Blackmagic Designs Ursa Mini 4.6k with the B4 Lens Adapter

Is this the bridge between HD and 4K?

NOTE:  Please go to the addenda box at the end of the article to read about an embarrassing mistake and credits for all the help I got in creating this article.

Fair warning:  If you are here to get a full, top-to-bottom review of the Blackmagic Ursa Mini 4.6k camera, I’m afraid you’ll be a bit disappointed.  I’ll get into that a little bit, but in reality I’m more inclined to examine a specific use-case scenario of the Ursa Mini with an accessory – the B4 lens adapter.

A B4 ENG lens mounted to the Blackmagic Designs Ursa Mini 4.6k camera

First, let’s define our terms.  What is a B4 lens?  Specifically, it is a lens most commonly mounted to electronic news gathering (ENG) video cameras, usually working with 2/3” imaging chips.  It is also a zoom lens, with varying degrees of wide-angle and close-up capability.  As a TV photographer for the last 35 years, I have become intimately familiar with the workings of both the B4 lens and the cameras they attach to.  On the other hand, the Ursa Mini 4.6k camera features a Super 35-sized chip, which is far larger than 2/3”.




(Side note:  In case you were wondering, it is the size of the imaging chip – in conjunction with properly-paired lenses – that makes ultra-short depth of field possible. Of course, there are other factors involved, including the F-stop your lens is operating at, but as a rule of thumb: Larger the chip, shorter the DOF. )

The beauty of the B4 ENG lens is simply this:  It is “parfocal,” which means that – when properly adjusted – you can zoom the lens from the wide end to the zoom end and stay in sharp focus every millimeter of the way.  In my experience, very few if any DSLR lenses offer anything close to this functionality.  I was recently on a shoot with a Canon C100 and a zoom lens, and I had a sudden epiphany – the reason you see so many DSLR shooters racking their focus in the middle of shots is because they have to – they zoomed in or out and the focus went soft. Canon, Fujinon and others have recently brought ENG-style large-format lenses to market, but with the exception of the around-$6000-with-handgrip Canon CNE 18-80mm, their prices are north of $20,000 – some over $70,000.

So, why have I come to this particular place?  I have to figure that a lot (if not the majority) of today’s DSLR shooters have never used a camera with a B4 lens on it.  If your production is in any kind of a hurry – and believe me, at any TV station, you are always in a hurry – the idea of carrying several limited focal range lenses and constantly swapping them out is just not practical in any way, not to mention that quite often you are a one-man band.  These days, I’m thrilled to have an audio person with me, and I can count on one hand the times I’ve had a focus puller, and never a lens wrangler. But even at that, there is no doubt that the future is coming, and incredibly capable camera bodies cost a mere pittance of what a camera cost as recently as ten years ago.  Is there a bridge for the B4 lens owner to make great HD pictures today, have the ergonomics and flexibility a true shoulder-mount camera offers, and have a path to the 4K future?

You can say a lot of things about Blackmagic Designs, but one word that will always crop up is “imaginative.”  The make a wide range of products, some great, some OK, but they do seem to be always striving to fill a need.  I will confess that I was very disappointed when they announced several cameras, including the Ursa, Ursa Mini, and Studio Camera, all featuring chipsets that could not natively take advantage of the thousands of B4 lenses that are out in the field.



Well, at least in the case of the Ursa Mini, they have addressed that problem with the B4 Lens Adapter.




