Variable ND screw on filters - any good?

Wingnut Warrior · 16 Apr 2012

I have been looking on possibly getting a set of slide in square filters until i saw a screw in Variable ND Filter. It claims to go from ND2 to ND400.

They seem very cheap which worries me about the quality. Does anyone have any experience of these and can offer some advice?

AESamuel · 16 Apr 2012

Essentially they are two polarising filters which when aligned let plenty of light through and when they are 90 degrees to each other they hardly let any through.

I've bought a cheap one (8 quid from ebay) but my step ring hasn't arrived so I can't use it yet. The build seems fairly solid and the glass quality looks pretty good to the eye. There is plenty of price range out there but being a student on a budget I went for the cheap one. As soon as my step ring arrives I'll let you know.

tdodd · 16 Apr 2012

They have limitations which may or may not be a problem for you. I bought a fairly expensive one and returned it because it did not meet my needs. If you shoot with very wide angles you may find you can't go as far as ND400. If you shoot with long lenses you may find the IQ (sharpness/contrast) deteriorates. Here are some notes from the importer about the LCW Fader ND II, which I bought and returned.....

http://www.premier-ink.co.uk/photog...rkshop-77mm-fader-nd-filter-mk-ii-p-2828.html

They added the section on limitations based on feedback from myself and other customers as they were not made aware of the constraints by the manufacturer. If I'd known these things prior to purchase I would not have bothered.

HoppyUK · 16 Apr 2012

I had the same filter as Tim, and also returned it.

I have also used some of the most expensive vari-NDs on the market. They're all basically the same, and all, IMHO, useless.

They're maybe okay if you only use them at moderate densities, and on normal-ish lenses - nothing too wide (or you get that dark cross appearing) and nothing too long (as they reduce sharpness).

Cross polarisers are used in the movie industry as faders, and that's where they should stay. Get a fixed ND.

nobby noname · 16 Apr 2012

Got a cheapo one to play with (20 quid from uk online shop of fair repute) and totally unimpressed after a quick try. The 'cross effect' appeared at much lower nd setting than I expected. Will have another go before giving up on the thing, but images were so bin-worthy I'm not holding my breath for much. Would suggest stick to the non variable type...

philthejuggler · 16 Apr 2012

I tried a Light Craft one for a portrait shoot outdoor so I could get a low enough shutter speed to sync my flash while using wide apertures. I wasn't impressed - shots not sharp (not sure if it was focus accuracy or the glass softening the image).

Phil

john_e · 17 Apr 2012

I bought the 7dayshop version and I have to say that for the price I'm quite pleased with the results. I haven't seen any of the 'cross effect' despite using it on the 5DII @ 24mm. A few examples...

nobby noname · 17 Apr 2012

john_e said:
I bought the 7dayshop version and I have to say that for the price I'm quite pleased with the results. I haven't seen any of the 'cross effect' despite using it on the 5DII @ 24mm. A few examples...

Yep, they look just what I was after (and failed at!). Was the nd set fairly low for these, or were you able to darken the filter a fair bit to decently slow the shutter?

I noticed a 'cross' developed as i increased the nd value, but seemed to occur at a much lighter setting than I expected (was just using kit lens on a 550d on a fairly bright day - perhaps I was expecting far too much!)

john_e · 17 Apr 2012

These were more or less at full density, the third shot was at midday and is a 30 sec exposure IIRC. I found that at full density it was hit and miss but just backing it off a fraction gave a huge improvement and much more consistent results.

hollis_f · 17 Apr 2012

I've tried two of these (7-dayshop and Polaroid) and they were both rubbish with my 10-22, which is the lens I'm most likely to use them with.

One problem with them is figuring out exposure. With my 10-stop ND I know I need to multiply the shutter speed by 1000. But with a vari-ND I dunno if I'm using 4 or 8 stops - so I dunno what exposure to use. And you can't rely on exposure metering because they'll let in IR - which will affect the metering but not the exposure.