What's the real focal length for 18-55mm in my APS-C camera? [duplicate]

Question

This question already has an answer here:

• What is crop factor and how does it relate to focal length? 11 answers
• Does my crop sensor camera actually turn my lenses into a longer focal length? 7 answers

I want to buy a new lens (canon ef 50mm f/1.8 stm) that I know that the real focal length in my camera is around 80mm, but my question is if this happens in the same way whit my actual lens (18-55mm). If I take a photo whit the 18-55mm in 50mm and take another one whit the 50mm will I have the same focal length?

edit: First of all, thank you for your answers! I know that the focal length is in the lens and it doesn't change.

I think that I wont to say it was about the 'crop factor' or "how many people enter the two photos without me or the people moving?" the same? less in the EF? more in the EF? I think that the same.

Thank you again and sorry for my bad English.

Answer 1

Your 50 mm lens is a 50 mm lens, and will have the same field of view on your camera as a zoom lens set to 50 mm. The "real" focal length (the only one it has) is 50 mm.

The notion of 80 mm is a common misunderstanding. But the 50 mm lens is a 50 mm lens, period.

Yes, your camera has a crop factor of 1.6x, and 1.6 x 50 mm is 80 mm. That is a standard comparison to 35 mm film size (full frame), and the only meaning is that the 35 mm film camera would use the 80 mm lens to see the same field of view that your 50 mm sees on your sensor.

So the 80 mm lens is on some other camera, not yours. Your 50 mm lens remains 50 mm, period. The fields of view are equivalent, but Not the focal lengths. The appropriate focal lengths make the fields of view equivalent.

This comparison is assuming you have any interest in what the full frame sensor would see. Users with years of 35 mm film experience certainly would, it is what they know about, but beginners who never saw a 35 mm camera likely could not care less about 35 mm film. Enjoy the 50 mm.

If you might want a fixed focal length lens with the so-called "normal view" of 50 mm on 35 mm film, on your camera, that would be something near 50 mm / 1.6 = 31 mm. Otherwise, the 50 mm on 1.6x crop would be a mild telephoto view, comparable to 80 mm on 35 mm film.