29

In general there are no secrets to lens design. Everything important, all breakthroughs, etc., are shared publicly or semi-privately with modification through patents, conferences, papers, etc. There are "temporary secrets" where something is closely guarded until it is published: For example, we have completed the final piece of the puzzle in free-form ...


23

There are two hard limits on how fast a lens can be: The first is a thermodynamic limit. If you could make a lens arbitrarily fast, then you could point it to the sun and use it to heat your sensor (not a good idea). If you then get your sensor hotter than the surface of the Sun, you are violating the second law of thermodynamics. This sets a hard limit at f/...


22

Yes, it is possible and a "Lens Turret" is one way of accomplishing it. It was very common to use a "Lens Turret" on film and movie cameras in the 1950's before zoom lenses became practical. Source: Bolex 16mm Source: Macro lens turret Source: 8mm film camera with lens turret


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 focal length is the distance from the (theoretical) center of the lens to the image plane. On the large format camera, there's a lot more camera between the lens and the film. The lenses are also often relatively simple — there's no need for a focusing mechanism in the lens itself, for example. @osullic gives the example of the Schneider PC TS Makro-...


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 ...


20

There is a clear difference in intent and design philosophy. The Canon 50 f/1.2L is a bokeh machine, offering not only shallower depth of field (due to the ultra wide f/1.2 aperture) but also a smoother background blur on account of the decision to leave a certain amount of spherical aberration in the design. It's a lens with character and a distinct look, ...


19

Single lenses with real thickness refract the different wavelengths of light at slightly different angles. For anywhere other than the exact optical center of the lens, this causes a prismatic effect that gets more noticeable as one moves further from the optical center of the lens. This is what we refer to as chromatic aberration. It isn't the only optical ...


18

Your observations of the lens leads you to both a correct, and incorrect, conclusion. Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly should be. Only the front element is anywhere near 10 cm diameter. Where the iris mechanism is in the lens barrel, the diameter is substantially smaller than 10 ...


17

Short answer: The digital photography revolution has pretty much eliminated any idea of a standard display size and viewing distance. Depth of Field calculations are always based on several variables including the display size and viewing distance. First, a word about what depth-of-field is and is not: In a way, depth-of-field is an illusion. There is only ...


16

First, let's get a bit of nomenclature out of the way: EF-S means a lens in the Canon EOS system that will only work on cameras with APS-C or smaller sensors (if any smaller than APS-C EOS sensors are ever created). They can not be used on cameras with larger 35mm film sized "full frame" sensors. 55-250mm is the focal length of the lens. On an APS-...


15

Bokeh is formed by many points of light spreading out, passing through the aperture and being projected onto the image plane as series of overlapping discs (assuming a round aperture). This can lead to harsh textures and effects when there are strong contrasts in the out of focus parts of an image, especially when lenses feature overcorrected spherical ...


15

It just means you push / pull the front of the lens to zoom, rather than twisting a zoom ring. The mechanism is simpler to design/manufacturer but is less precise and has a reputation for sucking dust into the lens due to the large change in volume when zooming.


15

First: Sony doesn't necessarily disagree with Nikon's claim. It's just that Sony designed their 'E' mount with a throat diameter of 46.1 millimeters at a time when it appeared it would be an APS-C only mount for the NEX series of compact mirrorless ILCs. Sony later made the decision to move into full frame territory using the all-electronic 'E' mount, ...


14

I think the use of the term 83X while true, is most misleading. The Coolpix does a remarkable job when it comes to its optical range which is 83X. This is actually called the zoom range. The math is: The power of the camera’s lens is adjustable from 4.3mm wide-angle to 357mm telephoto that’s 357 ÷ 4.3 = 83. In other words the span of the zoom is 83X.To ...


14

There is no direct relationship between Telephoto focal lengths and Macro capability. There are some fixed focal length prime lenses that fall into the Telephoto range in terms of focal length and also are capable of close enough focus to be Macro lenses. But a lens doesn't have to be a telephoto lens to have Macro capability and there are many Macro lenses ...


