Any Difference Stitching with Longer Lens vs. One Shot Wide Angle?

[mrkjhn]

Shooting interiors with wide angles, I'm never happy with the amount of distortion in perspective (not talking about curving lines but more the distorted perspective / look of wide angles, the extreme foregrounds and shrunken distant objects, the relationship between near and far).   I was wondering if stitching together multiple frames from a vertical 50mm would solve that, giving the look of a 50mm, but covering a wider angle of view.  I did some preliminary test, rather unscientific and quick in execution, and really didn't notice much if any difference which was puzzling. Is the perspective of an image the same regardless of how it's created, multi shot with a longer lens vs. one shot wide angle?

[Slobodan Blagojevic]

Perspective depends on your standpoint, not lens focal length. So, to achieve a different, less distorted perspective, you'd need to step back, which would in turn require a moderate telephoto to cover the same angle. Trouble is, with interiors, you typically can't step back further than the room's corner, unless you remove walls. You could do it in huge buildings with a lot of open space however.

[BernardLanguillier]

The perspective only depends on the relative position btw camera and subject. Stitching won't make any difference.

Now, you will be impacted less by lens aberations for 3 reasons:
1. The good pano software correct for distorsion,
2. You use mostly the central part of your image circle,
3. You will be downsampling from a higher resolution. You can also look at this as reducing the enlargement ratio since stitching creates a larger virtual sensor.

From a look standpoint, the usage of a longer focal length will reduce DoF at equal aperture.

Cheers,
Bernard

[mrkjhn]

I'm not talking here about lens distortion or depth of field, more about the visual effects (compression vs. expansion (?)) say between a tele lens vs. a wide angle, and if you took that same angle of view of a 21 or 24mm and created it by stitching together a multi panel pano shooting with a 50mm or longer taken from the same point.  Something like a Hockney but with precision.  I would think the image's visual perspective would reflect that of the 50 or tele lens in the composite, rather than that of the 21 in the single shot.

[Slobodan Blagojevic]

....  I would think the image's visual perspective would reflect that of the 50 or tele lens in the composite, rather than that of the 21 in the single shot.

Lenses do not have their inherent perspective. Standpoints do.

[pegelli]

Is what you are talking about that a well corrected rectilinear wide angle lens (seems to) distort the corners by "pulling them out" (actually it's not distortion, but the rectilinear correct projection of the plane of focus on the sensor through a short focal length lens).

Depending on the projection you use in your stitching algorithm this can be (partly) avoided by for instance using a cylindrical vs. rectilinear projection.
I'm not a specialist, but Cambridge in Colour has some good tutorials on the effect of using different projections on the resulting image.

The perspective (relationship of closer vs. further subjects) won't change by using different projections since that's dependent on the standpoint where the picture is taken.

[BernardLanguillier]

I'm not talking here about lens distortion or depth of field, more about the visual effects (compression vs. expansion (?)) say between a tele lens vs. a wide angle, and if you took that same angle of view of a 21 or 24mm and created it by stitching together a multi panel pano shooting with a 50mm or longer taken from the same point.  Something like a Hockney but with precision.  I would think the image's visual perspective would reflect that of the 50 or tele lens in the composite, rather than that of the 21 in the single shot.

The perspective only depends on the relative position btw camera and subject. Stitching won't make any difference.

Cheers,
Bernard

[LesPalenik]

If it helps:
Quite a few years ago, when I used rotational Seitz Roundshot Super35 (really the same principle as stitching)
 
- to do a full 360 degree rotation, using 19 to 28mm lens, the whole scene fit onto a relatively short film strip (as I recollect, about 12-25cm)
- doing the same 360-degree rotation with a 400mm lens, I used the entire 5ft film roll equivavalent to 36-40 exposures (I was cutting bulk film and loading my own rolls).
this particular photo was printed on a 50ft long, 8" wide paper. Going to 16" paper width, it would have required 100ft long paper.

[Bart_van_der_Wolf]

The perspective only depends on the relative position btw camera and subject. Stitching won't make any difference.

In a nutshell (taking camera position as the position of the lens' entrance pupil), that's it. A slightly more verbose answer was given here.

Cheers,
Bart

[AlfSollund]

Interesting question,

In principle taking more shots with a longer focal lengt will give mutiple photoes that each will give a different perspective than the original wideangle shot since you have to move camera for each shot. So final result should be different?

I have started using LR6 stitching. My humble observation is that the final result is a bit different than wideangle croppped shot. See example where roof seems bent: at_door_Lisboa by Alf Sollund, on Flickr.

It also seems that LR chooes Cylindrical projection when using auto?

Please feel free to correct me, since Im quite new to stitching.

[Bart_van_der_Wolf]

Interesting question,

In principle taking more shots with a longer focal lengt will give mutiple photoes that each will give a different perspective than the original wideangle shot since you have to move camera for each shot. So final result should be different?

Normally, yes, but with dedicated stitching software that has a better understanding of projection geometry, a flat plane can remain a flat plane even when it is shot in parts from different positions.

It also seems that LR chooses Cylindrical projection when using auto?

I assume LR chooses a cylindrical projection when the FOV exceeds some number of degrees, e.g. 100 degrees? Rectilinear projection (like most lenses) will produce extreme stretching of corners due to the shallow angle of the rays when projected on a flat plane. The practical limit is something like 110 or 120 degrees. It's much easier to project a wide angle of view on the inside of a cylinder, but it will only maintain straight vertical lines as straight and vertical when the camera is leveled, and all straight (more) horizontal lines will get more curved the further they are removed from the horizon.

