So we all like to dress our cameras up with all kinds of accessories. One of the most common being a Matte Box. So, what’s a matte box for? Well the obvious thing is to hold filters for creating an artistic look, for colour correction or light level reduction. But the other very important role is to block unwanted light. I’ll take a brief look at filters later in the article.

We all know that if you shoot into the sun or a bright light source you might get a lens flare in the shot. You know, those sometimes pretty rings of light that can look cool on a good day or ruin a shot on another. But the other thing you can get is lens flare. So whats the difference between “a lens flare” and “lens flare”.

Well, lens flare is when light bounces around inside the lens between the glass elements in an uncontrolled way, some of this unfocussed light making it’s way to the sensor where it spills and bleeds into darker parts of the image reducing contrast and raising the black level. Whenever you reduce the contrast in an image it will appear softer, so to get the sharpest and highest resolution images, we really want to keep as much unwanted light out of the lens as possible. In addition some cameras can suffer from other image artefacts when off-axis light finds it’s way to the edges of the sensor. So anything we can do to stop this happening is obviously a good thing.

Higher end cameras will often have an electronic flare adjustment that pulls down the cameras black level when the overall scene light level gets high. The idea is that this helps compensate for the almost inevitable flare that will occur in the lens when a lot of light enters the lens. This flare setting is normally adjusted on a lens by lens basis as different lenses will flare by different amounts. As lenses get older, very often vapour from the oils and materials used in the construction of the lens will coat the internal glass surfaces with a very fine haze that increases flare. This can make an older lens more prone to flare and is one reason why getting an older but expensive lenses professionally cleaned is often worth the expense. The other thing you can do is to make be sure to use a good matte box or lens shade to prevent excess light from entering the lens.

Don’t use a matte box that is excessively large. You want a Matte Box big enough to fit your lenses and hold the size of filters you need. It also needs to be wide enough to allow you to use the aspect ratios you want to shoot in, but no larger. If it’s too big, the shade/hood will be less effective. Make use of an adjustable top flag and side flags to keep out as much light as possible. Looking through the cameras viewfinder bring the flags in close to the lens until they start to creep into the edges of your shot, then back them off just a little bit.

Also make sure your rear donut or other light seal is doing it’s job and keeping out the light. A flexible bellows or “nun’s knickers” can be used to allow you to move the matte box forwards so that the lens sits deeper in the nice dark recess of the matte box. Light entering the Matte box from the rear will cause reflections off the back of any filters used, especially any ND filters or glimmer glass filters and this can easily spoil a shot.

A Matte Box can be attached to the lens directly via a clamp ring that clamps around the end of the lens or more commonly attached to rods or bars connected to the bottom of the camera. If you only ever use one lens then a lens clamp might work well for you, but if you swap and change lenses regularly then a rod or rail mount is often easier as a flexible donut will fit a multitude of lenses. The donut on the Alphatron Matte Box will fit a wide range of lenses and the neoprene insert can easily be exchanged or replaced simply by unscrewing the two halves of the donut holder. The neoprene is sandwiched between the two halves and just drops out once released.

Some Matte Boxes like the Alphatron one shown here have small extra “eyebrows”. These are like mini flags that can be adjusted to provide extra shade for the lens. In the picture you can see how the shadow from the top eyebrow is keeping stray and unwanted light from falling on the lens. This will help minimise flare and preserve contrast in the images. It’s a small thing but it can make a big difference. Eyebrows and flags also keep light out of the matte box itself and help prevent reflections between any filters that you might use and the lens itself.

If you’re using prime lenses then you will probably need to change lenses regularly. A great time saver is the use of a swing-away adapter. The Alphatron Matte Box that I use has an optional quick release swing away mount option. By twisting a single lever the Matte Box opens up and swings away from the lens. This gives you easy access to the lens for cleaning or for a quick lens change without having to remove the Matte Box. When shooting out on location this is a big deal as there’s never anywhere clean to put your Matte Box when you want to do a lens swap.

Matte boxes can have both fixed and rotating filter trays or a combination of the two. Fixed trays are fine for ND filters and most diffusion filters. For graduated filters a rotating tray is preferable and for polarising filters a rotating tray is essential. The Alphatron Matte Box here has one fixed tray and one rotating tray. So I can use the fixed tray for any ND filters and then the rotating tray for grads or polarisers. I very nice feature of the Alphatron is a little recess in the very front of the sun shade and a little locking tab that allows you to put a safety glass in place in front of any filters to protect you filters and lens. This is very handy especially if your shooting something that could possibly splash on your expensive filters and damage the coatings.