13

From the "Recommended For" tab of the Tamron web page for that lens: Tamron Di-II lenses are engineered expressly for digital SLR cameras with image sensors commonly referred to as APS-C, measuring approximately 24mm x 16mm. This means the image circle is sized for the smaller APS-C sensor, and is too small for a full-frame camera like the 6D. This is ...


13

Historically, the unit of exposure was a doubling or halving of the exposing energy. This is the origin of the f/stop. Initially, this adjustment was made by inserting a thin metal plate with a circular hole, into a slit in the lens barrel. The photographer had a series of these metal slides called Waterhouse Stops after John Waterhouse circa 1858. The ...


13

The opposite of a fisheye is a rectilinear lens. You probably did not find one because your definition is wrong. Distortion of a fisheye lenses is not barrel distortion, it is that a different projection or mapping is obtained by design. Angles are usually preserved but not straight lines, unless they pass through the center of the frame. A rectilinear ...


12

Here is the description from Nikon's own web site: D-Type NIKKOR Lenses A D-type lens relays subject-to-camera-distance information to Nikon D-SLRs that feature 3D Color Matrix Metering (all versions), 3D Matrix Metering, 3D Multi-Sensor Balanced Fill-Flash and i-TTL Balanced Fill-Flash. Many D-Type lenses have an aperture control ring and can be used on ...


11

Yes it is technically possible. The question is whether this will have practically same limitations as a zoom or not. There are two objectives from Leica with stepped focal length adjustment: the 16-18-21mm Tri-Elmar and Tri-Elmar 28-35-50 and a Canon zoom objective with built-in teleconverter which would do what you want if placed inside a fixed focal ...


11

whether lens could be repaired without loosing big amount of money? Whatever the damage, repairing the 18-55 almost certainly isn't worth it. People upgrading sell them for not very much, just get a new one.


10

There are a few potential advantages, for example: The really long focus throw on some cine lenses is very nice for accurate manual focus. A stepless aperture enables some extremely specific special effects (e.g. simulated apodization) by way of changing aperture during an exposure. None of them I would call "significant" when compared to the added weight ...


10

Not including a DOF scale can make the lens barrel smaller and allows the use of different focusing mechanisms such as linear motors instead of the traditional helicoid (which is where the DOF scale used to be printed). It is less important to have the scale as you can get instant feedback on what is and isn't in focus with a digital camera, and differences ...


10

STF stands for "Smooth Transition Focus", and is a Sony-specific* term indicating that the lens includes an apodization filter to create smooth bokeh (out-of-focus blur) — and smooth bokeh is generally considered to be the best bokeh. So, you'd generally use it for non-studio portraiture or in other cases where that blur is an important artistic element. ...


10

Because most interchangeable lens cameras typically use larger-format sensors than 1/2.3"-format. The close-focusing capability of most small-sensored compacts comes from the fact that small sensors use proportionately short lenses. Very short lenses (those under 10mm focal lengths) tend to have very deep depth of field--deep enough to have close focus ...


10

The distinct "look" it provides. In addition to adding more pleasing bokeh blur to background objects near the edges of the frame, it also allows objects on the periphery that are in the same plane as the subject when that plane is perpendicular to the optical axis of the lens to be blurred as well, although not to the same degree that background items can. ...


10

It is possible and Canon has done it, although in a different way than you'd expect - their EF 200-400mm f/4L IS USM Extender 1.4x. It's a zoom lens with a built-in teleconverter that could be toggled (instead of unmounting the lens and mounting it again with a teleconverter like you would normally do). This, however, reduces the amount of light you have ...


10

A fisheye lens isn't designed to have extreme barrel distortion -- the distortion is the result of trying to map a sphere onto a plane. A regular lens follows the equation image height = focal length * tan(half angle of view). Tangent blows up near 90 degrees, so you cannot map a 180 degree field of view onto a plane. Near this, equal changes in angle map ...


10

This is simply where the market is converging to at the moment. The typical kit lens is still 18-55mm on an APS-C sensor but most people find wider angle more useful, so some manufacturers made a few lens that start at 16mm. Olympus still sells many of their entry-level cameras with a 14-42mm which is equivalent to 28mm, while the 18-55mm mentioned earlier ...


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