5 ms·

There is no such effect. Telephoto lenses do not compress. You could see the same perspective by taking the center part of an image shot with a normal lens, ie

by w0mbat 6y ago

There is no such effect. Telephoto lenses do not compress. You could see the same perspective by taking the center part of an image shot with a normal lens, ie by cropping. This is easily verified.

csours 6y ago
That sounds like a distinction without a difference to me.
- w0mbat 6y ago
  It’s really not. The lens is not the key thing it’s the distance from the subject. There is no flattening effect. Amateurs typically plant their feet and use variable focal length lenses to frame the shot, and are missing out on the perspective control you get from using your feet.
  - p1necone 6y ago
    But the only type of lens you could use to get a reasonable resolution at the distance required is a telephoto lens, hence distinction without a difference.
franga2000 6y ago
Of course, but at a distance where the effect is noticable and the crop level required, you would be left with just a handful of pixels, so effectively, this is limited to high focal length lenses. And sice high enough focal lengths onyl come in telephoto lenses, this is basically limited to those.
- w0mbat 6y ago
  Telephoto means long focal length. (Long not “high”). It’s not true that only a handful of pixels would be left with a modern sensor. The point is that perspective is a result of distance from the subject or subjects. Long lenses make it convenient to work from further away without having to crop later, but the key thing is distance. If you shoot portraits from too close they will look bad regardless of lens and later cropping. If you shoot a crowd from close up, that intimacy is baked into the pictures.
  - franga2000 6y ago
    No, it doesn't. Telephoto is a specific category of long-focal lenses, where the focal length is longer than the lens itself - that is achieved using a special lens element that isn't present in regular long lenses. (as for the "high focal length", I guess it's just a language quirk as it makes perfect sense in my native language) Looking at the math, cropping a picture taken with a 28mm lens to the equivalent of 300mm is a crop factor of 0.093. Using the highest-res camera I've used (a Sony A7R IV) at 61MP, this results in a photo of around 900x600 pixels - not something you'd ever see published and taking into account the significant amount of noise that is unavoidable at that pixel density, the photo would be utterly unusable even at that resolution. So sure, it's a distance effect, but since no sane person would do that kind of crop and if they did, it would be painfully obvious or at least highly suspicious-looking to most people (also keep in mind the DoF!), it's pretty safe to conclude that this effect will be significant only with telephoto lenses.
    - w0mbat 6y ago
      Any long lens you buy is going to use the telephoto design, it's a given. A fairly mild crop to say make a 85mm simulate a 105mm is almost undetectable in terms of quality, and the difference that can make to the look of a portrait because you took a few steps further back and then cropped to get the same framing as a 105mm, is very noticeable.
      - franga2000 6y ago
        You need much more than a 20mm difference to make social-distancing people look like they're basically hugging, which is what the article is about. Either way, none of this matters anyways because the whole point of the article is the compression effect, not where it comes from and in their case, it came from a telephoto lens, not a cropped wide-angle, so the terminology is entirely fine.
6gvONxR4sf7o 6y ago
Consider the angle formed by the left side of the picture, the camera/viewer, and the right side of the picture. The higher the zoom (or the crop), the smaller this angle is. It's called field of view (FOV). You've seen this in horror movies when they pull the camera back while zooming in (or out). The protagonist fills the same amount of the screen while their face distorts and the angle spanned by the background narrows (or expands). The fireplace in the background that originally was a small part of the background now spans the whole background. Or the crowd. https://filmschoolrejects.com/wp-content/uploads/2021/01/Jaws-dolly-zoom.gif https://filmschoolrejects.com/wp-content/uploads/2021/01/Jaw... That's the kind of distortion under discussion. You're right that zooming and cropping are the same, but that doesn't actually refute the point, because both affect FOV the same way, and FOV differences are the topic under discussion.
- w0mbat 6y ago
  You are actually making my point for me. The perspective change you are talking about is called "a dolly zoom". A dolly is a little cart that runs on a track, so the camera can be physically moved in a straight line, in this case moving towards or away from the subject. The change in perspective is caused by this change in distance, made more noticeable because the zoom lens continually changes focal length to keep the subject the same size. It forces us to see the effect distance has, something our eyes normally tunes out.

