Nor, you're not thinking correctly. (I am referring to your webpage).
From Wikipedia :

"Perspective (visual), is the way in which objects appear to the eye"

And this is determined by the length of your arms and the focal length.

Why? because to get the 'correct' perspective there is only one

viewing distance for a picture so that all angles you see do correspond with

the angles in real life. If the angle is 'Larger' in the picture than in
real

live the picture seems to be "compressed", if the angle is 'Smaller' in

the picture than in real live, the picture will seem "expanded".

The viewing distance is determined by the length of your arms.

(I am making the assumption that you can touch your monitor while

reading this, and therefore the distance of your monitor is still within

the length of your arms. I might be mistaken about this off course).

The correct viewing distance of any picture :

Viewing distance = focal length * width of the picture / width of the
sensor.

Examples prints on 6 x 4 inches. ( 150 mm x 100 mm)

Focal length 28 mm, 50 mm, 85 mm and 300 mm

With of the sensor (36 mm for analogue 24 mm for some DSLR's)

I'll be calculating with the 36 mm from the analogue because this

is often used for the equivalent focal length's.

Viewing distance for 28 mm focal length

(focal length 28)   28 * 150 / 36 = 116 mm   (About 4.5 inches)

(focal length 50)   50 * 150 / 36 = 208 mm   (About 8.125 inches)

(focal length 85)   85 * 150 / 36 = 354 mm   (About 14 inches)

(focal length 300)   300 * 150 / 36 = 1250 mm (About 48 inches)

Most people can not focus on 116 mm (4.5 inches) so the 28 mm focal

length pictures will be looked at from a distance which "expandes" the

picture.

Most people have arms shorter than 1250 mm (48 inches) so the 300

focal length pictures will be looked at from a distance which "compresses"

the picture.

The appearance to the eye therefore is different from a 28 mm compared

to a 300 mm. And therefore according to the definition in Wikipedia;

"(Perspective (visual), is the way in which objects appear to the eye",

the perspective of a 28 mm is different to a 300 mm.

Off course when the picture is taken and the result is never viewed by

an eye, the description of Wikipedia is not applicable because the result

does not appear to an eye. So your description is totally correct for

taking pictures, but I think the viewing part is more important.

Why is a portraitlens a portrait lens. Because we like to look at people

undistorted. If you look in the above calculations you see that a 85 mm

or 85 mm equivalent has a viewing distance of about 14 inches which

is a fairly standard distance to hold our pictures. To get a portrait

with say a head and shoulders in a picture with a 85 mm we need some

distance from the subject. About 1.20 meters to 2.00 meters (about

4 to 7 feet). This is also the distance where we are closest to people

without letting them into the comfort zone. So this is the distance where

we are still comfortable with people and are close enough to see them

well. The portrait lens is very suitable for making pictures where a large

part of the frame is filled with the head of the subject.

If the subject gets closer to us and it is not a close member of the

family we feel threatened by the proximity of the person. So we do

not like to see this type of distortion in pictures, because the person

looks to close. (This is build into our genetically).

Ben Brugman

*)

To do the calculations you need all distances in the same system.

Focal length is in mm. And in the metric system the other distances

are easily converted to mm. This is a bit more difficult when using

the imperial system, so I used the metric system instead.

For readers not confident in the metric system I added

some imperial distances. My apology for that.

**)

Off course we have other enlargements of pictures and other

ways of viewing them. But still most pictures are viewed on

arm length distance, even pictures on a monitor.

***)

People are nowadays so used to pictures compared a few

decennia back that for example wide angle lenses are now

completely acceptable even for taking pictures of people.

Where a few decennia back pictures taken with a 28 mm

were considered not suitable for taking pictures of people

because of the distortion when viewing them at normal

distances. Now we have to use a 17 mm lens to get the

same reaction from people.