forensic photography final

"normal" lens

A lens that shows objects without severely exaggerating or reducing the depth of the scene's planes.

Focal Length and Viewing Angles

The longer the focal length, the narrower the angle of view and the higher the magnification.

EVIL

Electronic Viewfinder, Interchangeable Lens

Perspective (Visual Clues-Vanishing Point)

a point on the image plane of a perspective rendering where the two-dimensional perspective projections of mutually parallel lines in three-dimensional space appear to converge.

Prime vs. Zoom Lenses

one has a has a fixed focal width and one has a zoom ring

Full Frame (FX) vs. Crop Sensor (DX)

one is the smaller sensor at 24x16mm; the larger format sensor measures 36x24mm

Proper Camera Holding

To support the front of your camera, place your hand underneath the lens. Placing your hand on top of the camera not only takes away support, but you can sometimes accidentally push the camera, resulting in blur due to camera shake. Be sure to stand up as straight as possible.

Diopter Viewfinder Adjustment

an optical tool that adjusts your camera's viewfinder to suit your eyes

F-Stops (Focal Length/Diameter of Lens Opening)

= focal length/diameter of the effective aperture (entrance pupil) of the lens. Length/diameter

The Inverse Square Law

a law relating the intensity of an effect to the inverse square of the distance from the cause

Image Quality Settings (Resolution)

the amount of compression that is performed on the photo. Lower-quality photos that are highly compressed are smaller in size. This will allow you to store more photos on a memory card. Quality. Resolution

Camera Filters (UV-Haze, Polarizing, ND, Color Contrast-Wratten)

UV: for protection of the lens, reduction of haze, and warming

polarizing: reduction of glare and reflection

color contrast warren: originally designed for use in photography but is also used in imaging applications from industrial manufacture to medical

ND: reduce the intensity of all wavelengths, or colors, of light equally from entering the camera, in measured amounts

Linear vs. Circular Polarizers

- is technically more efficient at changing light angles however it has drawbacks for certain camera systems

-Reduce unwanted glare & reflections

Digital Image Archival (RAW, TIF, JPG, GIF, BMP)

- Large, Highest, Good now; Questionable years later

- Largest, High, Excellent

- Smallest, Lowest, Excellent

- a simple raster graphics image file format designed to store bitmap digital images independently of a display device

Lossy vs. Lossless compression

every single bit of data that was originally in the file remains after the file is uncompressed. All of the information is completely restored. This is generally the technique of choice for text or spreadsheet files

reduces a file by permanently eliminating certain information, especially redundant information. When the file is uncompressed, only a part of the original information is still there (although the user may not notice it). Lossy compression is generally used for video and sound, where a certain amount of information loss will not be detected by most users

SWGIT "Category 1" vs. "Category 2" Images

Category one images are those that are used for overviews or scene setting, whereas category 2 images are used for analyses or accurate reproduction.

DPI vs PPI

When printing, use dpi (dots per inch).

When displaying digitality, use ppi (pixels per inch).

Bayer Pattern

Square grid photosensors in digital cameras use a Bayer Pattern to capture light. There are two green sensors for every red and blue because the human eye is more sensitive to green than to red and blue.

moire pattern

the geometrical design that results when a set of straight or curved lines is superposed onto another set; means watered in French

Factors Affecting Light Reaching the Film Plane(Ambient Light, Scene Reflectivity, Shutter Speed, Aperture)

- any light a photographer or cinematographer did not bring to the shoot

- short focal length lenses produce wide-angle distortion.

- Longer (slower) shutter speeds allow more light onto the camera's sensor or film, while shorter (faster) shutter speeds allow less light into the camera

- size will regulate the film's or image sensor's degree of exposure to light

F-Stops (Aperture) and Depth of Field (DOF)

The lower the f/stop—the larger the opening in the lens—the less depth of field—the blurrier the background. The higher the f/stop—the smaller the opening in the lens—the greater the depth of field—the sharper the background.

DOF and Focal Length

The longer the focal length, the larger the hyperfocal distance and, thus, the less DOF. The smaller the aperture (large f-numbers), the shorter the hyperfocal distance and, thus, the more DoF. The wider the aperture (small f-numbers), the larger the hyperfocal distance and, thus, the less DoF.

Aperture-Induced Diffraction

Diffraction is the interference or bending of waves around the corners of an obstacle or through an aperture into the region of the geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave.

Camera Exposure Modes(Program, Shutter Priority, Aperture Priority, Manual)

Aperture Priority (A) lets you choose the aperture (aka f-stop) setting you want, but the camera chooses the shutter speed. Shutter Priority (S) lets you choose the shutter speed you want, but the camera chooses the aperture setting.

