from your own home without fear of embarrassment or social ostracism.


Ingredients:

1) A view camera with tilt and swing angle scales on the front standard. The scales should be marked in 2 degree increments, or smaller (the smaller the better).
Substitutions: If your camera doesn’t have a scale to show the actual tilt or swing angle, you could use a protractor, but it makes thing much more difficult, and is probably not worth the trouble.

2) The view camera should have some sort of focus scale for the rear standard. Any sort of scale that shows focus change in mm should work well.
Substitutions: If your camera doesn’t have a focus scale, you could easily jury-rig one with a piece of masking tape marked in mm.

3) A ground glass with grid markings, preferably in 1cm squares.
Substitutions: Any sort of grid system should work, but it’s easier to do the calculations if the grid is metric, and in squares.

4) Any cheap scientific calculator or cell phone calculator app that has the arctan function. (Often shown as tan-1 on calculators)
Substitutions: You could tabulate potential results on a piece of paper, so you could carry that in your pocket instead of an electronic calculator.

5) Something to record notes with. A pad and pen works great (pencil works too). Anything that you like to keep a record of values to enter into the calculator.
Substitutions: If you have a very good memory, that could potentially work too (but I wouldn’t know).


Baking Instructions for Lens Tilt:

1) Compose your scene on the ground glass, and decide if you’d like to change the plane of focus by tilting the lensboard. If you decided that a lens tilt would be beneficial, then proceed to step two.

2) Choose two features in your scene that you would like to be in focus. One of these should be nearer to the camera, and the other further away. Focus one of these features on the ground glass using the rear standard focus knob. Record the reading of the rear standard focus position in your notepad.

3) Focus on the other feature, also using the rear standard focus knob. Record the reading of the rear standard focus position for that one in your notepad too.

4) You should now have two focus position readings in your notepad. The difference between these two readings will probably only be a few mm. It’s that difference between readings that we need to use.
It’s basically the amount of focus shift at the ground glass when you focused each feature. We’ll call that focus difference “FD”, since it represents the displacement of the film plane between the two focused positions.

5) Next, we need to measure the vertical distance between the two features on the ground glass. This can easily be done by counting grid squares on the ground glass. If one feature is 5 squares above the other one, then the vertical distance on the ground glass will be 50mm, if each grid square is 1cm (10mm). You can also estimate ½ squares and ¼ squares to get 5mm and 2.5mm. We’ll call that the ground glass vertical distance “GGVD”, since it represents the vertical height difference between the two features on the ground glass. Write the “GGVD” value in your notepad.

6) The front tilt angle can now be calculated using the “FD” and “GGVD” measurements. The front tilt angle = arctan(FD/GGVD). Plug that into your calculator. The result will be the front tilt angle in degrees.

7) Tilt the front standard to the result calculated in step 6. You need to have a tilt angle scale on the front standard in order to do this with any accuracy.

8) Once the front tilt angle is set and locked, go back to the ground glass and refocus on one of the features. If you check the other feature, they should now both be in focus (or very close).


Baking Instructions for Lens Swing:

1) Compose your scene on the ground glass, and decide if you’d like to change the plane of focus by swinging the lensboard. If you decided that a lens swing would be beneficial, then proceed to step two.

2) Steps 2 thru 4 are the same as for lens tilt, so see above.

5) Next, we need to measure the horizontal distance between the two features on the ground glass. This can easily be done by counting grid squares on the ground glass. If one feature is 5 squares to the right of other one, then the horizontal distance on the ground glass will be 50mm, if each grid square is 1cm (10mm). You can also estimate ½ squares and ¼ squares to get 5mm and 2.5mm. We’ll call that ground glass width distance “GGWD”, since it represents the horizontal width between the two features on the ground glass. Write the “GGWD” value in your notepad.

6) The front swing angle can now be calculated using the “FD” and “GGWD” measurements. The front swing angle = arctan(FD/GGWD). Plug that into your calculator. The result will be the front swing angle in degrees.

7) Swing the front standard to the result calculated in step 6. You need to have a swing angle scale on the front standard in order to do this with any accuracy.

8) Once the front swing angle is set and locked, go back to the ground glass and refocus on one of the features. If you check the other feature, they should now both be in focus (or very close).

