urgent filter question

[sabenemmons]

I am new to using filters and think i could really use a diffuser (soft focus, fog whatever) in a upcoming "photoshoot" i am doing. My dumb question is what does the size mean i dont understand what the mm size has to do with anything or does the size determin the intencity of the effect.
saben

 

[Big Mike]

Most filters have threads and screw onto the front of your lens. Therefore, the the filter threads have to match the thread size of your lens. 52mm, 55mm, 58mm etc.

If you have a few different lenses with different thread sizes, you should buy all of your filters at the biggest size. You can then buy step-up rings which will adapt the smaller threads to the bigger filter.

 

[Rogue Monk]

If all you're going for is a soft focus, you can also use something like a shear scarf or pantyhose.

This link explains one method (in daylight, I'd probably use white instead of black and use an elastic in place of an old filter ring)

 

[Digital Matt]

If you are shooting digitally, you can reproduce that effect with photoshop easily. The benefit then is that not all of your photos are bound to it.