Originally posted by oceanxp
1) what is the difference between a lower F value and high F value ? e.g. F1.4 and F1.8 ?
Only 2/3 stop difference....
Here's an example of aperture in 1/3 stop increment.
f 1.0, f 1.2, f1.3, f1.4, f 1.5, f 1.7, f 2.0, f 2.2, f 2.5, f 2.8 ...... and so on.
Originally posted by oceanxp
2) how will lower F value improve sharpness ? coz from my experiences there are other factors involved ....
This depend on whether if the lense is a zoom or prime....
Zooms are designed to operate with a range of focal length. Therefore, they'll be pushing the limit of physics to achieve reasonable quality at aperture such as f/2.8. As such, the more expensive zoom will give very good performace at f4, but usually only "acceptable" quality at f 2.8. Cheaper zoom will have "improve sharpeness" at f 8.
Primes are dedicated for one focal length, Therefore, custom designs can be made for smaller lenses to prevent image distortion, improve sharpness, color and aperture speed. As such, all primes usually give super performance at f/2.8 and the more expensive ones will give "acceptable" quality at f 1.4. But, have you ever find a zoom with f 1.4? Lastly, Primes with max aperture at f2.8 usually give very good performance even at wide open.
