Rise/shift the same as raising the camera or relying in lens geometry distortion?

[AgX]

In case anyone is really in doubt. Simple shots from a wide iPhone camera.

The first one is equivalent to what you do with shift (I imagine) expect the bottom of the projection would be cut off by the film plane.
Shot straight on with a lot of "distortion" or elongated perspective at the top.
View attachment 306887


This one has the top of the tower in the middle and is how a human would perceive the structure if free to look around. But of course the structure appears to be tilting away from you, something we are familiar with through vision, but that is again corrected by the fact that we are scanning with our eyes and head and not analysing stills.


View attachment 306888

The last one has the lens looking down to get sort of the opposite effect of the previous one, of the tower leaning towards you.

View attachment 306889

My original question is: Does shift as it is used on LF and other shift lenses, use this effect (for lack of better term) to correct converging lines?
Namely mostly the effect in the first photo where the "film plane" is parallel to the vertical structure? But the same basic principal goes for the all of them.
All 135 shift lenses are some kind of wide. That would support what I'm thinking?
So yes, it is in essence perspective I'm talking about. Namely near vanishing point perspective. Or wide perspective if you will.

Helge,

The effect you show in the first picture

-) is called over here perspective distorsion
-) it is due to the subject plane and the film or sensor plane NOT being in parallel (as would more or less be at much larger distance)

To avoid this

-) go far enough away with camera
or
-) arrange your camera so that the film plane is exactly in parallel with the subject (the facade in this case)
-) move the front standard in parallel upwards so that you gain the same subject area as when directing your camera obliquely upwards


With all respect, this is the very most basis of camera movement and does not necessitate such a discussion.
Unless I still did not got the point you got difficulties with.

 

[Helge]

With this type of shot (whether or not the camera is pointed straight ahead or tilted upward), if you tilt the rear of the camera -- forward or backward -- you can increase (or decrease) the perceived amount of tilt in the tower. As a result, you can set it to where it appears untilted -- if that is what you want. As Stroebel labels it, you are controlling the shape of the subject. Others might say you are controlling the perspective or the distortion.

Shifting a lens is completely different, and will not change any of this. Shifting/Rise&Fall only moves the lens around the image circle. It has no affect on the shape/perspective/distortion of the subject.

If I’m right, moving a tele lens (with large projection circle) around will have very much the same effect as just moving the camera the same distance.
The magic happens when you use a wide.

 

[Helge]

Helge,

The effect you show in the first picture

-) is called over here perspective distorsion
-) it is due to the subject plane and the film or sensor plane NOT being in parallel (as would more or less be at much larger distance

To avoid this

-) go far enough away with camera
or
-) arrange your camera so that the film plane is exactly in parallel
-) move the front standard in parallel upwards so that you gain the same subject area as when directung your camera olbliquely upwards


With all respect,, this is the very most basis of camera movement and does necessitate such a discussion.
Unless I still did not got the point you got difficulties with.

But the subject, lens and film plane is parallel in the first shot.

I know it’s a basic movement. But so far I have seen very little explaining or analogies of exactly how this works. And a lot explanation of how to do it and it’s effects. All of which a “basic”.

 

[Helge]

90mm T/S for 135 format are not wide. Shift in LF is not used only with wide lenses and yet it "just works".

There is a 90mm T/S for 135?
Is there any examples of how this looks with a tele or normal?

Edit: Oh, you are talking macros of course!
In that case tilt can of course be useful, especially with teles, and shift to a lesser degree to fine tune the composition from a tripod.
But do you have examples of it’s use at “normal” scales?

 

[Helge]

With this type of shot (whether or not the camera is pointed straight ahead or tilted upward), if you tilt the rear of the camera -- forward or backward -- you can increase (or decrease) the perceived amount of tilt in the tower. As a result, you can set it to where it appears untilted -- if that is what you want. As Stroebel labels it, you are controlling the shape of the subject. Others might say you are controlling the perspective or the distortion.

Shifting a lens is completely different, and will not change any of this. Shifting/Rise&Fall only moves the lens around the image circle. It has no affect on the shape/perspective/distortion of the subject.

I know the fundamental movement doesn’t have the effect. But I can’t see how moving a tele with very orthogonal projection would result in something very much different from just moving the camera the same distance (edit, correction: The distance that would achieve the same projection on the screen/film). Not “the same distance”).

 

[xkaes]

If I’m right, moving a tele lens (with large projection circle) around will have very much the same effect as just moving the camera the same distance.
The magic happens when you use a wide.

If -- let me make that a big IF -- you move the lens (left/right/up/down -- not forward or back) without moving the camera back, you are exposing a different section of the image circle without changing the perspective -- the relation of objects in the scene.

