the camera i used has a focal length in a range of 18mm to 105mm. different types of cameras have different ranges and speciality lenses can extend outside the 500mm range. when using the Nikon D7100 today i noticed that using an 18mm focal length is a more wide lens so captures more of the scene and that the 105mm focal length was more narrow and captured only a small section of the scene.
here i have shown how changing focal length affects the image you take drastically the first image was taken at a focal length of 105 this results in most of the image being in focus and creating a shallow depth of field. the second image has a focal length of 50, and the 3rd image a focal length of 18mm you see the focal point of the image become more in focus as it is more zoomed in. I’m not sure ho well i have framed these images but you get the gist of the whole idea, the larger the mm of focal point the more just the focal point is in focus.
when changing focal point in portraits you have to be careful not to distort the face as using a smaller focal length as i have done on the first image here creates a more ‘odd’ looking face body ratio problem. as you become further away and zoom into the same frame to which i was before the background blurs a little creating depth of field and i also have a better angle on the photo creating a more flattering for portrait effect on the ratio of the person’s face. i use 18mm for the first image which created a distorted body ratio, 50mm on the second image which was slightly better but on the third image i took a much better image which looked like the correct ratio and also the better angle and good depth of field with not too much blur although the image itself isn’t completely identical to the others in the background an a little under exposed.