AF = Auto Focus. The idea is that the camera does the focusing itself (the word auto comes from Greek "self").
Aperture = (also written as f/) = The metal blades inside a camera lens that regulates how much light passes through the lens. On a f/1.4 lens, the lens is "fully open" at f/1.4. At f/2.0 the aperture inside the lens make the hole through the lens smaller so only half the amount of light at f/1.4 passes through. For each f/-stop (like f/4.0 - f/5.6 - f/8.0 - f/11 - f/16) you halve the light. The f/ fundamentally means "f divided with": The aperture of the lens is basically the focal length divided with the f/-stop = size of the hole (50mm divided with f/2.0 = the hole is 25 mm in diameter, or 50mm at f/1.4 is 50mm divided with 1.4 = the hole throug is 36mm. ). ORIGIN: Late Middle English : from Latin apertura, from apert- ‘opened,’ from aperire ‘to open’.
The aperture blades inside the lens is clearly visible in this photo.
ASPH = stands for "aspheric design".
Most lenses have a spherical design - that is, the radius
of curvature is constant. These are easy to manufacture by
grinding while "spinning" the glass. This design
however restricts the number of optical corrections that can
be made to the design to render the most realistic image possible.
ASPH lenses, however, involve usually 1 element that does
*not* have a constant radius of curvature. These elements
can be made by 1) expensive manual grinding, 2) molded plastic,
or 3) Leica's patented "press" process, where the element
is pressed into an aspherical ("non-spherical")
shape. This design allows Leica to introduce corrections
into compact lens designs that weren't possible before. Practically,
the lens performs "better" (up to interpretation)
due to increased correction of the image, in a package not
significantly bigger than the spherical version. Sphere: ORIGIN Middle English : from Old French espere, from late Latin sphera, earlier sphaera, from Greek sphaira "ball".
|Normal spheric lens (grinded)
||ASPH (note the shape of the glass as result of pressing rather than grinding)
Bokeh = The visual quality of the out-of-focus areas of a photographic image, especially as rendered by a particular lens: It's a matter of taste and usually photographers discuss a 'nice' or 'pleasant' bokeh (the out-of-focus area is always unsharp why the quality discussed is if one likes the way it renders or not by a particular lens). The closer you get to something, the 'more' bokeh' you get (in that the focus becomes less for the background and foreground at close distances than at long distances). ORIGIN from Japanese 'bo-ke' which mean 'fuzzines' or 'blur.'.
Bokeh: The visual quality of the out-of-focus areas of a photographic image. Photo at Bar del Fico in Rome. Leica TL2 with Leica 35mm Summilux-TL ASPH f/1.4. © 2017 Thorsten Overgaard.
Camera - is today’s short name for Camera Obscura (meaning “a dark room”). Camera means Chambre and was used only as a Latin or alien word, actually only for Spanish soldiers’ rooms, until popularized in connection with photography in 1727: “Camera Obscura”. In 1793 the slang term “camera” was used by Sterne Tr. Shandy: “Will make drawings of you in the camera” and by Foster (1878), “The eye is a camera”. Camera Obscura was described by Iraqi scientist Ibn-al-Haytham in his book, “Book of Optics” (1021) and by Leonardo da Vinci in 1500; popularized and made widely known in 1589 by Baptista Porta when he mentioned the principle in his book “Natural Magic”. Johannes Kepler mentions Camera Obscura in 1604.
Camera = chambre (room), Obscura = dark (or cover).
Contrast - The degree of difference between tones in a picture. Latin contra- ‘against’ + stare ‘stand.’
||Lens distortion looks like this. The lines are not straight. Our eye uses distortion correction. Lens designers can design lenses so they have very little distortion, or they can make less complicated lens designs and "fix" the distortion in software.
Distortion = In photo optics/lenses: When straight lines in a scene don't remain straight because of optical aberration.
Lens designers can correct for distortion to a degree so the whole image field is perfect corrected and all lines remain straight. In modern lens design many designs rely on Software Distortion Correction (SDC).
