Category Archives: Rigging

New accessories announced at NAB 2015 (for both A7s and Shogun)

NAB 2015 is over and done with, and here are some interesting accessories for the A7s and Shogun:

Accessories for the Sony A7s

Movcam Start Stop Trigger for the A7s:

It’s a neat adapter cable that connects to the USB port, and the other end is a standard LANC port you can connect any trigger to. Here are some details:

  • Availability: 30 days from now.
  • Price: $60 approx.

APUTURE DEC EF to E mount lens adapter:

  • Availability: May 2015
  • Price: $389

Indipro power and audio solution

The IndiPRO Tools Dual Power Grid & XLR Audio Box is used to power your Sony A7S camera using two available Canon LP-E6 Battery Packs (not included). It also adapts two XLR inputs to a 3.5mm stereo mini output to provide 2 audio channels directly to your camera.

One end of the Dual Power Grid has a dummy Sony A7 battery that is inserted into the camera’s battery bay. The other end is connected with an 18″ cable and features a space saving dual-sided battery plate that mounts one LP-E6 Battery Pack on each face. The batteries snap securely into the plate.

A clamp allows you to mount the unit to Light Weight Standard (LWS) 15mm support rods (not included). A built-in blue LED indicates sufficient voltage supply to the camera. You can hot swap the batteries without having to power off your camera

To know more, click here.

Accessories for the Atomos Shogun

Motion9 Cube Shogun cage:

This cage looks tough enough to protect the Shogun, but it does increase the weight substantially. Just to let you in on some engineering bad news – if the Shogun is impacted from the sides, the force will be transferred to the screen and it will crack, similar to what might happen without the cage. The only thing that can mitigate such a force is foam, like the kind you find inside Pelican cases.

  • Availability: Right now.
  • Price: $297

Shape cage for the Shogun:

 

If I come across anything else I’ll update this here. If I’ve missed something, please let me know, and I’ll share it with everyone.

Rigging Gear Specific to the Atomos Shogun

In this lesson I’ll go over a few rigging options required by the Atomos Shogun specifically.

One of the cool things about the Shogun is that it ships with a ton of important accessories. I’ve found these particularly helpful:

  • XLR to Hirose breakout cable
  • P-tap battery adapter
  • AC power outlet (otherwise I wouldn’t have been able to carry out all the tests that I did!)
  • supposedly unbreakable HRPC case

The stuff that it doesn’t ship with is what annoys me:

  • No sunhood, though the new one is coming at a $70 price point.
  • Stupid male P-tap adapter – who makes male to male P-tap cables?
  • The AC power adapter is so short that on a medium height tripod it doesn’t touch the ground!
  • Poor battery, though you can get a 5200 mAh battery now.
  • Poorly designed foam cutouts – it’s a large wastage of space.
  • Atomos’ exclusivity with Datacolor

Let’s address these issues.

Battery power

This is an important problem. There are only three general solutions:

  • AC power – really impractical with a short cable. You’ll need an extension cord and a hook to support it on your tripod.
  • Anton Bauer/V-mount batteries – probably the best solution, but increases weight, size and price.
  • Use multiple batteries – it’s what most users will opt for.

For those looking at Anton Bauer and V-mount solutions

Since you need a male-to-male P-tap (D-tap) cable, here are your choices:

  1. Switronix Coiled PowerTap Cable ($71) – 4 feet
  2. Laird male-to-male P-tap adapter ($38.95) – 3 feet
  3. Dolgin Engineering male-to-male P-tap cable ($49.95) – 3 feet – this is what I bought, because it was cheaper with shipping.
  4. Anton Bauer PowerTap Open End cable – ($27 x 2) 3 feet – you’ll need to solder two of these together.
  5. D-tap connector ($8.79×2 incl shipping) – I bought these as well, as backup incase the Dolgin didn’t work. Of course, you’ll need to buy wire and solder it yourself (Don’t do it if you don’t know what you’re doing!)

I’m happy to report that the Dolgin cable works fine, and I am able to power both my A7s and the Shogun on just one Anton Bauer mount battery. The “half-disadvantage” is that neither the A7s nor the Shogun can predict remaining battery life. I say “half” because the battery itself has an indicator, so I’m okay.

Seriously, the cables are just connectors wired together DIY style, and then resold:

dolginjoint

If you know how to do it yourself, that should be the best and cheapest option. If you don’t want the inconvenience, do what I did, or buy the Switronix that plugs directly into the Shogun.

