Nikon 50mm 1.8 or Rokinon 85mm 1.4?
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I already own a 35mm 1.8 Nikon and use it mostly for portraits and street photography, however, I want to try a different focal length, I think it should be interesting. The 50mm is good, the aperture is great, but I don't know if I'm gonna be working in almost the same range of the 35mm one. The 85mm would be a fine choice because I have never worked with a lens with that focal length, and it requires me to do things I want to learn like metering. I'm interested in learning, but I don't know if the 85mm is a good choice if I'm gonna be using it for portraits and street photography.
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The 85 mm is a fine portrait lens if you have a full frame camera, like a 35 mm SLR or D3/D700 series dSLR. The 50 mm lens is considered THE portrait lens for Nikon cropped sensored cameras.
Actually the street photographers I know use a 35 mm lens on a 35 mm rangefinder camera. If you have a cropped sensored dSLR, that would be equivalent to about a 24 mm lens. Even your 35 mm lens is a little too long to shoot "street" photography, the 85 mm is certainly too long to get those intimate, all in focus street photos that describe the genre.
I think you may want to visit this site and see what field of view each focal length will give you.
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85mm will work well for what you want. However, manual focussing on a f1.4 will be a challenge. I'd say look for a used 85mm f1.8 AF