The eye adjusts for distortion so we always see vertical and horizontal lines straight when we look at things. Even when you get new prescription glasses (if you use such), you will often experience distortion in your new glasses. After a few days they eyes have adjusted for the glasses and the distortion you saw to begin with is now gone. Software Distortion Correction (SDC) is far behind what the human eye can perform of adjustments. (Also see my definition on Perspective for more on the eye and optics)
DNG = Digital Negative, an open standard developed by Adobe. It is a single file that contains the raw image data from the sensor of the camera as well as date, time, GPS, focal length, settings, etc.
The alternative is a RAW file + XLM file where the RAW file contains the image information and the XML contains the rest of information about where, how and when the picture was taken.
A Camera Raw profile (that is specific for that camera) in the computer helps the software program, for example Adobe Lightroom, to translate the RAW data into the image.
DOF = Depth of Field. This is how much of the image will be in focus. Shallow DOF is a generally used term in photography that refer to lenses with very narrow focus tolerance (which can be used to do selective focus; for artistic reasons or for specific storytelling, like making irrelevant subjects in the foreground and background blurry so only the subjects of essence are in focus and catches the viewers eye).
Depth of Field: The trees and buildings in the background is very much out of focus, and the handrail you can see behind, in the bottom of this photo is slightly out of focus. Princess Joy Villa. Leica TL2 with Leica 80mm Summilux-R f/1.4. © 2017 Thorsten Overgaard.
Depth Of Field scale from Fujifilm.
Depth - Distance between front and back. Distance from viewer and object.
Elmarit = Refers to the maximum lens aperture - here f2.8 . The name is obviously derived from the earlier (and slower) "Elmar" designation. Not every f/2.8 lens is called an "Elmarit" though, the most obvious current exception being the 50mm f2.8 Elmar-M collapsible lens which for nostalgia and marketing reasons has kept the original 1930's Elmar name (the 50mm f3.5 collapsible Elmar, manufactured 1930-59, was one of Leica's most famous and popular lenses).
Focus, in - Sharp and clear in appearance. Focus - “The burning point (of a lens or mirror)”. In Latin the word focus meant fireplace or hearth. The word was probably first employed outside of its Latin literal use as “the burning point of a lens or mirror” in optics, and then came to mean any central point. The German astronomer Johannes Kepler first recorded the word in this sense in 1604.
||A 28 mm lens has a 74° viewing angle
Focal length = (also written as f-) = On the Leica 35mm Summilux-TL ASPH f/1.4 it is 35mm and originally referred to the distance from the sensor (or film in older days) to the center of focus inside the lens. Nobody uses that measurement, except those who construct lenses! For users of lenses, focal length refers to how wide the lens sees. The viewing angle, which is often given in for example 90° viewing angle for a 21mm lens, 74° viewing angle for a 28mm lens, 6° viewing angle for a 400mm lens, etc.
Each human eye individually has anywhere from a 120° to 200° angle of view, but focuses only in the center.
The Leica TL2 has a APS-C sensor, which "crops" the traditional focal lengths with 1.5X, reducing the angle of view of view with 1.5X.
Summicron = Refers to the maximum lens aperture - here f/2.0 . There are many guesses how this name came about, a popular one being that the "summi" came from "summit" (summit means the highest point of a hill or mountain; the highest attainable level of achievement) while the "cron" came from "chroma" (ie. for colour). Not so: The name (Summi)cron was used because the lens used Crown glass for the first time, which Leitz bought from Chance Brothers in England. The first batch of lenses were named Summikron (Crown = Krone in Deutsch). The Summi(cron) is a development from the orignal Summar (the 50mm f2.0 lens anno 1933).
Summilux = Refers to the maximum lens aperture - normally f1.4 , "-lux" added for "light" (ie. the enhanced light gathering abilities). In the Leica Q the lens is a Summilux even it is a f/1.7 and not f/1.4.
Leica = A compound word derived from " (Lei)tz" and "(ca)mera". Apparently they were originally going to use "LECA", but another camera company already used a similar name in France, so they inserted the 'i' to prevent any confusion.
Lens - A piece of glass or similarly transparent material (like water or plastic). It has a shape so that it can direct light rays. The word “Lens” is used both for single piece of glass as well as a camera lens with several lenses that works together. From ‘lentil’ because similar in shape.