A 130Wh (9000mAh) battery should drive both A7s and Shogun for 2.5 hours (tested on my battery). Each hour needs about 3500mAh (using both the A7s and the Shogun).

For those looking at cheap battery solutions

You can buy original Sony batteries, but they are expensive. You can also buy Atomos branded ones but they are made in China as well.

If you’re in the US, the best bet is to buy a few Watson NP-F975 7800mAh ($60) batteries. Each one will give you about 2 hours of use. You’ll need at least three (I suggest at least four, one as backup) for a full-day’s shoot. To charge them, go for the Watson Duo LCD Charger ($79.95) which should charge two batteries in about 4 hours or so. It also has a USB charging port so that could come in handy.

Sunhood DIY Hood

The Atomos sunhood is reported to cost about $70, which is insane. I made my own out of two plastic covers from a folder (box file) and spandex (Lycra) stockings:

offside

I call it Lawrence of Arabia. And it doesn’t even cover the heat vents. Total cost: $5. You might want to replace spandex with velvet and velcro. Actually, I’m working on a better-looking option with plastic on all four sides.

My advice? Don’t waste money on a sun hood. Make it yourself or use a black cloth.

The above image shows what the Shogun looks like when switched off, with a direct backlight on it. This image is the same with the Shogun switched on:onside

Obviously, it gets better if you stand between it and the sky:onbehind

This DIY project is so easy you shouldn’t bother buying whatever they’re selling for $70.

HPRC Case Foam

The bottom layer has all sorts of cutouts for unnecessary accessories. Who would want to carry multiple power plugs all the time?

The case shipped with the Shogun is the HPRC 2400, and for cubed foam, it costs about $45. You can also purchase a lid organizer for $24.40. I’ve also read that you can use Pelican 1450 foam which is only $25.

Atomos Spyder

Unfortunately, the general consensus from serious color professionals and developers is that the Datacolor Spyder (all versions, including 4) are unreliable for color critical calibration. Some units are fine, but it’s a total crapshoot on whether you’ll get a decent one, and the odds are stacked against you.

It is even more unfortunate that Atomos has tied up with Datacolor so you can only calibrate the Shogun with the Atomos Spyder ($149). There is no choice, so I can’t make any recommendations in this regard. If possible, try before you buy!

Do you need the Spyder? No. Color calibration of monitors takes into consideration ambient light. On an external monitor like the Shogun, you’re going to be using it in a wide variety of lighting conditions, with different light levels and color temperatures. You’ll have to carry a laptop with the software in the field along with the Spyder4 and calibrate it for each shot. Hardly practical.

And don’t even think of calibrating it in the studio or home and then taking it outdoors and expecting it to work. Pointless exercise. Save your money and don’t buy it.

Action Pack Offer (July 1st to 31st only)

For existing Shogun users, Atomos will give you 50% off on the Action Pack ($240 originally, but you get it for about $120). The Action Pack includes:

  • Sunhood
  • Matte LCD protector
  • Armor bumper – extra protection for your Shogun
  • Travel case

Here’s the offer:

shogun_action_pack_june_2015

 

For more offers in your area, go here: http://atomos.com/offers/

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

FAQs

These are important topics raised by subscribers that shed more light on this lesson.

Q. How much does it cost to replace a cracked Shogun screen?

A. From a couple of readers: $300 approx. Don’t hold me to it, just passing it along.

How to rig an external monitor and electronic viewfinder

In this video I’ll go over the options to rig two external monitors and an electronic viewfinder:

Download Video

Since two of the three monitors I’ve shown are discontinued, here are alternate suggestions:

Monitors

Viewfinders

Mounts

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

FAQs

These are important topics raised by subscribers that shed more light on this lesson.

Q. Can you recommend a cheap but good 7″ monitor?

A. Here’s a cheap 7” monitor one of my subscribers bought on my recommendation and loves: http://www.aliexpress.com/store/product/Support-Waveform-Vector-Scope-7-inch-IPS-broadcast-Display-Anton-mount-plate-Free-shiping/701605_1806865854.html

I was planning to buy it too, but I already have the Shogun so it is unnecessary. Here’s what the satisfied user had to say:

I actually bought the 7″ Neway monitor that you so kindly sent me the Ali Express link for. You’re absolutely correct in that it is definitely sharper than the F&V F3 and has all the features that I need. I’ve now mounted the F&V permanently on my SteadyCam.

