Digital Photograph Flashcards
Camera Settings should be checked prior to photography?
C - Compensations
S - Size (Quality)
W - White Balance
I - ISO
M - Metering
What is SWGIT?
Scientific Working Group on Imaging technologies and systems within the criminal justice system.
Describe Admissible Digital Images?
Relevant properly authenticated digital images that accurately portray a scene or object are admissible in court. Digital images that have been enhanced are admissible when the enhancements can be explained by a qualified person.
Why is Image Integrity important for court?
A legal prerequisite to the admissibility of any evidence is that the evidence being offered in court can be authenticated. If authenticity is challenged, the proponent must be prepared to show that the image (or data) has not been altered.
Image processing vs. Image analysis
Image processing transforms an input to an output image. Image analysis involves the application of image science and domain expertise to examine and interpret the content of an image and/or the image itself in legal matters. Any processed image subjected to image analysis should be documented with an image processing log.
Standard Operation Procedures (SOPs)
Documented policies and procedures that govern the use of images and imaging technology for use in the criminal justice system.
What is the perspectives required for forensic photography?
Overall, midrange and close-up. Then As Close As Possible (ACAP) with scale.
How do you preserve digital images? What is the benefit of RAW images.
The primary image is the images that is captured on the media. An original image is an accurate and complete replica of the primary image. RAW format images are ideal for evidence because they cannot be altered. Any enhancements are made to copies of the original images.
What are the criteria for preforming image enhancements
- Must be trained and have an understanding of the enhancement processes used. 2. Written documentation of enhancements is required. 3. Must be reproducible - similar results but does not have to be same pixel for pixel.
What are the properties of Digital Camera Sensors?
- consist of a matrix of millions of microscopic light sensitive photodiodes. - these create pixels by sensing light intensity of a small portion of the image. - can only record grayscale information. - colour determined via colour filter.
What is a Pixel?
- Images are composed of rows and columns of pixels.
- Abbreviation of Picture Element.
- The basic building block of a digital image.
The three properties of a pixel.
- Location. 2. Colour. 3. Size.
Describe how Colour Interpolation works?
Colour filter is placed in front of photo diode. Filter will allow one type of coloured light through, which is measured by the sensor. Colour values are calculated based on surrounding pixel values.
What are the concerns of small CCD sensors?
Charged Coupled Device. Smaller sensors have less area to focus, which can lead to over flow from one pixel to the next resulting in electronic noise.
What are three common file formats for digital images?
- JPEG - lossy compression and loses information each time it is saved. Ideal for printing, stages and sharing. Small file size.
- TIFF - lossless compression, very large file size.
- RAW - other file formats processed from RAW, no compression, smaller size than TIFF, cannot be changed or altered, and requires special software to open. Only exposure and ISO applied from the camera. “Electronic Negative”.
