Using a variable ND filter question

I'm still toying with learning how to use this…and I find at times when I have it dialed up to the max end, that I get these uneven dark shades in my image.

What causes that…or what is happening when I get this?

thx

Ive no experience in that but i guess it is just a cheap filter?

What kind of filter is it? brand?

I would only use variable ND's for videographic purposes. For still it is just too unqualitative...

The variable ND filters achieve their effect by having two polarizing filters in front of each other. As you dial in the strength the filters reduce the light coming in on each axis, but if you go too far they begin crossing to the point of actually blocking light, hence the x's. A regular ND filter is just neutrally colored glass so you dont have such issues.

CatchingUp wrote in post #16733498
I'm still toying with learning how to use this…and I find at times when I have it dialed up to the max end, that I get these uneven dark shades in my image.

What causes that…or what is happening when I get this?

thx

Does this seem to occur with any particular lens focal length? Can you post an image for us to see?

Go to http://photo.net …-accessories-forum/00aItm. Is the image there what you are getting?

if it's the X shape, that's just what they do to a degree. I have a cheap one and the Tiffen, the later is better. A test somewhere not too long ago, maybe in Advanced Photographer, rated the Tiffen highest, even better than the Singhray (spelling?) which costs a lot more. You just have to play with it, don't close all the way down. You can't see the effect in live view since the screen is too dark and it only shows up after long exposure. Sometimes it can be fixed in PP to some degree, but best to not fully close it down. Since it's polarizers, it might also be different depending on where the sun is.

To go really dark, it's best to use a 10stop or a stack of other smaller stops in a filter holder. I use HiTech and am pretty happy with them. Lee are the top of the line here but are so expensive and I use them so rarely, it's' not worth it for me.

You can also use very cheap welding glass (replacement glass for welding masks) that you can attach to the front of your lens with rubber bands, they won't fit into any holder I'm aware of. Might give a light color cast that's easy to fix. I attach mine by reverting the flower shaped lenshood on my wide angle, then use rubber bands around the 'petals' of the hood to hold the welding glass in place. A cheap option to play with, before jumping in for the really expensive stuff.

The filter is a 'pro-master' variable ND It was the only one available when I was in Maine this past summer. I use it on my 17-40. I'm uploading two samples…rather extreme case but on the max setting. I paid about 85.00 for the filter. I've gotten good results on other occasions…but usually at a lower setting.

wow.

This just reinforces my approach of static filters.

I have had some positive results as well:

IMAGE LINK: http://www.flickr.com …nycorsoimages/9​409571570/

CatchingUp wrote in post #16734590
The filter is a 'pro-master' variable ND It was the only one available when I was in Maine this past summer. I use it on my 17-40. I'm uploading two samples…rather extreme case but on the max setting. I paid about 85.00 for the filter. I've gotten good results on other occasions…but usually at a lower setting.

This is one of the main reasons why I don't use VNDs. The dark X will start appearing at quite low densities when using a wide-angle lens. The price and quality of the VND doesn't make any difference.

hollis_f wrote in post #16735580
This is one of the main reasons why I don't use VNDs. The dark X will start appearing at quite low densities when using a wide-angle lens. The price and quality of the VND doesn't make any difference.

This is correct. I also don't use VNDs because of this.