APS-C lens mm are correct

[ahab1372]

My 8-15 and 200 have the same perspective? If I cropped the 8-15 to the same framing of the 200 it's the same perspective?

An ef 35mm lens on a on a crop is not the same perspective as a 56mm on full frame.

Yes, yes and yes. Distance only makes the perspective. The focal length and the sensor size determine the framing for a given distance from a subject.

As to the focal length equivalents: It is really a function of the sensor size, not of the lens. EF or EF-S doesn't matter. People/companies talk about the equivalent length to be able to compare how a lens on a certain camera feels in regards to the FOV, but they should really do so when talking about the camera, not the lens.

 

[KyleSTL]

The thing is, a 50mm image cropped down to the perspective of an 85mm lens will have the same perspective and compresion as the same image taken with an 85mm lens.

So if I frame a photo the same with my 24mm lens and then with my 200 lens, the photos will have the same perspective? Perspective, like the mm length, is part of the lens, not the sensor behind it.

No. Perspective is determined by the distance from the camera to the subject. Focal length, sensor size, cropping - none affect perspective.

If you frame the same subject with a 24mm vs. a 200mm lens, you've changed the distance and that's what changes the perspective. If you took the two shots from the same distance, the perspective would be the same, but the framing would be different. If you then cropped the 24mm shot to the framing of the 200mm shot, both the perspective and the framing would be the same.

My 8-15 and 200 have the same perspective? If I cropped the 8-15 to the same framing of the 200 it's the same perspective?

An ef 35mm lens on a on a crop is not the same perspective as a 56mm on full frame.

An ef 35mm lens on a on a crop is not the same perspective as a 56mm on full frame.
From a framing standpoint, so long as the camera and all objects within the frame have not moved, the images will have identical perspective, with different depths of field (assuming the same aperture). EDIT: Although at macro-like distances, that may change. Neuro might have to chime in on that.

My 8-15 and 200 have the same perspective? If I cropped the 8-15 to the same framing of the 200 it's the same perspective?
Yes, after applying distortion correction they will have identical perspective.

 

[PackLight]

The horse is dead but we go on;

As Perspective would apply to a picture;

"the technique or process of representing on a plane or curved surface the spatial relation of objects as they might appear to the eye; specifically : representation in a drawing or painting of parallel lines as converging in order to give the illusion of depth and distance"

Perspective as it would apply to you;

"the appearance to the eye of objects in respect to their relative distance and positions"

Thank you Merriam Webster

So would a picture taken at the same distance with two diffrent focal lengths have the same perspctive.
The wider lens would have contained in it, the ability to have the same perspective (illusion of depth and distance) as the long lens. However the picture with the long lens will not be able to give the same perspecitve (illusion of depth and distance) as the wide lens.

Choose your definitions and I believe most arugments so far can be made to fit.

 

[Daniel Flather]

But an ef 35mm lens projects the same image behind it regardless of the sensor behind it. If I take a head shot with an ef 35mm lens, then change to a 200mm lens, back up to the same framing, they are different images. The 35mm lens' subject will have a bigger nose. So, an ef 50mm on a crop is different than an ef 80mm on FF. Maybe something was lost in the ether, but 50mm is not 80mm.

 

[Sporgon]

But an ef 35mm lens projects the same image behind it regardless of the sensor behind it. If I take a head shot with an ef 35mm lens, then change to a 200mm lens, back up to the same framing, they are different images. The 35mm lens' subject will have a bigger nose. So, an ef 50mm on a crop is different than an ef 80mm on FF. Maybe something was lost in the ether, but 50mm is not 80mm.

In this example perspective would indeed be different because your distance would be (very) different. Take the shot with 35mm from the same position as your 200, then crop 35mm in post to the same framing - perspective will be identical.

 

[TexPhoto]

Noses are generally big in wide angle portraits, Because the camera is so much closer to the subject, not because of the use of a wide angle lens. A headshot with an 85mm looks right, and a 28mm headshot looks wrong because you would not/could not take these photos at the same distance.

 

[Sporgon]

Noses are generally big in wide angle portraits, Because the camera is so much closer to the subject, not because of the use of a wide angle lens. A headshot with an 85mm looks right, and a 28mm headshot looks wrong because you would not/could not take these photos at the same distance.