[Vaughn]

The customers left the restraunt because the new chef forgot his calculator and the food was out of focus. ;)

Thanks for writing that up. I'll keep to doing everything on the GG as usual, where I generally judge focus, movements, and aperture needs by when both near and far points come into focus on the GG at the same, or close to the same, time. In low light situations, I do find it handy to move a standard halfway between the FD and have a solid starting point.

[sharktooth]

.... a little background.

This came out of a discussion about the Sinar f2 over at Photrio. The poster was asking about one of the scaled knobs on the left side of the camera at the back. He was asking what it was for.
I didn't know either, so I looked it up. It turns out it's a tilt angle scale for focus adjustment, but I had no idea how this could work on a Sinar f2. The Sinar f2 has basic base tilts, and not the fancy in-frame asymmetrical tilt of the P series. It didn't seem to me that it would be possible to determine tilt angle on an f2.

I found a description for use of the tilt angle knob for the f2 (also f1, but not f), also on Photrio. When I read through the description it became immediately clear how it worked, and that the basic principle could also be useful for other cameras. With the Sinar f2, there are horizontal marked lines on the ground glass 35mm above and below the center line. There are also vertical marked lines 35mm to the left and right of the vertical center line. On the P series, these lines represent the asymmetrical tilt or swing axis (depending on orientation). These same lines can be used on the f series using completely different methodology to determine tilt or swing angle.

The Sinar lads were very smart, so they deserve all the credit for this. By focusing the back at two different points on the upper and lower marked lines, they could create a right angled triangle with the focus displacement as one leg, and the vertical ground glass displacement as the other leg. The angle of the resulting hypotenuse is the required back tilt angle. It's just simple high school trigonometry.
Since the vertical displacement on the ground glass is already fixed at 70mm, the only unknown is the focus displacement. Since the focus displacement is proportional to the rotation of the focusing knob, they only needed to put angle scale markings on a secondary knob that rotates with the focus knob. There is no need for a separate calculation.

The big downside of the Sinar system is that your two focus points have to reside on the marked lines. That's probably not going to be practical for many shots, since there may not be convenient points to focus on along those marked lines.

Nonetheless, it is indeed ingenious for Sinar to come up with this system, since it was an easy add to the f series, and would make use of the marked lines already on the ground glass for the Sinar P.

The method I'm using here is just an adaptation of this Sinar approach, but can be used with any camera with any two points on the ground glass. You're not limited to points along a marked line, but you will need a calculator to compute the tilt angle.

[sharktooth]

The customers left the restraunt because the new chef forgot his calculator and the food was out of focus. ;)

Thanks for writing that up. I'll keep to doing everything on the GG as usual, where I generally judge focus, movements, and aperture needs by when both near and far points come into focus on the GG at the same, or close to the same, time. In low light situations, I do find it handy to move a standard halfway between the FD and have a solid starting point.

You're right, it's the McDonald's approach, not the Maison Lameloise. :)

[Doremus Scudder]

sharktooth,

I'm sure your method will work flawlessly. And I'm sure I'll never, ever bother using it. In real-world practice, you don't need to calculate a thing to apply the proper amount of tilt or swing, using either standard or even both.

Really, all you need is steps 2 and 8 in your baking instructions at a bit of patience. Here's my "recipe" for applying tilts:

1. Choose a near and a far point that you want to be in the plane of sharp focus. Focus on the far point (bottom of the ground glass).

2a. If you have axis tilts, make sure one of your focus points lies on the tilt axis. Then simply tilt while watching the other focus point with your loupe (remember, tilt the front forward or the back backward to bring a nearer point into focus). Stop when the second point is in sharp focus. If you've done this right, your first point should still be in sharp focus too. Et voilà, tilt has been applied. If the first point is not quite sharp, then repeat the process and refine focus till both points are sharp. Note that this same method works for asymmetrical tilts on either standard as long as you get one of your focus points on the tilt axis, be it center or off-center. And, if your focus points don't lie on an axis, don't despair, just use step 2b instead.

2b. If you have base tilts, e.g., on a folding field camera (or if one of your focus points doesn't conveniently lie on an axis line), then carefully tilt, while watching the ground glass without the loupe. Stop when both points look equally out of focus. Refocus the first point and repeat. After a couple of iterations, use the loupe to make final refinements. For me, it usually takes three iterations to get both points in sharp focus. Et voilà, tilt has been applied.

