I have Nikon D3300 DSLR. I'm confused with 35mm and 50mm prime lenses on FX and DX cameras. Somewhere I read that if a 35mm prime lens is used on a FX camera the focal length is equivalent to around 50mm because of the Nikon crop factor of 1.5.
What would happen if I use a 35mm prime lens on a D3300 DX sensor?
What would happen if I use a 50mm prime lens on a D3300 DX sensor?
Will there be any focal length difference?
The "crop factor" multiplier must be applied to both FX and Dx lenses to compare the field of view of a 35mm lens when used on an APS-C/Dx camera to the field of view of a 35mm lens when used on a full frame/FX camera. Both 35mm Dx lenses and 35mm FX lenses will give the same field of view when used with an APS-C/Dx camera.
This is because the focal length of a lens is defined by the distance behind the lens' entrance pupil collimated light is focused. What changes between a full frame/FX camera and an APS-C/Dx camera isn't the focal length of 35mm lenses, it is the angle of view provided by the size of the sensor.
The exception to this is when a Dx lens is placed on an FX Nikon camera. Because the light circle cast by the Dx lens is not large enough to cover the FX sensor, the camera automatically only records the portions of the sensor equivalent to an APS-C/Dx sensor. So in effect you have converted the FX camera to a Dx camera and thus the "crop factor" applies to images obtained with this combination.
If you place any 35mm lens on a Nikon D3300 (or any other APS-C camera with a 1.5X crop factor) you will get the same field of view as you would get with a 52.5mm FX lens placed on a full frame/FX camera.
If you place any 50mm lens on a Nikon D3300 (or any other APS-C camera with a 1.5X crop factor) you will get the same field of view as you would get with a 75mm FX lens placed on a full frame/FX camera.
Any 35mm lens on your D3300, (DX- 1.5x crop sensor camera) will produce an image equivalent in focal length to 52.5mm on a full size (FX) sensor, thus making this similar to using a 50mm lens on an FX camera. Using a 50mm lens on your D3300 would produce an image equivalent in focal length to 75mm on a full frame (FX) sensor.
In terms of "What would happen" between the two lenses on your camera- Both would produce images of different sizes and compression ratios, as would 2 different focal length lenses on any camera.
Note: if a Nikon lens has "DX" in the title, using the lens on a full frame camera (FX sensor) would not give a complete image, due to vignetting. They make DX lenses with less glass, and thus the prices are a bit lower than FX lenses.