If you moved the back of the camera and leave the lens in the same place, the scene created by the lens is exactly the same and the film is exposed to the exact same part of the image circle.

You really need to read Stroebel's book. Shifts & Rise/Fall accomplish the same thing -- they move the film relative to the image circle created by the lens, just in opposite directions.

 

[Dwight Anderson]

You're trying to combine the effects of using different lenses with the effect of camera movements. But they are independent of each other. The function of a rising front is to expose a different part of the image circle, most frequently to capture a tall object while keeping the film plane parallel to the face of the object. This works with any lens that has a large enough image circle to allow movements. A wide angle of view lens will have perspective distortions, but that will always be the case, think of fisheye lenses that don't cover the film plane. A normal (or tele) lens that does not have those perspective distortions still benefits from a rise movement because you can keep the film plane parallel while capturing the top of the object.

Let's say you are taking a picture of something 10 meters tall and cannot capture the top 3 meters without movements or tilting the camera back. If the image of the object is only 10 centimeters tall on the film plane, you only need to raise the front standard 3 centimeters to capture the top. Lenses of different field of views will project a larger or smaller image, along with differing perspective distortions, but the function of moving that image around on the film plane remains the same.

I have dozens of old rollfilm and plate cameras that have rise and shift controls with "normal" lenses, I don't think they would include the feature if it didn't work.

It's hard to learn how to please a woman by reading a book, it works best to experiment with the real thing.

 

[brbo]

If I’m right, moving a tele lens (with large projection circle) around will have very much the same effect as just moving the camera the same distance.
The magic happens when you use a wide.

Right in what?

 

[AgX]

A wide angle of view lens will have perspective distortions, but that will always be the case, think of fisheye lenses that don't cover the film plane.

-) a classic wide-angle lens does not show the effect a fish-eye lens does

-) the effect a full-frame fishe-eye has is the same as a circular-image one has, just the center part of it now filling the full frame

-) the most typical distortion seen at wide-angle lenses is that due to strong scale differences at subject reproduction, as I explained at my earlier posts. It is not an inherent characteristic of these lenses but instead due to the "mis-use" so to say by the photographer by going too near his subject.



Helge,
I still did not get your point. But I shall contemplate on it. But not today.

 

[Helge]

Right in what?

That it’s wide FL effects that create the perspective correction.

 

[Doremus Scudder]

Which gives more "rise"?

Alan,

The "point-and-tilt/swing" method of getting extra rise or shift is a time-tested and effective method. If you use "point-and-tilt-parallel" together with front rise, you'll get all the rise your particular camera is capable of. Displace that all by 90° and you are "pointing-and-swinging-parallel." That, together with maximum shift, will get you all the shift your camera has to offer.

It's not a question of "more or less," rather how to get as much as you need/can.

Doremus

 

[xkaes]

If I’m right, moving a tele lens (with large projection circle) around will have very much the same effect as just moving the camera the same distance.
The magic happens when you use a wide.

All you are saying is that wide lenses have a different angle of view than a long lens. A wide angle sees more, that's all. So a small change in location with a wide lens will make a bigger difference than the same change with a long lens. Just as moving slightly closer to a subject with a wide lens will make a BIG difference, moving laterally will make a bigger difference with a wide lens than a tele lens.

WOW!!!

So you are correct. Wide lens are different than long lenses.

 

[Dwight Anderson]

-) a classic wide-angle lens does not show the effect a fish-eye lens does

-) the effect a full-frame fishe-eye has is the same as a circular-image one has, just the center part of it now filling the full frame

-) the most typical distortion seen at wide-angle lenses is that due to strong scale differences at subject reproduction, as I explained at my earlier posts. It is not an inherent characteristic of these lenses but instead due to the "mis-use" so to say by the photographer by going too near his subject.

Sorry, just trying to use a worst case example of a wide angle lens. You are correct that the distortion of a wide angle lens is primarily due to scale, along with some barrel distortion, depending on the lens design.

Helge's argument seems to be that a rise movement is only useful with a wide angle lens, which is incorrect.

 

[brbo]

That it’s wide FL effects that create the perspective correction.

Well, you are not right on that.

If wide FL by itself would create perspective correction then why would you still need to have your plane of film perfectly parallel to the subject? And why is it still possible to maintain parallel lines when shifting non-wide lenses?

BTW, rectilinear perspective correction is "built into" every, well, rectilinear lens. You probably don't believe that wide FL by itself will also "create perspective correction" in fish eye lenses, do you?

 

[grat]

I know the fundamental movement doesn’t have the effect. But I can’t see how moving a tele with very orthogonal projection would result in something very much different from just moving the camera the same distance (edit, correction: The distance that would achieve the same projection on the screen/film). Not “the same distance”).

