It's a bird

by Vian Esterhuizen

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1

Aperture is a bit of a misnomer; a hold-over from simpler times and simpler lens designs. What matters is the entrance pupil, or the apparent size of the aperture as viewed through the front (business end) of the lens. With a simple lens design (a double-Gauss or Tessar, for instance), the physical aperture and the entrance pupil are approximately the same ...


0

It seems to be real. If you are shooting the moon with a 800mm lens, the image of the moon will be approximatly 8mm in diameter. If Paco used an APSC sensor, the dimensions of the image frame make sense. Thomas Mueller


1

There is a relationship between the focal length and the size of the sensor. For a larger sensor, the same focal length gives a smaller angle of view thus for an "equivalent" field of view you need to multiply the focal length by the same factor as the sensor size. Before the onset of digital cameras, by far the most popular film format was commonly called ...


0

The farther the subject, the smaller the part of the field of view it will cover. Therefore the picture of the object will be composed of less pixels which means that the image will effectively be less sharp.


-4

Most of the answers above are misleading. A Canon APC sensor has a crop factor of 1.6 which effectively changes the focal length by 1.6, therefore a 100mm lens has an effective length of 160mm. A simple exercise is to use the same lens on two difference bodies, one full frame and one cropped and you will instantly see the difference. You cannot use a full ...


0

If a sensor diagonal approximates focal length, this suggests a rectilinear image with vanishing point perspective. Consider one vertical edge, and project a triangular surface from that edge to the the centerpoint of the image. Do the same from the opposite edge to the centerpoint. This presents something like a tunnel view of single vanishing point ...


11

It's most likely a commercial decision based upon cost and performance. Let's take your prime at f/1.2 example. Canon makes a number of 50mm lenses. The EF 50mm f/1.8 II is about $100. It has 6 elements in 5 groups, 5 aperture blades and a plastic barrel. It takes a 52mm filter and weighs 130g. The EF 50mm f/1.4 USM is about $350. It has 7 elements in 6 ...


6

I think the answer you seek is in terms of "angular magnification" as it is used with binoculars. In the world of binoculars there is a number that is referred to as "magnification". For example a 10×45 set would offer 10× magnification (and a 45mmØ ocular). This means that the subject appears 10 times closer than with the unaided eye. This ...


4

Zoom is zoom and magnification is magnification. Apples and oranges. Optical Magnification is the ratio between the apparent size of an object (or its size in an image) and its true size. It is calculated with the following formula: M = (di - f) / f with di as found in the following image: Zoom is the ratio of focal length as you mention it in ...


0

A 3x is not a mesure. It is a proportion, a ratio of the minimum and the maximum. Taking the minimum focal lenght as a base you start making multiplications. But this proportions have no meaning regarding the size of the picture either becouse it does not take into acount the sensor size. In your first example, the ratio 3x dosen't imply that the photo is ...



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