I would like to realize an image of the cantilever. The dimensions are (450x50) microns. I would like to use a self-constructed telephoto lens. This consists of two lenses. The image magnification can be 4 to 8. The magnification of the image is nothing more than the ratio between the two focal lengths of the two lenses. E.g. for f1= 320mm f2=40mm the total f= 35.5mm and the imaging magnification is 8 . Since typical focal lenghts of telephoto are over 50mm, I would like to ask if the total focal length matters? I.e. for f1= 800mm and f2=100mm the total focal length is f=88.89 mm but the image magnification remains the same.