Filters for Sigma 18-35 f1.8

[seasamshoot]

Hi Canonrumors,

I am looking at getting a Variable ND filter for my kit ( I know a set of ND's is better, but it seems like it would be out of my budget. I also like the ability to use variable ND for video purposes).

My question is two fold:
1. Because it is a wide angle lens, do I need to get a "slim" version and is it out of the question using a 77 with a step up ring to the 72mm filter size of the lens?
2. Which Variable ND's, if any have you had success with? My budget is about 150 for the filter.

Thanks,

Sam

[Etienne]

Tiffen Vari ND is your best bet at that price:  http://www.bhphotovideo.com/c/product/813278-REG/Tiffen_77VND_77mm_Variable_Neutral_Density.html

Step up rings are fine, step down not so good for obvious reasons

[Hjalmarg1]

You don't  need to get a "slim" version since most of the time you will be using high stop numbers (f11-f18) and I also use my ND 77mm filter with a step up ring to the 72mm filter size of the lens.
There are many good Variable ND's but they are expensive. Tiffen and Hoya may fit in your budget.