Swings on any view camera I've worked with are axis swings, front and back, so steps 1 and 2a are all that are needed to apply swings, just 90° transposed.

The real challenge when using swings and tilts is choosing where you want the plane of sharp focus to lie in the scene to optimize the depth of field you desire. Once the position of the plane of sharp focus has been decided upon, then choosing a couple of focus points and a couple of steps tilting are all you need.

Not to be a wet blanket and pour water on the more mathematical approach, but I don't think I'd ever do any such calculations in the field.

Best,

Doremus

[Maris Rusis]

This one is simpler than Easy Bake but may take longer:

Focus on the far,
And tilt toward the near,
Then fiddle with the camera,
Until everything is clear.

[sharktooth]

Chef Boyardee! :)

[Paul Ron]

very good. thanks for sharing. when presented in its simplest form, it makes sense.

[sharktooth]

very good. thanks for sharing. when presented in its simplest form, it makes sense.

Thanks, man. Admittedly, this approach has limited practical application, but it's still interesting to discover that you can actually "calculate" the tilt angle, without physically tilting anything.

[Sandokan]

Thanks, I have just done this calculation for two theoretical objects, one at top of ground glass 60cm away and other at bottom of ground glass 600cm away with a 15cm lens.
Focal Difference = 14.62cm (Classical formula gives V = 20 and V = 15.38 for these U values and F = 15)
GGVD = 8cm
61 degrees which is slightly more tilt than available

Try again for first object at 300cm and second at 600cm (classical formula gives V = 15.78 and V = 15.38)
FD = 0.4
GGVD = 8
21.8 degrees which is possible.

Would this still work for a telephoto lens where the FD will be less than for a simple lens?

[sharktooth]

Thanks, I have just done this calculation for two theoretical objects, one at top of ground glass 60cm away and other at bottom of ground glass 600cm away with a 15cm lens.
Focal Difference = 14.62cm (Classical formula gives V = 20 and V = 15.38 for these U values and F = 15)
GGVD = 8cm
61 degrees which is slightly more tilt than available

Try again for first object at 300cm and second at 600cm (classical formula gives V = 15.78 and V = 15.38)
FD = 0.4
GGVD = 8
21.8 degrees which is possible.

Would this still work for a telephoto lens where the FD will be less than for a simple lens?

I don't get some of your calculations. In the first example you say V1=20 and V2 =15.38. To me this would make the difference in focal positions 20-15.38=4.62. I don't know how you got the focal difference to be 14.62
.
if you use 4.62 as your FD and 8 as your GGVD, then the tilt angle will be 30 degrees.

In the second example, arctan(.4/8) gives 2.86 degrees (not 21.8 degrees)

It's an interesting exercise to look at the lens calculations in this way, but that wasn't my original intent. I was considering just measuring the actual distance between the two positions along the monorail.

If you want to use the lens calculation for a telephoto lens, then the nodal point of the lens lies somewhere out in space, and not within the lens. U and V will be with respect to this nodal point, so you need to be careful how those are measured for the calculation. If you just measure the actual distance between the two focused positions on the monorail, it doesn't matter what type of lens you use.

[Alan Klein]

.... a little background.

This came out of a discussion about the Sinar f2 over at Photrio. The poster was asking about one of the scaled knobs on the left side of the camera at the back. He was asking what it was for.
I didn't know either, so I looked it up. It turns out it's a tilt angle scale for focus adjustment, but I had no idea how this could work on a Sinar f2. The Sinar f2 has basic base tilts, and not the fancy in-frame asymmetrical tilt of the P series. It didn't seem to me that it would be possible to determine tilt angle on an f2.

I found a description for use of the tilt angle knob for the f2 (also f1, but not f), also on Photrio. When I read through the description it became immediately clear how it worked, and that the basic principle could also be useful for other cameras. With the Sinar f2, there are horizontal marked lines on the ground glass 35mm above and below the center line. There are also vertical marked lines 35mm to the left and right of the vertical center line. On the P series, these lines represent the asymmetrical tilt or swing axis (depending on orientation). These same lines can be used on the f series using completely different methodology to determine tilt or swing angle.

