VND filter recomendations

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

simple search will give you tonnes of good data on fader ND's.

Here's a VND mini shoot-out that I did.

I can't recommend a stop range without more details about your camera and lens selection.

Will you be shooting in a log profile?

What's your camera's native ISO?

What's the aperture range of your lenses?

What aperture do you anticipate shooting at? In my experience, most lenses are sharpest between f/4 – f/8).

Andrew S10 said:

Here's a VND mini shoot-out that I did.

I can't recommend a stop range without more details about your camera and lens selection.

Will you be shooting in a log profile?

What's your camera's native ISO?

What's the aperture range of your lenses?

What aperture do you anticipate shooting at? In my experience, most lenses are sharpest between f/4 – f/8).

Click to expand...

Thanks for the reply. Camera is an EOS-R , I will be shooting in log but not exclusively and will use whatever aperture is required for the effect desired. With most of the filters being 2-5 stops or 5-9 stops I'm truing to determine which would be the most useful .

I like the Hoya ones, they also open brighter than many others so you can leave them on to quickly shoot some stills.

Usually at most you'd want to get down 5 stops unless you were being very arty (i.e shallow DoF + bright light), when more is good. Although yesterday I was shooting f/1.8 in bright Sun and not quite getting to -4 stops, but on a phone so ISO 22 (with a £8.95 variable ND I thought I'd give a go).

Note NDs have a limit as to how low you can go then they start to fall apart, some have hard stops to stop you going too far, the Hoya don't.

Also cheaper ones can lose a lot of resolution at longer focal lengths.

Heliopan are also good, but heavy and expensive.

They can be a pain to use with lens hoods (although as few have a sliding door for VNDs and CirPols, the Canon 100-400 II for example).

SJPadraig said:

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

Click to expand...

I understand from another post of yours that you have 3 stop and 6 stop fixed ND filters.

At LV15 (bright sunlight), a 3-stop filter will get you from f/22 to about f/8. And the 6-stop filter will get you to about f/2.8.

Maybe a fixed 4-stop filter would work for you?

I'm not aware that you have a polarising filter, or are familiar with using them. Perhaps you are.

A polarising filter could make a significant difference to your still photography. Making use of polarisation can bring out or suppress colours, and suppress or enhance reflections.

Polarising filters used at wide-angle tend to have obviously uneven effects across the field, which are usually highly undesirable, though they can be used creatively.

Panning video while using a polarising filter implies similar colour and luminance shifts within the pan.

So why do I mention this stuff about polarising filters?

Because a variable ND filter is a polarising filter.

Most VND filters screw into the lens, and allow adjustment of attenuation by rotating a ring.

But polarisation is random if the filter is screwed down. Polarisation can be adjusted by unscrewing the filter, leaving it loose on the lens. Which is not exactly ideal.

Some of the better and more recent VND filters allow control of polarisation.

I have an SLR Magic VNDII, which allows locking the polarisation by use of a locking ring on the lens filter threads. It allows setting the polarisation independently from the attenuation. It's not ideal. That system risks the filter falling off the lens, or the lens filter threads being stripped if the operator is in a hurry, or unfamiliar with the equipment.

In a multi-camera shoot, polarising filters such as VND make little sense, since the different angles of the cameras imply differently polarised light received by different cameras from the same points in the scene.

My recommendations:

1. Forget VND. Just get a good 4-stop multi-coated ND filter.
2. Get a good polarising filter, and get used to that with stills (Hoya Fusion works well for me).
3. If you're happy with using polarising filters, and your shoot is single-camera, and doesn't involve panning, get a VND with control of polarisation.

Andrew S10's post makes it clear that many VNDs are rubbish.

John Vickers said:

SJPadraig said:

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

Click to expand...

I understand from another post of yours that you have 3 stop and 6 stop fixed ND filters.

At LV15 (bright sunlight), a 3-stop filter will get you from f/22 to about f/8. And the 6-stop filter will get you to about f/2.8.

Maybe a fixed 4-stop filter would work for you?

I'm not aware that you have a polarising filter, or are familiar with using them. Perhaps you are.

A polarising filter could make a significant difference to your still photography. Making use of polarisation can bring out or suppress colours, and suppress or enhance reflections.

Polarising filters used at wide-angle tend to have obviously uneven effects across the field, which are usually highly undesirable, though they can be used creatively.

Panning video while using a polarising filter implies similar colour and luminance shifts within the pan.

So why do I mention this stuff about polarising filters?

Because a variable ND filter is a polarising filter.

Click to expand...

I think I disagree, as they should be designed not to.

In a C.Pol you get a linear polariser (that you can rotate) followed by a layer (QWP) that randomises the polarisation of the light (so stuff inside the camera that wants different polarisations to work doesn't break).

In a VND you get a QWP first, so you throw away the polarisation of the incoming light (!!), then two linear polarisers, the first of which can be rotated (along with the front QWP). (As you rotate them the image gets darker, like with two pairs of polarised sunglasses.) The light is then polarised so you go through another QWP to randomise it and not screw over the camera.

Of course if the filter maker skimped on the QWPs it would have polarisation effects. I don't think that is the case but what I think happens is some manufacturers actually leave out the front QWP so you get two filters in one (C.Pol and VND).

John Vickers said:

Most VND filters screw into the lens, and allow adjustment of attenuation by rotating a ring.

But polarisation is random if the filter is screwed down. Polarisation can be adjusted by unscrewing the filter, leaving it loose on the lens. Which is not exactly ideal.

Some of the better and more recent VND filters allow control of polarisation.

I have an SLR Magic VNDII, which allows locking the polarisation by use of a locking ring on the lens filter threads. It allows setting the polarisation independently from the attenuation. It's not ideal. That system risks the filter falling off the lens, or the lens filter threads being stripped if the operator is in a hurry, or unfamiliar with the equipment.

In a multi-camera shoot, polarising filters such as VND make little sense, since the different angles of the cameras imply differently polarised light received by different cameras from the same points in the scene.

My recommendations:

1. Forget VND. Just get a good 4-stop multi-coated ND filter.

Click to expand...

If you're going with fixed filters for video I'd be inclined to add a 2-stop to the 3-stop, so you have 2,3 and 5. (Unless you want to shoot really wide apertures on bright Sunny days.)

John Vickers said:

1. Get a good polarising filter, and get used to that with stills (Hoya Fusion works well for me).
2. If you're happy with using polarising filters, and your shoot is single-camera, and doesn't involve panning, get a VND with control of polarisation.

Andrew S10's post makes it clear that many VNDs are rubbish.

Click to expand...

I hate a lot of VNDs too... but some seem good (I like Hoya and Heliopan).

I use a B&W variable ND, it works really well and is much more convenient than swapping and stacking various fixed nd filters, but it's expensive and big, so you can't use it with a normal lens hood.

Dr_Jon said:

John Vickers said:

SJPadraig said:

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

Click to expand...

I understand from another post of yours that you have 3 stop and 6 stop fixed ND filters.

[...]

So why do I mention this stuff about polarising filters?

Because a variable ND filter is a polarising filter.

Click to expand...

I think I disagree, as they should be designed not to.

In a C.Pol you get a linear polariser (that you can rotate) followed by a layer (QWP) that randomises the polarisation of the light (so stuff inside the camera that wants different polarisations to work doesn't break).

In a VND you get a QWP first, so you throw away the polarisation of the incoming light (!!), then two linear polarisers, the first of which can be rotated (along with the front QWP). (As you rotate them the image gets darker, like with two pairs of polarised sunglasses.) The light is then polarised so you go through another QWP to randomise it and not screw over the camera.

Of course if the filter maker skimped on the QWPs it would have polarisation effects. I don't think that is the case but what I think happens is some manufacturers actually leave out the front QWP so you get two filters in one (C.Pol and VND).

Click to expand...

Hi.

Thankyou for posting that.

Yes, scene->quarter-wave-plate->polariser->rotation->polariser->quarter-wave plate would do the job.

I hadn't realised that there were VND filters built like that.

But it seems that some VNDs are scene->polariser->rotation->polariser->quarter-wave plate.

The Tiffen VND seems to have a front QWP: https://www.ephotozine.com/article/tiffen-variable-nd-filter-review-20475

This SRB VND doesn't: https://www.ephotozine.com/article/srb-variable-nd-filter-review-20451

With a QWP on the front, there'll still be some polarising effect: about 1/2EV peak-peak, with the maximum transmitted amplitude from the first polariser occurring when the polarisation of the incoming light matches the first polariser (designed to be half-way between the fast and slow axes of the QWP).

[If I've understood that right - I'm a bit rusty on this stuff ;-) ]

This is assuming we have an ideal broadband (i.e. achromatic) QWP on the front.

Regards,

John Vickers said:

Dr_Jon said:

John Vickers said:

SJPadraig said:

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

Click to expand...

I understand from another post of yours that you have 3 stop and 6 stop fixed ND filters.

[...]

So why do I mention this stuff about polarising filters?

Because a variable ND filter is a polarising filter.

Click to expand...

I think I disagree, as they should be designed not to.

In a C.Pol you get a linear polariser (that you can rotate) followed by a layer (QWP) that randomises the polarisation of the light (so stuff inside the camera that wants different polarisations to work doesn't break).

In a VND you get a QWP first, so you throw away the polarisation of the incoming light (!!), then two linear polarisers, the first of which can be rotated (along with the front QWP). (As you rotate them the image gets darker, like with two pairs of polarised sunglasses.) The light is then polarised so you go through another QWP to randomise it and not screw over the camera.

Of course if the filter maker skimped on the QWPs it would have polarisation effects. I don't think that is the case but what I think happens is some manufacturers actually leave out the front QWP so you get two filters in one (C.Pol and VND).

Click to expand...

Hi.

Thankyou for posting that.

Yes, scene->quarter-wave-plate->polariser->rotation->polariser->quarter-wave plate would do the job.

I hadn't realised that there were VND filters built like that.

But it seems that some VNDs are scene->polariser->rotation->polariser->quarter-wave plate.

The Tiffen VND seems to have a front QWP: https://www.ephotozine.com/article/tiffen-variable-nd-filter-review-20475

This SRB VND doesn't: https://www.ephotozine.com/article/srb-variable-nd-filter-review-20451

With a QWP on the front, there'll still be some polarising effect: about 1/2EV peak-peak, with the maximum transmitted amplitude from the first polariser occurring when the polarisation of the incoming light matches the first polariser (designed to be half-way between the fast and slow axes of the QWP).

[If I've understood that right - I'm a bit rusty on this stuff ;-) ]

This is assuming we have an ideal broadband (i.e. achromatic) QWP on the front.

Regards,

Click to expand...

Holding my Heliopan filter and rotating it (the whole filter, not the two parts) while looking at my LCD monitor (a polarised light source) makes small colour changes on rotation, but nothing goes black. My 58mm Hoya does exactly the same. The 62mm goes black at one point (but only looking from one side, the camera one, so I assume Pol-Rot-Pol-QWP) so maybe is a fake, eeek, okay it's only 18 months old so getting a replacement...

(Edit) I also asked Hoya:

I have the following variable ND filters...
Heliopan 77mm
Hoya 58mm
Hoya 62mm
I was discussing how they work in an online forum and looking for a test to show they should have minimal polarising effects (someone was suggesting they act like circular polarisers, I think they shouldn't). Anyway I found a test but my newest filter, the 62mm, fails it. So I'm wondering if you changed the design or it's a fake. It also doesn't feel as smooth and solid in rotation as the 58mm, despite that being older.

Technical bit:
I expect a quality VND to consist of one rotating element consisting of a QWP then a Polariser, then a fixed part with a Polariser then a QWP (so: QWP-Pol rotation Pol-QWP). This should minimise the polarisation effect as you rotate it.

Looking at a source of polarised light (my LCD monitor) the 58mm and 77mm filters show minor colour changes as they are rotated (the whole filter, the two sections are kept in the same relative position). This is to be expected as (I assume) the QWPs will be optimised for one wavelength and so handle the other colours less well. However the 62mm one does this when looking in from the "outside" side but when looking from the "camera" side the image goes black at one point, like a circular polariser. Hence I deduce it has no front QWP (and the front polariser blocks the polarised light at some rotation; when looking from the "outside" the rear QWP unpolarises the light before it reaches a polariser and so you don't get the effect). This is very undesirable.

So my question is have you changed the design to make the filters less good but presumably cheaper to make (and I should stop recommending them) or did Amazon U.K. (it was them, not a marketplace company) sell me a fake?

Sorry if it's a bit complicated.
Best Regards

Cool!

If you don't get an answer, I have a couple of contacts in Hoya.

John Vickers said:

Cool!

If you don't get an answer, I have a couple of contacts in Hoya.

Click to expand...

So Hoya said:

"This product got a minor updated two years ago to improve performance. (The new version is without MIN/MAX with a O and a X to indicate useful range)
The reason for the update was to improve the color balance when shooting.
The change in color balance when changing the density has been improved.

In the visual test with the LED monitor with PL effect as the light source, the PL effect of the LED monitor and the PL effect of the filter interfere with each other.
It is not possible to perform an accurate test under the conditions assumed for normal subject shooting.

This filter is not for shooting LED monitors with PL effects, but is evaluated and developed for general shooting.
Even when shooting using LEDs, shooting tests under conditions where normal LED lighting without PL effects is used instead of the LED monitor can show significant improvement in color balance."



To which I replied:

"Okay, to clarify here’s my issue and why I think the new design is unacceptable…

Variable ND filters (VND) shouldn’t significantly change the look of the image as you adjust them. Also the image shouldn’t look different as you move the camera.

I believe the old design of the filter had a front Quarter Wave Plate (QWP) which is the best design, as it stops the VND behaving like a circular polariser. The new one appears not to have this feature, so the sky colour will, for example, change colour as you look in different directions, also reflections from water or glass will change as you rotate the filter.

Using the LCD is just a simple test to show the filter is not behaving correctly.

What should happen in a VND is incoming light passes first through a QPM layer. Think of this as randomising the polarisation of the incoming light. Obviously none of this is polarised anything like a LCD monitor, but there will be quantities of polarised light from things like the sky and any reflections. This then passes through a polarising filter, which isn’t a problem as the polarisation is by then randomised and so the sky or any reflections will only be changed by a small amount and it won’t change noticeably as you rotate the filter (the front QWP and first Polariser are in the rotating part).

It then passes through another polariser which will be reduce the light level depending on the polarisers rotation with respect to each other (easily demonstrated with two pairs of polarised glasses, look through both and rotate one). It then passes through another QWP to randomise the now polarised light, as the Auto-Focus (AF) systems of some cameras use light polarisation and heavily polarised light would cause them problems.

The is the way my “old” Hoya VND works.

However the new one appears not to have the front QWP, so the first polariser will interact with the polarisation in the incoming light. As an example if I shot a scene with two cameras outside on a sunny day and they were pointing in different directions the sky would be a different colour due to polarisation effects. Also light reflected on water/glass would look different in the two cameras. Even with one camera, panning around would change the blue of the sky, as would adjusting the rotation of the filter.

Effectively I believe the new VND is a Circular Polariser (C.Pol) as well as a VND. (A Circular Polariser is one rotatable polariser in front of a QWP to avoid AF problems.) Of course the rotation of the C.Pol in the VND isn’t controllable as it is set by the desired light level reduction.

Now if someone can point out how my LCD monitor test isn’t valid please proceed. The point of the test is you send highly polarised light at the VND. This shouldn’t be an issue as the front QWP will randomise it and the filter will work as expected. (Which is what my older Hoya filter does.) However the new one causes the LCD to go black at one rotation, the same as it would be if I rotated a lens of some polaroid sunglasses in front of it (or rotated a C.Pol). This says to me the front QWP has been removed in the new model, which is extremely undesirable as it will then act as a C.Pol as well as a VND, with the sort of effects I mention above.

Please ask your technical department if they agree the old model was QWP-Pol-(Rotation)-Pol-QWP and the current one Pol-(Rotation)-Pol-QWP.

Thanks for bearing with me, but VNDs that are also C.Pols are just a complete pain for shooting video and historically have been seen as the ones to avoid, especially as it’s easy to remove the issue with a front QWP. Finally note I don’t want to run around complaining about your filters if there’s any possibility I’m misunderstanding, so look forward to your technical department's opinion (although I fail to see how the LCD test couldn’t be correct, but am open to alternate suggestions).

Best Regards"


Does that sound clear enough to you? Also if you fancy asking your Hoya contact about it I'd appreciate it.

SJPadraig said:

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

Click to expand...

My documentary team uses Heliopan 77 mm VNDs, which have hard stops at the max and min settings. Optical quality is excellent and I see no degradation at 200 mm @ f/2.8 on either our Canon 70-200 or Sony G-Master 70-200 lenses. It fits inside the lens hood of the Canon but not the Sony.

The regular Hoya 77mm VND, plus the higher-end Hoya NDX both fit inside the lens hood of the Sony 70-200 2.8 G-Master lens hood. That lens has an sliding cutout in the hood which allows turning the VND with the lens hood on.

I've used the regular Hoya and it seems good. It does not have hard stops but I don't see any X-effects or other artifacts. The NDX is on back order so I haven't tested it yet.

We also use NiSi VND filters which seem good - they have hard stops, no X effects, and optical quality is good. However the bezel is larger so a lens hood doesn't fit over those.

joema1 said:

SJPadraig said:

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

Click to expand...

My documentary team uses Heliopan 77 mm VNDs, which have hard stops at the max and min settings. Optical quality is excellent and I see no degradation at 200 mm @ f/2.8 on either our Canon 70-200 or Sony G-Master 70-200 lenses. It fits inside the lens hood of the Canon but not the Sony.

The regular Hoya 77mm VND, plus the higher-end Hoya NDX both fit inside the lens hood of the Sony 70-200 2.8 G-Master lens hood. That lens has an sliding cutout in the hood which allows turning the VND with the lens hood on.

I've used the regular Hoya and it seems good. It does not have hard stops but I don't see any X-effects or other artifacts. The NDX is on back order so I haven't tested it yet.

We also use NiSi VND filters which seem good - they have hard stops, no X effects, and optical quality is good. However the bezel is larger so a lens hood doesn't fit over those.

Click to expand...

Any chance you could run my test on some of your Hoya VNDs please? (I have a Heliopan 77mm and it is fine. I have an old Hoya that passes and a new ones that fails.)

Test - find an LCD monitor (not OLED) and make a white screen, e.g. in Windows open Notepad and maximise it. Set the filter to a reasonably clear setting. Look through it from the outside and rotate the whole filter (i.e. not changing the filter setting) 360 degrees. Repeat from the camera side.

Pass - image is a little yellow and a little blue with rotation.
Fail - image goes black (and ND setting hasn't been accidentally changed).

Old Hoya - says MIN/Max at ends of range.
New Hoya - has 0 and X at ends of range.


Old-style Hoya Variable ND Filter (top) and new style (bottom)

Jon555 said:

Dr_Jon wrote:Any chance you could run my test on some of your Hoya VNDs please? (I have a Heliopan 77mm and it is fine. I have an old Hoya that passes and a new ones that fails.)...

Pass - image is a little yellow and a little blue with rotation.
Fail - image goes black (and ND setting hasn't been accidentally changed).

Old Hoya - says MIN/Max at ends of range.
New Hoya - has 0 and X at ends of range.

Click to expand...

I tested my $100 Hoya 77mm, my 77mm Heliopan and and 82mm NiSi. I have not received my $350 Hoya NDX yet.

The "cheap" Hoya fails the above test from the camera side, the Heliopan and NiSi pass.

However I shot a lot of material last week using the $100 Hoya on my Sony 70-200 2.8 G-Master, much of it at 200mm and 2.8, and it looks pretty good.

I just did a quick test of the $100 Hoya vs the more expensive Heliopan at 200 mm and f/2.8 (on the Sony G-Master) with the filters at about 50%, and I can't really see any difference in sharpness. Unfortunately I don't have time for more tests right now as I'm getting ready for a field assignment.

Thanks for mentioning this I am looking forward to more extensive testing when I receive the expensive Hoya NDX.

Dr_Jon said:

joema1 said:

SJPadraig said:

Hey people

Looking for recommendation on a VND , possibly brand and how many stops would be needed for general outside video work . Thanks in advance

Click to expand...

My documentary team uses Heliopan 77 mm VNDs, which have hard stops at the max and min settings. Optical quality is excellent and I see no degradation at 200 mm @ f/2.8 on either our Canon 70-200 or Sony G-Master 70-200 lenses. It fits inside the lens hood of the Canon but not the Sony.

The regular Hoya 77mm VND, plus the higher-end Hoya NDX both fit inside the lens hood of the Sony 70-200 2.8 G-Master lens hood. That lens has an sliding cutout in the hood which allows turning the VND with the lens hood on.

I've used the regular Hoya and it seems good. It does not have hard stops but I don't see any X-effects or other artifacts. The NDX is on back order so I haven't tested it yet.

We also use NiSi VND filters which seem good - they have hard stops, no X effects, and optical quality is good. However the bezel is larger so a lens hood doesn't fit over those.

Click to expand...

Any chance you could run my test on some of your Hoya VNDs please? (I have a Heliopan 77mm and it is fine. I have an old Hoya that passes and a new ones that fails.)

Test - find an LCD monitor (not OLED) and make a white screen, e.g. in Windows open Notepad and maximise it. Set the filter to a reasonably clear setting. Look through it from the outside and rotate the whole filter (i.e. not changing the filter setting) 360 degrees. Repeat from the camera side.

Pass - image is a little yellow and a little blue with rotation.
Fail - image goes black (and ND setting hasn't been accidentally changed).

Old Hoya - says MIN/Max at ends of range.
New Hoya - has 0 and X at ends of range.


Old-style Hoya Variable ND Filter (top) and new style (bottom)

Click to expand...

Interesting stuff!!

Although I have four Hoya Polarisers and three Hoya ND's, I only have one variable ND...and that is enclosed within an NF-M43 adapter.

I was curious about your test, so just tried it with my Variable ND:



I have only had the above for a couple of months, and haven't noticed any obvious polarising with my use of it so far, but I suspect that was mainly due the exact situations I have been using it in, as your test reveals it does indeed have a polarising effect.

Using your screen test, I do get a yellow > blue tint...separated by a brief black, during rotation of the entire adapter, with the ND set to its minimum setting {approx. 1.3 stops}.

Not a huge fail for my personal use {telephoto}, in most of the situations I use it....but I would prefer it to behave as an ND only.

That said, this adapter is excellent value for money, and a god-send for my wildlife video stuff, regarding versatility with m43 use with my two most used nikkor prime telephotos, which are not noticeably degraded with it.

Interesting thread!

joema1 said:

joema1 said:

Dr_Jon wrote:Any chance you could run my test on some of your Hoya VNDs please? (I have a Heliopan 77mm and it is fine. I have an old Hoya that passes and a new ones that fails.)...

Pass - image is a little yellow and a little blue with rotation.
Fail - image goes black (and ND setting hasn't been accidentally changed).

Old Hoya - says MIN/Max at ends of range.
New Hoya - has 0 and X at ends of range.

Click to expand...

I tested my $100 Hoya 77mm, my 77mm Heliopan and and 82mm NiSi. I have not received my $350 Hoya NDX yet.

The "cheap" Hoya fails the above test from the camera side, the Heliopan and NiSi pass.

However I shot a lot of material last week using the $100 Hoya on my Sony 70-200 2.8 G-Master, much of it at 200mm and 2.8, and it looks pretty good.

I just did a quick test of the $100 Hoya vs the more expensive Heliopan at 200 mm and f/2.8 (on the Sony G-Master) with the filters at about 50%, and I can't really see any difference in sharpness. Unfortunately I don't have time for more tests right now as I'm getting ready for a field assignment.

Thanks for mentioning this I am looking forward to more extensive testing when I receive the expensive Hoya NDX.

Click to expand...

The long version of what I think is going on is here (you have probably seen it, but it is a little buried):
https://www.dpreview.com/forums/post/62888698

Dr_Jon said:

I like the Hoya ones, they also open brighter than many others so you can leave them on to quickly shoot some stills.

Usually at most you'd want to get down 5 stops unless you were being very arty (i.e shallow DoF + bright light), when more is good. Although yesterday I was shooting f/1.8 in bright Sun and not quite getting to -4 stops, but on a phone so ISO 22 (with a £8.95 variable ND I thought I'd give a go).

Note NDs have a limit as to how low you can go then they start to fall apart, some have hard stops to stop you going too far, the Hoya don't.

Also cheaper ones can lose a lot of resolution at longer focal lengths.

Heliopan are also good, but heavy and expensive.

They can be a pain to use with lens hoods (although as few have a sliding door for VNDs and CirPols, the Canon 100-400 II for example).

Click to expand...

As you may have noticed from my posts below I think there is an issue with the latest Hoya Variable ND filters, so withdraw my recommendation. Sorry.

Dr_Jon said:

John Vickers said:

Yes, scene->quarter-wave-plate->polariser->rotation->polariser->quarter-wave plate would do the job.

I hadn't realised that there were VND filters built like that.

But it seems that some VNDs are scene->polariser->rotation->polariser->quarter-wave plate.

The Tiffen VND seems to have a front QWP: https://www.ephotozine.com/article/tiffen-variable-nd-filter-review-20475

This SRB VND doesn't: https://www.ephotozine.com/article/srb-variable-nd-filter-review-20451

With a QWP on the front, there'll still be some polarising effect: about 1/2EV peak-peak, with the maximum transmitted amplitude from the first polariser occurring when the polarisation of the incoming light matches the first polariser (designed to be half-way between the fast and slow axes of the QWP).

[If I've understood that right - I'm a bit rusty on this stuff ;-) ]

This is assuming we have an ideal broadband (i.e. achromatic) QWP on the front.

Click to expand...

Click to expand...

Apologies:

My maths was a bit off: an ideal quarter-wave-plate in front of a linear polariser alligned half-way between the fast and slow axes of the QWP should give linearly polarised output with amplitude independent of the input polarisation. In this ideal case, attenuation of the front QWP+polariser would be 1EV, regardless of incoming polarisation.

[I think I forgot that the fast and slow outputs of the QWP are in quadrature, not in phase]

Making good polarisers dosen't seem so hard.

But the behaviour of the front QWP on a dual-QWP VND seems quite critical. Wavelength-dependent deviation from wavelength/4 delay will give elliptical polarisation after the first QWP: skintones could vary depending on the angles between the the light source, the skin, and the camera.

The quality of the output side QWP doesn't seem to matter so much: it's mostly there so that metering works OK on a DSLR - used as a DSLR, not in live view. There will be some minor polarisation issues at extreme low f/numbers, related to reflections off the sensor front cover, AA filter (if present), and microlenses.

Here's an Edmund Optics application note on waveplates: https://www.edmundoptics.eu/resources/application-notes/optics/understanding-waveplates/

It's interesting to compare their examples of the behaviour of narrowband and broadband (achromatic) waveplates.

I wonder if the limitations of the front QWPs are why some folk report weird colour effects with VND filters:
Mr Dugdale has some relevant comments on lens hood compatibility earlier in the video.

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But then some folk here seem quite happy in actual use with the VND filters they're using.

Dr_Jon said:

So Hoya said:

"This product got a minor updated two years ago to improve performance. (The new version is without MIN/MAX with a O and a X to indicate useful range)
The reason for the update was to improve the color balance when shooting.
The change in color balance when changing the density has been improved.

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I can perhaps believe that (see other comment).

Jon555 said:

In the visual test with the LED monitor with PL effect as the light source, the PL effect of the LED monitor and the PL effect of the filter interfere with each other.

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The LED/LCD confusion is, umm, unfortunate.

Of course the polarisation interferes!

Jon555 said:

It is not possible to perform an accurate test under the conditions assumed for normal subject shooting.

This filter is not for shooting LED monitors with PL effects, but is evaluated and developed for general shooting.

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Huh? "General Shooting" where all light is unpolarised?!?

Jon555 said:

Even when shooting using LEDs, shooting tests under conditions where normal LED lighting without PL effects is used instead of the LED monitor can show significant improvement in color balance."

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Low grade marketing BS. You're not talking about LED lighting.

Jon555 said:

To which I replied:

"Okay, to clarify here’s my issue and why I think the new design is unacceptable…

Variable ND filters (VND) shouldn’t significantly change the look of the image as you adjust them. Also the image shouldn’t look different as you move the camera.

I believe the old design of the filter had a front Quarter Wave Plate (QWP) which is the best design, as it stops the VND behaving like a circular polariser. The new one appears not to have this feature, so the sky colour will, for example, change colour as you look in different directions, also reflections from water or glass will change as you rotate the filter.

Using the LCD is just a simple test to show the filter is not behaving correctly.

What should happen in a VND is incoming light passes first through a QPM layer. Think of this as randomising the polarisation of the incoming light. Obviously none of this is polarised anything like a LCD monitor, but there will be quantities of polarised light from things like the sky and any reflections. This then passes through a polarising filter, which isn’t a problem as the polarisation is by then randomised and so the sky or any reflections will only be changed by a small amount and it won’t change noticeably as you rotate the filter (the front QWP and first Polariser are in the rotating part).

It then passes through another polariser which will be reduce the light level depending on the polarisers rotation with respect to each other (easily demonstrated with two pairs of polarised glasses, look through both and rotate one). It then passes through another QWP to randomise the now polarised light, as the Auto-Focus (AF) systems of some cameras use light polarisation and heavily polarised light would cause them problems.

The is the way my “old” Hoya VND works.

However the new one appears not to have the front QWP, so the first polariser will interact with the polarisation in the incoming light. As an example if I shot a scene with two cameras outside on a sunny day and they were pointing in different directions the sky would be a different colour due to polarisation effects. Also light reflected on water/glass would look different in the two cameras. Even with one camera, panning around would change the blue of the sky, as would adjusting the rotation of the filter.

Effectively I believe the new VND is a Circular Polariser (C.Pol) as well as a VND. (A Circular Polariser is one rotatable polariser in front of a QWP to avoid AF problems.) Of course the rotation of the C.Pol in the VND isn’t controllable as it is set by the desired light level reduction.

Now if someone can point out how my LCD monitor test isn’t valid please proceed. The point of the test is you send highly polarised light at the VND. This shouldn’t be an issue as the front QWP will randomise it and the filter will work as expected. (Which is what my older Hoya filter does.) However the new one causes the LCD to go black at one rotation, the same as it would be if I rotated a lens of some polaroid sunglasses in front of it (or rotated a C.Pol). This says to me the front QWP has been removed in the new model, which is extremely undesirable as it will then act as a C.Pol as well as a VND, with the sort of effects I mention above.

Please ask your technical department if they agree the old model was QWP-Pol-(Rotation)-Pol-QWP and the current one Pol-(Rotation)-Pol-QWP.

Thanks for bearing with me, but VNDs that are also C.Pols are just a complete pain for shooting video and historically have been seen as the ones to avoid, especially as it’s easy to remove the issue with a front QWP. Finally note I don’t want to run around complaining about your filters if there’s any possibility I’m misunderstanding, so look forward to your technical department's opinion (although I fail to see how the LCD test couldn’t be correct, but am open to alternate suggestions).

Best Regards"

Does that sound clear enough to you?

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Pretty clear.

Jon555 said:

Also if you fancy asking your Hoya contact about it I'd appreciate it.

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Will do.

Regards,