Shooting with B4 mount Video lenses on large sensor cameras.

A short article to explain how to shoot with B4 (traditional HD) lenses on large sensor cameras.

(can I have my documentary camera back please?)

The new generation lens adapters promise the range and convenience of shooting traditional ENG lenses (usually HD resolution) with large sensor cameras and Ian has tried them out.  Here is his article on everything that you need to know about shooting with video-style lenses on large sensor cameras


It goes without saying that over the last five years that the actual physical dimensions of acquisition both in terms of sensor size and body size have changed in all areas of production apart from feature film and high-end commercials. The drive to shooting on digital 35mm size sensors as an alternative to film was pioneered by the RED One and the ARRI D21 and ‘guerilla’ised by the Canon 5D MkII.

The pursuit of the holy grail of shallow depth of field enabled filmmakers on any budget to produce movie style creativity for an audience that appreciated the pictures without necessarily understanding the science behind them. Below is a brief article highlighting (or lamenting) some of the facets of fast paced acquisition for documentary world that have been left behind in the pursuit of 35mm creativity.

Part One: Holding on.

The introduction of medium and small size cameras with 35mm and Full Frame sensors with commensurate improvement in sensitivity, dynamic range and codec depth all seem to have ignored one of the fundamentals of professional camerawork- the operational ergonomics required for hand held work. Now, of course, there is an argument that requires a small but capable camera to be able to be positioned where a larger chassis would struggle, and the Canon C300 III is probably the best example of such a complementary function, usually performing as a ‘B’ or ‘C’ camera alongside Alexa cameras in a narrative situation. However, when used a main camera, the C300 does not lend itself to shoulder mounting, having been designed with more than a nod to DSLR ergonomics and therefore requires third party accessories in order to address this issue. Similar modifications are required for the Canon 5Ds and equivalents and none of them are particularly satisfying as the camera designs are fundamentally flawed for this type of operation.

Here at VMI we have a selection of third party accessories (VMI-Grip-Handheld/Shoulder Rigs) that can provide some degree of flexibility and comfort but cannot overall solve the inherent design impediments to this type of filming. For example there are no third party electronic viewfinders available that do not introduce an unacceptable level of delay into the viewing system, so the operator will always be ‘behind the beat’ of what is being recorded as opposed to what is being viewed.

To counter balance a front mounted camera positioned where the operator can use the original viewing screen and have neutral balance on the shoulder, would require the same amount of dumb weight and distance behind the shoulder to achieve this. At VMI we ‘work-shopped’ this with a C300 when they first came out and found we ended up with a hybrid slightly longer than an Alexa and about a kilo heavier!  Equally as most of these solutions are based around ‘moose’ bars for handles, it then means that the operator has to move their hand off the rig in order to adjust zoom, focus, iris etc- VMI can supply centre mounted handles leaving the left hand free to operate the lens but with a slight loss of stability.

However I would just like to clarify that VMI have one of the largest fleets of C300s in the UK and nearly two years into their lifespan, they are constantly working and that their small size is generally a positive attribute, it is more a case of a type of professional camera design that has been marginalized in the pursuit of small chassis large sensor cameras.

ARRI Amira Camera VMI

The release of the ARRI Amira camera and subsequent others addressed the ergonomic issues discussed above reverted to a more traditional documentary camera design, which lend themselves perfectly for documentary production.

The fundamentals of this design have been around since the late seventies when 16mm cameras (Aaton and Arri SR) were designed to sit neutrally balanced on the shoulder with the eyepiece comfortably parked for the operator, whose eye would be close to the focal plane (avoids the feeling of ‘swinging’ when panning) and because the shoulder was bearing most of the weight, it meant that the hands could used to ‘guide the camera whilst being able to perform the appropriate lens adjustments. Early video cameras with on board recording became known as ENG cameras and followed the same principles but with the added advantage that the lenses had electronic zoom and iris functions built into an ergonomic block, so that the right hand was able to perform usable adjustments to focal length and the left to ride focus whilst still supporting some of the weight.  

This is why older B4 mount cameras such as the Sony PMW-F800 and PMW-500 are still being used to good effect in a documentary environment as they are just modern electronics in a traditional and proven housing using standard documentary lenses like Canon HJ22x7.7. It is this intuitive flexibility that has been lost from some of the large sensor cameras and hopefully the introduction of the Amira will address some of those issues, however…

Part Two: Can you zoom into the tears?

The ARRI Amira camera is being released with an Alexa 16:9 sensor, so is 100% a 35mm camera and will take PL lenses. It delivers the shallow depth of field based on the focal lengths required for 35mm acquisition. It will also be able to take EF mount lenses as well, no mean engineering feat as the flange focal depth for PL is 52mm and for EF is 44mm, but these are still 35 mm lenses throwing an image size that covers a 35mm size sensor.