Two HDMI lock options compared

HDMI is a flimsy standard, but there’s no need to buy expensive HDMI locks! Here are two really cheap solutions:

Download Video

Buy these from B&H:

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

FAQs

These are important topics raised by subscribers that shed more light on this lesson.

Q. Is the HDMI port on the A7s strong enough?

A. Not really, but it’s really a hazy area. Many have had broken HDMI ports, but at least as many (or more, because they stay silent) haven’t.

With an HDMI lock you never really have to remove the cable unless absolutely necessary.

Q. What HDMI cable do you use?

A. I use the cable that came with the A7s. It’s a bit long, but I wrap it around the Oconnor baseplate so it stays out of the way. You can also wrap it around the cage on the top left. Removing the cable is just a turn of a screw, and the Movcam adapter stays on flat, and does not protrude out. The only downside is the HDMI port door stays open, but even that can be remedied in the field if you have a coin handy.

For longer cable runs, you will need a longer cable of course. HDMI extensions are not a good idea. You might want to buy multiple cables and test them for a few hours. This is a necessary step with HDMI. You’re looking for pattern noise, dropped frames, artifacts, etc.

Note: Some countries don’t ship with an HDMI cable. Guess I got lucky! Pearstone (from B&H) works, and Sony also sells original HDMI cables. I’ve used mine under tough conditions and they have performed excellently.

Configuration and Rigging Walkthrough with all Accessories

Here’s how I rig my A7s:

Download Video

For more detailed advice on rigging a camera from scratch, there is no better guide than the free Comprehensive Guide to Rigging ANY Camera, available for free at wolfcrow.com.

The entire weight of my rig, as it stands now, is about 6 kg (13 lbs). If I add a matte box, filters and Atomos Shogun, it will reach about a maximum weight of 8-10 kg (Max 22 lbs). Now I need to find a tripod for it!

Here’s what I intend to add to the rig:

To buy parts, please support wolfcrow by buying from B&H.

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

FAQs

These are important topics raised by subscribers that shed more light on this lesson.

Q. What is the weight of my rig?

A. The weight of my rig without external monitors, matte box or viewfinder is about 6 kg (13.2 lbs). With a monitor, EVF and mattebox, it is 8 kg (17.6 lbs).

If I add cinema lenses instead of Nikon primes, it will increase to about 10 kg (22 lbs). Factor in about 20% for contingencies and the rig will never go over 12 kg (26.4 lbs).

Q. What should be the specifications of a decent fluid head?

At its lowest the system is about 2 kg (4.4 lbs). I would probably need a 14 kg (30.8 lbs) maximum payload capacity as well.

So, a decent fluid head should counterbalance my rig from 2-14 kg. The two options I’m currently interested in are the Sachtler DV 12 SB and the OConnor 1030D. If either of these are expensive (and they are!), then I suggest you take a look at the Cartoni Focus HD.

Q. How do you protect the back LCD of the camera?

A. I don’t use anything, but you could try the Fotga LCD Screen Protector from Ebay.

Q. Do you know of any loupes for the A7s?

A. I’ve found this one: KAMERAR QV-1 M LCD Viewfinder

How to power the Sony A7s: Various Options

First, watch this video for two power solutions for the Sony A7s:

Download Video

The Sony A7s comes with an AC to USB adapter (AC-UB10) which also charges the battery.

For a more ‘regular’ AC adapter, you will need to purchase the AC-PW20 ($80 for original Sony, about $20 unbranded). The camera does not have a DC port, and the adapter has a battery attachment instead.

The camera comes with a charger (BC-TRW, which retails otherwise for $48) and two batteries (NP-FW50: 7.7Wh, 1080mAh, $40 for original Sony, about $5-7 for unbranded). Some of the unbranded batteries, like this one for $7, are rated at 2300mAh, or twice the capacity. Be extremely careful before using unbranded batteries. I’ve generally had no problems using them, but you must buy after reading many reviews. Don’t blame me if something goes wrong!

You can also extend the recording times by using a vertical grip, like the original Sony VGC1EM, which sells for $298. You get to use two batteries at the same time, and it might help you handholding the camera as well. The negatives are:

  • It adds weight, almost double with two batteries
  • It might interfere with the mounts on the lens adapter, especially the Metabones adapter.

