Quantifying a Picture: Calculating D & theta

In summary, the conversation is discussing how to quantify and find the values of D and theta in a given picture. The suggested solution involves using similar triangles and known quantities of the camera and film height to find D and then using the tangent function to find theta. However, it is noted that the value of theta will change depending on the value of D.
  • #1
jcpwn2004
49
0

Homework Statement



I'm supposed to quantify the picture below and show how to find D and the angle theta.

http://img10.imageshack.us/img10/7079/labg.jpg

Homework Equations



none i can think of

The Attempt at a Solution



I guess S and H are the same. I really can't think of a way to find D or theta though. Don't you need D to find theta?
 
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  • #2
Opening of the camera, object and image from two similar triangles. Their sides are proportional.
Length of the camera and film height are known quantities. From that find D and theta.
 
  • #3
rl.bhat said:
Opening of the camera, object and image from two similar triangles. Their sides are proportional.
Length of the camera and film height are known quantities. From that find D and theta.

Alright so my camera's length is 14.6cm and the film height is 5cm. Even if I know they're proportional how can i find D?
 
  • #4
To find D you must know H. As your guess S need no be equal to H.
 
  • #5
rl.bhat said:
To find D you must know H. As your guess S need no be equal to H.

Alright well we aren't given H so how would I theoretically get H?

Would I do 5/14.6 = h/d? And after I find D how would i find theta?
 
  • #6
You can find theta. 2.5/14.6 = tan(theta/2). But that won't give you D unless you know the size of the object.
 
  • #7
rl.bhat said:
You can find theta. 2.5/14.6 = tan(theta/2). But that won't give you D unless you know the size of the object.

Alright but even if i know my H, isn't the theta different? let's say my H is 7.5 cm. I got theta/2 for the left triangle to be 4.86 degrees. Where do I go from there though?
 
  • #8
Yes. For same H theta depends on D. When D changes size of the image also changes.
Theta will be unique only for one setting.
 

FAQ: Quantifying a Picture: Calculating D & theta

What is D and theta?

D and theta are measurements used to quantify an image's features. D represents the distance between objects in an image, while theta represents the angle of rotation between objects.

How are D and theta calculated?

D and theta are calculated using mathematical algorithms that analyze the pixels in an image. These algorithms determine the distances and angles between objects based on their pixel coordinates.

Why is it important to quantify an image?

Quantifying an image allows for a more objective analysis of its features. It can provide valuable information about the size, shape, and orientation of objects in the image, which can be useful in various fields such as medicine, biology, and engineering.

What factors can affect the accuracy of D and theta calculations?

The accuracy of D and theta calculations can be affected by factors such as image resolution, noise, and the complexity of the image. It is important to carefully select and optimize the algorithms used to ensure accurate results.

Can D and theta be used to compare images?

Yes, D and theta can be used to quantitatively compare images and identify similarities or differences in their features. This can be particularly useful in tasks such as image recognition and pattern matching.

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