[boriscleto]

I think i am posting this in the right place. I have been experimenting with film photography and learning along the way for a nearly a year now, mainly with a K100 and an ME Su albeit with varied results. I believe i have managed to grasp the fundamentals such as exposure, metering, f stops, iso, aperture etc.

However i still wave no idea what makes a decent lens or what the benefits are of different lenses past wid angle, tele macro etc. Could somboady please explain to me what all this f1.8 business means and why an f1.8 lens might e better to use in certain situations rather than an f2 etc.

Excuse my ignorance and thanks in advance.

https://en.wikipedia.org/wiki/F-number#Standard_full-stop_f-number_scale

The difference between f/1.8 & f/2 is 1/3 of a stop. One full stop would be f/1.4.

A stop is a unit of measurement used to quantify ratios of light. Each added stop is a factor of two, each subtracted stop is a factor of one-half. So changing one stop, ie from f/2 to f/4, is a halving of the light intensity.

F stops also have an effect on Depth of Field.

https://en.wikipedia.org/wiki/F-number#Effects_on_image_sharpness

In addition to DoF there are the effects of diffraction to be concerned with above f/11 or so. But in some situations you have to bite the bullet and accept diffraction for the added DoF.

Lens speed - Wikipedia, the free encyclopedia

Aperture - Wikipedia, the free encyclopedia