Does perspective change when you change the focal length?
Aug 20, 2018 18:47:06 #
Some of us will understand this without needing to do this simple experiment. If you are not sure and you have an FX camera, do the following:
Look for a scene with objects close to and far from the camera.
Use any lens and aim it at a scene in FX mode. Take a picture.
Without changing the lens focal length or the camera's position, switch to DX mode and take a second picture.
Did the relative locations of any of the surviving portions of the scene change? They will not! That's because the perspective did not change.
When switching from FX to DX the effective focal length gets increased by 50% (Nikon) or 60% (Canon). The field of view changes but the perspective does not.
Increasing the focal length is just like cropping an image.
The only way to change the perspective for objects at different distances from the camera is to move the camera.
Look for a scene with objects close to and far from the camera.
Use any lens and aim it at a scene in FX mode. Take a picture.
Without changing the lens focal length or the camera's position, switch to DX mode and take a second picture.
Did the relative locations of any of the surviving portions of the scene change? They will not! That's because the perspective did not change.
When switching from FX to DX the effective focal length gets increased by 50% (Nikon) or 60% (Canon). The field of view changes but the perspective does not.
Increasing the focal length is just like cropping an image.
The only way to change the perspective for objects at different distances from the camera is to move the camera.
Aug 20, 2018 18:59:27 #
selmslie wrote:
Some of us will understand this without needing to... (show quote)
Because in your example, you did not change focal length, if you change nothing but from ff to dx mode, the focal length stays the same, hence no change in perspective!
If you actually do change the focal length, yes, the perspective does change!
Aug 20, 2018 19:13:56 #
speters wrote:
Look, Scotty, a new playmate in your sandbox (soapbox?)!...If you actually do change the focal length, yes, the perspective does change!
While you are educating people about the physics, please don't neglect the conversations about lens compression with telephoto or the properties of an ultra-wide angle lens re distortion. For people who actually take pictures, those are the creative aspects of focal length and lens choices.
Aug 20, 2018 19:21:18 #
speters wrote:
Because in your example, you did not change focal length, if you change nothing but from ff to dx mode, the focal length stays the same, hence no change in perspective!
If you actually do change the focal length, yes, the perspective does change!
If you actually do change the focal length, yes, the perspective does change!
NO sir. Never. Ever. The ONLY thing that changes perspective is to move. Simply changing focal length will not change perspective. It cannot, since your relationship with the objects around you has not changed. If you are going to make me prove it, I will.
Aug 20, 2018 19:52:25 #
Aug 20, 2018 19:56:26 #
speters wrote:
Because in your example, you did not change focal length, if you change nothing but from ff to dx mode, the focal length stays the same, hence no change in perspective!
If you actually do change the focal length, yes, the perspective does change!
If you actually do change the focal length, yes, the perspective does change!
Uh, no. You can change the focal length and the perspective will not change. Anytime you move the camera, the perspective changes. You have that exactly backwards.
Aug 20, 2018 20:00:44 #
selmslie wrote:
When switching from FX to DX the effective focal length gets increased by 50% (Nikon) or 60% (Canon).
When switching from FX to DX the effective focal length gets increased by 50% (Nikon) or 60% (Canon).
Exactly which Canon camera can you select APS-C crop mode in?
Aug 20, 2018 20:05:16 #
speters wrote:
Because in your example, you did not change focal length, if you change nothing but from ff to dx mode, the focal length stays the same, hence no change in perspective!
If you actually do change the focal length, yes, the perspective does change!
If you actually do change the focal length, yes, the perspective does change!
You seem skeptical. Why not repeat the experiment at progressively longer focal lengths.
Start with 50mm at FX. At DX the effective focal length is 75mm.
Set your camera back to FX and your zoom to about 75mm (Nikon) or 80 (Canon). Take the FX and DX images and compare them.
Now set the focal length to about 115 (Nikon) or 130 (Canon) and repeat the FX and DX comparison.
If you continue to repeat the progression until you reach your maximum focal length, you will continue to record the same perspective.
Your perspective is synonymous with "where am I standing" - your viewpoint. If you don't change your viewpoint, you don't change your perspective.
Aug 20, 2018 20:07:50 #
Linda From Maine wrote:
... While you are educating people about the physics, please don't neglect the conversations about ...
Perspective is not physics. It's not rocket science. It's simple geometry.
Aug 20, 2018 20:12:57 #
MT Shooter wrote:
Exactly which Canon camera can you select APS-C crop mode in?
