Hoya Variable ND filter

[Ferraro]

Bough a Hoya Variable ND filter 3-400, 77 mm for my 10-22 mm Canon (160 AUD). I did it just after seeing some reviews, I've been a Hoya customer for 40 years.
OK, now what happened?
The filter is not clean, it produces an "S" pattern that ends up vignetting two opposites corners of the image. Besides that it flattens the image so much that is practically unusable.
Attached a compressed one of a series of 400 files for a failed time lapse.
Anybody with a similar problem?
Thanks

[antoeknee]

Re: Hoya Variable ND filter

Variable ND are known to give problems with wide angle lenses IIRC.

[Ferraro]

Re: Hoya Variable ND filter

Thanks for the info, then what to do, single ND's?
That would be a "collection"...
I need to work on Bulb for Bramping Time Lapse, with max 1/60 sec and f:5.6 at bright sunlight, tipical aperture is F:16 at iso 100 at that speed.
If I would to buy two, wich one would you recommend?, nd4, nd8?
Thanks

[Ferraro]

Re: Hoya Variable ND filter

Which..

[S_J_P]

Re: Hoya Variable ND filter

Any filter on an ultra-wide-angle such as the 10-22mm is likely to vignette, variable ND are worse due to their increased thickness. A low-profile filter may improve matters, but is likely to still vignette to some degree.

However, I don't think that vignetting is your problem as it's affecting the image asymmetrically. Variable ND's comprise two opposing circular polariser elements (and a quarter-wave plate if I remember correctly) and polarisers with ultra-wa lenses do tend to give an asymmetric effect due to the widely differing angle of incident light across the frame - the result is a highly polarised portion and a gradient to an un-polarised portion, this gives a dark area and a light area in the same frame. The way to check this is to take a series of images from the same standpoint and same ND setting at 45º angles and see whether the dark-area remains static in space (i.e. it moves from the left of frame, to the centre, and then to the right of the frame)

Stacking two standard ND filters will eliminate the polarisation effect, but will almost certainly lead to true vignetting due to their thickness. Your only real option is a single low-profile ND filter, which may still vignette at 10mm.

As for ND filter specification, you'll need to consider the required light intensity reduction. For 1/60 on a beach (EV16) you may need f/32 at ISO100, to achieve f/5.6 you'll need 5 stops of light reduction which equates to 1/32 of the light transmission, and is equivalent to a ND32 filter

[Ferraro]

Re: Hoya Variable ND filter

Thanks Steve..
After leaving behind photography for video on the late 80's I am coming back but for time lapse, trying to make 4K lapses both still and with movement (Genie), a new challenging word where I have a lot to learn. Using rotating polarisers never caused me any problem in the past, neither on photo (17 & 24 mm Kodachrome 64 era) nor in video with equiv w.angle lenses of 24 mm, the widest area of video zoom lenses.
As a former scientist I understand the physics of the problem and appreciate your advise. Will try with cokin type square filters and see the results.

[antoeknee]

Re: Hoya Variable ND filter

I have some Cokin square and IIRC have used with my Sigma 10-20. Bear in mind you'll probably have to get the Z Pro which are 100mm or if you have cash then there are Lee.