Friday Headlines – June 5, 2020 – #BlackLivesMatter

Friday Headlines, March 6, 2020

PEOPLE OF COLOR IN THE GEOSCIENCES

In light of the recent death of George Floyd and the following #BlackLivesMatter protests, I feel it is appropriate and necessary to highlight geoscientists of color.

I do not fully understand the struggles that are faced by people of color in this country, but I’m listening. Your pain is real. Your protests are valid.

Paleontology

Geology

Environmental Science and Climate Change

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I is for ISO – #AtoZChallenge – 2020

I is for ISO

ISO is a measure the sensitivity of film to light, or “film speed.” Higher ISO films are more sensitive to light and therefore better for taking photos in low-light conditions. (However, as noted in an earlier post, more sensitive films tend to have larger grain.)

ISO stands for the International Organization for Standardization, located in Geneva, Switzerland. While many different classifications for film speed have been used (e.g. DIN and ASA), in 1974 the universal ISO system became the standard.

A 36 exposure roll of ISO 400 35mm black and white film. It’s what Penny is shooting with lately.

Typical film speeds are 100, 200, and 400. ISO 100 is best used under sunny conditions. ISO 400 (or the even faster ISO 1600) are best used in low-light conditions like indoors or outdoors at night. ISO 200 is a general purpose film that does well in sunlight and in the dark.

H is for Hot Shoe – #AtoZChallenge – 2020

H is for Hot Shoe

Frequently on top of cameras is a clip of sorts. Most frequently, there is a flash unit pressed into the clip for taking photos under low-light conditions.

This clip is called a shoe. I have no idea why.

When hand-held cameras became popular, manufacturers provided additional equipment (typically flashes, but also rangefinders and light meters) that could be bought to go with that camera. Each add-on was specific to that camera, and most times could not be used with any other camera.

The standardized shoe on top of the camera made it possible for the extras to be moved between different cameras of different makes and models. It became possible for companies to specialize in devices that would work with any camera (provided it had a shoe) and not have to also make a camera as well.

Shoes on many different makes and models of camera.

The “Hot” shoe took the concept one step further. It has an electrical contact that is triggered when the shutter is activated, making it possible for a flash placed into the shoe to strobe simultaneously with the shutter.

Hot shoe on a Minolta SLR.

Suddenly, manufacturers could make elaborate flashes that would also work with any camera and always be synchronized with the shutter for the optimal photograph.

Modern camera shoes are far more complicated and have gotten back to being more specific to the camera. Today’s cameras are computerized with sensitive electronics. Extra contacts allow the camera’s computer to communicate with and control the attached flash as needed.

Hot shoe on my Nikon DSLR. The middle contact is the synchronize the flash, but the other three allow the flash to communicate with the computer inside the camera.

Because of the new complexity, one has to exercise caution when switching flashes between cameras. The wrong flash can destroy the sensitive electronics of a camera. So be careful.

G is for Grain – #AtoZChallenge – 2020

G is for Grain

Grain is used in photography as a measure of the size of the photosensitive particles (generally silver) on film or photographic paper. With modern digital photography, one might compare it to the resolution of the image in pixels per inch.

Film with large grains will appear to be at lower resolution and less focused than those with smaller, finer grains.

Examples of different grain size and distribution on photographic plates (i.e. glass negatives). Plate VII from “The Silver ‘Grain’ in Photography” by Robert James Wallace, The Astrophysical Journal, Vol. XX, No. 2, Sept. 1904, pp. 113–122, Chicago.

The sensitivity of film to light is related to grain size. Films with low sensitivity to light work best in bright situations, like outside on a sunny day. These films have very fine grain structures and yield a sharp image. But, if one wishes to take photographs in low-light conditions, say around a campfire at night, a more sensitive film is needed. These films tend to have larger grain sizes resulting in a less-sharp image.

Grain can also be used for photographic effects.

Halicki uses coarse grains to produce an interesting effect. CC By 3.0

F is for f-stop – #AtoZChallenge – 2020

F is for f-stop

The f-stop or f-number (denoted N) is used to represent the size of the aperture in a camera. It’s usually written with the script f followed by the number, e.g. f/1.4. In general, smaller f-numbers mean the aperture is more open which results in more light getting to the film.

