How Focal Length Affects the Images
Choosing a focal length has everything to do with what scene you're shooting and how you wish to showcase the subject. What’s the depth of field supposed to be, how do you wish it to be stylized? Below are various focal lengths, what their strengths are, and which scenes are best for each.
Focal length: Full-frame around 24-40mm; APS-C 15-24mm; MFT 10-17mm
Wide lenses are useful for filming master shots of a whole scene, or for achieving closeness within cramped spaces. They’re easy to hold in the hand and its perspective is dramatic with a quality depth of field. Colseups will be more distorted, however, which is a noted drawback.
Focal length: Full-frame around 50mm; APS-C around 35mm; MFT 20-25mm
Standard lenses offer a more natural-looking perspective. Perfect for portraits, shots with two people, and mid-shot scenes from one’s hip to head. 50mm prime lenses are smaller in size, yet give a wider aperture to allow more light in. Maximum apertures allow for a shallow depth of field; idea if you want to use focus creatively, but not great everything needs to be sharp.
Mis-Telephoto or ‘Portrait’
Focal length: Full-frame around 85-100mm; APS-C around 50-60mm; MFT 35-50mm
These types of lenses offer the least distortion on closeups, while continuously maintaining a maximum aperture for more light. While bulkier in size, they are trickier to handhold so it's best to use them on a tripod or gimbal. Such depth offers a flatter perspective to craft a strong composition.
Focal length: Full-frame, 135mm and above. APS-C 85mm and above. MFT, 60mm+
The even longer telephoto lenses are best for the most flattened perspective to isolate the subject from the background while bringing distant subjects near. These are the largest and heaviest lenses available, very tough to bring around and recommend for a tripod.