Why not to buy cheap Chinese variable ND filters

[Nesster]

I figured I'd try one, I understood there would be color shift, but planned on converting to b&w anyway. The item in question is a FOTGA Variable ND Filter; it promises "Optical Glass from Japan" etc Click here to see on Ebay... I suppose I'll have to try their
'professional after sales support.'

Apart from the obvious, the filter screws up sharpness at infinity.


#1

#2


Ai'd Nikkor-P 24/2.8, D600

[calvin83]

From the auction link:

[Nesster]

Thanks for that... what causes that, just the geometry of the thing?

[SonicScot]

I have a cheap one too (approx £12-Amazon) and mine also softens images, though not much. The colour cast is minimal and easy to correct in Lightroom.

I don't know what causes the 'X' at wide angles but it's not too difficult to avoid after a few test shots.

I keep promising myself I'll buy a 'good' one but the best ones cost over £200.

[GeorgeSalt]

The cheapest way to a VND is to add a linear polariser to any CPL you already own.

[philslizzy]

[eddieitman]

If you want a good nd filter i can recomend the haida 10 stop nd great and not to expensive hardly any colour cast

[GeorgeSalt]

[calvin83]

[Orio]

Discussion moved to appropriate section ("Accessories")

[cooltouch]

What GeorgeSalt said about linear polarizers. Also, I'll often buy camera outfits that are for sale locally, typically through Craigslist. This has netted me a rather large stack of both linear P's and circular P's. Anyway, stacking two is an easy way to get an ND, and one of them does not have to be circular. Something I recall from a physics class I took over 30 years ago is that when two polarizers are stacked, setting them at 90 degrees to each other renders 100% opacity, or darkness, if you will. The ones we had to demonstrate this weren't circular, either. However, stacking two circular Ps doesn't give you this effect.

Since the lens used was a 24mm Nikkor, I'm assuming the example ND filter is a 52mm, right? SonicScot's comment that one would run over £200 seemed -- well, just implausible, let's say. So I did a bit of googling. And £200 is indeed a bit high. I can buy a B+W variable ND from B&H Photo for "only" $226.95. Whoa! Such a deal! Criminy! Tiffen makes excellent filters. Theirs carries a list price of "only" $129.95. Geez, I don't understand why they're so expensive. I've just assumed they were two polarizers stacked. How else would they work?

[SonicScot]

Here's one on Amazon for £279 + postage http://www.amazon.co.uk/gp/offer-listing/B005CTT974/ref=dp_olp_new?ie=UTF8&condition=new&qid=1381075784&sr=1-1
I am talking about a 77mm variety because that covers all but two of my lenses.

[GeorgeSalt]

If you're just looking for very long exposures with the cheapest filter, you can't beat a DIY using welding glass..

coquet island by SaltGeorge, on Flickr

[SonicScot]

Nothing wrong with that George.

[Lloydy]

Welding glass comes in different darkness grades ( for different types of welding ) and it's optically flat, if welders are looking through it all day then it has to be good because of all the health and safety issues.
I use MIG welding glass which fits Cokin P filter holders. I take the sharp edges and corners off with an oilstone or one of the cheap diamond dust sharpening stones.
A visit to your local engineering supplier will get you the glass quite cheaply, but a DIY / motoring store might be sell the glass singly.

[metalhund]

[GeorgeSalt]

I bought it several years ago after someone sent me a link to the welding glass filled thread on Talk Photography. It's just a cheap shade 8 (I think) from EBay, I think it is green tinged. I use a Lightroom preset for the colour correction.

You can't completely take away the colour cast, but with the right scene you can get extremely close.

[metalhund]

Thx - the photo looks great by the way

[GeorgeSalt]

This one was shot with a linear-circular polariser VND.



As long as you don't push the effect to hard, you can recover the colour quite well. It's odd to use though, you set the exposure you want and then Meyer to set the filter.

[metalhund]

I found this page with all the information I needed. I insert it here, if there are others who have the same questions as I do.
http://www.alexwisephotography.net/blog/2013/07/07/create-yourself-a-neutral-density-filter-for-under-10/

[GeorgeSalt]

He misses out a vital piece of equipment, you must cover up the eyepiece when doing thus to prevent light coming in from the back. It does happen during long daylight exposures.

[metalhund]

it's nice to know. Thanks for the information.
I have ordered a piece of glass, and am excited to try it.

[GeorgeSalt]

My filter set-up for welding glass..


welding glass filter, mk2 by SaltGeorge, on Flickr

You need to file the bump on the back down because once you epoxy the welding glass on you can't flex the holder to get the lens ring in.

[skida]

[Lloydy]

Standard MIG welding glass with the sharp edges smoothed off with diamond dust sharpening stone, unmodified Cokin P Series filter holder.





Works perfectly, no gluing or messing about.