Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-07-2012, 09:00 AM   #46
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
fist of what is perspective distortion since i doubt you mean this?
Perspective Correction Tutorial - Lonestardigital.com

ps. this is called perspective distortion, for fun look up what a perspective correction lens is and what it does.

07-07-2012, 09:03 AM   #47
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
QuoteOriginally posted by Marc Sabatella Quote

Not sure what you mean by .angle of view of the viewer of print"? If you mean, the angle subtended by the print itsrlf from the viewing position, then the answer is as I have been stating: size of and viewing distance from the print. But wheter or not this will result in the optical illusion known as perspective distortion depends on whether that angle matches the angle of view depicted in the image or not.
Why do i need to argue you already say so yourself "size of and viewing distance from the print" so case solved, or do you want to explain why this does not aply to the camera?
07-07-2012, 09:06 AM   #48
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
QuoteOriginally posted by Marc Sabatella Quote
As with perspective, there are two very different senses of the word magnification. You are using the sense that applies to macro photography. But the issue of viewfinder magnification is entirely separate. Two completely unrelated topics that just happen to share the same word.

It is true that neither sense of the word magnification has anything to do with either sense of the word perspective, though..
Who said it was about viewfinder magnification?
Only after my explaination the word viewfinder was named not before that.

Afterall the magnification that our eyes see is different then the magnification our eyes see through the viewfinder but the first one was said not the last one.
It's the same problem with Blue, i at least can't mind read.
07-07-2012, 11:31 AM   #49
Veteran Member




Join Date: Nov 2006
Location: central Singapore
Photos: Gallery
Posts: 409
QuoteOriginally posted by Marc Sabatella Quote
Not true. You erroneously stated that point of view has an effect on perspective distortion. .
Actually I have never really understood what perspective distortion is supposed to be. Perspective is what you see when you stand (or shoot a photograph) in a certain position with relation to a set of objects. Field of view = 'crop' varies according to focal length and/or sensor size, as does DOF, but the perspective doesn't. The foreshortening effect of telephoto lenses is no different from what you would see if you cut a small rectangular hole in a piece of card and looked through it at a distant scene. Similarly if you take a landscape shot with a wide-angle lens, and crop a small bit out of the middle, and resize it up, this mimics the effect of a telephoto lens (forget resolution for a minute) and you will see a similar 'foreshortening' effect. But there's no difference in perspective. Nothing in the image has 'moved' with respect to anything else in the image.

I understand the sort of distortion that occurs when a wide-angle view has to be mapped in rectilinear form - i.e. stretched out corners - but that's something different.

All this stuff about 'standard' lenses is a lot of hooey - the old 50mm standard is a convention which happens to be quite convenient from a compositional point of view on 35mm film, and was simple to make. There's nothing magical about it, and to claim that 50mm on an APS-C sensor has analogous qualities (as some have done on occasion) makes no sense at all. And the size and/or magnification of the viewfinder is irrelevant.

07-07-2012, 11:59 AM   #50
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,525
lol guys, I would just like to point out this discussion is going completely off-topic. Might as well start a thread about it, or just drop it. I think the OP got all sorts of info, though, I hope he is happy with his decision
07-07-2012, 05:35 PM   #51
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
QuoteOriginally posted by timo Quote
Actually I have never really understood what perspective distortion is supposed to be. Perspective is what you see when you stand (or shoot a photograph) in a certain position with relation to a set of objects. Field of view = 'crop' varies according to focal length and/or sensor size, as does DOF, but the perspective doesn't. The foreshortening effect of telephoto lenses is no different from what you would see if you cut a small rectangular hole in a piece of card and looked through it at a distant scene. Similarly if you take a landscape shot with a wide-angle lens, and crop a small bit out of the middle, and resize it up, this mimics the effect of a telephoto lens (forget resolution for a minute) and you will see a similar 'foreshortening' effect. But there's no difference in perspective. Nothing in the image has 'moved' with respect to anything else in the image.
The 'foreshortening' effect is what Marc means and it's part of the perspective.
Like you said the relatively in the images not changes but you preception of it as viewer does change.
To go a bit further there is no true distortion if you want to call it that since there is a point where the viewing distance make all the perspective angles come over as natural.