The number itself (N) is a ratio between the focal length (f) of the complete camera plus lens and the diameter of the opening of the camera’s aperture (D):

N={\frac {f}{D}}\

The focal length is the distance between the front of the lens and the focus point on the film.

F’ is approximately where the film would be in a camera. f’ is the focal length – the distance between the lens and the film. CREDIT: JiPaul / from Henrik on Wikimedia Commons CC By-SA 3.0

D is the measurement across the aperture from one side to the other. It changes as we adjust the aperture. This value being on the bottom of the fraction is why larger f-numbers mean smaller apertures.

Typical lenses have these f-number settings:

f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and f/32

Older lenses tend to have a narrower range and often lack the very low f-numbers because the aperture is too small.

You’ll see these numbers with or without the f/ somewhere on the lens like on this Argus C3:

The aperture adjustment is across the top of the lens. This lens is set on f/8. The phrase “f/3.5 50mm” across the bottom shows the user the lowest f-number possible for the lens as a measure of lens ‘speed’ and provides the focal length for the lens. In this photo, you can also see the open aperture behind the lens.

E is for Exposure – #AtoZChallenge – 2020

E is for Exposure

Exposure is a general sense for how much light that reaches photographic film (or an image sensor, in the case of digital cameras). How much light that reaches the film is affected by:

  • shutter speed
  • aperture size
  • amount of light illuminating the subject

Faster shutter speeds reduce the amount of light hitting the film. Larger apertures result in much more light reaching the film. Low light scenes do not put much light onto the film.

A photographer must balance these three variables with the sensitivity of the film to optimize the amount of light getting into the camera in order to get the ‘perfect’ picture. Many modern cameras (including those on cell phones) automatically adjust each of these.

D is for Depth of Field – #AtoZChallenge – 2020

D is for Depth of Field

Depth of field describes the distance in front of and behind an object that is in focus at the same time that the main object is in focus.

We are, in general, familiar with this. If something is close to us and we focus on it, things in the background will be out of focus. Or, when we focus on something in the distance, things in the foreground become blurry.

Depth of field is slightly more specific in that it actually quantifies the space in front or behind an object that will be in focus. The construction of the lens has a strong effect on this. However, depth of focus can also be affected by the size of the aperture. As an aperture gets smaller, the depth of focus increases.

Depth of field can be used to create interesting photographic effects. It’s also important to control depth of field when photographing objects for professional publication or study.

C is for Camera Obscura – #AtoZChallenge – 2020

C is for Camera Obscura

The words “camera obscura” are derived from the Latin meaning “dark chamber.” In general, a camera obscura refers to an image formed as light passes through a tiny opening, like a pinhole.

Credit: Public Domain

Many original camerae obscurae were simply a darkened room with a small hole in a wall separating the darkened room from a well-lit space. People would gather inside for entertainment to watch took place in the illuminated space.

Today, pinhole cameras are a more common camera obscura that people may play with. People may also take advantage of pinholes to project images when solar eclipses occur.

See the other 25 letters of the 2020 A to Z challenge from Animal’s Place by clicking here! All about how cameras work!

B is for Bellows – #AtoZChallenge – 2020

B is for Bellows

Many older cameras possess bellows, an expandable dark chamber connecting the lens of the camera body to the camera body where the film is.

Polaroid Land Camera – The 800. 1957-1962

By being expandable, the position of the lens relative to the film can be changed to focus the image.

The Brownie Automatic. Also called the No. 2A Folding Pocket Brownie, Model A. A folding camera manufactured from 1910 to 1915.

More practically, being able to move the lens means that a camera can be folded up to a smaller size, therefore making it more convenient to carry.

Jiffy Kodak six-20. 1933-1937

See the other 25 letters of the 2020 A to Z challenge from Animal’s Place by clicking here! All about how cameras work!

A is for Aperture – #AtoZChallenge – 2020

A is for Aperture

The aperture is the opening in a camera through which light passes to get to the film. It is adjustable much as our own pupil expands or contracts with changing light conditions.

In photography, the size of the aperture not only affects the amount of light that gets into the camera (and onto the film) but also characteristics of the focus of the object being photographed.

A smaller aperture allows less light in. However, the resultant image is more likely to be in sharp focus. Larger apertures result in reduced focus, as anyone who’s had their eyes dilated will tell you!

See the other 25 letters of the 2020 A to Z challenge from Animal’s Place by clicking here! All about how cameras work!