Find number abc
If bc699 - 5aa20 = 2b5b9 find number abc. Multiple solutions may exist.Correct answers: 1
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Portrait cameraIn 1841, Austrian inventor Friedrich Voigtländer began selling the world's first purpose-built portrait camera. Since a person wanting a portrait would have to hold a pose for the time required for a successful exposure, it was critically important to be able to do that in the shortest time—which depends on the lens. Voigtländer incorporated a rapid double-combination lens designed according to the calculations of Viennese mathematician Josef Max Petzval. What used to take 20-30 minutes could now be done in two. The brass-bodied camera was shaped somewhat like a Lava Lamp bottle on its side. It made circular daguerreotypes about 3½-in (9cm) diam. The Voigtländer family business was started by his father in Vienna in 1756, making scientific instruments.« |