So what filters should you get for your nice new Matte Box? First of all do be prepared to spend a little bit of money to get good quality filters. Filters can be plastic, resin or glass. Optical grade plastics and resins can make very good filters, but they tend to be prone to collecting dust through static electricity and they scratch easily. In addition if left in a hot car they can distort and warp. But, plastic and resin filters are light weight and normally a lot cheaper than the glass equivalent. Better quality filters will have anti-reflective coatings. A good quick test of the quality of any filter is to use a long focal length lens or zoomed-in zoom lens to check for distortions or focus issues introduced by the filter. You might not notice this at wide angles or zoomed out. So do check at longer focal lengths.

Good brands include Tiffen, Formatt and Schneider. These won’t be the cheapest on the market, but the quality is consistently good.  Filters come in different sizes, the most common is the 4×4 or 4″ by 4″. For longer focal lengths these are fine, but if you want to shoot at wider angles you may find that 4×4’s are not wide enough. The next size up is the 4″x 5″ but the next commonly used size is the 4″ x 5.65″ which is close to the old 4:3 TV aspect ratio. The extra width really helps when shooting wider shots in 16:9.

My most commonly used filters are ND filters. These help manage light when it’s too bright allowing you to use a smaller aperture to gain a shallower depth of field. If your using a CMOS camera you should use IR ND filters that cut not only the visible light but also infra red light that most CMOS cameras are sensitive to.

Next is a polarising filter. A circular polariser is great for reducing or controlling reflections from windows, cars etc, it’s also good for enhancing the contrast in clouds and the sky making the sky a richer, deeper blue. When using a polariser it needs to go in a rotating tray so you can turn it when composing your shot to alter the polarising effect.

Graduated ND filters are also useful to help deal with excessively bright sky. The top of the filter is a ND filter or coloured filter and the bottom is normally clear. By sliding the filter up and down within the matte box you can alter level where the brightness reduction takes place. A tobacco or orange coloured graduated filter can be used to create or enhance a sunset type look. Just watch for the graduation crossing through foreground objects in the scene which can give the game away and look odd.

Hi all. I’m off to Austin Texas to run a workshop at Omega Broadcast on the 22nd and 23rd of May. This should be an informative and fun workshop where I will be teaching how to shoot and light interviews, green screen. How to set up cameras with picture profiles or scene files as well as looking at shooting log, raw and in 4K. For more info take a look at the Omega Broadcast Web Site.

Bit of a rant this I’m afraid, but since the decline of the traditional shoulder mount camera there has been an annoying (to me at least) shift of the standard shot shooting angle from eye height to chest hight. The upshot of this is that once upon a time the majority of shots looked directly into the talents eyes from a normal eye level, so it mimicked what most of us see with our own eyes, day in day out. But now with more and more cameras being used hand-held at chest or even waist height a very large percentage of shots end up looking up peoples noses rather than straight into their faces.

Don’t get me wrong, when the shot benefits for creative reasons from being shot at a low angle I have no objections whatsoever. But I really don’t like looking up someones nose just because its harder to hold the camera at eye level. What’s more I’m starting to see this phenomenon creep in to ever more shots as tripods get used at lower levels because camera operators are used to, or find it easier to look down at their LCD screens.

Camera gimbals and stabilisers are also helping this trend as the camera is often used hung below the handles, handles held at chest height, so now we have cameras at waist level or even groin level. One of the great things about the original stedicam is that the camera ended up at around eye level, so during a walking-talking shot you had the impression that you were walking with the subject, not grovelling  along on your hands and knees.

So, please everyone, consider this when your setting up your shots, which looks better, eye level or lower than eye level and then adjust your shooting height to get the best shot. Consider getting a monopod to help you hand hold your camera a bit higher or one of the many other contraptions available today that will help you support your camera at eye level.

A little while back I took the opportunity to run some tests during the CML camera assessments at UWE Bristol with the Sony PMW-F55 and both the 4K and 2K Optical Low Pass Filters. The results were largely as expected, but I didn’t have the time until now to share those results, so here they are.

I shot two different series of test shots. The first series are of a resolution test chart, the second set of the model that was on set, in order to asses the impact on skin tones etc. It should be noted that the resolution chart did not have patterns that can show 4K resolution, really what I was looking for was aliasing and other image undesirable artefacts.

What’s the 2K OLPF filter for?

When the PMW-F5 and PMW-F55 are shooting at high speeds above 70fps the camera sensor is read as a 2K sensor instead of the normal 4K. There are two ways that this can occur. 2K Full Sensor Scan and Center Crop 2K.

