In the past several years smartphone cameras have taken a big step forward. The image quality of the best iPhone, Samsung, HTC cameras is equivalent to low-priced Canon, Nikon, Pentax and Sony DSLR cameras. Because of their convenience, compact size, network connection and huge array of applications many people prefer taking photographs with smartphones.
However, there is one advantage of DSLR cameras, the ability to use many stock lenses for different applications - macro lenses, telephoto lenses, fisheye lenses and more. The attachment market is much newer for smart phones. It is not possible remove a smartphone lens because it's embedded into smartphone body, designers of smartphone attachments need to work with the existing optics of the phone.
We have tested many integrated smartphone lenses and have found they usually have 3-4 mm of focal length, with f/1.8-f/2.2 aperture, with a pupil location inside the lens. These generally corresponds to 35 mm film cameras with about 25-30 mm focal length. The job of the lens attachments is to change focal length of native lens and hence change field of view or minimize the focusing distance.
While the lens parameters may be close for different smart phones, how universal a given attachment can be is often highly depends upon mechanical considerations. For a lens attachment to work property it needs to be mounted accurately relative to the native camera lens. This can be challenging with the wide variety of smart phone designs.
When made correctly, the image quality of a lens attachments should be close to the image quality of native lens with minimum distortion and chromatic aberrations.
In future posts we will look at different types of lens attachments in more detail.