ND Filters - Can I get some info on them?

[Headshotzx]

Hey guys, I've got a question on ND filters, but first, let me tell you how I'm and why I'm going to use them.

I don't shoot landscapes, or at least don't intend to always shoot landscapes with the ND filter. I shoot portraits with off camera flash, strobist style.

The thing is, on a bright and sunny day, I can never ever get as low as 1/200 ISO100 while shooting wide apertures. I'll always get something like 1/400 while shooting f/2, and this means that the flash will only be present in the upper half of the image, sometimes even less.

When shooting off camera flash, I always aim to underexpose the bg by at least 2 stops and use flash to light my subject properly. Can't do this in the day with fairly small apertures (f/5.6) and definitely not at f/2.

So anyway, I know an ND filter will solve the problem. My question is, how many stops of ND filter should I get, and will I be able to retain AF on them?

Cheers,
Zexun

 

[Hitman]

Hi Headshotz,

One way is to calculate how many stops you need to bring the flash/shutter/aperture combination to a level you want on that bright sunny day, and then you can decide the strength of the ND filter that you need... :think:

Actually I don't know what I'm writing up there, but in simple words - a safe bet is to get at least a 2-stop (or 0.6) ND filter, and you should be able to take portraits using a large aperture on a bright sunny day...

If you are using flash, you can even try a 3-stop (or 0.9) ND filter to further open up the aperture...

You don't really need to worry about AF, even with a 3-stop ND filter, on a bright sunny day, the camera will have no issues with AF.

I personally use a 3-stop ND filter when taking pictures of water falls, streams etc...

Good luck!!

 

[J-Chan]

just happens I got my ND filter today for my 50 1.4.. a ND8 should be enough, tested it out abit and got abt 1/200th wide open but considering today is abit cloudy.. AF appears fine, and of cos the viewfinder appears dark..

 

[Headshotzx]

You don't really need to worry about AF, even with a 3-stop ND filter, on a bright sunny day, the camera will have no issues with AF.

just happens I got my ND filter today for my 50 1.4.. a ND8 should be enough, tested it out abit and got abt 1/200th wide open but considering today is abit cloudy.. AF appears fine, and of cos the viewfinder appears dark..

Great! Just what I wanted to hear. Jchan, you said you managed 1/200 wide open (1.4) with a correct exposure, right? That'd allow me an exposure that's only 1 stop underexposed @ f/2, but I guess I could go about shooting f/2.8 as well.

How about stacking of filters? Kinda like ND8 (3stops) + ND2 (1stop)? Vignetting many many?

Cheers,
Zexun