Full Scan 2K uses the entire sensor but now the sensor is read as a 2K sensor instead of a 4K sensor. The camera is fitted with a 4K optical low pass filter (OLPF) at the factory. However when shooting using 2K full scan the 4K filter is ineffective and needs to be replaced with a 2K OLPF. Fortunately Sony made the OLPF on the F5/F55 interchangeable and an optional 2K filter can be purchased from Sony. It takes just a couple of minutes to swap the filters.

The 2K OLPF is also required when shooting in 2K raw when the Sensor Scan in the cameras “Base Settings” is set to 2K Full Frame (2KFF).

Another possible application for the 2K OLPF is to soften the pictures a bit when shooting in 4K. If you find the 4K images with the 4K OLPF too sharp you can use the 2K OLPF to provide a softer, creamier look. Unlike a soft effect filter in front of the camera lens a filter behind the lens is not effected by changes in aperture of focal length, so the results are highly consistent.

On to the tests.

Click on any of the images to enlarge them and see the full size 4K images. NOTE THAT YOU MAY SEE ALIASING THAT ISN”T IN THE TRUE IMAGE WHEN VIEWING A SCALED IMAGE ON YOUR COMPUTER SCREEN, SO PLEASE VIEW WITH 1:1 PIXELS.

The first test was to see what happens when you shoot using 2K Full Frame with the standard 4K filter. Really there is no surprise here. Because the factory fitted 4K OLPF is ineffective at 2K you will get a lot of aliasing and moiré as can be seen by the rainbow patterns on the test chart.

So what happens if you swap the 4K OLPF for the 2K OLPF while shooting in 2K Full Frame? Well all the unwanted aliasing simply goes away and you have a nice artefact free image.

So it’s easy enough to see that if you want to shoot 2K Full Frame, whether for slow motion or for 2K raw you really do need the 2K OLPF option.

But what about when shooting 4K Full Frame, how does the OLPF effect the sharpness of the image. Below are both the full frame, frame grabs plus a couple of crops of the girl so you can see how skin tones are effected.

Notice how the shot done with the 2K OLPF is noticeably softer, the texture in her hair is softer, her skin looks smoother, yet the difference between the two images is not really that great. The 2K OLPF does not excessively blur the image, but it does give it a pleasing softness. This could be beneficial for cosmetics or fashion shoots, dream sequences etc. However it is also possible to soften footage in post production to produce a similar effect. Below are the full frame originals if you want to see the entire shot.

One thing that you definitely don’t want to do is to accidentally use the 2K OLPF when you are shooting in any of the center scan modes. Remember that in center scan mode the sensor is still in effect a 4K sensor, just now you are only reading out a smaller 2K section from the center of the 4K sensor. As a result the 4K OLPF is still optimum. Below are some further crops from the whole image just shown the center of the test chart. Starting with 4K full frame scan using the 4K OLPF, which is beautifully sharp and clear.

Next is with the 4K OLPF in 2K crop mode. The lens was changed to give a similar field of view.

It’s not really that surprising that the image is a little softer, the first image is part of a 4K image while this is from a 2K image, so it is lower resolution. There is some coloured moiré in this image, probably a result of changing the the lens, perhaps this lens is slightly sharper than the original lens so has greater resolving power. It is almost impossible to entirely eliminate coloured moiré with a bayer sensor and a chart like this will show it up, it’s a very tough test for a sensor. But compare this to a similar section of the shot done with the 4K OLPF with the camera shooting in 2K full frame scan mode and you can see that actually the moiré isn’t actually all that bad. In most real world applications you are not going to see the aliasing above unless you have a very very fine, in focus, repeating pattern similar to the one on the chart:

But what about using the 2K OLPF in 2K center scan mode, well take a look at how soft the image is. It just looks completely blurred and soft.

You really don’t want to shoot like this your pictures will look very soft indeed.

So there you have it. The 2K OLPF really is needed if you want to avoid heavy aliasing and moiré when shooting in any of the 2K Full Scan modes. You can also use it if you want to soften your 4K images a little for a smoother creamier look. But you definately don’t want to use the 2K OLPF in combination with any of the sensor center scan modes.

Here is the latest version of my PMW-F5 and PMW-F55 quick reference PDF guide. This will be updated and exapnded on a regular basis so please bookmark this page: http://www.xdcam-user.com/2014/04/pmw-f5-and-pmw…eference-guide/ so you can come back to download the latest version.

Please do let me know of any errors or omissions and anything else you would like to see added. Feel free to share and distribute the document, but note that a lot of work has gone into this and it is copyright, so hand it out, give it away, but don’t sell it and don’t remove the copyright notices or links.

Here it is: F5-F55-quick-reference-guide (updated 20th August 1014 V8.1) click on the link to see the PDF.