Long Lens Landscape

[DanK]

It's a matter of magnification. If you expand your drawing to the left and draw a sensor in it, you'll easier see what happens. To keep it simple take a magnification of 1 for the first subject.

George

No, it's not. Magnification affects the size of everything projected onto the sensor by a uniform amount (a constant multiple). The impression of compression arises because of changes in the relative size of different elements in the image.

[rpcrowe]

Mike, you are correct! While technically it is not the focal length of a lens that causes the compression, that compression is normally achieved when using long focal lengths...

If there are two images shot from the exact same position, one shot with 28mm and the other shot with 400mm, I "COULD" crop the 28mm image to show the same angle of view as does the 400mm. The compression would look the same. However, the image would probably fall apart due to the extent of cropping and the magnification required to match the 400mm field of view from the 28mm...

In reality, we end up with more compression of images when using a longer focal length and less compression of images when we use a shorter focal length. IMO, what specifically caused that phenomenon doesn't matter.

You have the same relationship between long and short focal length lenses when shooting head and shoulders portraits. If you try to frame a head and shoulders portrait with a shorter focal length lens, you usually need to shoot from a closer lens to subject distance. That distorts the facial features, especially the nose. When shooting with a longer focal length, you will normally be shooting from a longer lens to subject distance which tends not to distort (unless you are shooting with a really looooong focal length). However we really most often shoot from a longer lens to subject distance when we are using a longer focal length...

[Mike Buckley]

In reality, we end up with more compression of images when using a longer focal length and less compression of images when we use a shorter focal length. IMO, what specifically caused that phenomenon doesn't matter.

I completely agree. However, it is important from my point of view that when we do describe the resulting characteristic that we do it in a way that doesn't mislead people. Calling the characteristic lens compression as opposed to just compression has misled countless numbers of people over the decades to think the lens is causing it.

[george013]

No, it's not. Magnification affects the size of everything projected onto the sensor by a uniform amount (a constant multiple). The impression of compression arises because of changes in the relative size of different elements in the image.

No, magnification is about a subject. In your example the first line is your subject. The lens creates an image equal to the sensor height. Your second line is a subject on a fixed distance a from subject 1. The magnification of that subject is less as of the first one. Now you change your focal length, which means using another AOV, and change your distance so that the magnification of the first subject is the same. If you use a wide angle as in your second drawing, the AOV will be bigger. The magnification of the second subject will be less.

Let's assume your lines in the first drawing are your subjects. The first line does have an equal magnification. For the second line the magnification will be 7.5/13.2 times of the one in the first drawing.

In formula M=hi/hs, hi image height and hs subject height. A line parallel to the sensor represents the image height. If you draw to subjects of the same size at a certain distance from each other, you'll see the difference in magnification. It's what you call relative size.


About the picture of Donald, it's a wonderful picture of a wonderful landscape. And I'm glad he's using the term perspective in the same context as I do.


George

[DanK]

In your example the first line is your subject

If you say so. For the point I was making, it is entirely irrelevant which of the two lines you label as "subject."

The first line does have an equal magnification. For the second line the magnification will be 7.5/13.2 times of the one in the first drawing.

Yes, the change in relative size is what I was explaining. Adding the term "magnification" doesn't change the issue.

Put simply, the issue is this: a change in AOV changes the relative size of near and far elements in the projected 2-dimensional image. that change in relative size is what we perceive as "compression" in using long-focal-length lenses, and conversely, it is what produces the weird, bulbous noses in portraits shot with extreme wide-angle lenses.

[tbob]

Donald: Shame on you for ignoring an arbitrary dictum that serves little if any purpose and being creative. If is sort of thing is encouraged people may start to consider how best to present a scene and anarchy will reign.

[george013]

If you say so. For the point I was making, it is entirely irrelevant which of the two lines you label as "subject."



Yes, the change in relative size is what I was explaining. Adding the term "magnification" doesn't change the issue.

Put simply, the issue is this: a change in AOV changes the relative size of near and far elements in the projected 2-dimensional image. that change in relative size is what we perceive as "compression" in using long-focal-length lenses, and conversely, it is what produces the weird, bulbous noses in portraits shot with extreme wide-angle lenses.