by w0mbat 6y ago

There is no such effect. Telephoto lenses do not compress. You could see the same perspective by taking the center part of an image shot with a normal lens, ie by cropping. This is easily verified.

csours 6y ago

That sounds like a distinction without a difference to me.

w0mbat 6y ago
It’s really not. The lens is not the key thing it’s the distance from the subject. There is no flattening effect. Amateurs typically plant their feet and use variable focal length lenses to frame the shot, and are missing out on the perspective control you get from using your feet.
- p1necone 6y ago
  But the only type of lens you could use to get a reasonable resolution at the distance required is a telephoto lens, hence distinction without a difference.

franga2000 6y ago

Of course, but at a distance where the effect is noticable and the crop level required, you would be left with just a handful of pixels, so effectively, this is limited to high focal length lenses. And sice high enough focal lengths onyl come in telephoto lenses, this is basically limited to those.

w0mbat 6y ago
Telephoto means long focal length. (Long not “high”). It’s not true that only a handful of pixels would be left with a modern sensor. The point is that perspective is a result of distance from the subject or subjects. Long lenses make it convenient to work from further away without having to crop later, but the key thing is distance. If you shoot portraits from too close they will look bad regardless of lens and later cropping. If you shoot a crowd from close up, that intimacy is baked into the pictures.
- franga2000 6y ago
  No, it doesn't. Telephoto is a specific category of long-focal lenses, where the focal length is longer than the lens itself - that is achieved using a special lens element that isn't present in regular long lenses. (as for the "high focal length", I guess it's just a language quirk as it makes perfect sense in my native language) Looking at the math, cropping a picture taken with a 28mm lens to the equivalent of 300mm is a crop factor of 0.093. Using the highest-res camera I've used (a Sony A7R IV) at 61MP, this results in a photo of around 900x600 pixels - not something you'd ever see published and taking into account the significant amount of noise that is unavoidable at that pixel density, the photo would be utterly unusable even at that resolution. So sure, it's a distance effect, but since no sane person would do that kind of crop and if they did, it would be painfully obvious or at least highly suspicious-looking to most people (also keep in mind the DoF!), it's pretty safe to conclude that this effect will be significant only with telephoto lenses.
  - w0mbat 6y ago
    Any long lens you buy is going to use the telephoto design, it's a given. A fairly mild crop to say make a 85mm simulate a 105mm is almost undetectable in terms of quality, and the difference that can make to the look of a portrait because you took a few steps further back and then cropped to get the same framing as a 105mm, is very noticeable.
    - franga2000 6y ago
      You need much more than a 20mm difference to make social-distancing people look like they're basically hugging, which is what the article is about. Either way, none of this matters anyways because the whole point of the article is the compression effect, not where it comes from and in their case, it came from a telephoto lens, not a cropped wide-angle, so the terminology is entirely fine.

6gvONxR4sf7o 6y ago

Consider the angle formed by the left side of the picture, the camera/viewer, and the right side of the picture. The higher the zoom (or the crop), the smaller this angle is. It's called field of view (FOV). You've seen this in horror movies when they pull the camera back while zooming in (or out). The protagonist fills the same amount of the screen while their face distorts and the angle spanned by the background narrows (or expands). The fireplace in the background that originally was a small part of the background now spans the whole background. Or the crowd. https://filmschoolrejects.com/wp-content/uploads/2021/01/Jaws-dolly-zoom.gif https://filmschoolrejects.com/wp-content/uploads/2021/01/Jaw... That's the kind of distortion under discussion. You're right that zooming and cropping are the same, but that doesn't actually refute the point, because both affect FOV the same way, and FOV differences are the topic under discussion.

w0mbat 6y ago
You are actually making my point for me. The perspective change you are talking about is called "a dolly zoom". A dolly is a little cart that runs on a track, so the camera can be physically moved in a straight line, in this case moving towards or away from the subject. The change in perspective is caused by this change in distance, made more noticeable because the zoom lens continually changes focal length to keep the subject the same size. It forces us to see the effect distance has, something our eyes normally tunes out.