Variable ND

I bought an ND Fader II and returned it after using it once.

I wanted to tame some portable studio lights so I could flash on location at wider apertures.

I found that the AF became inconsistent and I missed lots of shots because of this. The IQ was also reduced, although this was only obvious at 1:1.

If you were shoot at smaller apertures where absolute focus accuracy was less important and using the ND for longer exposures in landscapes the fader would have been fine

Phil
 
I noticed no colour issues btw, but I was shooting in raw.
 
Thanks for that. I will be using the ND mainly on landscapes / waterscapes.

I was expecting to open up the ND, compose the shot, flick the camera into manual mode, then stop down the ND to the required level.
 
I've tried two of these - they're useless. With a wide-angle you get a cross pattern past 2-stops.

CPL_vs_VND.jpg


CPL on the left, VND on the right.


With a long lens it totally screwed the image quality - like this.

VND%20Test.jpg


That's the VND on the right and a Heliopan 10-stopper on the left. Both manually focussed.
 
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If you work within the limitations of a variable-ND you can get some interesting effects. Cheap ones are not precision pieces of optics, so if you're a pixel-peeper or a member of the sharpness-constabulary you should look elsewhere.. but I quite like the effects I can achieve and the adaptability they offer that makes them different to using a set of standard NDs. If you want sharpness and perfection, look for a set of quality ND filters instead.

If you're a fan of welding glass filters, then give a variable-ND a go.





Both of these were taken with a DIY variable-ND, stacking a linear polariser in front of a circular polariser. If you already have a circular polariser, you can often pick-up a linear polariser for £5-10. I haven't seen the "cage" artifacts (see Frank's image above) with this set-up, which makes me think that either it's an effect that's only apparent with wide-angle or that the 7DS variable-ND is constructed differently from my variable-ND.

I can't speak for wide-angle or telephoto lenses with these filters, I've standardised all my oddball filters (welding glass, DIY variable-ND, R72) onto my 30mm f/1.4.
 
Agree with Frank.

The dark-cross effect is inherant to using cross-polarisers in this way, even the £300 Singh-Ray version does it, but really only visible with wide-angles at high densities. At 24mm effective focal length and below, they're useless.
 
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