Explain photography to a novice

Nobel Prize · Feb 28, 2023

Deafboy
Actually, is it a myth that the camera's focal length affects image perspective (which is what is discussed in this thread). Two pictures taken at the same camera location with lenses of different focal length will yield the same perspective.

Not quite. The longer focal lenses will compress, and the opposite will happen with a wider lens (Barrel distortion) While it is true that the actual effects are enhanced as you get closer to the subject with a wide angle lens or further away with a zoom lens (affecting the geometrical distance to the lens and sensor) the effect is still there.

In photography, when we buy lenses, we pay very close attention to the minute differences in distortion between lenses, not only within different focal lenses but even within the same focal lens. That's why you pay much more for a Leica or Hasselblad lens than other brands.

As an obvious example of this, a fish eye lens is a super wide angle lens...it distorts.

Braindrain · Feb 28, 2023

Nobel Prize
This is the answer here. Most lenses distort to some level, Some more than most, others (Very few) almost nothing. Wide-angle lenses (Like a phone) tend to distort more. Mid-distance lenses like 35mm still distort a little but give a more natural look. At 44, to 50 mm lenses offer the most natural undistorted look, Closest to the natural eye. 35 is the most popular range since it is close to natural but offers a wider context. 50 is next as it offers a great natural view for contextual portraits...75 to 100 is best after that for undistorted portraits etc etc.

Longer range and Zoom lenses tend to compress the image (opposite to wider angle). Meaning you often perceive the background and subject as closer together than it actually is.

The closer the object is to the lens the more these properties are displayed. So, for example, on a wide-angle lens, the objects closest to the lens will be more distorted. This can be either pinched or pulled (distortion from the center to the image's border or distortion from the border to the center. ) Or think fish eye or inverted fish eye...

When you take the image directly on your wrist, the distance from the dial to your arm is huge in terms of wide-angle lens closeup unless you use a specialized lens. When you take an image in a mirror, you are doubling the distance to the subject, hence reducing the distortion.

In non-photographic terms, the issue is a matter of geometry and how close subjects are to the lenses (no matter what lens). This is scientifically a more accurate explanation since the wide angle lenses are closer to the subject than the zoom lenses to bring the same ratio.

See here for a comparison. Just imagine the nose is your watch and the face your arm. On the mirror, you see a jump from x to 2x

Good explanation.

Here's a nice graphic, as well.

And the accompanying article.

While it helps to have a basic understanding of physics, trial and error can also suffice.

Deafboy · Feb 28, 2023

Nobel Prize
Not quite. The longer focal lenses will compress, and the opposite will happen with a wider lens (Barrel distortion) While it is true that the actual effects are enhanced as you get closer to the subject with a wide angle lens or further away with a zoom lens (affecting the geometrical distance to the lens and sensor) the effect is still there.

In photography, when we buy lenses, we pay very close attention to the minute differences in distortion between lenses, not only within different focal lenses but even within the same focal lens. That's why you pay much more for a Leica or Hasselblad lens than other brands.

As an obvious example of this, a fish eye lens is a super wide angle lens...it distorts.

Better lenses will have less distortion, granted, but this is not what the OP is experiencing.

Perspective compression from a long focal length lens does not occur because it is long, but because the camera is generally further away from the object.

Your set of pictures show that the camera-to-object distance was different for each picture. If you take two pictures with two lenses (say a 50 mm and a 105 mm) without moving the camera or object will yield the same "compression". The field of view will obviously be different, but crop the photo taken with the 50 mm, you will get the same image as the one taken with 105 mm lens.

Deafboy · Feb 28, 2023

To prove my point, I just took 3 pictures of my backyard on this rather drab day. Each taken with the camera in the same position but with 3 different focal length lenses: 77 mm, 26 mm and 13 mm.

Obviously, the field of view is much wider with the short lens -the shed is way, way back in the yard.
OTOH, if I crop the above images taken with the 26 and 13 mm lenses so the field of view is identical to that of the longer lens (77 mm), we see that the perspective (relative size of foreground and background objects) are identical. Image perspective (a.k.a compression) is not a lens effect.

Nobel Prize · Feb 28, 2023

I agree and stated the distance and geometrical ratio affect the distorsion. But it’s there. It is just more prominent, depending on the lens, on infinity, medium and short focusing and from center to edge.

Anyway. I think it’s clear now what combination of factors is creating the watch image to be different on the reflected mirror version.