It's like you put a wide angle close to someone face, it does look distorted from a typical viewing distance but if you move close to the print yourself then the image will look more natural the closer you get up until a point.

That's what i mean that it's not correct to say that distance doesn't change the perspective of what Marc means.
07-08-2012, 07:04 AM   #52
Veteran Member




Join Date: Nov 2006
Location: central Singapore
Photos: Gallery
Posts: 409
QuoteOriginally posted by Na Horuk Quote
lol guys, I would just like to point out this discussion is going completely off-topic. Might as well start a thread about it, or just drop it. I think the OP got all sorts of info, though, I hope he is happy with his decision
Yeah, well, it'd be a pretty boring old forum if the arguments didn't drift off topic from time to time ... Unapologetic.
07-08-2012, 07:11 AM   #53
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,658
QuoteOriginally posted by timo Quote
Yeah, well, it'd be a pretty boring old forum if the arguments didn't drift off topic from time to time ... Unapologetic.
+1.

Since they're called "threads," they're expected to weave back and forth!

Besides, the most interesting parts of these discussions are often the side issues that creep in.

07-08-2012, 07:58 AM   #54
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
QuoteOriginally posted by lytrytyr Quote
+1.

Since they're called "threads," they're expected to weave back and forth!

Besides, the most interesting parts of these discussions are often the side issues that creep in.


why can't i just use a smiley and do i need to type this to get the amount of characters needed?
07-08-2012, 09:42 AM   #55
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,658
QuoteOriginally posted by Anvh Quote


why can't i just use a smiley and do i need to type this to get the amount of characters needed?
xxxxx is enough, I believe.

But some forum members might mistake those for kisses!
07-08-2012, 02:19 PM   #56
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Anvh Quote
fist of what is perspective distortion since i doubt you mean this?
Perspective Correction Tutorial - Lonestardigital.com
While related in a way, that is a different phenomenon still, although confusingly, it is lumped in with other forms of perspective distortion in that article. But that is not what we are talking about here. The optical illusion known as perspective distortion is the same phenomenon we have been discussing on and off in different threads for months now: the fact that images taken with a telephoto create the opitcal illusion of apearing to compress disance between objects, and the opposite for wide angle lenses. It is not correctable - it is completely inherent in the whole idea of shooting an image at one AOV and then displaying it such that it subtends another. It is just as present in painting as in photography. Any means of displaying an image that subtends a different angle than the AOV depicted will create the illusion. It is unavoidable and uncorrectable; it simply *is*. All telephoto lenses will create a compression effect, all wide angle an expansion effect.
07-08-2012, 02:22 PM   #57
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Anvh Quote
Why do i need to argue you already say so yourself "size of and viewing distance from the print" so case solved, or do you want to explain why this does not aply to the camera?
Because it is size of print and distance to it that determines the angle it subtends, but nothing having to do with with size or distance affects AOV. Only focal length (and/or cropping) affects AOV for any given format. That is why size of and distance to the print are relevant to the optical illusion known as perspective distortion, but not shooting position - print size and viewing distance affect the angle subtended by the print, but shooting position doesn't affect AOV of the scene depicted.

Last edited by Marc Sabatella; 07-08-2012 at 02:45 PM.
07-08-2012, 02:25 PM   #58
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Anvh Quote
Who said it was about viewfinder magnification?
There are many different aspects to this discussion. The specific post you were responding to was talking about how a "normal" lens on a FF produces a ciewfinder images that appears the same size as with the unaided eye. We were simply observing that this only happens to be true if the viewfinder produces that particular magnifiation. But it does happen to be true reasonably often of FF camera, and hardly ever for larger or smaller formats.
07-08-2012, 02:42 PM   #59
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by timo Quote
Actually I have never really understood what perspective distortion is supposed to be
The concept is quite simple. Images taken with a telephoto lens can create an optical illusion in which objects depicted can appear closer together than they actually were. And the opposite for wide angle lenses.