The Sinar lads were very smart, so they deserve all the credit for this. By focusing the back at two different points on the upper and lower marked lines, they could create a right angled triangle with the focus displacement as one leg, and the vertical ground glass displacement as the other leg. The angle of the resulting hypotenuse is the required back tilt angle. It's just simple high school trigonometry.
Since the vertical displacement on the ground glass is already fixed at 70mm, the only unknown is the focus displacement. Since the focus displacement is proportional to the rotation of the focusing knob, they only needed to put angle scale markings on a secondary knob that rotates with the focus knob. There is no need for a separate calculation.

The big downside of the Sinar system is that your two focus points have to reside on the marked lines. That's probably not going to be practical for many shots, since there may not be convenient points to focus on along those marked lines.

Nonetheless, it is indeed ingenious for Sinar to come up with this system, since it was an easy add to the f series, and would make use of the marked lines already on the ground glass for the Sinar P.

The method I'm using here is just an adaptation of this Sinar approach, but can be used with any camera with any two points on the ground glass. You're not limited to points along a marked line, but you will need a calculator to compute the tilt angle.

Couldn't you just rise or fall the standard until the line overlaps the distant object. Then focus the bellows. Then return the standard to its original position that you framed the picture. Make sure it stays parallel to the film plane.

[sharktooth]

Couldn't you just rise or fall the standard until the line overlaps the distant object. Then focus the bellows. Then return the standard to its original position that you framed the picture. Make sure it stays parallel to the film plane.

That works on the P series with asymmetrical rear tilt, but it doesn't work with the f1 and f2 that have standard base tilts. Sinar figured out a way to utilize the marked lines on the ground glass for the P series, to make them useful for the f series, but using entirely different methodology. That's what I'm trying to point out here. The same basic principle that Sinar uses for the f series can be modified to be used on other view cameras with any tilting design. It's just a novel approach that others my find interesting, but it isn't better than other methods, just different.

You seem to be misunderstanding the purpose of the asymmetrical rear tilt. It was designed to be a convenience in some shooting situations, primarily in commercial tabletop work, where time is money. If you read through the Sinar instructions for the asymmetrical rear tilt, it says to transfer the tilt angle at the back to the front standard, so that you don't disturb the image perspective. It's a bad habit to be using the rear asymmetrical tilt to adjust the focusing plane for every shot. Yes, it can be used this way in some situations without causing problems, but using this for every shot and not understanding it's limitations is poor practise.

There's a pretty good explanation of view camera use and setup here on this site by QT Luong. https://www.largeformatphotography.info/how-to-operate.html I'd suggest reviewing that, especially regarding the subsections on perspective and focusing.

[Sandokan]

sorry - 14.62 should have been 4.62 and 30 degrees
No idea how I got 21.8 ... unless I did arctan of 0.4. Doh!
Anyway, I did it to try to understand how this Sinar calculation works, which I do now - even if I wont actually use it.

[Alan Klein]

That works on the P series with asymmetrical rear tilt, but it doesn't work with the f1 and f2 that have standard base tilts. Sinar figured out a way to utilize the marked lines on the ground glass for the P series, to make them useful for the f series, but using entirely different methodology. That's what I'm trying to point out here. The same basic principle that Sinar uses for the f series can be modified to be used on other view cameras with any tilting design. It's just a novel approach that others my find interesting, but it isn't better than other methods, just different.

You seem to be misunderstanding the purpose of the asymmetrical rear tilt. It was designed to be a convenience in some shooting situations, primarily in commercial tabletop work, where time is money. If you read through the Sinar instructions for the asymmetrical rear tilt, it says to transfer the tilt angle at the back to the front standard, so that you don't disturb the image perspective. It's a bad habit to be using the rear asymmetrical tilt to adjust the focusing plane for every shot. Yes, it can be used this way in some situations without causing problems, but using this for every shot and not understanding it's limitations is poor practise.

There's a pretty good explanation of view camera use and setup here on this site by QT Luong. https://www.largeformatphotography.info/how-to-operate.html I'd suggest reviewing that, especially regarding the subsections on perspective and focusing.