How much battery life does the NP-FW50 provide? According to the official specifications, here are the ratings:

  • Approx. 55 min with viewfinder, approx. 60 min with LCD screen – if you also zoom while recording
  • Approx. 90 min with viewfinder, approx. 90 min with LCD screen – if you are not using any functions except recording.

In real world use, one can estimate about 60 minutes (one hour) of usable battery life in video mode, using a 1080 mAh battery. The viewfinder draws more power than the LCD.

What about charging time? The stock charger takes about 220 minutes (just shy of four hours) to charge one battery! Now that’s a problem. Therefore, I recommend getting a Wasabi Charger+2 battery kit for $26.99. It will also charge the stock batteries. Even though the Wasabi is rated at a higher energy level, you get about the same or slightly lesser battery life. For professional use, I recommend getting two Wasabi kits to supplement the Sony kit. You’ll end up with three chargers and six batteries. Consequently, you can also use dual chargers.

The Atomos Shogun takes a Sony NP-F970 (6300 mAh, retails for about $120) battery which will give it about 2.5 hours of life. You could get a Wasabi kit with two batteries and a charger for $84 instead and that would be the route I would take.

Of course, you could power up an entire rig with Anton Bauer batteries as well, which is what I’m doing. Ultimately, I highly recommend getting a V-mount of AB mount brick. Nothing beats that solution, unless you specifically need to lower weight.

Check out the options at B&H:

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

FAQs

These are important topics raised by subscribers that shed more light on this lesson.

Q. Does the camera display battery life correctly on an external battery?

A. No. In fact, it is totally misleading, and just shuts off quickly. I rely on the indicator on the battery instead.

Finding the best cage for the Sony A7s

Here are my suggestions for cages for the A7s, and which one I chose:

Download Video

After considering all the cage options in the market, I can’t find any that are better than the Movcam cage. Not only does it look good, but it does everything you need it to, including having an HDMI lock and an EVF mount. Really stellar piece of engineering and manufacturing.

At first, it took me about 10 minutes to screw everything on. It’s much easier if the camera is on a secure tripod or table. Now, it takes me about 2 minutes to dismantle or rig up. The top handle comes out with two screws, so it takes about a minute. Same applies to the side plate, which needs three screws.

You can buy it here:

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

FAQs

These are important topics raised by subscribers that shed more light on this lesson.

Q. What about the Varavon cage?

A. A user has this to say about the Varavon:

really works well: good fit, accessible everything, good engineering and materials … love the leather handle and the cable locks.

Q. What about the Motion9 cage?

A. Here are reasons why I didn’t recommend this over the Movcam:

  • It is only slightly cheaper than the Movcam (on Ebay, that is).
  • It has no riser for the right height
  • The HDMI lock really isn’t a lock, just a hole (at least from the pictures)
  • It doesn’t have an EVF mount
  • The grip side isn’t detachable, in case your hands can’t get to the controls for handheld shooting

Q. What about the LookCircle Birdcage?

A. I am not personally acquainted with it, though I don’t like the open-ended cage design. Also, there are no hot/cold shoe mounting points.

However, because it interfaces with the PL mount, I believe it is good enough and mandatory for high-end work, even on jibs or gimballs. The A7s mount is not reliable for heavy lenses or clip-on matteboxes, so the extra support is welcome. Plus, it is made by P+S, no complaints!

If you want to use heavy PL glass, then go for it, otherwise it’s too expensive.

Do you need the LockPort? No, I don’t think so. See my answer here.

How to choose the right base plate for the Sony A7s

The Sony A7s has a 1/4″ tripod mount without a registration pin. Lucikly, if you use the Metabones lens adapter you have another mount that will provide you the second point of contact.

Except there’s a problem – they are not at the same height. Watch my video on two base plate solutions for the Sony A7s:

Download Video

Check out these solutions from B&H:

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

Guide to ND Filters to use on the Sony A7s

There are two parts to this question:

  • What ND filters for non-S-Log2 modes?
  • What ND filters for S-Log2 mode?