+1

 

[Chuck Alaimo]

Noses are generally big in wide angle portraits, Because the camera is so much closer to the subject, not because of the use of a wide angle lens. A headshot with an 85mm looks right, and a 28mm headshot looks wrong because you would not/could not take these photos at the same distance.

doesn't lens curvature play into this too? anything on the wide end has that bend to it, even if its at a distance right? Isn't that due to the curvature of the lens, which is much more pronounced on wide angle lenses? (also why wide angle tilt shifts are both specialized and pricey because they have comples systems inside to reduce curvature?)

 

[PackLight]

But an ef 35mm lens projects the same image behind it regardless of the sensor behind it. If I take a head shot with an ef 35mm lens, then change to a 200mm lens, back up to the same framing, they are different images. The 35mm lens' subject will have a bigger nose. So, an ef 50mm on a crop is different than an ef 80mm on FF. Maybe something was lost in the ether, but 50mm is not 80mm.

They would most likely be diffrent because of the depth of the background may appear diffrently, but maybe not. Since a picture is only creating an illusion of depth, if all things in the picture were of the same framing and the pictures were identical in appearance, then they would have the same perspective. Although you shot them from a diffrent perspective.
You are dealing with two diffrent things, what the picture shows and what your physical location is.
You can say your perspective changed, but it is still possible for the picture to have the same perspective.

 

[Loswr]

My 8-15 and 200 have the same perspective? If I cropped the 8-15 to the same framing of the 200 it's the same perspective?

An ef 35mm lens on a on a crop is not the same perspective as a 56mm on full frame.

Yes and yes. So does a 1200mm lens. People incorrectly believe that the perspective is different because the distances at which such focal lengths are different. But it's the distance that determines the perspective.

But an ef 35mm lens projects the same image behind it regardless of the sensor behind it. If I take a head shot with an ef 35mm lens, then change to a 200mm lens, back up to the same framing, they are different images.

You changed the distance. Take the head shot with 200mm, then stay out and use the 35mm lens. Crop the latter to the same framing as at 200mm, you'll have the same perspective.

 

[PackLight]

My 8-15 and 200 have the same perspective? If I cropped the 8-15 to the same framing of the 200 it's the same perspective?

An ef 35mm lens on a on a crop is not the same perspective as a 56mm on full frame.

Yes and yes. So does a 1200mm lens. People incorrectly believe that the perspective is different because the distances at which such focal lengths are different. But it's the distance that determines the perspective.

But an ef 35mm lens projects the same image behind it regardless of the sensor behind it. If I take a head shot with an ef 35mm lens, then change to a 200mm lens, back up to the same framing, they are different images.

You changed the distance. Take the head shot with 200mm, then stay out and use the 35mm lens. Crop the latter to the same framing as at 200mm, you'll have the same perspective.

Or shoot a perfectly flat wall with the 35mm at 10', and the 200mm picture would have the exact same perspective at 57.14'. However you will not have the same perspective.

 

[Sporgon]

I think that to help clear this up a bit it is worth mentioning that in the practical application a 200mm does have a more compressed perspective than say a 20mm, because you have to be using the 200mm from much further away to achieve equal framing, that is assuming you are using the same sensor size !!

 

[PackLight]

I think that to help clear this up a bit it is worth mentioning that in the practical application a 200mm does have a more compressed perspective than say a 20mm, because you have to be using the 200mm from much further away to achieve equal framing, that is assuming you are using the same sensor size !!

Excellent

Now we can start a discussion on compression and how it affects ff vs crop framing and crop factor. Really though it might just part of the explanation for the diffrence in perspective.

 

[Videoshooter]

But an ef 35mm lens projects the same image behind it regardless of the sensor behind it. If I take a head shot with an ef 35mm lens, then change to a 200mm lens, back up to the same framing, they are different images. The 35mm lens' subject will have a bigger nose. So, an ef 50mm on a crop is different than an ef 80mm on FF. Maybe something was lost in the ether, but 50mm is not 80mm.

That is because you changed the distance to subject in your example. If you stand in the same spot and take a photo of the same subject, the perspective will be identical with any lens, save for any distortion introduced by the lens (ie field curvature in a fisheye lens). Of course the framing will be very different, though cropping to the same framing will overcome this (though will not result in the best picture quality).