QuoteQuote:
Field of view = 'crop' varies according to focal length and/or sensor size, as does DOF, but the perspective doesn't.
Precisely why the illusion exists. Someone looking at the image doesn't know right away it was taken with a telephoto lens. So when he seems objects depicted a certain size in the frame, he mistakenly believes the photographer was closer to the objects than he actually was - in the absence of information to the contrary, he will try to process the image as if it were taken from whatever distance would have been necessary with a normal lens to render the subject that size.. But if the photographer had been that close to the subject, then the perspective would have different. The viewer sees an image taken from one position - with the perspective that implies - but sees it as if it were taken from a diffeent position, which should have have a different perspective. This mismatch in perspectives is what creates the illusion.

QuoteQuote:
The foreshortening effect of telephoto lenses is no different from what you would see if you cut a small rectangular hole in a piece of card and looked through it at a distant scene.
No, not true at all. Again, the illusion absolutely dpends on an actual image being printed or displayed somehow, and the angle subtended by the print/display of the image not matching the AOV depicted in the image. You can't make that happen without actually printing , displaying, or projecting an image. There is no way to reproduce that effect just by looking at the image live.

Similarly if you take a landscape shot with a wide-angle lens, and crop a small bit out of the middle, and resize it up, this mimics the effect of a telephoto lens (forget resolution for a minute) and you will see a similar 'foreshortening' effect. But there's no difference in perspective. Nothing in the image has 'moved' with respect to anything else in the image.

QuoteQuote:
I understand the sort of distortion that occurs when a wide-angle view has to be mapped in rectilinear form - i.e. stretched out corners - but that's something different.
Yes, and that is what the link Anvh gave earlier deals with.

QuoteQuote:
All this stuff about 'standard' lenses is a lot of hooey - the old 50mm standard is a convention which happens to be quite convenient from a compositional point of view on 35mm film
Yes, for one very important reason - it creates an AOV that is similar to the angle that is subtended to by a ttpical print viewed from a typical distance. With the result that the image produced is devoid of perspctive distortion, and is perceived as looking "natural" - as if the framed image on the wall were just a window looking out on the scene itself.

QuoteQuote:
to claim that 50mm on an APS-C sensor has analogous qualities (as some have done on occasion) makes no sense at all. And the size and/or magnification of the viewfinder is irrelevant.
That much is all true, at least as regards persepctive distortion. It is a 35mm lens on APS-Cthat creates the same AOV as a 50mm lens on 135 format, and hence possesses this quality. And size / magnification of the viewfinder plays no role in this. But viewfinder size / magnification does play a role in the *other* attribute that is often erroneously attributed to normal lenses: the "fact" that the apparent size of objects in the viewfinder is the same as that when viewed with the naked eye. This only happens to be true if the viewfinder happens to be of the right magnification to achieve that effect. This does often happen to be more or less true with viewfinders for 135 format cameras, but it is hardly ever true for viewfinders on other formats. Which does make the 135 kind of special.
07-08-2012, 02:57 PM   #60
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
QuoteOriginally posted by Marc Sabatella Quote
Because it is size of print and distance to it that determines the angle it subtends, but nothing having to do with with size or distance affects AOV. Only focal length (and/or cropping) affects AOV for any given format. That is why size of and distance to the print are relevant to the optical illusion known as perspective distortion, but not shooting position - print size and viewing distance affect the angle subtended by the print, but shooting position doesn't affect AOV of the scene depicted.
So why does if you move closer as a viewer change the perspective of the image but if you move closer with a camera it doesn't?
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
40mm, cost, k-mount, lenses, ltd, pentax lens, quality, slr lens, xs
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Voigtlander Ultron 40mm f/2 vs. Pentax 40mm Ltd (warning: amateur test) dasuhu Pentax SLR Lens Discussion 48 12-05-2013 08:34 AM
DA 40mm F2.8 Limited or DA 35mm f/2.4 AL .... rrwilliams64 Pentax SLR Lens Discussion 14 07-14-2011 11:40 AM
DA 40mm 2.8 Ltd vs DA (L) 35mm 2.4 Metalwizards Pentax SLR Lens Discussion 19 02-14-2011 09:36 AM
DAL 35mm 2.4 vs. DA 40mm 2.8 LTD paperbag846 Pentax SLR Lens Discussion 51 10-30-2010 12:50 AM



All times are GMT -7. The time now is 06:29 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top