Cheers,
Bart

[Petrus]

Interesting question,

In principle taking more shots with a longer focal lengt will give mutiple photoes that each will give a different perspective than the original wideangle shot since you have to move camera for each shot. So final result should be different?

I have started using LR6 stitching. My humble observation is that the final result is a bit different than wideangle croppped shot. See example where roof seems bent: at_door_Lisboa by Alf Sollund, on Flickr.

It also seems that LR chooes Cylindrical projection when using auto?

Series of photos meant for stitching should be taken so that the position of the lens entrance pupil does not change. This way the perspective and the exact point of each photograph stays the same. This is important especially if there are any objects near the camera. With scenes which have no nearby objects id does not matter so much.

This might be helpful: http://www.reallyrightstuff.com/Be-a-Gear-Expert/Panoramas-Made-Simple_2/Intro-to-Panoramic-Photography.html

When the stitched photo gets wide enough it is impossible to use rectilinear projection anymore (like one WA shot is). Stitching a photo which approaches 180 degree angle in any direction would approach infinity in size…

Cyliderical projection makes wider than 180 degrees possible, but seems to bend walls. BUT: if you bend the picture to the correct angle and view it from the middle point of the curve, the curvature disappears… That actually is the correct way to view cylindrical panoramas.

[Bart_van_der_Wolf]

Cyliderical projection makes wider than 180 degrees possible, but seems to bend walls. BUT: if you bend the picture to the correct angle and view it from the middle point of the curve, the curvature disappears… That actually is the correct way to view cylindrical panoramas.

Correct, and it's not something new either. Here is a link to the "Panorama Mesdag" painting from the year 1881, located in The Hague / Netherlands. It measures approx. 14 metres (46 feet) high and has a circumference of some 120 metres (394 feet), and is a UNESCO monument. The beaches were used for other things than sunbathing then. Other viewing methods use a modified projection, and require viewing with a curved/cylindrical mirror in the center of the image.

Very wide landscape scenes, with few straight line features, lend themselves best for this projection, and it limits the amount of cropping so all resolution from the capture can be preserved.

Cheers,
Bart

[Lightsmith]

Focal length has a tremendous impact on perspective. The shorter the focal length the larger a foreground object appears as compared to an object in the background. It is why a wide angle lens when used improperly to photograph a person will result in oversized hands or feet or nose in a picture. With a long telephoto lens there is not only the foreshortening effect but also a magnification of objects in the background.

This section on wikipedia illustrates this very well.

https://en.wikipedia.org/wiki/Shot_%28filmmaking%29

Look at the images of the water bottles taken with lenses of varying focal lengths and how the size of the water bottle in the background changes in size but not the bottle in the foreground.

This is a common technique in underwater photography where flash distance is limited. An ultra wide angle lens is used with a foreground object less than 2 meters from the camera (and within the range of the flash) is juxtaposed with a large fish or mammal or diver in the background. The size of the background object is reduced in size but with no way for the view to denote size versus distance it does not matter for the purposes of the picture.

[Slobodan Blagojevic]

Focal length has a tremendous impact on perspective...

Seriously!?

[BernardLanguillier]

Seriously!?

Yes, the laws of photography changed yesterday.

Some things are better posted under a pseudo, but still only the "remove post" icon can provide salvation beyond a certain point...

Cheers,
Bernard

[Bart_van_der_Wolf]

This section on wikipedia illustrates this very well.

https://en.wikipedia.org/wiki/Shot_%28filmmaking%29

Look at the images of the water bottles taken with lenses of varying focal lengths and how the size of the water bottle in the background changes in size but not the bottle in the foreground.

Hi,

It illustrates something else, namely:

How focal length affects perspective: 18mm (ultra wide-angle), 34mm (wide-angle), and 55mm (normal lens) at identical field size achieved by different camera-subject distances.

By different camera-subject distances means moving the entrance pupil of the lens (a different shooting position, to achieve the same FOV, but only in the plane of focus), and viewing the resulting image from the same distance. Had the viewing distance been proportionally changed with focal length, then at least the impression of stretching towards the corners would be eliminated. But changing the shooting distance is what caused most of what seems like relative foreshortening at longer focal lengths, and size differences.

So, it's not the focal length, but the position of the entrance pupil of the lens that determines perspective (the apparent (relative) size of subjects at different distances).

Cheers,
Bart

[smthopr]

Yes, there is a difference. If you stitch together 3 vertical 50mm images, you'll have the horizontal fov of a wider lens, but the vertical fov of the 50mm. It's a different look than shooting with a 24mm and cropping to the same aspect ratio.

[Slobodan Blagojevic]

Yes, there is a difference....

Care to demonstrate?

[BernardLanguillier]

Yes, there is a difference. If you stitch together 3 vertical 50mm images, you'll have the horizontal fov of a wider lens, but the vertical fov of the 50mm. It's a different look than shooting with a 24mm and cropping to the same aspect ratio.

You typically need 2 rows to cover with a 50mm the the fov of a 24mm.

The look is exactly the same once you cover enough fov.

Absolutely zero difference.

Cheers,
Bernard