I have a newbie question about focal length, what it actually means for lenses and how I can translate this into "how close to the target it's going to practically take me" (I don't want to use the term zoom here to avoid confusion, perhaps magnifying power is what describes best what I'm after, basically shots from the distance, not macro).
Here's an example:
I currently have a Sigma 18-200mm lens (therefore approx. 11x zoom), which I use with Canon EOS 400D and also a compact Sony Cyber-Shot DSC-HX60 with focal length 4.3-129mm (approx. 30x zoom).
Even though 200mm is obviously more than 129mm the Sony camera takes me closer to the target.
Looking at zoom factor (30x comparing to 11x) this may seem obvious, but it's less obvious when you compare it to other lenses, e.g. 200-500mm lens, which effectively has "only" 2.5x zoom, but actually takes me closer to the target.
How can I make sense of this when looking at other lenses?
For example let's consider Tamron 16-300mm, its zoom is obviously approx. 20x, but how can I compare it to Sigma 18-200mm or Cyber-Shot 4.3-129mm? Is it going to take me closer to the target, e.g. magnify objects better then both of them or only better than Sigma, but still not as good as Sony? (ignoring quality of picture of course)