Apply this to a 50mm and 85mm lens, taking a portrait, and you get a perfect example of why we use equivalent FOV's. Put the 85mm lens on the FF camera, and take a photo. Now put your 50mm lens on that same camera and take another photo. The perspective will be exactly the same, but the framing is different - you have a whole bunch of extra area around the edges of the image. But, if you crop that 2nd photo to the same framing, it will have the exact same perspective as the first photo. Now, pair your 50mm lens with a APS-C camera. It will give the same photo (in terms of perspective and framing) as in photo 2, although it is already cropped straight out of the camera. The FOV will be the same (give or take a few mm), and the perspective will be the same, as the photo taken with the 85mm on the FF camera.

 

[Daniel Flather]

My 8-15 and 200 have the same perspective? If I cropped the 8-15 to the same framing of the 200 it's the same perspective?

An ef 35mm lens on a on a crop is not the same perspective as a 56mm on full frame.

Yes and yes. So does a 1200mm lens. People incorrectly believe that the perspective is different because the distances at which such focal lengths are different. But it's the distance that determines the perspective.

But an ef 35mm lens projects the same image behind it regardless of the sensor behind it. If I take a head shot with an ef 35mm lens, then change to a 200mm lens, back up to the same framing, they are different images.

You changed the distance. Take the head shot with 200mm, then stay out and use the 35mm lens. Crop the latter to the same framing as at 200mm, you'll have the same perspective.

Backing up is the ether.

 

[Daniel Flather]

Having a new baby keeping me up at night is clouding my thinking.


EDIT: Does CR compress photos when I attach them to a thread? The attached photo look great on my iMac and iPad. I think my monitor at work here is getting old (it's a $199 special from day one).

 

[Sporgon]

Daniel, I have to admire your tenacity !

Are you sure you didn't sneak a little further back for the APS-C shot - it is a little wider framed but this might be the focal length of the lens.

If nothing else the two pictures are a good example of how the modern 85L has improved contrast control and tones over the film era 50 1.4, which tends to have more abrupt highlights - but that's another topic altogether.

I assume you are showing the toy in the APS picture is smaller in relation to the child. If you were only a foot or so further away this would explain it. However, if you were not....................maybe we can open a complete new can of worms! I'm very short sighted, and without my glasses on things that are out of focus appear much bigger than when viewed in focus if I put my glasses back on. Could it be that on a very fast lens like the 85 1.2, the out of focus element looks bigger due to the blur ? As there is less focus blur with the 50, this could explain it.

 

[Sporgon]

Nice example privatebydesign. I presume the lady in the photo is trying to explain this over the phone to one of the doubters............. ;D

 

[KyleSTL]

Re. Perspective and focal length.

As a picture is worth a thousand words.

First comparison, 17mm lens and 200mm lens both on same camera from same place and both f8, these are the full images.

Second comparison, same images with the 17mm cropped to match the framing of the 200mm.

As you will see, whilst the dof is very different, the perspective (the size of the various elements within the frame with regards each other) stays constant. The woman, the trees and the jumps are the same size in both examples when the 17mm is cropped.

This is also a very graphic demonstration of why smaller sensors have deeper dof, the second image crop is effectively a small sensor shot with an 11 times crop factor, which still puts it way bigger than P&S's and phone cameras.

Not true, below are crop factors of various sensor sizes:

FF - 1x
APS-C (Canon) - 1.6x
m4/3 - 2x
Nikon 1 - 2.7x
1/1.7" - 4.6x
1/2.5" - 6.0x
1/3" - 7.2x
1/4" - 10.8x

I believe the iPhone sensor is in the ballpark of 1/3", for example.

 

[sandymandy]

I cant understand why this topic always gets discussed so much? a 50mm lens is a 50mm lens

A photo taken from the same position with a FF camera will look like it was taken with a 50mm lens. A photo taken with an APS-C will look like it was taken with an 80mm lens.

Thats all what the crop factor is about and its so easy and clear to understand, why gotta discuss so much?

Its just common to say "equivalent of blabla on APS-C". Maybe its just the wrong term used but so what? everybody knows what it supposed to mean.