Dsloan · Feb 28, 2023

Deafboy
To prove my point, I just took 3 pictures of my backyard on this rather drab day. Each taken with the camera in the same position but with 3 different focal length lenses: 77 mm, 26 mm and 13 mm.

Obviously, the field of view is much wider with the short lens -the shed is way, way back in the yard.
OTOH, if I crop the above images taken with the 26 and 13 mm lenses so the field of view is identical to that of the longer lens (77 mm), we see that the perspective (relative size of foreground and background objects) are identical. Image perspective (a.k.a compression) is not a lens effect.

Thanks for doing the legwork on this. I have this conversation with my students all the time. They'll say something along the lines of, "I don't want to use the 25mm for this shot because people will look distorted on a wide angle" and I'm like, "why don't you try experimenting with your distance from the subject instead of just worrying about the focal length."

Tire-comedon · Feb 28, 2023

IMHO the answer is simpler and has nothing to do with focal length or distortion, but just with optics.

Your watch is closer to your camera than your arm and like many objects, it hides what's behind. So it hides part of your arm.

As said, when you take your picture in a mirror you double more or less the distance compared to the picture taken directly without mirror.

Now just realise that the closer you are to an object, the more it hides what's behind it.

To illustrate this, a simple drawing (OK i'm not Leonardo da Vinci!) where you have two objects seen from two different distances. In both case, what's hidden by the closest object is the yellowed part :

Nobel Prize · Feb 28, 2023

Deafboy
To prove my point, I just took 3 pictures of my backyard on this rather drab day. Each taken with the camera in the same position but with 3 different focal length lenses: 77 mm, 26 mm and 13 mm.

Obviously, the field of view is much wider with the short lens -the shed is way, way back in the yard.
OTOH, if I crop the above images taken with the 26 and 13 mm lenses so the field of view is identical to that of the longer lens (77 mm), we see that the perspective (relative size of foreground and background objects) are identical. Image perspective (a.k.a compression) is not a lens effect.

There is still some distortion there, especially on the 13mm. But your point is correct...that is, if your intent is to crop every image. At which point you are wasting pixels and lowering your definition. On the uncropped images, there is a clear difference. As stated, more clear on closer objects and on the edges, but present nonetheless. To state that a wide-angle lens does not distort and then crop the distortion out of the lens as an example does not carry merit. Cropping is equal to electronically zooming or...changing the focal lens. But still, three lenses of different focal lengths cropped to have an equal focal length (why would you do that though, if you have the right prime) will still carry slightly different forms of distortion. All be it, not quite as onerous as to their native FL.

Try to crop the edges instead of the center (same crop ratio) and you will see some strong distortion.

Also, I am assuming (without reason I admit) that there is a lens correction configuration in whatever program you use or in-camera. Disable that function and you'll be able to see what lenses do.

We are not in disagreement, though, the effect is clearly magnified by the distance and geometrical configuration of the image...or "optics" as simply stated by @Tire-comedon. This does not mean every wide-angle image is distorted and unusable...it just has to be used right. There are practical uses for wide-angle lenses for artistic and technical reasons. There are a number of scenarios where I always use a 21, 28 or 35 and would not go narrower than that... but let's not disregard the fact that compression (which is a form of distortion that is acceptable and pleasant) Barrel distortion and a number of other issues Like diffraction, curvature of field, Coma, astigmatism Chromatic aberrations etc etc are inherent in photography and natural to lenses.

STANDY · Feb 28, 2023

This has blown out from a just push the button with the red mark 😁

And thanks @Nobel Prize

Paulomega · Apr 4, 2023

Dsloan
Yep! The closer things are to your eye (your watch), the bigger they will appear relative to nearby things (your wrist). I think seeing it on your wrist in the mirror is a closer approximation of how others will perceive the watch to wrist proportion.

Ok then why do look FAT????

Trog · Apr 4, 2023

SpeedyPhill · Apr 5, 2023

I have been making (Astro-) photographs for almost 50 years now... best results for whatever photography = Use a sturdy tripod ! 😁

Dsloan · Apr 5, 2023

SpeedyPhill
I have been making (Astro-) photographs for almost 50 years now... best results for whatever photography = Use a sturdy tripod ! 😁

Well that and an equatorial mount!

I'd really like to try some astrophotography one day - but no time for new hobbies in the near term.

Explain photography to a novice

Nobel Prize

Braindrain

Deafboy

Deafboy

Nobel Prize

Dsloan

Tire-comedon

Nobel Prize

STANDY

Paulomega

Trog

SpeedyPhill

Dsloan

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