What you call a change in relative size is the same as a change in magnification. But there's a condition that doesn't count for this thread: the closer distance.
I made a drawing of 2 situations. The two objects are equal and the distance between them is fixed. When changing to a wider aov I kept the magnification of the first object equal. That can only be done by getting closer.
Let's say in the first drawing the image distance is 100 and the distance between the subjects is 100. The magnification of the second object will be 100/200=0.5.
Now we use another lens and the image distance will be 50. The subject distance of the first subject will become also 50 to get the same magnification. But the magnification of the second subject will be 50/150=0.33.
So what really matters is not the aov but the subject distance to the first subject. When the subject distance doesn't change and only the aov, then nothing changes. Well, not for this discussion.



And for in landscape the subject distances are mostly big, you won't tell the difference between long and wide, except for the framing.

George

[george013]

And for thos who're interested I tried to put it in a formula.

Magnification=image distance/subject distance or M=di/ds.
Given a situation with 2 subjects on different distances and focusing on the first one will give for each
M1=di/ds
M2=di/(ds+a) For focusing on the first subject the di will not change.

When you use another lens and want to keep the magnification of the first subject the same you've to multiply the di and the ds with a factor x. This can be more or less as 1.
M1=xdi/xds
M2=xdi/(xds+a)

The closer you com, the smaller di and ds will be, the more influence a get.
Further away the figures di and ds grow and the less influence a get.

That's what get visible with wa lenses on the short distance.

Hope I didn't make a fault.

George

[Donald]

I wonder what it means that there is more discussion about the science that about the image?

Perhaps it just shows that photography is a subject of interest to a broad constituency.

[george013]

I wonder what it means that there is more discussion about the science that about the image?

Perhaps it just shows that photography is a subject of interest to a broad constituency.

Your opening sentence.

I'm so glad I didn't know the 'rule' about landscapes being shot with wide angle lenses before I went out and bought myself a long lens.

It's only a matter of framing. You used a long lens to shoot 2 mountains, but you probably couldn't shoot a mountain ridge with this lens.
I already mentioned it's a wonderful image of a wonderful place. I don't know what to say more.
I like to know the technique behind it. In matter of fact many members here did com here due to the tutorials on this forum.

George

[Donald]

George - You seem to perceive my comments as criticism. They are not. They are a record of an observation.

[george013]

Ok.

George

[mugge]

It is about a photograph. Amen.
Cheers Ole

[pnodrog]

I don't know why they call it compression when it is just viewpoint and cropping...

[DanK]

I don't know why they call it compression when it is just viewpoint and cropping...

Because it creates an impression of compressed distances. Saying "a longer length compresses distance" is a more useful description than the less specific "a longer length changes viewpoint and cropping."

Donald, I can explain for myself. To some extent, I find that figuring out why things happen helps me with my photography--or at least, certain types of photography, particularly macro and night photography. However, that's not the biggest motivator for me. The biggest is that I have always wanted to know how things work and why things happen.

In this case, the explanation to which you linked, while helpful to a degree, didn't satisfy me. Why does relative distance matter? And more important (to me), relative distance isn't a characteristic of the lens. There has to be a characteristic of the lens itself that explains the appearance of compression. And the characteristic that differentiates lenses of different focal lengths is AOV. So I found it nagging at me: why does a difference in AOV create this effect? I finally had to sit down and draw examples to explain it to myself. Those are the diagrams I posted.

The relative distances cited in the link to which you posted are a consequence of AOV. So is what George labeled magnification--which I would call differences in relative magnification.

But to go back to where I started in this thread: a great image.

Best,

Dan

[JBW]

I wonder what it means that there is more discussion about the science that about the image?

Perhaps it just shows that photography is a subject of interest to a broad constituency.

Yes it does. And we need all types.

[george013]

Because it creates an impression of compressed distances. Saying "a longer length compresses distance" is a more useful description than the less specific "a longer length changes viewpoint and cropping."

Donald, I can explain for myself. To some extent, I find that figuring out why things happen helps me with my photography--or at least, certain types of photography, particularly macro and night photography. However, that's not the biggest motivator for me. The biggest is that I have always wanted to know how things work and why things happen.

In this case, the explanation to which you linked, while helpful to a degree, didn't satisfy me. Why does relative distance matter? And more important (to me), relative distance isn't a characteristic of the lens. There has to be a characteristic of the lens itself that explains the appearance of compression. And the characteristic that differentiates lenses of different focal lengths is AOV. So I found it nagging at me: why does a difference in AOV create this effect? I finally had to sit down and draw examples to explain it to myself. Those are the diagrams I posted.

