Hot answers tagged focal-length
57
In layman's terms (assuming a layman who knows some very basic geometry), imagine your nose as the apex of a triangle. The left side of the triangle is the left edge of your peripheral vision, and the right side is the right edge. The horizontal angle of view is simply the angle between those edges, and the vertical angle of view is the same thing for up and ...
43
No, it is not a bad thing. It is not really "good" or "bad" in any sense. Its simply a different format than full-frame, which is different than medium format, etc. There are pros and cons to each. The smaller APS-C style "cropped" sensors do have some effects on lens focal length due to their field of view, and that can be beneficial or detrimental, ...
32
The "times zoom" notation is simply the big number divided by the small one, so the examples you give are correct. "3x zoom" simply means the longest focal length is three times the shortest.
This number really isn't very useful, though. On point and shoot cameras, it became popular because the starting focal length was generally about the same across all ...
26
Well, I hate to break it to you, but you can't exactly emulate your eyes. There's a few reasons, let me explain.
Humans see much higher resolution in the central fovia (center part of our eyes) than near the edges. Cameras have uniform resolution everywhere.
The dynamic range is handled differently between cameras and humans. I can't explain it, but a ...
24
You can find detailed definition of Crop Factor in Wikipedia there is also a good explanation on dpreview site where it is referred to as "Focal Length Multiplier"
In short in your scenario if you have one full frame camera (crop factor 1) with 80mm lens and a second camera with 1.6 crop factor and 50mm when taking photos from the same position you will get ...
24
The eye moves
I'd like to add to the answer of @Pearsonartphoto, that human eyes do not see a still scene, instead they scan it continuously, adjusting their “aperture” and refocusing as they scan it. So thanks to this scanning process we can perceive:
the higher dynamic range,
an infinite depth of field,
a wider scene as a whole,
much more detail than a ...
23
Focal length is focal length, regardless of sensor size or whether the lens is a zoom lens. If you have tried your kit lens at 35mm and 50mm, then the framing will pretty much be the same with prime lenses of those focal lengths. Prime lenses will offer a couple things your zoom lens does not, however.
For one, they should offer better quality, as prime ...
21
A range of focal lengths indicates a zoom lens. There are two major classes of lenses. Primes, or primary lenses, have a single focal length. They tend to be higher quality, as there can be fewer lens elements, and fewer moving element groups. One exception to this rule is super telephoto prime lenses, particularly faster lenses (f/2.8), which are some of ...
20
It depends a bit on the kind of portrait you want to take, but there are two key things you want to do regardless:
Not distort your subject. If you're too close to the subject things get warped, so whilst using your wide-angle and getting right up to the nose of your subject may produce an amusing result, it's seldom what you want (but as with all things, ...
19
If you know or can estimate the distances, use this equation:
Focal Length = Sensor Dimension * Distance / Scene Dimension
Where you match the dimension of the sensor and the scene. e.g:
Focal Length = Sensor Width * Distance / Scene Width
Note that the the advertised size of your sensor is typically not the width, height, or even the diagonal, which ...
19
I conducted a large number of accurate measurements on a 50 mm lens on a Pentax K7.
The bottom line, Shake reduction/VR/IS (call it what you will) is very beneficial.
A link to the full study is on www.scribd.com (pdf)
The graph below shows the main results.
Motion blur, in pixels, was used as a measure of image stabilisation. The tests show that motion blur ...
19
Focal length is a measure of the lens's ability to bend light. As such this figure doesn't change when you use a smaller sensor. What actually happens when you use a smaller sensor is that your field of view narrows. Field of view is dependant both on the focal length and the format (the size of your film or sensor). The ubiquity of 35mm film among amateur ...
19
Parfocal lens is a lens which remains in focus when you change the focal length. The non-parfocal lens is called varifocal.
It is very convenient to focus at the maximum focal length and change the zoom afterwards. It is more important for manual-focus lens because a well functioning auto-focus can quickly adjust the lens to keep it in focus.
19
Those are done using the compression of a telephoto lens. Longer lenses will magnify the subject, so will make the moon look bigger. It will also make buildings and other objects bigger, but by moving yourself further away from those earthbound objects you can reduce them back to a smaller size. But you can't really get further away from the moon, so it ...
18
There is a fairly simple explanation here: http://www.paragon-press.com/lens/lenchart.htm
To summarize from that site:
Simply put, the focal length of a lens
is the distance from the lens to the
sensor, when focused on a subject at
infinity. To focus on something closer
than infinity, the lens is moved
farther away from the sensor.
