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04-15-2010, 07:49 AM   #31
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QuoteOriginally posted by audiobomber Quote
Normal isn't the lens that was supplied with the camera, and it isn't the FL someone feels most comfortable shooting. Normal refers to normal perspective (i.e. normal depth perception, not compressed or stretched perspectives). Normal is in between wide angle and telephoto. The exact range is debatable, but is always stated as somewhere between 40-60mm. I'd call the DA 40mm normal (barely) on an APS-C sensor. I wouldn't call 35mm normal on a film camera, but that is what I used for years, and it worked great as a "compromise" lens for me. I find normal length is too in-between; not wide enough or not long enough for most subjects.

Normal lens: Information from Answers.com
This article is somewhat lose about "perspective" and "angle of view". Perspective has NOTHING to do with the focal length of the lens, because it is ONLY dependent on the position of the camera = distance of the camera from the subject.

Photos taken from one spot will have exactly the same perspective, whether you use a 21mm lens or a 50mm lens! The only difference is the field of view.

This is often confused, because, quite obviously, to get the same image field into view you need to go nearer to the subject with a wide angle lens and keep more distance with a "normal" or tele lens. It is this difference in distance, that changes the perspective, not the focal length.

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04-15-2010, 08:07 AM   #32
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QuoteOriginally posted by Ben_Edict Quote
Photos taken from one spot will have exactly the same perspective, whether you use a 21mm lens or a 50mm lens! The only difference is the field of view.
I totally disagree. If you take a photo of a subject in the foreground with a wide angle lens, the background will look further back than what you saw with your eye. If you use a telephoto, the background will appear larger than what you saw with your naked eye. A normal lens will not distort the perception of depth.

This photo below was taken with a telephoto lens. The water tower was nowhere near as prominent when I viewed the scene. The telephoto lens changed the perspective, compressed the depth of the scene, making the tower much more imposing.

04-15-2010, 08:15 AM   #33
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QuoteOriginally posted by audiobomber Quote
I totally disagree. If you take a photo of a subject in the foreground with a wide angle lens, the background will look further back than what you saw with your eye. If you use a telephoto, the background will appear larger than what you saw with your naked eye. A normal lens will not distort the perception of depth.

This photo below was taken with a telephoto lens. The water tower was nowhere near as prominent when I viewed the scene. The telephoto lens changed the perspective, compressed the depth of the scene, making the tower much more imposing.
Were you standing in the same spot when you took the images?
04-15-2010, 08:20 AM   #34
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QuoteOriginally posted by audiobomber Quote
I totally disagree. If you take a photo of a subject in the foreground with a wide angle lens, the background will look further back than what you saw with your eye. If you use a telephoto, the background will appear larger than what you saw with your naked eye. A normal lens will not distort the perception of depth.

Disagree if you like, but if you tale a picture with a wide angle and then mount a telephoto and take a picture without moving the camera you will be able to perfectly superimpose the telephoto picture onto the wide angle picture.
I'd suggest you might want to go out and take some pictures with this thought in mind.

04-15-2010, 08:43 AM   #35
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QuoteOriginally posted by audiobomber Quote
I totally disagree. If you take a photo of a subject in the foreground with a wide angle lens, the background will look further back than what you saw with your eye. If you use a telephoto, the background will appear larger than what you saw with your naked eye. A normal lens will not distort the perception of depth.

This photo below was taken with a telephoto lens. The water tower was nowhere near as prominent when I viewed the scene. The telephoto lens changed the perspective, compressed the depth of the scene, making the tower much more imposing.

QuoteOriginally posted by Wheatfield Quote
Disagree if you like, but if you tale a picture with a wide angle and then mount a telephoto and take a picture without moving the camera you will be able to perfectly superimpose the telephoto picture onto the wide angle picture.
I'd suggest you might want to go out and take some pictures with this thought in mind.
Wheatfield is absolutly right. If you take 2 images with say a 21 and a 50 from the same place and in the same direction. The image at 50 will be a crop from the image at 21.

If you want to have the same elements in both images, you will have to step back with the 50 and therefore change the perspective.
04-15-2010, 09:10 AM   #36
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QuoteOriginally posted by ghelary Quote
Wheatfield is absolutly right. If you take 2 images with say a 21 and a 50 from the same place and in the same direction. The image at 50 will be a crop from the image at 21.

If you want to have the same elements in both images, you will have to step back with the 50 and therefore change the perspective.
I agree that cropping a wide angle photo will give the same results as using a longer lens. That's not what I'm talking about. I'm talking about looking at the scene with your unaided eye. The scene I linked as an example. To my eye, the water tower was in the far distance. When I took the photo with the long end of an 18-250, the water tower looked a lot closer than it looked in real life. The telephoto lens perceptually compressed the depth of the scene. The distance from the train to the water tower looks unnaturally close to me when I view the photo.
04-15-2010, 11:14 AM   #37
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QuoteOriginally posted by audiobomber Quote
I totally disagree. If you take a photo of a subject in the foreground with a wide angle lens, the background will look further back than what you saw with your eye. If you use a telephoto, the background will appear larger than what you saw with your naked eye. A normal lens will not distort the perception of depth.
There is nothing to agree or disagree about, because the very definition of perspective is a fact. You could, for instance, look it up in the "bible" of photography, the Focal Press Encyclopedia of Photography.