If the telephoto's field of view at the plane of focus is as small as the field of view projected onto the film plane, then you're correct. But now you're operating at 1:1 magnification, and that's not really what a telephoto does.

If I'm focused on a 200cm high target, and projecting it onto a 10cm piece of film, then a 1cm movement of the front standard should result in a 20cm movement of the area of focus, which will have a corresponding effect on the image circle projected onto the film.

If your target is 20 meters high, and you're still projecting onto the same 10cm piece of film, then the effect is magnified by 10.

 

[Doremus Scudder]

Helge,

A couple of things:

First, it confuses the issue by using the terms "tele" (for telephoto, I presume) to mean a long focal-length lens for a given format and "wide-angle" to mean a short focal-length lens for a given format. "Telephoto" is a lens design that allows longer focal lengths to focus at infinity with the lens physically less than its focal length from the film plane. On the other side, many short focal-length lenses for 35mm and medium formats are "retrofocus" lenses, a design that allows them to physically focus infinity on the film at a distance greater than their focal length. "Normal" lens designs focus at infinity when the center of the lens is roughly the lens' focal length from the film. All this to try to get you to use "short," "normal" (for the format), and "long" instead, just for clarity's sake.

Also, don't confuse the "distortion" introduced by short focal-length lenses with perspective control accomplished by positioning the camera back/film plane. Objects at the edges of the field of coverage with short focal-length lenses appear stretched out, and thus "distorted" due to the steep angle of the projection. Similarly, short focal lengths tend to render near objects larger than we expect in comparison to more distant objects due to the wide angle of view (this, when compared to the "normal" angle of view we get with our eyes makes images made with short focal lengths seem unreal). This has nothing to do with perspective changes that happen when the film plane is repositioned relative to the subject.

In the three images you post, you make one with the camera back/film plane/sensor parallel to the tower, one with the camera pointing up, causing the verticals to converge toward the top of the image and one with the camera pointing down, causing the verticals to converge toward the bottom of the image. This is exactly what happens when the position of the film plane/ground glass/etc. is changed relative to the subject. If you don't want convergence, the film plane must be parallel to the parallel lines in the subject.

The converging verticals toward the top of the image in your second image is what many try to avoid by using front rise on a view camera or special shift lens on smaller cameras. You may find it more "natural," but many of us don't. As you point out, the eye/brain system straightens the image out in our imagination; even when we look up at something, we somehow recognize the parallel lines. Rendering parallel vertical lines parallel on the film is a convention of architectural photography done with view cameras that has been around for years. Until recently, converging verticals in professional architectural photography were purposefully avoided.

As for the vanishing points: With the lens axis centered on the film plane, receding parallel lines will always come to a vanishing point in the center of the image. Converging horizontal and vertical lines will have their vanishing points on vertical and horizontal lines that intersect the center of the image (either within or outside of the image borders). By using rise/fall or shift, we change where the lens axis intersects the film. That point is no longer at the center of the image but displaced up, down or to one side. The positions of the vanishing points move together with the displacement.

Moving the entire camera while keeping the film parallel to parallel lines in the subject is not the same thing as using lens rise from a lower viewpoint to keep vertical lines parallel. In the first case, you are moving the viewpoint, in the latter, not. Let's say you have a six-story building. If you move the camera up to be at the height of the third floor, your viewpoint, i.e., the point in the scene that is on the lens axis of view, will be on the third floor and in the center of the image. That will be the "straight-on" point in the image and the windows and doorways at the edges of the image will be all viewed from an angle.

If you keep the camera position low, say in the middle of the ground floor, keeping the film plane parallel to vertical lines in the subject, and then use rise to get the top of the building in the image (thus keeping parallel vertical lines from converging), the point in the image that is on the lens' axis of view will be on the ground floor, which ends up being at the bottom of the image projected on the film. Everything above that point will be viewed from an angle. This effect is very different from moving the entire camera up.

You say that focal length is "very closely tied to angle of view..." Well, for any given format, the lens' focal length determines the angle of view. The angle of view for a particular focal length and film format never changes. It doesn't matter if the lens has a large or small image circle, etc. The image size (i.e., magnification) is a function of the focal length.

Note also that one can use front rise on a view camera with any focal-length lens one chooses, long, short or "normal." I often used lots of rise with a 210mm lens on 4x5 for architectural work. This is a slightly longer than normal focal length for 4x5, so the stretching of off-axis objects that happens with very short focal lengths doesn't happen at all (that's because the lens' angle of view is similar to that of our eye). In your photos, there's lots of stretching off-axis because the lens you used was a very short focal length for the format and the angle of view is much wider than that of your eye. All that stretching "distortion" is due to the wider angle of view.