Lens hood = A tube or ring attached to the front of a camera lens to prevent unwanted light from reaching the lens and sensor. ORIGIN Old English hod; related to Dutch hoed, German Hut 'hat,' also to hat.
Light = Tiny particles called photons that behaves like both waves and particles. Light makes objects visible by reflecting off of them, and in photography that reflecting off of subjects is what creates textures, shapes, colors and luminance. Light in its natural form (emanating from the sun) also gives life to plants and living things, and makes (most) people happier. So far, nobody has been able to determine exactly what light is. The word photography means “writing with light” (photo = light, -graphy = writing). Read more about light in my book Finding the Magic of Light.
mm = millimeter(s), as in a 50mm lens. (Earlier in lens history lenses focal length was given in cm = centimeters; as in a 5 cm lens). For anyone used to centimeters and millimeters, it’s no wonder. But if you grew up with inches, feet and yards, you may have had a hard time grasping what a 50mm lens was. But as lenses were designed first in Europe, the metric system with centimeters and millimeters was used to describe lenses.
The reason a 50mm lens is a 50mm lens is that there is 50mm from the focus plane (the film or sensor) to the center of focus inside the lens. When photography was a young subject, it was engineers who made it all, and the users were expected to understand. The engineers were so into the making of the lenses, that it apparently never dawned upon them that today’s users would think of a 21mm lens as a wide angle lens rather than a lens where there is 21mm from the sensor to the center of focus inside the optics.
OIS = Optical Image Stabilization. This is used in tele lenese lenes where blurring motion of the camera from inevitable vibrations are adjusted by the lens. At low shutter speeds and/or wit long lenses, any slight movement would result in a picture with "motion blur" unsharpness. The Leica TL2 supports optical iamge stabilization when A) OIS is turned on in the camera menu, and B) when you use lenses with OIS (the Leica SL longer lenses has OIS). An alternative is EIS = Electronic Image Stabilization, which the Leica T has. Here the problem of "motion blur" is currected electronically after, which might lead to image degradation. However, the larger the sensor resolution, the less one will notice small 'degradation'.
Optic = Eye or vision. From French optique or medieval Latin opticus, from Greek optikos, from optos ‘seen.’
Perspective - The way objects appear to the eye; their relative position and distance. Also, selective focus (foreground and background out of focus) can change the perception of perspective (also see Three-dimensional). A wide angle “widens” the perspective and makes objects further away appear smaller than they are to the eye, and objects nearer, relatively larger than they are to the eye. A tele lens will “flatten” the perspective and often objects further away will appear relatively larger than nearer objects, compared to sizes in real life. A 50mm lens is the one closest to the perspective and enlargement ratio of the human eye.
Perspective is relative position and distance. As here where the girl in front is more than two times taller than the peoplle walking, and 8 times taller than the people in the far background. Also, the parts of the buildings closer to the viewer are "taller" than the parts of the same building further away. Late afternoon sun in Denmark. Leica TL2 with Leica 35mm Summilux-TL ASPH f/1.4. © 2017 Thorsten Overgaard.
Saturation: How colorful, intense or pure the color is. Less saturation would be less colorful, more saturation would be more colorful. In today’s photography, desaturating a photo on the computer will gradually make it less and less colorful; and full desaturation would make it into a black and white photo.
Sharpness - See “Focus”
Summilux = Refers to the maximum lens aperture - here f1.4 , "-lux" added for "light" (ie. the enhanced light gathering abilities). In Leica terminology a Summilux is always a f/1.4 lens and a Summicron is a f/2.0 lens.
Three-dimensional = Having the three dimensions of height, width and depth. In photography and lens design, three-dimensional effect is also the perception of even small micro-details; the texture of skin can appear flat and dead or three-dimensional and alive. Also, selective focus (foreground and background out of focus) can change the perception of depth. Also see Perspective.
Three-dimensional = Having the three dimensions of height, width and depth. Melrose Avenue in Los Angeles. Leica TL2 with Leica 35mm Summilux-TL ASPH f/1.4. © 2017 Thorsten Overgaard.