Perspective quiz

Discussion in 'Digital Photography' started by Ruahrc, Mar 2, 2012.

?

Which photos have the same perspective?

  1. A=B and C=D but A and B are not the same as C or D

    1 vote(s)
    3.3%
  2. A=C and B=D, but A and C are not the same as B or D

    2 vote(s)
    6.7%
  3. A=B, C and D are different than each other and A or B

    17 vote(s)
    56.7%
  4. A=B=C=D (all photos are the same)

    8 vote(s)
    26.7%
  5. None of the above (write your answer below)

    2 vote(s)
    6.7%
  1. Ruahrc, Mar 2, 2012
    Last edited: Mar 2, 2012

    Ruahrc macrumors 65816

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    #1
    I saw this quiz put up on a different forum, and found it to be very educational. I thought I would reproduce it here.

    Assume you take the following four photographs:

    A) Full-frame camera with 300mm lens
    B) 1.5x crop camera with 200mm lens, shot from the same distance as A
    C) Full Frame camera with 200mm lens taken at 2/3rds the distance as photo A
    D) 1.5x crop camera with 300mm lens, taken at 3/2 the distance as photo A

    For the purposes of this quiz, ignore any depth-of-field issues. Assume adequate depth of field for both subject and background in all cases.

    Now, the quiz- which photo(s) have the same perspective?

    Edit: if you know the answer, please do not write the explanation, simply vote your choice. I will put the answer up after a few days of voting.
     
  2. Phrasikleia, Mar 2, 2012
    Last edited: Mar 2, 2012

    Phrasikleia macrumors 601

    Phrasikleia

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    #2
    [Edit: answer removed by special request. Don't want to spoil the fun! ;) ]
     
  3. Designer Dale macrumors 68040

    Designer Dale

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    #3
    I guessed the right answer but the math confused me, so I didn't vote..:eek:

    Dale
     
  4. NeGRit0 macrumors 6502a

    NeGRit0

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    #4
    :confused: When you reveal the answer, will you say why, or do the math or whatever is involved? Cause I have no clue where to even begin with this.
     
  5. fitshaced macrumors 68000

    fitshaced

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    #5
    I'm either wrong or the only one who got it right :p
     
  6. Ruahrc thread starter macrumors 65816

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    Jun 9, 2009
    #6
    I will put up the answer on wednesday. Get your votes in now!
     
  7. ChrisA macrumors G4

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    Jan 5, 2006
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    Redondo Beach, California
    #7
    This is to easy. The only way to get it wrong is to not know the meaning of "perspective".

    For example if a teacher asks a student for the area of a 2x3 rectangle and he says "10". It means the student has confused "area" with "perimeter". It's a vocabulary, not a math error. You would need to make an analogous mistake to miss this quiz.

    What you are doing here is testing people to see if they know the meaning of the word "perspective".
     
  8. Designer Dale macrumors 68040

    Designer Dale

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    #8
    Math is only part of the answer. If you understand the relationship between sensor size and focal length, intuition gives the right answer.

    Dale
     
  9. Phrasikleia macrumors 601

    Phrasikleia

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    #9
    You don't even need to understand that much, but I won't give away the answer.
     
  10. Ruahrc thread starter macrumors 65816

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    #10
    Okay guys here's the answer. The correct choice was option #3, Photos A and B share the same perspective, and Photos C and D are both different from each other and A or B. Congrats to the ~61% (as of this writing) of you who got it right!

    Here's the explanation, but first to address ChrisA's comment, which IMHO is really appropriate to what I am about to say.

    He is of course totally right. If you know what perspective is, then the answer was easy, and there is absolutely no math involved. The definition of photographic perspective could be defined as the size relationship between different objects in the scene.

    The only thing that matters in the original question is the part about the shooting distance. Perspective only matters on the camera to subject distance. Anything shot from the same distance will have the same perspective, regardless of the sensor format, focal length, whatever.

    The specific situations and numbers described in each choice was a bit of a red herring, intended to deceive. I constructed it such that in every photo, the size of your subject would remain constant. You get (more or less) equivalent shots of your subject in each case, but the size relationship between your subject and the background has changed in both C and D.

    Now, why do we care? Imagine the following conversation:

    Photog A: "Man that zoom lens looks great, but it's so heavy/expensive!"
    Photog B: "Yeah I know. I can't afford it so I got this prime lens instead. It gets the same job done, I just zoom with my feet."

    Sounds familiar, right? We hear it a lot, here on the DP forum and elsewhere too. Note the bolded part. "I just zoom with my feet". The thing is, this statement is not true. From what we have learned above, when you move your shooting position by "zooming with your feet", you are not changing the zoom (framing), but rather the perspective.

    The difference is subtle, but critically important. And to further answer ChrisA's comment that this was a test about who knows the definition of perspective, that was part of the point. It would appear that 40% of us don't know the definition of perspective as it applies to photography. But once you learn, it will (hopefully) lead to better shooting, because now when you look through your viewfinder and don't like what you see, you can identify if the problem is with perspective (the solution to which is to adjust your shooting position), or framing (the solution to which is to adjust the focal length of your lens) and correct accordingly.

    Think of the relationship between focal length and perspective sort of like the relationship between aperture, shutter speed, and ISO. Each factor will affect the final exposure, but you would elect to alter one over the other in specific situations, because each affects the exposure in a specific way. For example you would not increase shutter speed to increase the exposure of action, because you would introduce motion blur into your shot. Instead you would open the aperture more, or increase ISO.

    Focal length and shooting distance work the same way with regards to photographic composition. You may see a composition you don't like, but you have to know which one to change in order to adjust the composition to what you prefer. Focal length and shooting position are not interchangeable.

    In order to have full control over the composition of your shot, you need to:
    a) stand in the right place to get the intended perspective
    b) select the correct focal length to give the intended framing

    Hopefully you enjoyed this exercise, understand the concept of perspective now, and can start applying it to your shots. When framing your compositions, thinking about the concept of perspective, how it is not related to focal length, and how you can use it to enhance your images.

    If you don't believe me, or want a great shooting exercise, try taking some test shots yourself. Take shots with different focal lengths but standing in the same place. See how you are changing the field of view or framing, but not the perspective of the objects in the scene. I wanted to shoot some test photos to illustrate this, but I have been far too busy. The wikipedia page on perspective distortion, however, has some very illustrative examples: http://en.wikipedia.org/wiki/Perspective_distortion_(photography)#Examples

    Anyhow, hope you enjoyed! If you got the answer right, congrats! If you didn't, I hope you learned something!

    Ruahrc
     
  11. Designer Dale macrumors 68040

    Designer Dale

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    #11
    If you look up a lens review in DPreview, they have image samples that demonstrate this.

    Dale
     
  12. Phrasikleia macrumors 601

    Phrasikleia

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    #12
    They do? I can't imagine why. The principle has no relevance in a lens review. Perhaps you're confusing the issue of crop factor/field of view with perspective? Do you have a link?

    Here's the short description: Perspective is determined solely by the distance between the subject and the camera--any camera with any lens. All else is irrelevant.
     

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