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Photoshop Contest Forum Index - General Discussion - Perspective / Reflections - Reply to topic

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vokaris
Site Moderator

Post Mon Aug 13, 2012 7:03 pm   Reply with quote         


My favorite pet peeve - perspective at reflections

Fact: photos taken looking up at an angle have vertical perspective - all vertical lines, edges, etc. get closer near the top, and will meet at a conversion point in the distance



Problem: what happens if the object is reflected in, let's say, a body of water at the bottom?

Can you sketch the reflection in the photo below?





kinetic_be

Location: Belgium

Post Mon Aug 13, 2012 8:46 pm   Reply with quote         


I've always had problems with making reflections if the object didn't have a straight line at the bottom.
I mean, when there is a straight line, you just copy vertically to get a reflection. When the object is not straight, I end up warping or drawing them myself.

As for this image, my guess would be something like this:





PotHed

Location: San Antonio, Tx

Post Mon Aug 13, 2012 11:43 pm   Reply with quote         


kinetic_be wrote:
I've always had problems with making reflections if the object didn't have a straight line at the bottom.
I mean, when there is a straight line, you just copy vertically to get a reflection. When the object is not straight, I end up warping or drawing them myself.

As for this image, my guess would be something like this:


This.

Perspective is about the distance from the observer. The top of the building is farther from the observer, so it appears smaller. In the reflection, the "top" of the building is equally far away since the observer is at ground level, so it should appear equally small.

However, if the picture were taken at roof-top level, the ground floor would appear smaller and the reflection of the roof would appear even smaller because in the reflection, it is even farther away from the observer.

Don't think of reflections as being distorted. Think of them as exact-but-opposite duplicates of the object itself, existing beneath the surface.




vokaris
Site Moderator

Post Tue Aug 14, 2012 12:14 am   Reply with quote         


Well, no. To make a correct reflection, the straight lines will continue to taper out.



Disclaimer: this is the "geometrically correct" or "camera" view, especially visible in wide angle shots, and it is different than the way a human eye sees, or, to be more accurate, how the brain processes vertical lines.

More examples:







PotHed

Location: San Antonio, Tx

Post Tue Aug 14, 2012 12:58 am   Reply with quote         


vokaris wrote:
Well, no. To make a correct reflection, the straight lines will continue to taper out.



Disclaimer: this is the "geometrically correct" or "camera" view, especially visible in wide angle shots, and it is different than the way a human eye sees, or, to be more accurate, how the brain processes vertical lines.

More examples:

That's really interesting. No wonder it's your pet peeve!




kinetic_be

Location: Belgium

Post Tue Aug 14, 2012 4:48 am   Reply with quote         


vokaris wrote:
Well, no. To make a correct reflection, the straight lines will continue to taper out.




I don't get that. I'm sure it's correct what you are showing, but I don't understand it.
How would this image look like if you were to reflect the whole building?




Zoeon

Location: Belgium

Post Tue Aug 14, 2012 6:45 am   Reply with quote         




i think this is an good example what a wide angle camera does with reflextions




anfa

Location: Geordieland, UK

Post Tue Aug 14, 2012 7:34 am   Reply with quote         


vokaris wrote:
Well, no. To make a correct reflection, the straight lines will continue to taper out.



He's bloody right you know! Wink


Great thread brother! It really bugs me when people do a reflection as if it was a shadow. Evil or Very Mad




_________________

vokaris
Site Moderator

Post Tue Aug 14, 2012 8:08 pm   Reply with quote         


kinetic_be wrote:
I don't get that. I'm sure it's correct what you are showing, but I don't understand it.
How would this image look like if you were to reflect the whole building?
Feel free to Google "Principles of Perspective" to find out more, e.g.
http://www.webexhibits.org/sciartperspective/tylerperspective.html

Most camera lenses are built to make straight lines as straight as possible, even at wide angles. Depending on the quality of the lens, there are some distortions, but the general design intent is to eliminate the distortions. This results in a more 'natural' image near the center of the photograph but it gets distorted near the edges. Remember: we are trying to represent a spherical image on a flat surface.

When the camera is pointed level and horizontally, all true verticals are parallel to the edge of the frame. This is, generally, the best way to photograph buildings.


When the camera is pointed up, the vertical lines appear to converge at a point up in the sky.


When the camera is pointed down, the vertical lines appear to converge at a point below the ground.


Back to the main point of my ramblings about reflections: vertical lines (e.g. building edges) reflected in a horizontal surface (e.g. pooled water) remain vertical.

When the camera is pointed horizontally, the verticals are 'vertical', or parallel to the edge of the frame.


When the camera is pointed up, the verticals taper in at the top, the reflections follow the same vertical perspective lines and appear to taper out.


When the camera is pointed down, the verticals taper out at the top, the reflections taper in.


In this animation, on the left the blue lines show the camera angle, on the right, what the camera "sees".





kinetic_be

Location: Belgium

Post Tue Aug 14, 2012 8:16 pm   Reply with quote         


I get it now Smile
The last image (the .gif) made it all clear.

Thanks for the very intersting lesson!




Tesore

Location: On the way to Utopia!

Post Tue Aug 14, 2012 8:20 pm   Reply with quote         


This is cool stuff. Thanks vokaris!

I still don't understand, but on a much higher level!

Cool




TJ

Location: Utah, USA

Post Tue Aug 14, 2012 8:27 pm   Reply with quote         


That is awesome. Very cool and thanks vokaris!!!

thumright




Werdnaibor

Location: Albany, NY

Post Tue Aug 14, 2012 8:34 pm   Reply with quote         


I get it now, very helpful. I'll still avoid reflections if possible.




PotHed

Location: San Antonio, Tx

Post Tue Aug 14, 2012 8:59 pm   Reply with quote         


vokaris wrote:



Do our eyes do this as well, w/o us realizing it?




TJ

Location: Utah, USA

Post Tue Aug 14, 2012 9:16 pm   Reply with quote         


thumright




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