Suppose you wish to make a false-colour image from several images of the same piece of sky taken in different energy bands (or at different values of any other quantity). If the input images are event-based images of low exposure it may be rewarding to adaptively smooth them before combining them into a colour image. However, if each image is smoothed separately, in general convolvers of different widths will be allocated to the same place in the sky in the different images. This can cause a sort of chromatic aberration. To avoid this it is necessary to smooth each image according to the same template. This template might for example be established by adaptively smoothing the sum of all input images, then writing the result to file via the parameters writetemplateset and outtemplateset. This template image just stores the characteristic width of the gaussian used to smooth each pixel of the input image. If you select smoothstyle=`template' and supply the template set to parameter smoothstyle=`intemplateset', you will get the same smoothing pattern for any inset.
The same result can be achieved through outconvolversset and outindeximageset, which is a more robust method. I'll probably abandon the template facility eventually.
XMM-Newton SOC -- 2021-11-30