ND Filters for non-Slog-2 modes

The Sony A7s records 1080p video in Rec. 709 under an ISO range of 200-102400 (expandable to 409,600). Here are some general lighting scenarios from real life (Shutter is at 1/50s):

  • Sunny 16 rule (bright outdoors) – f/32 @ISO 100, f/2.8 only possible with an ND 2.1 (7 stops) filter
  • Studio environment (1000 lux) – f/2.8 @ISO 100
  • General office ambience/golden hour – f/2 @ISO 100, f/2.8 @ISO 200
  • Moody home ambience – f/1 @ISO 100, f/2.8 @ISO 800

As you can see, you will probably never need more than 8 stops, which is why the following cameras have these built-in ND filters:

  • Sony FS7 – 2, 4 and 6 stops
  • Canon C300 – 2, 4 and 6 stops
  • Arri Amira – 2, 4 and 7 stops
  • Arri Alexa XT – 1 to 8 stops

If the aperture isn’t a concern, in bright sunlight, you can get by with a 2-stop filter that will let you shoot at f/16 – which is what most lenses top out at.

Therefore, you can live with ND filters in the 1 to 6-8 stop range. If you’re staying under 6 stops, you won’t need IRND or hot mirrors. However, if you’re shooting between 6-8 stops over, then you need them, no doubt.

Specific recommendations are at the end of this article.

ND Filters for Slog-2 mode

In S-Log2 mode, the lowest ISO is 3200. You can’t go to ISO 1600 or 800 or 400 or whatever. You must start at ISO 3200. Here are some common lighting scenarios and f-stops at ISO 100, and what ISO 3200 does to it (Shutter is at 1/50s):

ISO 100 ISO 3200 ND for f/2.8 @ISO 3200 ND for f/1.4 @ISO 3200
Sunny 16 rule (bright outdoors) f/32 f/196 3.6 4.2
Studio environment (1000 lux) f/2.8 f/16 1.5 2.1
General office ambience/golden hour f/2 f/11 1.2 1.8
Moody home ambience f/1 f/5.6 0.6 1.2

We also need to consider the wolfcrow system of exposure, which is to expose at 3 stops over middle grey. If that’s the case, here’s what our chart looks like:

ND for f/2.8 @ISO 3200 ND for f/1.4 @ISO 3200
Sunny 16 rule (bright outdoors) 2.7 3.3
Studio environment (1000 lux) 0.6 1.2
General office ambience/golden hour 0.3 0.9
Moody home ambience n/a 0.3

The low light ability of this camera is phenomenal (Check out the results here). If you want the shallow depth of field aesthetic, you have no choice but to use ND filters. Most users will be satisfied with a set of 1-10 (0.3 to 3.0) ND filters for video work in S-Log2 mode.

How to pick ND filters for S-Log2

There are three ways to go about buying ND filters:

  • Buy one or more variable ND filters to cover the entire range. These are circular threaded filters.
  • Buy filters in one-stop increments over the entire range. In this case, you’d need 10 filters to cover the 10-stop range.
  • Buy five or less filters and then stack filters.

Stacking works like this:

  • 0.3 – 1 stop
  • 0.6 – 2 stops; 3 stops stacked with above
  • 1.2 – 4 stops; 5, 6 and 7 stacked with above
  • 2.4 – 8 stops; 9 to 15 stops stacked with above in various combinations
  • 4.8 – 16 stops; 17-31 stops stacked

It sounds cool, except for one major drawback – if you stack more than two ND filters, you are likely risking image degradation:

  • Internal reflections from various filters
  • Vignetting
  • Loss of resolution

Refer to the previous lesson to see what I mean.

One way to eliminate these factors is to buy really good filters. The second method is to get them as close as possible to the lens with good quality matte boxes or filter hoods. The last system is to use the right size filter and mattes so vignetting is minimized.

Most cheap filters are made of some form of plastic or resin. The really expensive ones are made of glass. If you stack ND filters and don’t want image degradation, you must stack glass filters.

In any case, it is unadvisable to stack more than two ND filters. I’m going to go with this rule of thumb.

Before I give you my advice, let’s also consider ISO. In many cases, you can bump up the ISO rather than remove ND filters, and this is what lets us stack filters. I have found you can comfortably shoot at ISO 3200 (the best), 6400 and 12800. You can stretch to 20000 if you like, but I wouldn’t advise it unless you’re desperate. Here’s what you end up with:

Optical Density Stops Stops you get by stacking
0.9 3 n/a
1.8 6 9
3.0 10 13, 16
Total Range 1 to 16 stops 

How does this work? What if you need to stop down by one stop only? You stop down by 3 stops, and then open the ISO by two stops. This way, you can stop down from 1 to 16 stops with just three filters!

