On the other hand, the magnification m is negative when the image formed is real and inverted. And the magnification m is positive when the image formed is virtual and erect. In general, the lenses come in two shapes: convex (curved outward) and concave (curved inward). Please note that the magnification formula is applicable both in convex lenses and concave lenses. Lenses, both converging and diverging, are the marvels of optical physics that use the ability of these media to refract, reflect, or bend light rays. Keep in mind that subsequent lenses can continue to invert your image. The eyepiece or ocular lens, is placed near the focal point of the objective to magnify this image. Lens Formula and Magnification - Lens Power. Formula to calculate magnification. For each lens, treat the image of the previous lens as its object and use the lens equation and magnification equation to find your answers. The objective lens gathers light from the specimen, which is focused to produce the real image that is seen on the ocular lens.