The relative distances cited in the link to which you posted are a consequence of AOV. So is what George labeled magnification--which I would call differences in relative magnification.

But to go back to where I started in this thread: a great image.

Best,

Dan

I reread Donald's link and it is exactly as I did put in the formula. In the example with that girl the magnification of that girl is kept constant. A longer focal length means more distance from the subject. So if you look at the formula of the magnification of the background, M2=xdi/(xds+a), the longer the subject distance ds is, the lesser influence a will have and the more the magnification of the background comes closer to that of the girl. Flattening or compressed, whatever one wants to call it.

Do you see that in your drawing you not only changed the aov but also the focusing distance? Make the same drawing with only changing the aov. The absolute magnification will change, but for both with an equal factor.

I know what you try to say. I had a thread about that here. And I still don't know how to describe that feeling of different perspective, in the way of the suggestion of a third dimension, when just cropping a picture or changing the aov.

George

[DanK]

Do you see that in your drawing you not only changed the aov but also the focusing distance?

George, that's the point. The wider AOV requires that you be closer to obtain the same framing of a near object, but that doesn't give the same framing for a distant object. That's why people experience compression in using a narrower-AOV lens. I am not sure what you are contesting.

I'm signing off.

[pnodrog]

Because it creates an impression of compressed distances. Saying "a longer length compresses distance" is a more useful description than the less specific "a longer length changes viewpoint and cropping."

Donald, I can explain for myself. To some extent, I find that figuring out why things happen helps me with my photography--or at least, certain types of photography, particularly macro and night photography. However, that's not the biggest motivator for me. The biggest is that I have always wanted to know how things work and why things happen.

In this case, the explanation to which you linked, while helpful to a degree, didn't satisfy me. Why does relative distance matter? And more important (to me), relative distance isn't a characteristic of the lens. There has to be a characteristic of the lens itself that explains the appearance of compression. And the characteristic that differentiates lenses of different focal lengths is AOV. So I found it nagging at me: why does a difference in AOV create this effect? I finally had to sit down and draw examples to explain it to myself. Those are the diagrams I posted.

The relative distances cited in the link to which you posted are a consequence of AOV. So is what George labeled magnification--which I would call differences in relative magnification.

But to go back to where I started in this thread: a great image.

Best,

Dan

Neither wide angle "distortion" or long focal length "compression" are particularly good terms to use to describe what is happening. The underling cause is that human vision and our resulting perception of what looks normal is based on our own angle of view which is about 50 to 60 degrees. Eye movement will widen it to about 70 degrees and our preferred zone down to about 30 deg. Any lens angle greater or less than these angles may to some extent make the image look unnatural. It is not due to any trick or fault of the optics. It is just a result of our perception.

The above is also why 70-90mm (FF) lenses are good for portraiture. They match the angle of out preferred vision which is used in face recognition (initial study of face on typical introduction/conversation distance). I think the current terms have been arrived at in an ad hoc manner and better more specific terms would be helpful.

[george013]

Neither wide angle "distortion" or long focal length "compression" are particularly good terms to use to describe what is happening. The underling cause is that human vision and our resulting perception of what looks normal is based on our own angle of view which is about 50 to 60 degrees. Eye movement will widen it to about 70 degrees and our preferred zone down to about 30 deg. Any lens angle greater or less than these angles may to some extent make the image look unnatural. It is not due to any trick or fault of the optics. It is just a result of our perception.

The above is also why 70-90mm (FF) lenses are good for portraiture. They match the angle of out preferred vision which is used in face recognition (initial study of face on typical introduction/conversation distance). I think the current terms have been arrived at in an ad hoc manner and better more specific terms would be helpful.

No, it's a mathematical issue. With a very short distance to the subject, wa lens, the differences in magnification in depth are big. The larger that distance, the less the differences in magnification will become. This can be archived with a wa lens too. It's mainly dependent on the distance. There's always a difference, the question is only what you think is not acceptable.

I can create pano's with an aov of 180 deg. Completely natural looking. something of 3 rows of 11 pictures.


I think I showed these pictures before. This one is taken at 18mm DX.


And this one with 170mm DX. It's a separate photo but I can crop it out of the other photo. Here you can see what's meant with compressing or flatening. The differences in magnification is getting less, so less feeling of that third dimension.



A portrait lens is a result of acceptable "wa distortion" and a practical distance to the model.

Let me know if you can see the pictures. They are from a Google archive.

George