If you just want to stay within the 3200 to 6400 ISO range, then you’ll need four filters:

Optical Density Stops Stops you get by stacking
0.6 2 n/a
1.2 4 6
2.1 7 9, 11
3.0 10 12, 14, 17
Total Range 1 to 17 stops

If budget is a concern, there’s nothing wrong with option one. What tilts the balance is the fact that:

  • You’ll need the ND filters for future cameras as well, and
  • You get a total of 10 “steps” with four filters, while only 6 “steps” with three filters.

What am I planning to do personally? I’m going to get five filters:

Optical Density Stops Stops you get by stacking
0.3 1 n/a
0.6 2 3
1.2 4 5, 6
2.1 7 8, 9, 11
3 10 11, 12, 14, 17
Total Range 1 to 17 stops

I get all the steps from 1 to 12, and then 14 and 17 as well for those really rare scenarios. I get 14 “steps”, and I’ll never have to stack more than two filters. Therefore, as a recommendation, I suggest you get this kit (if you’re not going for a variable ND solution, that is).

It goes without saying that all of my filters will be IRND or hot mirror filters. I must test further, because these are expensive things! If you want me to test Tiffen filters, I’ll do so, but I must get enough requests!

Recommendations come next.

ND filter suggestions

There are three options:

  • Variable ND filters
  • Threaded ND filters
  • Square filters (4×4, 4×5.65 or 6×6)

Variable ND filters

I recommend the following:

As you can see, these are not cheap. If you’re getting 6 stops for $444, that means you’re getting 1 stop for $75. I will never recommend cheap vari-ND filters. Variable ND filters are more convenient to carry, and you don’t need to change them around as much. You could buy one large size and then use step down rings for the rest of your lenses.

Here are four choices in the 82mm size. Buy one and be done:

Threaded Circular ND filters

The good ones are not cheap. Hoya makes cheap ones that are passable, but I can’t recommend them for professional work.

For Non-S-log2, we can have three filters – 2, 4 and 7 stops. I recommend you buy one large size, 82mm, for example, and then use step down rings for various lenses:

For S-Log2, here are the four options: 2, 4, 8 and 10 stops (notice how it’s not very different from the previous choice? But these need to be IRND filters):

One way to mitigate cost is to buy just one IR blocking filter, and then put all the ND filters behind it. Test!

Square filters

This one is easy. Go Tiffen or Schneider:

These expensive filters are used with matte boxes. They are made of high-quality glass, are thick, and offer the best possible image quality. Test! You can’t afford to buy expensive filters without testing. Remember, every combination is different!

That’s it. I hope this makes your filter buying easier. Or did I make it harder?

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.

FAQs

These are important topics raised by subscribers that shed more light on this lesson.

Q. How do you get an ND filter on a Samyang 14mm?

A. Check out the Samyang SFH-14 14mm Filter Holder!

IR Filtration Tests using ND Filters

Before we can look into ND filters, we’ll need to know what kind of ND filter to buy. The first important classification, one which certainly affects the price, is whether or not we need ‘hot mirror’ or IR ND filters.

Every camera has some form of IR (infrared) pollution. Many cameras have IR blocking filters right in front of the sensor to mitigate this (and to protect privacy). Under normal lighting conditions the infrared radiation passes on to the sensor along with visible light, and nobody notices anything.

However, when using ND filters (or even other filters that cut light to a certain extent, like polarizers, color filters, etc.), the visible light is cut, but the IR passes through.

This means, when you shoot in sunlight (or tungsten halogen, practically anything that emits heat and therefore, IR radiation) and use a ‘normal’ ND filter, the colors tend to shift due to the IR radiation. This is IR pollution, and the results are undesirable, as we shall soon see.

The test for IR pollution

The simplest test for this is to shoot outdoors in sunlight with green foliage, and under tungsten halogen lighting. If there is IR leaking the greens become brown, and some form of black clothing becomes brown. You can also use a color chart for this. This is what we’re going to do.

I have three kinds of ND filters, so I test all of them just to make sure it’s not any particular model but the camera itself. I have 4×4 ND filters, starting at 1 stop (ND 0.3) all the way to 10 stops (ND 3.0). I also have variable ND filters and threaded round ND filters. None of them are hot mirrors or IRND filters.

 

What are IR ND filters? These are filters (they don’t have to be ND, but can also be polarizing or others) that also have an IR blocking coating (or whatever) applied to them, so they serve double duty. Typically, they cut from between 680nm to 700nm (the beginning of IR radiation) and beyond. You can also buy pure IR blocking filters.

