33

You're right that the angle of view of the iPhone camera is a little bit wider than a 35mm lens on a full-frame film camera. Up until this point, you're not really confused. But the part after that, about the small room and zoom and distance — definitely confused. :) "Zoom" means the ability to change the field of view — it isn't magnification. See What is ...


22

It depends on what you're asking exactly, if you're asking what focal length provides the same magnification as the naked eye (as in you hold your hand out infront of the camera and look through the viewfinder, your hand appears the same size as it would without the camera), then the answer depends on sensor size and viewfinder magnification, but the answer ...


17

That depends on the sensor size of the camera. "A lens is considered to be a "normal lens", in terms of its angle of view on a camera, when its focal length is approximately equal to the diagonal dimension of the film format or image sensor format.[4] The resulting diagonal angle of view of about 53 degrees is often said to approximate the angle ...


16

I don't understand why anyone would buy it Optical quality, build quality, and overall durability. The EF 17-40mm f/4L USM is an "L series" lens -- essentially professional grade, while the EF-S 18-55mm f/3.5-5.6 is a consumer grade "kit" lens. L lenses are made with better materials, better designs, and more features. They're weather sealed to keep out ...


16

When a field of view is described as 120°, that refers to the total angle. So, 60° to the left of center and 60° to the right. Most camera lenses show a very restricted subset of the field of view perceived by the human eye and vision system. It is probably the case that the system is measured across the diagonal from corner-to-corner of a rectangle, ...


15

Provided you keep focus distance, ISO, aperture & shutter speed the same, and you zoom your 18-55mm lens to exactly the same focal length as the 50mm prime (which wont be exactly 50mm) then the images will very extremely similar when viewed as a whole. On closer inspection you will see differences in the level of distortion, sharpness, contrast and ...


14

Whether a lens is an EF or an EF-S lens, the actual focal length is always used. There are certain technical reasons why this is so, but the simplest is that a lens' focal length is defined as the distance from the film plane needed when the lens is focused at infinity to cast point light sources as a single point on the film plane. This doesn't change with ...


14

When you look through a viewfinder, a lens at around 50mm focal length will show objects at the same size as when you look at something with your eyes. You could test this by looking through the viewfinder with one eye, and looking next to it with the other eye. When you close one of your eyes, you will notice that your sight does not change, regarding the ...


14

The calculators you posted are for fairly standard, rectilinear lenses. This means you can use the Pinhole camera model to calculate the information. This graphic fairly well shows what is going on: On the horizontal axis you see f. This is the focal length of the lens. Then, the arrow labeled Y1 is the image plane (where the sensor sits). If the sensor ...


13

They're measuring the first on a crop-sensor camera and the second on a full-frame; specifically for a Canon APS-C sensor, 15mm x 1.6 = 24mm. Canon does this in general when referring to EF-S vs. EF lenses; see for example How can a 24-70mm and a 10-22mm both be "wide angle" lenses?, which has the same effective answer. The relationship between ...


13

The principle of physics behind this behaviour is nothing more than the thin lens formula: 1/o + 1/i = 1/f Where o is the object distance (distance from lens to subject), i is the image distance (distance from lens to sensor), and f is the focal length. For a very large object distance (approaching infinity) the 1/o term drops to zero, hence: 1/i = 1/f i ...


13

Assuming both lenses are being used on the same size sensor, the area in the frame with a 600mm lens should be one quarter the area in the frame with a 300mm lens. The linear dimensions should change by a factor of two, the areal dimensions should change by a factor of the square of two, which is four. If you are not seeing the same object shot from the ...


13

Answer with an image : the guy on the left represents your (vertical) field of view and its image on the sensor is inverted on the right (in other terms, the guy fills your entire image). As you can see in this illustration, the rays of light going through the center of your lens aren't concerned by your aperture settings, they are still getting in, no ...


12

According to this the iPhone SE has an 29mm-equivalent lens, so on a Fuji with a 23.6x15.6 sensor (Fuji XT-3)(crop factor 1.53) you need a 29/1.53=19mm lens for the same field of view.


11

There's really no such thing as a 'theoretically perfect' rectilinear lens with a perfectly flat field of focus and no geometric distortion. Even a lens that perfectly matches its blueprint would not demonstrate such perfection. A theoretical thin lens demonstrates field curvature as well as several other aberrations. Various corrective elements used to ...