Finally, to answer your question about how correcting converging verticals is done with a view camera. It's really fairly elementary. Step one, if you want the parallel lines in the subject to be parallel on the film, the film plane needs to be parallel to them. In practice in architectural photography, this means the camera back/film plane needs to be level and plumb (because we assume that the building we are photographing was constructed level and plumb). Then, the image is framed by moving the lens about with rise and/or shift. This moves the lens axis relative to the image and moves the point of view around in the image, but it keeps the parallel lines parallel. That's really all there is to it. Of course, we need a lens with a large enough image circle and a camera with enough movement to do this. Sometimes it's not possible to get what we want.

All for now

Doremus

 

[Helge]

Sorry, just trying to use a worst case example of a wide angle lens. You are correct that the distortion of a wide angle lens is primarily due to scale, along with some barrel distortion, depending on the lens design.

Helge's argument seems to be that a rise movement is only useful with a wide angle lens, which is incorrect.

Great, now we are getting somewhere.
Do you have some examples?
Shifting a tele or normal would seem to only move you to a slightly different part of the orthogonal projection.

If for example your camera is pointed at the bottom part of a building and you shift it what does that accomplish?

 

[Doremus Scudder]

... Shifting a tele or normal would seem to only move you to a slightly different part of the orthogonal projection.

If for example your camera is pointed at the bottom part of a building and you shift it what does that accomplish?

Lots of time I had to set up my camera in a place off-center from where I really wanted to be. And, I wanted the horizontal lines on the building façade to be parallel. So I set up the camera with the back parallel to the façade and then used shift to frame the image, i.e., to get what I wanted in the center to be in the center. Yes, the "optical center"/viewpoint is to one side of the image. That's what happens with shift.

Displace all that 90° and replace "shift" with "rise" and you have the recipe for keeping verticals from converging.

And, yes, with a longer focal length, shifting or raising your lens x-distance doesn't change the image as much as with a shorter focal length. However, longer lenses typically have larger image circles, so one can use a lot more shift or rise, if your camera has the capability, and really make quite a different framing compared to "zero" position.

Doremus

 

[grat]

Well, the amount of effective shift is going to be roughly the same as the ratio between the image circle on the film plane, and the image circle at the plane of sharp focus.

The reason shift "corrects" perspective distortion is that it doesn't. The perspective distortion is created by tilting the camera so that the lens and the film plane are no long parallel to the building. This is usually because you can't get a tall building fully into the frame standing on the ground without tilting the camera.

Shifting the lens allows you to get the rest of the building into the field of view, without tilting the camera, therefore no distortion is created.

 

[Doremus Scudder]

Well, the amount of effective shift is going to be roughly the same as the ratio between the image circle on the film plane, and the image circle at the plane of sharp focus.

The reason shift "corrects" perspective distortion is that it doesn't. The perspective distortion is created by tilting the camera so that the lens and the film plane are no long parallel to the building. This is usually because you can't get a tall building fully into the frame standing on the ground without tilting the camera.

Shifting the lens allows you to get the rest of the building into the field of view, without tilting the camera, therefore no distortion is created.

Why can't I be this succinct?

 

[flavio81]

There is a 90mm T/S for 135?

Yessssss

 

[flavio81]

The reason shift "corrects" perspective distortion is that it doesn't. The perspective distortion is created by tilting the camera so that the lens and the film plane are no long parallel to the building. This is usually because you can't get a tall building fully into the frame standing on the ground without tilting the camera.

Shifting the lens allows you to get the rest of the building into the field of view, without tilting the camera, therefore no distortion is created.

This is a great explanation.

And also explains why this has nothing to do with the lens being wide-angle or not.

 

[xkaes]

Shifting the lens allows you to get the rest of the building into the field of view, without tilting the camera, therefore no distortion is created.

Don't you mean "raising" the lens?

 

[Doremus Scudder]

Don't you mean "raising" the lens?

Another confusion: With 35mm cameras, the specialized lenses are marketed as "shift/tilt" lenses, even though they shift both sideways and up/down. I like rise/fall/shift personally...

 

[Dwight Anderson]

Great, now we are getting somewhere.
Do you have some examples?
Shifting a tele or normal would seem to only move you to a slightly different part of the orthogonal projection.

If for example your camera is pointed at the bottom part of a building and you shift it what does that accomplish?

if you are raising the lens it allows you to reduce the amount of foreground in the frame and see more of the upper part of the image circle, while keeping the film plane parallel with the subject.

Watch this video, he uses two different focal lengths with rise, for the same effect of keeping parallel lines straight and reducing the foreground.