GKR

What are stops, how do I use then and are they necessary?

RichardTaylor Loc: Sydney, Australia

Do you meean F stops (as in aperture settings)?

GKR

I went to the camera store to buy a ND filter and the person that was helping me asked me how many stops do I want.

RichardTaylor Loc: Sydney, Australia

A ND filter will alow you to shoot at longer exposures at the very least. The stops you want (need?) depend on the lighting conditions and long you want you want to shoot for.
A 10 stop ND filter will allow you to shoot very long exposures in bright sushine. A 2 or 3 stop ND filter will allow you to blurr water falls etc in overcast conditions.

GKR

Now, what are F stops? Here's a crazy question for you. Can I put a 3 stop filter over a 10 stop filter or is it best to use one filter at a time?

IBM

That's funny , and you were there , and he wouldent tell you I suppose ???

GKR

He did explain it to me, but in a hurry up way.

RichardTaylor Loc: Sydney, Australia

Re F stops: See some of the replies (and links) about "Understanding Exposure" to your previous post about long exposures.

You can combine filters however it is not a great idea as you may get some image degradion due to the light having to pass through multiple layers of "glass".

IBM

How many pains of glass would you have to put flat together before all you see on the other side is a big blure

GKR

Thanks for your help and I'll be heading to the book store this weekend. Need to get that book"Understanding Exposure". Take care and thanks again.

RichardTaylor Loc: Sydney, Australia

It's a very good book.

IBM

I would say , if you did not know what they were for , that you do not need them , unless you need them for what your planing on

Haydon

Yes you can stack filters but it requires prefocusing first if you were to use a 3/10 stop in combination. It is important to use higher quality glass as you continue to put layer upon layer of glass in combination. I have stacked a polarizer with a 6 stop ND filter with a 3 Stop graduated ND filter in front before with minimal impact. Using filters to obtain longer exposures will have a growing period in calculating length of time your shutter will be open.

SharpShooter Loc: NorCal

GKR, welcome to the Hog!
About the stops...., I might have to stop but don't have time to stop and explain it right now!!! LoL
SS

BHC Loc: Strawberry Valley, JF, USA

I don't think you have any idea of how shocked some of us were to read your question; it was basic, plain and simple - and remarkably wise and thought-provoking. As I began to write an answer, having used the term stops for 60+ years, I suddenly realized that it wasn't one of the sequence of numbers we use to explain an exposure variable. As I stop (pun not intended) and think about it, I realize that a stop is not just the size of the aperture; a stop is one of those ubiquitous terms we throw around about apertures, shutter speed, ISO, filter density, etc., without giving any thought to the complexities we are discussing. It has a myriad of definitions, meanings and purposes. When you read your book, you will know what the word generally means, but you will also learn the context of its use - and that will lead you to a better understanding of photography. I won't try to answer your questions; the answer is more meaningful than many of us understand. Thank you for your question and for having the courage to ask it. Don't let smarmy remarks and jokes lead you to think it was not a wise question.

And, by the way, the next time a sales representative asks you a question you don't understand, ask him/her to explain the question. You don't have to believe them; just listen to their sputtering inane explanation - because by that time you will know the answer and smile at their ineptitude.