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04-15-2010, 11:19 AM   #38
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QuoteOriginally posted by audiobomber Quote
Normal isn't the lens that was supplied with the camera, and it isn't the FL someone feels most comfortable shooting. Normal refers to normal perspective (i.e. normal depth perception, not compressed or stretched perspectives). Normal is in between wide angle and telephoto. The exact range is debatable, but is always stated as somewhere between 40-60mm. I'd call the DA 40mm normal (barely) on an APS-C sensor. I wouldn't call 35mm normal on a film camera, but that is what I used for years, and it worked great as a "compromise" lens for me. I find normal length is too in-between; not wide enough or not long enough for most subjects.

Normal lens: Information from Answers.com
Well, the topic of this thread implies that "normal" is a subjective term. If you want an objective answer then we can all just talk about the ~50, because that is what 90% of people who are familiar with 35mm think is "normal."

Our vision is actually 120 degrees. What many of us feel is "normal" is a very subjective sense based upon the interpretation of a portion of our vision by our brains. It is subject to what we get used to.

04-15-2010, 11:48 AM   #39
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QuoteOriginally posted by GeneV Quote
Our vision is actually 120 degrees. What many of us feel is "normal" is a very subjective sense based upon the interpretation of a portion of our vision by our brains. It is subject to what we get used to.
Normal is not related to our vision's field of view. It's only about the perception of depth.
04-15-2010, 12:17 PM   #40
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QuoteOriginally posted by audiobomber Quote
Normal is not related to our vision's field of view. It's only about the perception of depth.
That is a new definition. If by perception of depth you mean perspective, then I would agree that is part of the equation. I will also readily agree that 35mm is outside of what most people think of as "normal."
04-15-2010, 12:43 PM   #41
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QuoteOriginally posted by GeneV Quote
Our vision is actually 120 degrees. What many of us feel is "normal" is a very subjective sense based upon the interpretation of a portion of our vision by our brains. It is subject to what we get used to.
This is the reason, why I always saw 50mm as a compromise lens, which is nevertheless useful, not the least, because it is the fastest glass available.

The 120 deg field of view is very unsharp outside the central part, though (ofcourse the eyes scan the scenery) and the central sharp part is more like the angle of view an 80mm lens gives.

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04-15-2010, 12:57 PM   #42
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QuoteOriginally posted by Marc Sabatella Quote
That's an awful lot of math for something predicated on something that's basically just a guess. What makes you think 45 degrees measured horizontally is particularly special?
I assume you meant diagonal, Marc and I was thinking the same thing. If the film were 36mm x 36mm instead of 36 x 24, the diagonal would be different, thereby suggesting by that (the OP's) reasoning a different "normal" focal length yet the 36 x 36 image taken with a 45mm FL cropped to 36x24, would be identical to the 36 x 24 from a 45mm FL.
04-15-2010, 01:00 PM   #43
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QuoteOriginally posted by ghelary Quote
Wheatfield is absolutly right.
The world would be a much better place if more people thought like you..
04-15-2010, 01:03 PM   #44
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QuoteOriginally posted by Ben_Edict Quote
There is nothing to agree or disagree about, because the very definition of perspective is a fact. You could, for instance, look it up in the "bible" of photography, the Focal Press Encyclopedia of Photography.

Ben
I don't have that book, but perspective is not originally a photography term anyway, it's from drawing and art. Perspective in art uses techniques to show the relative distances between objects, through converging lines and relative sizes.

In photography, a telephoto lens compresses perspective compared to your vision, a wide angle lens expands perspective, that's all I'm saying. I don't see why it's controversial.

Last edited by audiobomber; 04-15-2010 at 02:48 PM.
04-15-2010, 01:03 PM   #45
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QuoteOriginally posted by audiobomber Quote
I agree that cropping a wide angle photo will give the same results as using a longer lens. That's not what I'm talking about. I'm talking about looking at the scene with your unaided eye. The scene I linked as an example. To my eye, the water tower was in the far distance. When I took the photo with the long end of an 18-250, the water tower looked a lot closer than it looked in real life. The telephoto lens perceptually compressed the depth of the scene. The distance from the train to the water tower looks unnaturally close to me when I view the photo.
Here's a little optical trick you can try:
Take a smallish sheet of cardboard, perhaps as big as 8x10 inches.
Cut a rectangular hole in it a few inches on a side.
Hold it close to your face and you have a wide angle lens.
Hold it a foot or so away and you have a normal lens.
Hold it at arms length and you have a telephoto.
You will be quite amazed at how removing peripheral vision can affect the way you see.
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