What’s the difference between IRND and Hot mirror? The end result is the same thing, both stop IR from reaching the sensor, but they differ in their technology. IRND filters, the most common kind, have dyes that “absorb” IR radiation, similar to color filters that absorb light of a particular color but lets the others through. On the other hand, hot mirrors are mirrors – they reflect IR radiation back completely. For this reason, they have mirror-like surfaces, and many say you shouldn’t stack hot mirror filters. The mirror side must face the scene, and be furthest away from the sensor if you’re stacking filters. It goes without saying that you must know which side of the filter is the mirror side, or if both sides are, etc.

One more thing, every ND filter shifts color to a certain extent. There have been recent tests with TrueND filters that show minimal color shift. I don’t know if it’s true (pun intended) or not, but both Tiffen and Schneider, the industry standards, have slight color shifts across the image. It is important to distinguish between a color shift and IR radiation. The latter only affects certain aspects of the image, while the former applies a tint across the entire image. A tint is easy to correct, but a color shift in certain regions is extremely hard.

So, there is no ‘formula’ to IRND filters. You must test each stop, each filter, each manufacturer, each technology and each sensor combination thoroughly! There is no easy way I’m afraid. Sometimes the results are surprising, especially with cameras that have their own IR blocking filter, such as the Sony A7s.

Variable ND Test

Let’s start with a simple variable ND test (right click and download 50% TIFF file for your study – browsers don’t display TIFF):

VariableNDTest

Some info: Variable ND filter, 6 stops total. Shot at f/16. Matrix metering exposed at middle grey in Standard Creative Style, Picture Profiles Off. ISO range from 100 to 4000. Auto White Balance.

Clearly, you don’t need any IR blocking up to 6 stops. That’s where my Var ND ends. However, note that there is a slight shift in the greens. Let’s dig deeper.

4×4 ND Filter Test

Here’s the same scene, but with 4×4 ND filters (right click and download 50% TIFF file for your study – browsers don’t display TIFF):

SquareFilterTest

Info: Some of the color shifts are definitely due to the poor quality of the ND filters. They are exclusively resin, and not glass. All were metered with matrix metering, Auto White Balance.

How do we know the color casts are not caused by color shifts and IR radiation? To do this, I must also shoot the filters against a normal background with cool lighting. In this case, fluorescent (right click and download 50% TIFF file for your study – browsers don’t display TIFF):

BlankWallTest

What I’ve noticed is that stacking ND filters actually makes the image ‘bluer’ under fluorescent lighting. You can easily verify this with a color picker. This is one cause for the major ‘tinted’ color shifts, but of course, not IR pollution shifts. That comes next.

We test the same thing with Tungsten Halogen light. In this case, custom white balanced to 2800K (right click and download 50% TIFF file for your study – browsers don’t display TIFF):

Tungsten2800K

Notes: The cloth on the left is pure 100% cotton. The cloth on the right is 95% Viscose (Rayon) with 5% Elastane (Spandex). The cloth on the back is synthetic photographic cloth. As you can see, cotton resists IR pollution a whole lot more than Rayon.

Quite clearly, you can see the effects of IR pollution in the Rayon even at 1.2 (4 stops). By 8 stops (1.2+1.2), the cotton and the chart are both affected. Some of this is due to the stacking of filters, as 2.7 (9 stops) is slightly better that 1.2+1.2 (8 stops).

Finally, we want to know – can IR pollution be corrected easily in post production? For this, I import these files into DaVinci Resolve and use the chart correction tool. Here are the results (right click and download 50% TIFF file for your study – browsers don’t display TIFF):

Tungsten2800KResolveCorrected The results are surprising, and very important. You cannot easily eliminate IR pollution effects, especially in the blacks.

Verdict

What do we learn?

If there is no sunlight or any IR radiation in the lighting plain ND filters will work just fine. But we need NDs most under sunlight, don’t we?

Under sunlight or tungsten lighting, there is a noticeable shift. If your talent is wearing synthetic clothing (which a large majority do), then you have no option but to use IRND or hot mirrors starting at 4 stops. If you’re shooting only daylight scenes, I’d say you can ‘get away with’ no IR blocking up to 6 stops, but clearly, the moment blacks become prominent, it starts to show.

You cannot easily correct it in a grading app, even if you shoot charts.

Bottom line, if you’re looking for professional results, you need IRND or hot mirror filters above 4 stops. It will save you a lot of time and agony in post.

This result has important repercussions, as we shall see in the next lesson.

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.