White Balance (Color Temperature-Degrees Kelvin)

from the warmest colors of sunrise and yellow indoor lighting around 2500Kelvin, all the way to the coolest colors you see in deep shade around 9000Kelvin.

Perspective Distortion

perspective distortion is caused by the position of the camera relative to the subject or by the position of the subject within the image frame

Stops of Light (Doubling & Halving)

Adding a stop of light by doubling the exposure will brighten an underexposed image, decreasing an exposure by one stop (halving the amount of light) will darken an overexposed image. To add or take away a stop of light we need to change the aperture, shutter speed, and/or ISO.

Alphonse Bertillon (Bertillonage)

This system consisted of five initial measurements — head length, head breadth, length of middle finger, length of the left foot, and length of the cubit. Along with these measurements, Bertillon used photography, now known as a mugshot, to complete this system of record.

Admissibility of Photographs

Under the "pictorial testimony" theory, photographic evidence is admissible when a sponsoring witness can testify that it is a fair and accurate representation of the subject matter.

Quality Photographs (Correctly Exposed, Maximum DOF, In Focus and Distortion Free)

To simplify the definitions, DOF concerns the image quality of a stationary lens as an object is repositioned, whereas the depth of focus concerns a stationary object and a sensor's ability to maintain focus for different sensor positions, including tilt.

Photography Log Contents

LOG is a specific video format processed in the camera, unlike RAW, which is totally unprocessed. LOG footage can be viewed on an external monitor without conversion. And, because it's a video format, certain components such as white balance and exposure are made part of the video.

Cardinal Rules of Crime Scene Photography

1. Fill the frame

2. Maximize depth of field

3. Keep the film plane parallel

Proper Composition (Filling the Frame)

Filling the frame is the technique of composing an image so that positive space takes up most or all of the frame. Filling the frame is the opposite of using negative space in a composition. Positive space, commonly a single subject, is framed close up so that it literally fills the frame

Case Identifier

A case identifier (CID) is a special type of attribute that can be used to uniquely identify a case class. It can be used in processes, scripts or API calls to delete or to find a particular case.

SLR camera

Single-lens reflex camera. The viewing system allows the user to see exactly what the lens sees.

DSLR camera

A digital camera that combines the interchangeable optics and mechanisms of a single-lens reflex camera with a digital imaging sensor, as opposed to using photographic film.

DSLM

Digital Single Lens Mirrorless

MILC Camera

mirrorless interchangeable-lens cameras

APS-C (Crop Sensor-1.6X Crop Factor)

If you use a 50mm lens on an (?) camera and want to shoot the same scene with the same field-of-view with a full-frame camera, you need a focal length of 50 x 1.6, which is 80mm.

Preview Button

allows the shooter to preview the depth of field that will be captured at the current aperture setting.

ISO settings

100-200:outdoor, sunny conditions

400-800: outdoor, cloudy conditions

1600:night time, low light

controls the amount of light your camera lets in, and therefore how dark or light your photos will be.

Camera Care

- utilize the camera strap

- protect camera

- utilize lens care

- use a storage/carrying case to protect the camera and equipment

- store the camera in well ventilated, cool, dry location

Dynamic Range (Highlights and Shadows)

- lightest elements in an image

- darkest elements in an image

Focal Length & Perspective

The longer the focal length, the narrower the angle of view and the higher the magnification. The shorter the focal length, the wider the angle of view and the lower the magnification.

Pixels

dots that make up an image

Color Filter Array (CFA)

limit the intensity of light being recorded at the pixel to be associated with the wavelengths transmitted by that color

Interpolation

determining a value from the existing values in a given data set.

XMP or EXIF "sidecar" file

An XMP file is what's known as a sidecar file.

Shutter Speed and Stopping Motion

1/500 second is a good starting point for stopping motion that's fairly fast.

Incident vs. Reflective Light Metering

An incident meter (sometimes called a bulb-meter) works by reading the intensity of the light that falls onto the subject, as opposed to reading the light reflected off of the subject as the reflective meter does. Usually, you take the reading from the position of the subject.

TTL Metering

Through the lens metering. An exposure meter built into the camera which measures reflected light from the subject passing through the camera lens.

18% gray card

is the standard used by camera reflective light meters to determine the proper exposure settings on the camera. If a particular scene does not reflect this "norm," proper exposure can be determined by aiming the camera at an (?) and taking a meter reading of it.

Image Histogram

a gray-scale value distribution showing the frequency of occurrence of each gray-level value

RGB vs. CMYK

RGB color mixing is the primary color mode for digital designs (like web, TV or phone files) while the CMYK mode is used for printed designs

Telescopic Effect of Telephoto Lens(Focal Length/50mm)

A telescope of a specific focal length will produce an image of a specific size and this cannot be changed.

