The fastest way to capture the images is to have a system that allows the images tobe captured directly into the software, if possible using some Image Authentication procedures to ensure the integrity of the images. This usually requires a camera with on board TIFF files formats as RAW (in this application only) makes capture slow and in some instances causes images distortion in some of the enhancement procedures. For this reason we generally recommend the high resolution Nikon digital SLR camera, currently D700, D800, D3, D4. The D4 his less pixels and therefore significantly less noise than the D800 camera range.
The biggest problem with forensic photography is the ability of the camera to capture fluorescent images. Many cameras with small chip sizes produce high levels of noise. These low light images result in poor quality fingerprint images. Look at the following images of a footwear impression, one shows good noise reduction while the other shows bad.
Cameras & Filters
Polarising filters have traditionally been used to remove reflections from surfaces such as water and mirrors. In fingerprint photography they can be used to remove the reflected light from the surface, this results in an increase in the image intensity and greatly improved clarity in the fingerprint ridges. The best results are obtained when a technique called ‘cross polarisation’ is used. Here a polarising filter is placed onto the light source and a second is added to the camera lens. The filter on the lens will turn, and as it does the visibility of the image will improve. The following slide show, has a series of images on different surfaces before and after cross polarisation.
The camera used for Forensic photography must have a minimum chip size of APSC and for very low light level work such as Luminol we would recommend a camera with a full frame sensor.
For more information see the article on ‘Camera Digital Noise’.
Pro UV Filter
Pro UV Filters for Digital Cameras
For years photographers have used UV filters to:-
1. Protect the lens
2. Improve the clarity and sharpness of the captured image
The Pro UV filters are much more expensive than standard filters so are they really worth the extra cash?
According to the information available the digital cameras have (amongst others) one major difference to their film based cousins. They have a much greater sensitivity to Ultra Violet light. This effects the image by causing greater image blue and colour bleed. The extra coatings on the Pro UV filters significantly reduce the blur of the UV light and increase the colour accuracy in the captured image. Where you are looking for really sharp images such as fingerprints or other areas of fine detail these filters really do make the difference - I was straight on the Internet to order some for my Landscape and wildlife photography (http://www.naturalworld.neateimaging.com)
Below are two images which I hope will help to illustrate the differences:-
|Fluorescence BY 40|
|Fluorescence RH 6g|
|Fluorescence & FFT|
|High Intensity Light Sources|
|Court Room Presentation|
|Blood on Fabric|
|Leuco Crystal Violet|
|Digital Noise & Image Quality|