101

Rockwell presents his opinion as fact even when it is actually a contested opinion. Yes, professionals use 24-70 lenses. They aren't for every situation, but there are plenty where they are great go to lenses. The Canon 24-70 f/2.8 II, for example, is one of the most popular zoom lenses ever. I do wedding photography and during the reception, the 24-70 ...


41

If you shoot from the same position with both lenses, then taking the 35mm lens and cropping it to the same angle of view of the 50mm lens will give you pretty much the same picture, other than the differences in optical quality between the two lenses and the resolution lost to cropping. But even if you were to shoot with the same lens, shooting from a ...


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 ...


31

You are not required to purchase any lenses at all. It all depends on your photography needs and what you're willing to spend your money on. Regarding range, the superzoom 18-200 mm covers the same range as the other four lenses you mentioned. All of the other lenses focal ranges are parts of the large range of the 18-200 mm lens. The 18-200 can surely ...


31

The answer to this question revolves around explaining how zoom lenses function because you are correct in your observation: As you zoom to higher and higher magnifications the image dims unless somehow compensation is applied. Suppose you zoom from 25mm to 50mm, should the working diameter of the aperture remain unchanged, image brightness would suffer a 4x ...


27

Do convex lenses make parallel light rays of different wavelength converge to different points? Yes. The separation of different wavelengths of light is called dispersion. Different wavelengths of light refract at different angles because the refractive index of a transparent medium is frequency dependent. We often describe different materials, such as ...


24

Oh, it is worse than that. Many lenses designed for still photography exhibit focus breathing, where the angle of view varies over the range of distances the lens can focus. Normally this isn't an issue for still photography, but lenses designed for cine use (video) will normally try to minimize focus breathing. Lenses, at their heart, are mass produced ...


23

Firstly, distance is used for focal length because it measures the distance between the plane of the lens and the point at which refracted rays meet at a point, when the incident rays were parallel. Below is a simple diagram of a single lens. Note: This is only for convex lenses. The use of millimetres is simply because it is a scale appropriate for this ...


21

The entrance pupil is limited by the diameter of the front element, and that is what usually restricts the maximum aperture of telephoto zoom lenses - not the physical size of the aperture diaphragm. The physical size of the diaphragm is only part of what determines the maximum aperture, expressed as an f-number, of a lens. Magnification between the front ...


21

The mirror lens design resolves two key optical problems: All lenses suffer from chromatic aberration. This is color fringing due to the failure of the lens to refract (bend inward) all colors of light accurately. In a conventional lens, this is accomplished by sandwiching two or more lenses, of different powers using different recipes for the glass. The ...


21

Light from a far distance object, like a star, arrive at the lens, as parallel rays. As they transverse the lens, they are forced to change their direction. They bend inward, we call this refraction from the Latin to bend backwards. We can draw a trace of these rays; they trace out the shape of a cone. What we find is, the apex of the violet cone of light ...


20

The effect is called field curvature. A good discussion comes from Nikon. It is a lens aberration that can reduce the resolution of the lens when coupled with a flat sensor. In the old days, the film could be bent a little to try to follow the image plane and reduce the effect, but our sensors today are rigid. It can be reduced with lens design.


20

The proof is in the pudding – the focal lengths are not exactly the same as yours, but the differences are obvious...


19

Let's start with lenses at the same location, and then address the moving the longer lens farther away to get the same field of view. Lenses at the same location The 50mm f/1.4 lens has an effective aperture that's twice the diameter, and four times the area, of the 25mm f/1.4 lens. The 50mm will, therefore, collect four times as much light (four times as ...


18

The easiest way to think of this is with an image. When you use a wider lens, you have to be closer to your subject, which emphasizes the distance between the subject and background by making the background smaller. In contrast, if the camera is far away from the subject, you'll have to zoom much farther to get the same size of subject relative to the ...


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 the engineers are designing a lens, the 70-300 is a target focal range they design to, but it's not important that they hit it exactly as long as it covers the advertised range. As they tweak the lens characteristics to get a suitably sharp and quality image for the target cost, the actual focal lengths may change slightly. Eventually, when everything ...


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 ...


15

Because saying you have a .0002485 furlong lens is a lot more cumbersome than calling the same lens "50 mm". Focal lengths of common lenses happen to be in the range so that integer mm works well. The numbers don't get rediculously large or small, and 1 mm is less than the accuracy we usually care about, but not overly so. In other words, it's a ...


15

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. Its replacement, the EF 50mm f/1.8 STM is about $125. It ...


15

It depends entirely on how the lens was designed, there is no general formula or way of determining the minimum focus distance. Lenses of the same focal length can have completely different minimum focus distances depending on which factors the lens designer chose to optimise.


15

Published focal length is rounded in some degree, normally to nearest 5 or 10, or in some short cases, to the nearest 1. More precision would not be realistic, because the marked focal length is only applicable to focus at infinity. The focal length (defined as the distance to the image plane) changes and becomes longer for any focused distance less than ...


15

When I started photography, this one took me ages to figure out, because people tend to explain it with a lot of math, or in a way that makes sense once you already grasp the principle but not before. How does crop factor affect perspective? It doesn't. Not at all, in the slightest. The only way you change perspective is to move the camera. Changing ...


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

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 ...


14

Whilst it is used to express the field of view, the focal length of a lens is an actual distance - the distance at which a focussed image is formed from parallel rays. As such any unit of distance could be used - if you look at really old lenses you'll often find it stated in inches. Most of the world has now adopted the metric system so that is what is used ...


14

The f-stop is more directly relevant to photographers because it normalizes out the focal length. It then gives you a measure of how bright the image will be on the sensor relative to the scene brightness. For example, if a scene is well exposed with a 50 mm lens at f/8 and 1/200 second, then it will be well exposed with any other lens at f/8 and 1/200 ...


14

Thanks to my schwifty skills in Inkscape, the rotation here is slightly off but the following shows exactly what you're comparing. These are the fields of view of a Nikon 35mm (inner) and a Nikon 50mm (outer). So even when you're getting approximately the same stuff in the frame, the 35mm is much wider, focal distances are slightly different too. If you're ...


14

No photoshop necessary for that background. That's simply what happens when shooting a telephoto lens, f/2.8 or larger, and having the subject closer to the camera and much further from the background. I don't see anything inherently special about the tone. We'd expect cool tones from the shade and that's what we've got. The nice part, imo, is the contrast ...


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 ...


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