DOF as a Function of Focal Length

The shorter the lens focal length, the longer the DOF

Reciprocity Between F-Stops, Shutter Speeds, and ISO Settings

Reciprocity is the law of the relationship between shutter and aperture. It stipulates that one-stop increase in aperture is equivalent to the shutter duration doubling. Both increase light by one stop. Photo by Amancay Maahs; ISO 200, f/13.0, 1/200-second exposure.

Basic Crime Scene Photography

The crime scene must be photographed from long-, medium-, and close-range vantage points. Each stage of the commission of the crime must be treated and photographed separately. Prosecutors must be able to use photographs not only to record conditions, but to reproduce events.

Long, Medium, & Close-Up Photographs

Generally speaking, we can break this down into three main shot sizes: Long, Medium, and Close. Long shots (also commonly called Wide shots) show the subject from a distance, emphasizing place and location, while Close shots reveal details of the subject and highlight the emotions of a character

Scale Guidelines

Pattern, Balance, Negative Space, Grouping, Closure, Colour and Light/Shadow.

F-stop (focal length,/diameter of lenses opening)

F-stop: Controls the amount of light entering the camera by adjusting the diameter of the lens opening. Smaller f-stop values (e.g., f/2.8) result in larger lens openings and more light, while larger f-stop values (e.g., f/16) reduce the lens opening and limit the amount of light.

The inverse square law

The inverse square law states that the intensity of a physical quantity decreases in proportion to the square of the distance from the source.

ISO setting

The sensitivity of a camera's image sensor to light. Higher ISO values make the sensor more sensitive, allowing for brighter images in low-light conditions, but with increased noise. Lower ISO values reduce sensitivity, resulting in darker images but with less noise.

Image quality settings (resolution)

The setting that determines the clarity and level of detail in an image. It refers to the number of pixels in an image, affecting its sharpness and size. Higher resolution means more pixels, resulting in better image quality. Lower resolution reduces file size but sacrifices image detail.

Camera filters (UV-haze, polarizing, ND, color contrast -wratten)

Camera filters are accessories used to modify the light entering the camera lens. UV-haze filters reduce haze and protect the lens. Polarizing filters minimize reflections and enhance colors. ND filters reduce the amount of light entering the lens, allowing for longer exposures. Color contrast filters, like Wratten filters, alter the color balance for creative effects.

Determining privilege direction of polarizer linear, circular, elliptical polarization

Determining the privilege direction of a polarizer:

1. Linear polarization: Use a polarizer and rotate it until maximum brightness is achieved.

2. Circular polarization: Use a polarizer and rotate it until the image appears unchanged.

3. Elliptical polarization: Use a polarizer and rotate it until the image appears partially darkened and partially brightened.

Linear vs circular polarization

Linear polarization: The orientation of the electric field of an electromagnetic wave is fixed in a single direction.

Circular polarization: The orientation of the electric field of an electromagnetic wave rotates in a circular pattern as it propagates.

Right-handed/left handed polarization

The direction in which an electromagnetic wave oscillates. Right-handed polarization occurs when the wave oscillates clockwise, while left-handed polarization occurs when it oscillates counterclockwise. It is determined by the orientation of the electric field vector.

Dynamic range (highlights and shadows)

The range of brightness in a photo, from the brightest highlights to the darkest shadows. It determines the level of detail and contrast in an image.

Focal length and perspective

Focal length: Distance between the lens and the image sensor. Longer focal length = more zoom, shorter focal length = wider view.

Perspective: How objects appear in relation to each other. Short focal length = exaggerated perspective, long focal length = compressed perspective.

NIST- minimum image resolution (1000ppi)

NIST- minimum image resolution (1000ppi): The minimum resolution recommended by the National Institute of Standards and Technology (NIST) for high-quality image reproduction. It stands for pixels per inch (ppi) and ensures sharp and detailed images.

F-stop (Aperture) and depth of field (DOF)

F-stop: Controls the size of the aperture, determining how much light enters the camera. Lower f-stop values result in larger apertures and shallower depth of field. Higher f-stop values create smaller apertures and wider depth of field.

Depth of Field (DOF): The range of sharpness in a photograph, from the nearest to the farthest point in focus. It is affected by the aperture size, focal length, and distance to the subject. A shallow DOF has a small area in focus, while a wide DOF has a larger area in focus.

Oblique lighting

Oblique lighting: Lighting technique where the light source is positioned at an angle to the subject. It creates shadows and highlights, enhancing texture and depth.