I'm not a Canon user. None of them offers a choice of crops? Guess they didn't think of that.
If you can't perform the experiment as defined, just change the focal length by a constant factor. It will be clear that changing the focal length only crops the scene.
As others with even more experience than mine have explained, the only way to change the perspective is by moving the camera.
Aug 20, 2018 20:23:28 #
selmslie wrote:
I'm not a Canon user. None of them offers a choice of crops? Guess they didn't think of that.
If you can't perform the experiment as defined, just change the focal length by a constant factor. It will be clear that changing the focal length only crops the scene.
As others with even more experience than mine have explained, the only way to change the perspective is by moving the camera.
If you can't perform the experiment as defined, just change the focal length by a constant factor. It will be clear that changing the focal length only crops the scene.
As others with even more experience than mine have explained, the only way to change the perspective is by moving the camera.
No they do not. Primarily because they intentionally cripple their crop sensor lenses so that there is no way to even mount them on their full frame bodies.
Unlike Nikon, Pentax, and Sony who make both FF and crop sensor cameras and allow for full interchangeability between their lenses and bodies.
Aug 20, 2018 20:26:41 #
MT Shooter wrote:
No they do not. Primarily because they intentionally cripple their crop sensor lenses so that there is no way to even mount them on their full frame bodies.
Unlike Nikon, Pentax, and Sony who make both FF and crop sensor cameras and allow for full interchangeability between their lenses and bodies.
Unlike Nikon, Pentax, and Sony who make both FF and crop sensor cameras and allow for full interchangeability between their lenses and bodies.
Other manufacturers offer a choice of crops (even if it's not DX) with their full-frame cameras.
I'm glad I don't use Canon.
Aug 20, 2018 20:27:52 #
selmslie wrote:
Some of us will understand this without needing to... (show quote)
WRONG. Using Captain C's own photos I did what he and selmslie advocated, merely cropping the shorter focal lengths to match the tele, in this case the far tower. The ACTUAL photos prove them wrong. The first photo here overlaps the 105 and 200mm photos of Catpain C. The far tower is perfectly aligned. But notice that everything else shows a different perspective. To demonstrate that even more clearly, the second photo shows some of the perspective lines, red for the 200mm, blue for the 105mm. They clearly are different. It would be much worse comparing a 28mm with a 200 mm.
I really don't care, but would like to warn new photographers that different lenses will distort the shot, e.g., especially close things in a wide angle and distant things in a tele.
Finished here, as the evidence has been presented, and each can decide, or do the experiment themselves.
Aug 20, 2018 20:39:54 #
artBob wrote:
WRONG. Using Captain C's own photos I did what he and selmslie advocated ...
If you saw a change in perspective, you did it wrong.
artBob wrote:
I really don't care, but would like to warn new photographers that different lenses will distort the shot, e.g., especially close things in a wide angle and distant things in a tele.
Really? You seem to care quite a lot or you would not spend so much effort trying to discredit all of the others who clearly understand the subject better than you do.
Of course, extremely wide angle and fisheye lenses exhibit distortion, especially if you get very close to the subject. But that's not the point. You can't take an image with a telephoto that looks distorted by a very wide angle lens because the subject is close to the camera. The telephoto probably can't focus that closely.
You wrote me in a PM earlier, "Think I know perspective? Dear man, I TAUGHT it for 40 years." I feel sorry for your students. You actually don't understand the subject.
Aug 20, 2018 20:52:51 #
In addition to many other sources I cited elsewhere, add Cambridge In Colour to your study list, "Many will say that focal length also determines the perspective of an image, but strictly speaking, perspective only changes with one's location relative to their subject." See UNDERSTANDING CAMERA LENSES for more explanations on perspective and focal length.
Also Focal Length, Angle of View & Perspective in Photography | Sony US, "The difference in apparent perspective is actually a result of how far you are from your subject."
And Understanding Perspective and Focal Length, "In photography, there’s a common misconception that focal length determines the perspective of an image, but the only thing that really determines perspective is where you put the camera."
I could go on but you should be getting the drift by now.
Also Focal Length, Angle of View & Perspective in Photography | Sony US, "The difference in apparent perspective is actually a result of how far you are from your subject."
And Understanding Perspective and Focal Length, "In photography, there’s a common misconception that focal length determines the perspective of an image, but the only thing that really determines perspective is where you put the camera."
I could go on but you should be getting the drift by now.
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