Over recent years one of the most common conversations the VMI rental team have had is with clients wishing to shoot with a shallow depth of field onto a 35mm camera but with the operational need to be able to have a large zooming range as lens changing would be inappropriate. There unfortunately has only really been one answer to this in that there is only really one lens that comes close to offering such a range and that is the Angenieux Optimo 24-290mm which at 11 kilos and nearly ½ metre long is a magnificent lens and about as much use as a chocolate fireguard for documentary shooting! Why then release a camera that is obviously destined for documentary and non-narrative projects if the lens choice is as restrictive as it currently is?

At this point we have to examine the relationship between the holy grail and operational practicality along with the ability of NLE software to ingest just about anything. We are no longer in a world where one acquisition media precludes another-everything can be ingested and homogenized. A project that is mainly shooting shallow depth does not have to be slaved to that as other methods may be more practical for sections of it.  There are a range of lenses made by Fuji- the Cabrios that inherit the usability of 2/3 sensor B4 lenses but not the range, 19-90mm or 30-300mm are reasonable but could be frustrating in some situations. So why can’t we get the lens range onto these cameras? Well we can but we have to sacrifice some of the shallow depth to achieve it. The smaller the sensor, the greater the magnification for a given focal length and the wider the mm can be before vignetting occurs. In documentary world the B4 standard would translate a 24-290mm Optimo into 10mm-120mm, or to spin it the other way round- a 24-290mm B4 lens would be the 35mm equivalent of 63-700mm approx..A Canon HJ22 is 7.6-168mm, which when scaled as above would be about 18-350mm or in other words an incredibly useful range for documentary use in either format.

The problem is of course that merely adapting a B4 lens onto a PL mount results in a useless little circular picture in the middle of the sensor. Arri will be producing a B4 adapter for the Amira but at this stage it would be inappropriate to speculate on how they will accomplish this.

Part Three: Watcha gonna do about it?

Which leads us to what we can achieve now and what will have to happen from the manufacturers in the future if they want to sell us 4K tellies. As you can see from the above comparisons, no 35mm sensors can achieve sports like coverage with the range of lenses available and given that it is major sporting events that drive TV sales (3D TV sales peaked at the last world cup and have nearly halved since then) it is essential to have 4K small sensor cameras with lenses of sensible MTF* quality to put on them. This is a way off but will solve all of these issues when lack of depth of field and range is a problem rather than a creative positive.

For now, there is an alternative solution provided by after market adapters that allow B4 lenses to be used on PL cameras.

There are some drawbacks to this process and it is only now that we at VMI have found one solution that we feel is sufficiently elegant to offer as rental item. The task of the conversion is to magnify a small image destined to hit a 2/3 sensor at 17mm to a large 35mm sensor at 52mm. Whilst some high end prime lenses are built to MTF* to 4K and beyond, long in the tooth documentary lenses are built to resolve to 1920-1080HD and by magnifying this image, we are essentially pushing beyond the design remit of the lens and firing it to a large high quality sensor where all the aberrations will be highlighted.

The optical methodology to achieve this is the key to success. The requirement is to un-converge the focusing light and spread it out in order to cover the larger sensor. The simplest and least satisfying way to accomplish this is by using the doubler element on the lens. This magnifies the image two fold creating more parallel light rays that are in turn easier to spread out to the sensor through the adapter. The disadvantages are that the doubler element magnifies the limits of the lens’ performance and the adapter does the same. Equally by using the doubler, there is a consequent 2 stops transmission loss, which could be significant. A more elegant solution is to use a relay lens system and a deeper (longer) adapter body. By using a combination of elements, such an adapter can magnify the image to the correct size without using the double element and stop loss.

The IB/E HDx35 MkII performs in such a way whilst also able to correct the chromatic alignments for a CCD block which the lenses were originally designed for-as they are now passing an image to a CMOS chip. The suitability of this device depends on your project and on camera choice. On a Sony F5, you have the ability to operate just as any documentary camera would, with possibly some extra weight out the back for balance if needed. A C300 and FS700 won’t comfortably shoulder mount as we know, but the range available when using an HJ22 is more than any available from 35mm lenses.

And finally…

The creative notion for shallow depth of field is well established but not cast iron. On a multi camera shoot you could have one camera with the HDx35 MkII acquiring close ups from 40 feet away whilst all the other cameras are on 35mm glass. ‘Run and gun’ on an F5 with its advanced codecs, slo mo and SLog rather than PMW500. Binocular vision on an Alexa. 200fps on an FS700 at thirty feet away from the subject. All things are possible in context and we believe the HDx35 MkII could be a very useful addition to your shooting kit whilst we wait for the documentary camera to return..

Please check out the demo video which exhibits both types of adapters in a simple zooming test with distance markers to demonstrate the range at:

We have deliberately not applied any explanation to the clip but invite your comments across our social media platforms as below.

*MTF measures the contrast and detail transmission of a lens

Ian Jackson
Nov 2013

Note that if you are reading this on an iPad or iPhone, using the VMI iPhone App, then the comments are not visible on the current version (though we are working on this!).  Please view this with a regular web browser to read and leave comments and share on social media.

Related articles

No Comments

Leave a Reply

VMI are proud sponsors of: