Blackmagic Forum

Hi cinematographers,

I'm looking at purchasing some ND filters for my lenses. I have four MFT Voigtlander lenses (10.5mm, 17.5mm, 25mm, 42.5mm) and would like to buy at least one ND filter for each lens filter size I need. So three in total. I'm using the Pocket 4K.

What is the most commonly used ND filter?
3 Stop, 6 Stop, or 10 Stop?

I don't want to buy all three ND filter sizes for each lens filter diameter if I don't need to- that being 52mm, 58mm, and 72mm. But I want to be on the safe side.

The film I am planning on shooting is a road movie shot mostly outdoors during the day.

A much simpler solution is to buy step-up rings so you can use filters that are all the same size. 77mm is common and will work for the lenses you have now, but some lenses are bigger and if you ever think you might get more lenses you might want to go with 82mm for future-proofing.

Get step up rings to bring all your lenses to 77 or 82 mm and then buy a set of ND filters for that size. If you ever think you'll need to use a matte box, check out the step up rings from Duclos Lenses, which have outside diameters sized to fit common matte box sizes.

Wow, step-up rings sound like a great idea! Thank you. I didn't know about them.

A suggestion I would like to put forward is using a variable ND with a Tilta or Smallrig matt box.

This is a budget solution but if you have deep pockets ignore this.

These inexpensive matt boxes take screw on filters. I know that the Tilta provides ring adapters as well as a way to work with 15mm rails.
You can attach the largest diameter variable ND to the matt box, use a doughnut on the lens to prevent light leakage.

Be aware that not all variable ND's can fit and work in the confines of these small matt boxes.

Step up rings is a good suggestion.

From experience, I’d say although stepup rings initially seem like a good, frugal idea, in the long term, you’d be better off getting an affordable matte box and going for either 4 × 4 or 4 × 5.65 filters for the most used type – ND, polarizer, or diffusion.

That’d free you from regretting being locked into a 77- or 82-mm filter diameter of a lens – I’d give the same advice to myself if I could go back in time 5 years earlier.

As for the ND filters, I use either 0.9 or 1.5.

Generally, it’s better to stick to 5 stops at the highest end for video and use that in combination with the iris – I certainly dislike opening my lenses above T4 in strong sunlight.

Also, inexpensive 6 and 10 stop filters as well as variables tend to effect color more. As you reduce the shorter waves of light (cool), the infra red pollution increases in ratio to the reduced upper wavelengths, making your blacks hard to neutralize.

Bromine 18 wrote:From experience, I’d say although stepup rings initially seem like a good, frugal idea, in the long term, you’d be better off getting an affordable matte box and going for either 4 × 4 or 4 × 5.65 filters for the most used type – ND, polarizer, or diffusion.

I totally agree but it's worth noting that those cinema filters are a lot more expensive than screw-ins, simply by virtue of their size.

Matte boxes that clamp on to the lens will work as long as your lens doesn't have a rotating front element; if it does the matte box will spin as you focus the lens (this is the voice of experience!). I have a matte box that can either clamp on to the lens or be mounted on rails; if you mount it on rails it'll work with all lenses except of course some zooms whose length changes as you zoom in and out. Lots of gotchas to think through.

I can’t speak to the most commonly used ND filters but I use 8 NiSi Nano 4x5.6” filters in a Misfit Atom matte box or 10 SLR Magic 82mm screw-on filters. They’re good but not perfect without some simple colour correcting around the 6-stop filter. I have video on Vimeo testing these.

I also use 86mm Tokina Kenko filters if shooting with the larger Tokina 11-20mm zoom which are good for 2/4/6 stops.

I'm looking at those Nisi.

I've seen the threads about IR pollution after cutting with ND. Fix one thing cause another it serms.

And the Rawlite in-cam filter for IR looks good but not cheap, and well ... you gotta take apart stuff where getting a slight bit of dust in will haunt you.

Was wondering if anyone installs those as a service without costing as much as the camera ...

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Brad Hurley wrote:Lots of gotchas to think through.

We’re on the same page.

But I think for Voigtländers, rotating front elements aren’t an issue, are they?

Plus, some of the good-quality full-spectrum NDs, such as the Tiffen NATurals, reach $160 for 77-mm circular sizes.

Then the approximately $130 price difference between them and the square ones needs to be weighed in considering potential lens investment in the future.

I'd say investing in the long term is best with ND filters. So buying a good set of 4x5.65 filters is a solid plan. Buy the matte box of course. Then get NDIR 0.3, 0.6, 0.9, 1.2, 1.5, and 1.8. This will give you the entire range from 1 stop up to 6 stops in 1 stop increments.

With the URSA Mini Pro models and the Pocket 6K you get built-in ND that does 0.6 (2 Stops), 1.2 (4 Stops), and 1.8 (6 Stops). Theoretically you could then get away with a single NDIR 0.3 filter to cover the 1 stop increment when you need it. However, external ND remains better than the internal ND options. More control. So having the full range can be very helpful.

Plus using a matte box really helps control light spilling on to the lens. I also use it for additional filters like a Polarizer, soft diffusion filters, and special effect filters like Blue Streak or Stars. So using a matte box gives you a lot more options. And, you can use flags on the matte box to help block more light from hitting the lens. Good way to get rid of pesky lens flares when you don't want them.

rNeil H wrote:I'm looking at those Nisi…

Just received a note that NiSi filters are on sale 10% off for the month of February 2022 at Duclos Lenses.