10

Your intuition is right. To validate it, we can dig into basic high-school geometry. Although a camera lens is actually a complex lens made from many elements, conceptually and mathematically for most practical purposes, this reduces to an ideal, where you can imagine a pinhole exactly a distance from the sensor equal to the focal length. Light might fall ...


9

It depends on the lens design, a wide angle retrofocus lens is mainly limited by the front element size, the lens barrel places a hard limit on the range of angles that can see the entrance pupil. As an example of this mounting a filter on an ultrwide can reduce the size of the image circle. This is why separate designs exist for APS-c DSLRs, but mostly for ...


9

The only way to simulate with a camera and lens what our brain does when we look at distant objects is to use a much longer focal length. This, of course, also reduces the field of view in a dramatic way. If you want a foreground object to remain the same size in your photo while increasing the size of objects in the background you can back away from the ...


8

The human eye is a very complicated organ, which only sees clearly for an angle of approx 2 degrees of the field of vision. The eye moves constantly focusing on different areas & the brain receives signals & converts these signals into the complete view that we see. Our angle of view would be approximately 180 degrees (forward facing) and ...


8

The actual focal length is 4mm. The 35mm equivalent tells you what focal length you'd need to use with a 35mm film/sensor to achieve the same result, but it doesn't have much optical sense. Assuming the sensor width is 4.54mm: FOV = 2*atan(.5*4.54mm/4mm) FOV ~ 1.03235913 rad FOV ~ 59.1498211 deg That is roughly 40% of a human's field of view.


8

The confusion here comes in entirely because "35mm" is the common name for the 135 film format, also known as "full frame" — and it happens to be the focal length of the lens you are looking at. The specification is: 35mm equivalent focal length when used with APS-C sensor camera 52,5 And you are reading this as: Equivalent focal length = 35mm ...


7

The crop factor applies to all lenses shot on camera with a smaller sensor. They look the same because 70mm is 70mm on both lenses, and they're both cropped in exactly the same way. I think the answers to Is an EF 50mm f/1.4 the same as 50mm with an EF-S lens on a Canon 550D? should help. Also check out my answer to What is Angle of View?, because the ...


7

There are several considerations that could be affecting the results of your test: Focal lengths for most lenses are measured with the lens focused to infinity. Depending on the design of the lens the field of view may change significantly when focused at much closer distances. An example: Nikon's 70-200mm f/2.8 VR set at 200mm and focused at MFD gives an ...


7

A “normal” lens is one that is not telephoto and not wide-angle. This works out be a lens with a focal length about equal to the diagonal measure of the format frame. The Advanced Photo System (APS) frame size is approximately 16mm height by 24mm length. The diagonal measure of this rectangle is about 30mm. Such a lash-up delivers the following angles of ...


6

The actual focal length of the lens is usually measured along with the crop factor of the sensor. Cell phones, needless to say, have a huge crop factor. For example, the Samsung Galaxy SIII and iPhone 4 are a 7.6x crop. So, if you have a 5mm lens on one of those, you're looking at an equivalent full frame focal length of 38mm. That's wide, but not that wide.....


6

Field-of-view is the angular extent shown through the lens. For fixed-lens cameras, and all web-cams that I know of, the field-of-view is normally stated relative to sensor-size. This is very reasonable since the lens is fixed and cannot server on something else. While this sounds like numbers could be compared, there several reasons why not: Field-of-...


6

Adjusting the focal length of your lens (ie, optical "zooming") will impact the depth of field of your image. This will change how much of the scene is in focus. It will also subtly change aspect of the distortion of the image in order to project it on to a rectangular surface as lenses don't quite perfectly project their image and the exact variations ...


6

Either can be the right answer, depending on circumstances. There is no one right or even usually right answer. Moving in will change the relative perspective of objects. Things that are a little closer will appear disproportionately bigger, whereas from further back this size difference due to distance difference is reduced. A great example is getting ...


6

I think you'll be best off with the 24-70mm zoom. You're going to want a smaller aperture than f/1.8 anyway -- at 10 feet, the 85mm set to f/1.8 will give you only a few inches of depth of field. Your example images have a lot more DOF than that. Using the zoom will give you a lot more flexibility with respect to focal length, and also let you change focal ...


6

Here are some possible sources of error: Manufacturer stated focal lengths are often rounded favorably or sometimes plain exaggerated (e.g. a 200mm might well be only 190mm). Focal lengths are also stated at infinity focus, lenses change focal length when focusing (though it is more common for a lens to get wider as you focus closer not narrower). Sensor ...


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