Toe

Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of their toes.

Structure

The toe refers to a part of the human foot, with five toes present on each human foot. Each toe consists of three phalanx bones, the proximal, middle, and distal, with the exception of the big toe (Latin: Hallux). The hallux only contains two phalanx bones, the proximal and distal. The phalanx bones of the toe join to the metatarsal bones of the foot at the interphalangeal joints. Outside the hallux bones is skin, and present on all five toes is a toenail.

The toes are, from medial to lateral:

Toe (automotive)

In automotive engineering, toe, also known as tracking, is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic and compliant effects. This can be contrasted with steer, which is the antisymmetric angle, i.e. both wheels point to the left or right, in parallel (roughly). Negative toe, or toe out, is the front of the wheel pointing away from the centerline of the vehicle. Positive toe, or toe in, is the front of the wheel pointing towards the centerline of the vehicle. Toe can be measured in linear units, at the front of the tire, or as an angular deflection.

In a rear wheel drive car, increased front toe in provides greater straight-line stability at the cost of some sluggishness of turning response. The wear on the tires is marginally increased as the tires are under slight side slip conditions. On front wheel drive cars, the situation is more complex.

Toe is always adjustable in production automobiles, even though caster angle and camber angle are often not adjustable. Maintenance of front end alignment, which used to involve all three adjustments, currently involves only setting the toe; in most cases, even for a car in which caster or camber are adjustable, only the toe will need adjustment. One related concept is that the proper toe for straight line travel of a vehicle will not be correct while turning, since the inside wheel must travel around a smaller radius than the outside wheel; to compensate for this, the steering linkage typically conforms more or less to Ackermann steering geometry, modified to suit the characteristics of the individual vehicle.

Sensitometry

Sensitometry is the scientific study of light-sensitive materials, especially photographic film. The study has its origins in the work by Ferdinand Hurter and Vero Charles Driffield (circa 1876) with early black-and-white emulsions. They determined how the density of silver produced varied with the amount of light received, and the method and time of development.

Details

Plots of film density (log of opacity) versus the log of exposure are called characteristic curves,Hurter–Driffield curves,H–D curves,HD curves,H & D curves,D–logE curves, or D–logH curves. The overall shape is a bit like an "S" slanted so that its base and top are horizontal. There is usually a central region of the HD curve which approximates to a straight line, called the "linear" or "straight-line" portion; the slope of this region is called the gamma. The low end is called the "toe", and at the top, the curve rounds over to form the "shoulder".

Different commercial film materials cover a gamma range from about 0.5 to about 5. Often it is not the original film that one views but a second or later generation. In these cases the end-to-end gamma is approximately the product of the separate gammas. Photographic paper prints have end-to-end gammas generally somewhat over 1. Projection transparencies for dark surround viewing have end-to-end gamma approximately 1.5. A full set of HD curves for a film shows how these vary with developer type and time.