Thanks, will check that out!

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I know it's not possible to shoot only with one ND filter. But I want to get my first one and I'm wondering which one. I think the 4 stops (ND16 - 1.2 density), from Smallrig is a good start. What you think? I have BMPCC6kG2 + Sigma 18-35.

Edit: Maybe as "Bromine 18" recommended: 0.9 and 1.5 are ultimate combo?

If you only get one filter at this time, then I would buy a variable-ND such as the SLR Magic Vari-ND II. It’s not a perfect solution, but effectively gives you a smooth range of filtration from 1.4 stops to six stops. That’s how I started in 2016, but I now have 86mm screw-on (ND 2/4/6 stops) and two complete sets of 82mm screw-on and rectangular 4x5.6” drop-in filters with a matte box. You can begin modestly, and expand to a set of filters when they’re on sale.

You may also need to get an IR Cut filter; most filters now are IRND which reduce infrared to the same degree as visible light. An IR Cut reduces infrared to near zero.

Čeněk Štrichel wrote:I know it's not possible to shoot only with one ND filter. But I want to get my first one and I'm wondering which one. I think the 4 stops (ND16 - 1.2 density), from Smallrig is a good start. What you think? I have BMPCC6kG2 + Sigma 18-35.

Edit: Maybe as "Bromine 18" recommended: 0.9 and 1.5 are ultimate combo?

You’ll learn a lot more about what ND filters you are likely to use, and whether there’s a clear pattern, by simply carrying a light meter with you and taking some readings in the conditions under which you shoot. It’s more cumbersome, but you can do the same thing with your camera.

The way that you use your camera has a bearing on whether you should purchase rectangular or round screw-in filters and on whether you should purchase variable filters (full coverage would require two) or individual filters. I don’t use variable ND filters, but I don’t film news stories or reality TV either.

Filter quality is also a consideration. Who actually makes the Smallrig filters that you’re considering? What’s their reputation? How much are they? It’s pretty counter-productive to purchase a good lens and then put second-rate ND filters on it.

rick.lang wrote:If you only get one filter at this time, then I would buy a variable-ND such as the SLR Magic Vari-ND II.

You may also need to get an IR Cut filter; most filters now are IRND which reduce infrared to the same degree as visible light. An IR Cut reduces infrared to near zero.

Agreed. I have the SLR Magic Variable ND and their IR Cut in 77mm and all my lenses have been modified to 77mm fronts via step-up rings. Some by Duclos Cine-Mod and some with cheap step-up rings. This setup is easy to screw in and adjust.

Please note that variable NDs, being based on polarizers, can have nasty side effects.
They seem very convenient at first, but after a while you may learn to hate them.

Most people start with VND's as they offer control, convinience and are cheaper than a full set of good fixed ND's. Then the run into the downsides such as color shifts in highlights, IR polution, x patterns, loss of resolution, a general dullness to the image and unwanted polarisation effects esp on skin which can look very strange. Spending more on high quality VND's can eliminate or reduce some of these downsides but not all so users then move on to a set of fixed screw in or matte box ND's depending on how practical these are in their particular usage scenario. Some of these have extended IR filtering so the need for seperate IR filters is reduced and with good screw in filters that have the best glass and coatings they can be doubled up to change the density rather than having to have a full set. IME 1 stop intervals are desirable but the very strongest filters are only ever needed if you need to shoot with wide apertures in very bright sunlight.

John Griffin wrote:Most people start with VND's as they offer control, convinience and are cheaper than a full set of good fixed ND's. Then the run into the downsides such as color shifts in highlights, IR polution, x patterns, loss of resolution, a general dullness to the image and unwanted polarisation effects esp on skin which can look very strange. Spending more on high quality VND's can eliminate or reduce some of these downsides but not all so users then move on to a set of fixed screw in or matte box ND's depending on how practical these are in their particular usage scenario. Some of these have extended IR filtering so the need for seperate IR filters is reduced and with good screw in filters that have the best glass and coatings they can be doubled up to change the density rather than having to have a full set. IME 1 stop intervals are desirable but the very strongest filters are only ever needed if you need to shoot with wide apertures in very bright sunlight.

Just want to say that I think your post is admirable for is content and for its to-the-point brevity

I was researching good quality variables, but I realized I could get 4 decent squares with IR cut for only about 30% more. Got the squares, and I was very pleased I did.

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Good move. What strengths of ND did you select?

Edwin Street wrote:What is the most commonly used ND filter?
3 Stop, 6 Stop, or 10 Stop?

10 stops is basically a special effects filter as it requires sloooow shutter speeds to get exposure. These are typically too low for motion capture.

3 stops isn't going to be enough. 400 ISO with a 1/50th shutter and a 3 stop ND would be properly exposed at ~f16 on a sunny day, not much wiggle room. A 6 stop filter would be sitting around f5.6 under the same conditions.

Good Luck

robedge wrote:
Just want to say that I think your post is admirable for is content and for its to-the-point brevity

The short answer is a 3 stop ND will cover most situations.

For variable ND I use Hoya Solas Variable NDX which I find closest to a fix ND and remove polarization effect. It is 1.3-8.7 stops but for anything up to 6 stops and lens no wider than 28mm on a full frame or 17mm on Super 35 it completely replaces the internal ND of my Pocket 6k Pro for run and gun.