81

There are many characteristics which make better lenses better. The basic goal of a lens is to render an ideal replica of the framed scene, but because of the limitations of the real world, that's physically difficult. Lenses inevitably introduce optical artifacts not present in the scene itself. So, an important aspect is minimization of artifacts. Good ...


65

Yes. There is development in four areas: computer design, material science, features, and finally a category I'm going to call "not better just different". Computer Design Lens design has always been a mix of art and science. In the first part of the previous century, art was clearly primary (even for scientific lens designers). Now, lens design software ...


37

Broadly speaking wide aperture lenses are easier to design the longer the focal length. The reason that you don't see any 400mm f/1.4 lenses is due to manufacturing difficulties, e.g. keeping dispersion low while producing elements of the size required for such apertures. It's worth restating that the designation f/1.4 means that the size of the aperture ...


37

Theoretically one can do anything. It just takes more glass — and correspondingly, size, weight, and cost. A 300mm f/1.2 lens would need an apparent aperture of 250mm — which is almost 10 inches in diameter. And for extra complication, that needs to project an image circle which fits through the lens mount, which is probably around 2 inches. So that's a ...


36

There is no simple relationship between the physical length of the lens and its focal length. For example, a retrofocus wide angle is generally longer than its focal length, while a telephoto lens is shorter than its focal length. Inside a zoom, you have several lens groups that move independently. The focal length of the zoom depends on the relative ...


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 ...


24

Fundamentally a telephoto design is used to make a lens body shorter than it's focal length, for practical reasons [what if your 18-300 ultrazoom was actually 30cm long?], a retrofocus design is the opposite, and makes a lens longer  than it's focal length in order to leave space for the mirror on an SLR. You can tell if your lens is a retrofocus or ...


22

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 ...


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 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, ...


20

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 ...


18

Given that you have explicitly disqualified fungus and dust inside the lens, then the answer is no. A lens will not "naturally" lose sharpness with age. Glass is glass. It is a fixed medium, and assuming a 100 year old lens is in good condition without any extraneous wear and tear like fungus, dust, or a strong enough jolt to misalign one of the internal ...


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

Speaking from the world of amateur astronomy, there's quite a bit of development happening with lenses. Eyepieces and objectives are all using new, exotic glass and computing resources to design well-corrected refractive devices. New glass mixes don't come along very often and the proper effort to better mate the shapes and characteristics still requires ...


16

You ask whether a lens can lose sharpness over time, but then go on to say: Please note, I am not talking about general wear and tear, or dust inside the lenses, nor am I talking about fungus in the lens. Which are exactly the reasons lenses lose sharpness over time. So the answer is no - once you exclude all the factors which causes lenses to lose ...


16

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 ...


16

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, ...


15

The pupil (aperture opening) area is proportional to the square of the focal length (at the same f-stop). So 105mm being about twice the focal length of the 50mm, it would need 4x the pupil (area) to be f/1.2. In other words f/1.2, or any f-stop, doesn't correspond to a fixed diameter - it increases for larger focal lengths. That also assumes both lenses ...


15

In my experience, IF lenses frequently autofocus faster, because there is less mass to drive back and forth. For non-zoom lenses, internal focusing probably means that the bellows effect (in which air is sucked into the lens) is minimised since the outside of the lens probably won't move during focusing. That means the interior of your camera doesn't get ...


15

I'd expect that virtually all lens design and analysis these days is done with optical design software like Zemax or Code V. Unfortunately, these products are priced for people and companies that make a (substantial) living working in the field. However, I have come across an optical design tool for Windows called OSLO that offers a free version with ...


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.


14

ED means extra-low dispersion, referring to a type of glass that to disperses light less than ordinary glass. Dispersion means breaking up light into its constituent colors due to bending different wavelengths of light to different degrees. Because uncorrected dispersion can cause chromatic aberration, ED glass elements can help reduce purple fringing and ...


14

Your question raises an interesting point as there are some lenses you really can't make, for example you'll never have a 50 f/0.2 as physics simply wont allow it. However a 300 f/1.2 is merely an engineering problem (building a barrel to hold and move the giant lens elements required), after all a 300 f/2.0 lens was made and sold commercially by Nikon, ...


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

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 ...


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