DOF and focal length

Flashcard: "DOF and focal length" DOF: Depth of Field is the range of distances in a photograph that appear acceptably sharp. It is influenced by aperture, distance to subject, and focal length. Focal Length: Focal length is the distance between the lens and the image sensor. It affects the angle of view and magnification of the image. Shorter focal lengths provide wider angles, while longer focal lengths offer narrower angles and magnification.

Shooting “thru” a fence (photography)

A technique where a photographer captures an image by shooting through the gaps or openings in a fence. This creates a visually interesting effect, adding depth and texture to the photograph while maintaining a sense of mystery or intrigue.

Attenuated lighting technique (scale with luminal)

Attenuated lighting technique: Adjusting the intensity of light to create a gradual decrease in brightness. It is used to control the overall lighting effect and create a sense of depth in a scene.

“Confident” magnification

2mm/foot of distance

Best practices in digital image enhancement

contrast stretch, density slicing, edge enhancement, and spatial filtering are the more commonly used techniques. Image enhancement is attempted after the image is corrected for geometric and radiometric distortions.

Histogram Analysis

Histograms show the shape of your data. The horizontal axis shows your data values, where each bar includes a range of values. The vertical axis shows how many points in your data have values in the specified range for the bar. In the histogram in Figure 1, the bars show the count of values in each range.

FFT plug-in or filter

Filters out large structures (shading correction) and small structures (smoothing) of the specified size by gaussian filtering in fourier space

Filters out large structures (shading correction) and small structures (smoothing) of the specified size by gaussian filtering in fourier space

Zone focusing

the act of turning your camera to manual focus and choosing a set distance away to be in focus.

Hyperfocal focusing

is a handy way of figuring out where to focus in a landscape to maximize the depth of field and to get as much of the scene as possible “acceptably sharp“

Rule of thirds

is a composition guideline that places your subject in the left or right third of an image, leaving the other two thirds more open.

Photographing impression evidence

a tripod and ruler (scale) must be used, and the ruler must be in the same plane as the impression. The camera needs to be directly over the impression, not taken from an angle. A level on the tripod is recommended.

Inversion effect

face-selective activity in the brain was delayed when the configural information of faces was disrupted (for example, when faces were inverted). This means that it took longer for the participants to recognise the faces they were viewing as faces and not other (non-facial) objects.

Examination quality photographs

A special set of close-up photographs that can be absolutely critical to an investigation is known as the Examination Quality Photographs. These images will be compared to real evidence to make an identification.

Flash photography (precautions to take)

blinding and too strong, leading to blown-out images. If you are using a DSLR, the problem can easily be rectified by investing in a camera-mounted flash accessory, which comes with the ability to be bounced in different directions.

Built-in vs external flash

a built-in flash does not need to be carried around separately, it also has disadvantages such as insufficient flash power and ability to cast light only in the front direction. To produce more professional results, the use of an external flash is recommended

Fill-flash

adds light to deep shadows cast harsh lighting.

Painting in light

expose image details in dark or near-‐dark conditions. In this technique, the shutter is held open for seconds or minutes and the photographer walks through the scene adding light from sources such as a flashlight or detached camera flash.

Bounce-flash

the use of an external flash unit (also known as hot shoe-mounted flash) to reflect the appropriate amount of light onto your subject so that your shot appears bright and sharp

Stroboscopic-flash

to stop the appearance of motion of rotating and other repetitively operating machinery and to measure, or adjust, the rotation speeds or cycle times

Second curtain sync-flash

the flash fires at the end of the exposure.

“Diffused” flash

soften or spread the harsh, concentrated light that bursts out of the flash. It also creates a more even and flattering light on the subject

“Bracketing” an image

Is a technique where a photographer takes shots of the same image using different camera settings. This gives the photographer multiple variations of the same image to choose from or combine to ensure that they get the perfect shot

Image histogram analysis

a type of histogram that acts as a graphical representation of the tonal distribution in a digital image. It plots the number of pixels for each tonal value. By looking at the histogram for a specific image a viewer will be able to judge the entire tonal distribution at a glance.

Perspective distortion (telephoto, wide angle)

This is because the field of view of wide-angle lenses is wider than the image sensor on a digital camera and therefore the image looks like it has been squeezed and constricted to fit in the edges of the frame.

often used to give the appearance of compressed distance between distant objects, such as buildings or automobiles in order to convey a feeling of congestion.

Telescopic effect of telephoto lens

makes near and distant objects seem closer together and more similar in size than they appear in real life

Magnification= focal length/50mm

Focal length/50mm

DOF asa function of focal length

The shorter the lens focal length, the longer the DOF