I don't really shoot architecture only landscapes. So I haven't noticed the distortion., But your point is well taken. It probably would be easier for me to just use multiple iterations of the front standard than have to also add rise and fall procedures when using rear asymmetrical method. It is handy though when the axis line on the GG lines up with the far object and I only have to tilt the rear back a little.

[sharktooth]

I don't really shoot architecture only landscapes. So I haven't noticed the distortion., But your point is well taken. It probably would be easier for me to just use multiple iterations of the front standard than have to also add rise and fall procedures when using rear asymmetrical method. It is handy though when the axis line on the GG lines up with the far object and I only have to tilt the rear back a little.

With landscape work, where your subject is relatively far from the camera, and tilts/swings will only be a few degrees, then using the rear asymmetrical tilt for focusing is a fast and convenient method. I'd do that too. It's not a matter of right or wrong, it's simply a matter of understanding all the implications, and using a method that makes sense for your own equipment and working habits.

I should add that it's not just architectural work that is a concern. When your subject gets closer to the camera, the focus displacement between your near and far subjects get larger, and this means the tilt or swing angles get larger too. If you have people in your image, then they can end up with swollen, or shrunken heads when using large back tilts/swings. The same applies to subjects that have well known shapes and sizes, such as balls, flowers, cans, boxes, etc. They can end up looking strangely distorted with larger back tilts and swings.

[sharktooth]

After looking at Sandokan's results using lens calculations, I thought it would be interesting to plot some curves to see how lens tilt changes with subject distance from the lens. I know that you need more tilt as the nearest object gets closer, but I didn't know how dramatic the tilt would need to be.

For this example I considered a typical landscape situation where you have some far objects near infinity (trees, mountains, etc.), and closer objects near ground level that you'd also like in focus. I used a 150mm lens, since that's a normal lens for 4x5. Sandokan used an 80mm height difference on the ground glass, meaning the far object and the close object are 80mm apart (vertically or horizontally), when measured on the ground glass. This seems reasonable for a 4x5 imaged viewed horizontally. An 80mm difference would put one point near the top of the frame, and the other near the bottom of the frame. I also looked at a 40mm height difference, which puts the near and far points closer together on the ground glass.

Here are the resulting curves:

237420

For those that are metrically challenged, here is the same graph, but with the distance scale marked in feet.

237421

When your near and far objects are further apart on the ground glass, the tilt needed is less than when the two objects are close to each other. The tilt angle to maintain both objects in focus remains fairly small (less than 10 degrees) when the near object is greater than about 3.5 meters (11.5 feet) from your lens. Once your near object gets closer than that, the tilt required starts to increase at a much faster rate. When the tilt angle gets greater than about 10 degrees, you'll need to be careful about changes in perspective (if tilting on the back). For lens tilts, you need to be aware of the image circle, since with large tilts your image may not cover the entire film area, causing vignetting.

[Alan Klein]

Do tilts effect exposure falloff when using a center filter? Are there these differences if you're doing the tilt from the front vs the rear standard?

Ditto if no center filter is used?

[sharktooth]

I don't know how center filters affect swings or tilts. Maybe someone else can chime in on this.

Without a center filter, you are using the outer areas of the image circle of the lens when you swing or tilt the lens. If your lens has falloff in this outer image circle, then it could become noticeable. It all depends on the lens. With back tilts or swings, you're actually using a smaller area of the image circle, so it shouldn't make any significant difference.

[Doremus Scudder]

Alan,

Your center filter just balances the illumination over the entire image circle, thus preventing the falloff. The tradeoff being having to give extra exposure, of course. It does not affect the size of the IC, nor distort anything. Tilts and swings (and rise and fall) work exactly the same with and without a center filter.

But, as sharktooth points out, if you don't use a center filter and are using a lens with lots of falloff and have a lot of the outside edges of the image circle in one part of the image, the falloff there will be noticeable. Using back tilt and swing does not move the image circle around, so the image stays in the center of the image circle. When you use front tilt or swing, you displace the image circle on the ground glass/film, so the center of the IC is displaced from the center of the image and one side/corner of the image will be closer to the edge of the IC than the rest of it. If falloff is an issue, use the center filter or plan on compensating with burning or whatever during printing.

If you use the center filter when tilting/swinging the front, there should be little apparent falloff.

Doremus