# Advanced detection settings: Method

Aim

To choose:

▪The detection method, that is, how EthoVision XT finds the subject over the background. Once you have selected the method, specify the background image (for the detection methods Static Subtraction, Dynamic Subtraction and Differencing only) and the level of contrast between subject and background. See below.

▪The method for estimating the body points. See Methods for estimating the body points

Gray Scaling

Choose Gray scaling when:

▪The animal's grayness differs from the background in all parts of the arena.

▪The background does not change during a trial.

▪Lighting is even (minimal shadows and reflections) during the trial.

example Tracking a white rat in a uniform black open field with no bright objects.

Static Subtraction

Choose Static Subtraction when:

▪The Gray scaling method does not work, for example because other objects in the arena have a similar color as the animal.

▪The background does not change in time.

▪The light is constant during the trial.

example Tracking a white rat in an open field with unavoidable reflections or bright objects.

Dynamic subtraction

Choose this method when during trials light conditions gradually change or the background changes, for example because bedding material is kicked around, food pellets are dropped, droppings appear etc.

example Tracking a mouse in a home cage provided with bedding material. The activity of the mouse causes the bedding to change appearance in the video image.

Differencing

Choose this method when there is a lot of variation in contrast between a subject and the background within an arena.

example There is a gradient in light intensity over the apparatus that cannot be removed, or a strong difference in the color of the fur of the animal, like in hooded rats.