Focal ...
18
The lens does not actually turn into a different focal length, since that's a real, physical property of the optics that can't be changed without more optics. So from that point of view, the answer is a definitive no.
However, when you get to the question of is it effectively the same in terms of magnification, the answer is "pretty much, given some ...
18
The flattening or compression effect is not caused by a particular kind of lens, it applies to all lens in the same way. Actually, this property of lenses applies to our own eyes as well. The factor that affects flattening is the distance from the camera to the subjects.
Consider the following exercise:
Place two friends 1 meter away from each other. ...
18
There is NO difference at ALL because the physical aperture has not changed.
The Fuji Finepix S4000 simulates a small aperture using an ND filter. When you stop-down the ND filter slides into the optical path. The Aperture written in the EXIF data is adjusted to reflect the transmittance of the ND filter, but note that since the size of the opening has not ...
17
The most obvious change that images shot with different focal length while keeping the main subject size intact will show is perspective. By using a longer focal length (and, by necessity, increasing the distance between the camera and the main subject), you will get a more "compact" perspective, with the background appearing to be closer to the subject than ...
16
Focal length is a measure how the lens focusses the light into a point. When light enters a 50mm prime lens, the light converges into a point the camera sensor after 50mm.
In addition the focal length determines the magnification of the object you photograph. A long lens (e.g. 300mm) magnifies the images a lot (useful for birding) while a short (wide angle) ...
16
Using the 1.6 crop factor certainly works, but it might be interesting to work it out from first principles, too. The "normal" focal length is generally considered to be close to the diagonal of the image area (sensor, film, whatever). For 35mm film and "full frame" digital, this is about 43mm - 50mm is the closest common focal length for reasons that are ...
16
Someone referred me once to Exposure Plot. This is a free Windows utility which is very simple. It shows you graphs of different parameters, one of them being focal-length.
If you already use image management application like Lightroom or Bibble Pro, then you can also usually see that data in the filter interface.
For Lightroom for example, you need to ...
16
Capturing an image exactly as your eyes see it? No problem, but it's not all in-camera, you'll have to do some work in post. And it almost certainly not what you really want.
First, you'll need a circular fisheye lens that vignettes badly with which to take the picture(s). (You'll actually need several pictures and a viewing system with built-in eye ...
16
There's a specification on (d)SLR bodies called viewfinder magnification; this refers to how large an object appears in the viewfinder when a 50mm lens is mounted and focused at infinity.
On mid-range DSLRs, which typically have around 0.95x magnification, an object will appear to be life-sized at 52.6mm. With entry-level DSLRs, you might have around 0.8x ...
15
Aperture is unaffected.
The field of view becomes 35mm x (the crop factor of your sensor), which is 1.5 in the case of Nikon DX cameras (It's also 1.5 for Pentax and Sony, 1.6 for Canon and 2 for Panasonic & Olympus).
So your 35mm Nikon lens has a 35mm x 1.5 = 52.5mm "35mm equivalent" field of view.
Note that the perspective doesn't change, just the ...
15
A prime lens still has a moving focus element allowing you to change the focal plane through the range of the focusing ring's range. A prime is a lens that has a fixed focal length (100mm, 50mm etc) as opposed to a zoom which will allow you to cover a range of focal lengths (70mm-200mm for example).
A fixed focus lens cannot change its focal plane, but this ...
15
A normal lens is one who's focal-length is equal to the diagonal of the sensor or film.
This is said to give a natural perspective similar to that of a single human eye.
On a full-frame DSLR, it is usually a 50mm lens. On a cropped-sensor (APS-C) DSLR, a normal lens falls around 35mm but from 30 to 55mm, it would still be considered normal. For Four-Thirds ...
14
The only other factor you need is the height of the object in real life (otherwise you could be photographing a model which is much closer to the camera).
The maths isn't actually that complex, the ratio of the size of the object on the sensor and the size of the object in real life is the same as the ratio between the focal length and distance to the ...
14
What you are seeing is the effect of viewfinder magnification. For whatever reason (probably simply to make the numbers sound better), this spec is usually given for a 50mm lens, even on APS-C. The Canon 60D, for example, has a 0.95x magnification with a 50mm lens focused at infinity. And that's why around 50mm gives you the magic double-vision effect. ...
Only top voted, non community-wiki answers of a minimum length are eligible
