Ultra Wide-Angle distortion\compression question

[xpatUSA]

When elevating you don't change your focus plaine(?).

It's focal plane, George.

I know the keystone in arches. Sometime nice decorated. But I can't see a correlation with photography

The keystone is wider at the top than at the bottom, as we all know. If, however, we take a shot of an ordinary brick (standing) with the lens axis and the brick center axis aligned, the front face will appear rectangular (perfect lens, no distortion). Next, if we tilt the brick toward the camera and shoot again, the image will be distorted per your magnification rule: the top wider than the bottom and the sides slanted - making it look like a keystone. Therein lies the correlation via similarity of appearance.

[george013]

It's focus plane, George.



The keystone is wider at the top than at the bottom, as we all know. If, however, we take a shot of an ordinary brick (standing) with the lens axis and the brick center axis aligned, the front face will appear rectangular (perfect lens, no distortion). Next, if we tilt the brick toward the camera and shoot again, the image will be distorted per your magnification rule: the top wider than the bottom and the sides slanted - making it look like a keystone. Therein lies the correlation via similarity of appearance.

I thought I checked plane. Wrong.
I meant the subject plane without the subject. The plane where the camera focuses on but the subject is out of it due to recomposing.

I understand the keystone.

Thanks.

By the way, I didn't faint.

George

[William W]

. . .
When elevating you don't change your focus plaine. ? {I meant the subject plane without the subject. The plane where the camera focuses on but the subject is out of it due to recomposing.}

In Image ‘D’, the camera was moved only vertically from the position it was when I made Image A.

Moving from Image A, to Image D, the camera was not tilted nor was it moved horizontally nor was it rotated (panned), and the camera’s focus was not adjusted: so, therefore the distance from the SENSOR PLANE (in the camera) to the PLANE OF SHARP FOCUS at the Subject – (what I think you refer to by the ‘Subject Plane’) remained the same for both Images A and Image D.

So assuming the Plane of Sharp Focus is straight in all directions, (which technically it probably isn’t, but we need to ignore that), what appears to be "in focus" in Image A will be exactly the same, in Image D.

So, to answer the question: when I elevated the camera I did NOT change the "Subject Plane".

***

Is there a reason for shooting photo's after elevation. It seems to me that one can do the final composition at once and focus on the subject out of the center. Or is this technique meant when you're not able to focus on the border?

I am not sure that I understand this question, but, I think it means why did I take the effort to shoot Image D, why didn’t I just ELEVATE the camera and also TILT the camera downward and make a better composition, as I did when making the last image in Post #39.

The reason is, that the set of four Images, A B C and D were made as a specific exercise to show that ELEVATING the camera VIEWPOINT changes the PERSPECTIVE. It was not an exercise showing COMPOSITION.

I trust that I understood the question correctly.

WW

[george013]

In Image ‘D’, the camera was moved only vertically from the position it was when I made Image A.

Moving from Image A, to Image D, the camera was not tilted nor was it moved horizontally nor was it rotated (panned), and the camera’s focus was not adjusted: so, therefore the distance from the SENSOR PLANE (in the camera) to the PLANE OF SHARP FOCUS at the Subject – (what I think you refer to by the ‘Subject Plane’) remained the same for both Images A and Image D.

So assuming the Plane of Sharp Focus is straight in all directions, (which technically it probably isn’t, but we need to ignore that), what appears to be "in focus" in Image A will be exactly the same, in Image D.

So, to answer the question: when I elevated the camera I did NOT change the "Subject Plane".

***



I am not sure that I understand this question, but, I think it means why did I take the effort to shoot Image D, why didn’t I just ELEVATE the camera and also TILT the camera downward and make a better composition, as I did when making the last image in Post #39.

The reason is, that the set of four Images, A B C and D were made as a specific exercise to show that ELEVATING the camera VIEWPOINT changes the PERSPECTIVE. It was not an exercise showing COMPOSITION.

I trust that I understood the question correctly.

