Eric Luis Photography (Hey, I’m completely new to buying lenses and am wanting get a 50mm for my Nikon D5000. The biggest part Of buying a lens that confuses me is full format and crop sensor. Since my Nikon is DX format I’d get a DX 50mm or an FX 35mm, right? Maybe you could explain full format and crop sensor better than what I’ve read. All I’m really wanting know is, does DX go with DX and give the actual focal length of the lens without cropping and does an FX lens on a DX and the crop. Oh and what 50mm -)

3 months ago

Anonymous asked: Hey, I'm completely new to buying lenses and am wanting get a 50mm for my Nikon D5000. The biggest part Of buying a lens that confuses me is full format and crop sensor. Since my Nikon is DX format I'd get a DX 50mm or an FX 35mm, right? Maybe you could explain full format and crop sensor better than what I've read. All I'm really wanting know is, does DX go with DX and give the actual focal length of the lens without cropping and does an FX lens on a DX and the crop. Oh and what 50mm -

Full frame (“FX” for Nikon) gives you the full ‘35mm’ (35mm is just the format that it’s denoted as) image circle, like that of traditional film cameras, meaning a 50mm lens gives you the true 50mm focal length. Nikon’s “DX” designation, on the other hand, gives you a 1.5x crop factor for your focal length, meaning a 50mm lens will still be a 50mm lens, but you use the center of that image circle with your DX camera, giving you a 75mm field of view. The DX camera has a physically SMALLER sensor as opposed to FX, which results in the crop factor. DX lenses don’t go with DX format cameras in a sense that they give the ‘actual’ focal length (i.e. 18mm will be 18mm). Since the sensor is physically smaller than FX and will always be physically smaller than FX, you will still have to apply the 1.5x to whatever focal length you’re shooting at to get the equivalent in FX. Meaning, an 18-55mm f/3.5-5.6 kit lens set to 18mm on a DX camera will give the same field of view as a Nikon 17-35mm f/2.8 (FX lens) set to 27mm.

If you still don’t understand it, Ken Rockwell’s write-up on Crop Factor actually sums it up very well. I’m typically against the type of things he says (in order to read his articles, one must know what and what NOT to take from them), but he sums this up pretty well - for the most part.

http://www.kenrockwell.com/tech/crop-factor.htm

And, to answer your last question.. Since you shoot DX, I’d suggest either the Nikon 35mm f/1.8 AF-S or Nikon 50mm f/1.8 AF-S for a fast and affordable prime. Both are stellar performers, so you can’t go wrong with either.