Solid App but... – Lux - Professional Light Meter for Film Photography Review

Maybe I missed it but I don’t see an action/input setting for focal length of the lens. If you were shooting 35mm on a full frame sensor DSLR, the ISO, shutter speed and f/stop would be different than if you were shooting a 200mm lens. The longer the lens, the further the light has to travel requiring the photographer to compensate with a higher ISO, slower shutter and higher f/stop number (smaller shutter opening). Another thing to consider when using the DSLR is the sensor size. You have full frame DSLR (true 35mm) and cropped sensor. Between Canon and Nikon the crop percentage is a 1.6 and 1.5x respectively. This means if you have a Canon 5D Mark III and you are shooting a 100mm lens, that lens is fitted perfectly as if it were a true 35mm camera therefore allowing you to shoot at exactly 100mm. Now if you take that same 100mm lens and place it on a Canon 70D or 7D Mark II, the cropped sensor will come into play causing the cropped sensor to magnify the lens focal length by 1.6 and therefore allowing you to shoot that same 100mm lens as if it were a 160mm lens on a full frame or 35mm camera. Also cropped sensors are smaller which will require more light than a full frame. Instead of an ISO of 400, you might need an ISO of 640 or 800. Hope this was helpful. Nikons crop percentage is 1.5 while Canons is 1.6.
Review by Maize4580 on Lux - Professional Light Meter for Film Photography.