WW

I know you just toke the pictures to show the differences and I, and for sure others too, thank you for that.
Somewhere in my grey head I think I've seen something of elevating the camera. But what I can remember of it, it was due to the impossibility of the old camera's to focus near the boarder. The subject needed to be in the middle, focussing and moving the camera taking care the subject stayed in the same plane. That's what I meant. Nowadays camera's, at least the DSLR's, have more focuspoints. Maybe that's the reason of that technique..

One more point about viewpoint. I tried to find out what it meant, a definition. A viewpoint is just what you see on the image and is determined by the position of the camera, the direction of the camera and the angel of view. It's just the image you're looking at. Since perspective is suggestion of a third dimension in a 2 dimensional plane, it's very likely that perspective is different in 2 different images/viewpoints. The forward going lines in image D, not being in image A, is giving me a feeling of depth.

As you can read out of my arguments, a different viewpoint is a different composition, but you can have different compositions in the same viewpoint.

This also declares the fault of people saying that cropping an image out of another image doesn't change the viewpoint or perspective. Cropping means changing the angel of view and thus the viewpoint. Perspective has been discussed before in this thread.

George

[William W]

Some cameras might have many Auto Focus Points.

Those are just points within the VIEWFINDER, and only ONE OF WHICH is used for Auto Focus to be locked.

Upon Locking Focus there is only ONE "PLANE OF SHARP FOCUS", no matter how many AF points are within the camera.

***

'Viewpoint' is the position where the camera sits.

CROPPING an image happens in Post Production,

Cropping an image does NOT change the VIEWPOINT.

WW

[george013]

Some cameras might have many Auto Focus Points.

Those are just points within the VIEWFINDER, and only ONE OF WHICH is used for Auto Focus to be locked.

Upon Locking Focus there is only ONE "PLANE OF SHARP FOCUS", no matter how many AF points are within the camera.

***

That's exactly what I wrote.

'Viewpoint' is the position where the camera sits.

CROPPING an image happens in Post Production,

Cropping an image does NOT change the VIEWPOINT.

WW

The definition of viewpoint as I found and use is the view from a certain point, in a certain direction and with a certain angle of view.. I don't think it's important if that view is in your viewfinder, screen, printed or just through the windows home. It's what you're seeing at that moment.
Cropping an image, if it happens in PP or in the camera or using another sensorsize, gives me a new image with another angel of view, and when the crop is decentral another direction, so another viewpoint, following that definition.
There's more than just the position of the camera. If it's only that, than it wouldn't matter what camera, what sensor or what lens you use and in what direction it is pointed.

George

[William W]

Thank you for explaining what you mean when you write 'viewpoint' and 'cropping'.

There is really no point in debating between what you mean and how those words are used, as precise technical words, in Photography.

WW

[george013]

Thank you for explaining what you mean when you write 'viewpoint' and 'cropping'.

There is really no point in debating between what you mean and how those words are used, as precise technical words, in Photography.

WW

I'm not sure if I understand that last sentence, but I think you should leave away the words "as precise technical words".

When debating it's handy to use the same defintions. I gave the definition of viewpoint as how I see it: position, direction, angle of view. That makes the image. I noticed you referre sometime to cinamatography. I don't know the way of working or expressing there.

Searching for a definition on internet isn't very helpfull. Even wiki doesn't have it.
I give one that suits me.
http://www.ehow.com/about_6548897_de...otography.html

And one more, somewhere in the middle.
http://photoinf.com/General/NAVY/Pho...on_Balance.htm

George

[xpatUSA]

I rather like this link which mentions the word "confusion" uttered by none other than Plato hisself!

https://en.wikipedia.org/wiki/Perspe...l)#Limitations

[george013]

I rather like this link which mentions the word "confusion" uttered by none other than Plato hisself!

https://en.wikipedia.org/wiki/Perspe...l)#Limitations

When you want to be fooled with perspective, look to the work of Escher.
https://en.wikipedia.org/wiki/M._C._Escher
Just google for his drawings.

George