To test the adapter, Blackmagic sent me an Ursa Mini, the ENG-style viewfinder, and the shoulder mount (all three parts are sold separately.)  A very forward-thinking inclusion on the Ursa Mini is a jack that you can plug the B4 lens cable into, which supplies power for the power zoom and iris controls.  I borrowed two B4 lenses from my employer, Wisconsin Public Television.  One was a fairly standard-issue Canon HJ17ex7.6B lens, with a zoom range from 7.6mm to 130mm, and the other is my favorite lens of all time, a wide-angle Canon J11EX4.5, with a range from 4.5mm to 50mm.  (Both lenses have built-in 2x extenders as well.)  The longer lens is found on Blackmagic’s approved lens chart, while the wide-angle is not; however, I didn’t see any ill effects from using it on the Ursa Mini.  Unfortunately, what was not included with the Ursa Mini was any kind of battery mounting device, so my actual testing was limited to the distance I could stray from a wall socket.  That oversight also required a bit of estimation as to the feel of the camera on my shoulder.  The first thing you sense when you pick up the Ursa Mini is “Hey! This thing is HEAVY!”

Wisconsin Public Television videographer Mike Eicher tries out the Ursa Mini.

But surprisingly, it’s not so much heavy as it is dense.  This thing is a chunk of METAL. (Magnesium, to be exact.) With the viewfinder, shoulder mount and the wide-angle lens on it, the Ursa Mini weighed in at about 14.5 pounds – add another two or three pounds for a lithium V-mount or Anton-Bauer battery on the back and that’s still several pounds lighter than the 2/3” ENG cameras that are common today.  Without the battery, the Ursa Mini was nose-heavy, but adding a battery would go a long way towards fixing that issue.  The shoulder pad slides fore and aft about 4 inches to personalize the balance to your situation.


Another nice design touch is found on the bottom of the shoulder mount.  There is a triangular wedge milled into the base that is designed to connect directly to the tripod plate on what we’ve always called a “Sony mount.”  In practice, it took some cajoling to lock in securely, but I’m sure that would get easier over time as the parts wear in.  (The “Sony-mount” tripod plate is not included in the shoulder-mount package.)

Blackmagic Design seems to pride themselves on what is often called “OOBE” – the “out-of-box-experience.” When you open the Ursa Mini box, you are first greeted with a small cardboard folder with an SDHC chip in it.  The chip contains the manual as a PDF file and an Ursa camera app.  I opened the manual and started paging through the menus on the 5” fold-out LED touchscreen.  Imagine my surprise when the menu pictures in the manual didn’t match the ones on the touchscreen at all!  After a little bit of head-scratching, I decided to run the Ursa camera app.  It turns out that the app’s singular function is to check if you are running the latest software – and I was not. A few minutes and a software flash later, things made a little more sense.

It’s important to remember that even though the Ursa Mini 4.6k has a Super 35-sized sensor, a B4 lens can only illuminate a small part of that.

Insert a 16:9 rectangle in the middle of that circle.







(There is an field-of-view calculator at that illustrates this issue beautifully.)

In the Ursa Mini menus there is a “windowing” option that essentially turns off the part of the chip that is not in use, magnifies the image to fill the monitors, and records the signal at 1920×1080 pixels.  This means that your depth-of-field is not going to be nearly as shallow as it would be with a Super 35 lens.  Still, if you keep your iris open and zoom in on your subject (by staying a bit farther away) it’s not hard to approximate the short-DOF look with a B4 lens.  There is no neutral density filter wheel on the Ursa Mini, but by adjusting the ASA, the shutter angle and using external ND filters, it’s not too hard to keep that iris open wide and your DOF short.

To a seasoned TV shooter, the display and language of the Ursa Mini will take a bit of getting used to.  For example, instead of gain in dB, the Ursa Mini offers ASA ratings (with ASA800 as the preferred setting.)  White balance is not achieved by pointing the camera at a white card and hitting the “white balance” button, but instead you have to select the Kelvin temperature manually from a range that runs from 2500 to 8000k.  Even more unusual is “shutter angle,” which is most analogous on an ENG camera to the “shutter speed” switch.  It has been several years since I found any reason to use the “shutter speed” switch on my ENG cameras, and that’s because tube-based computer monitors are almost completely gone from offices – a little manipulation of the shutter speed on the camera could often lose the roll-bar caused by odd monitor refresh rates.  On the other hand, shutter angle in film is often used to create a mood of heightened awareness or action – the D-Day landing from Steven Spielberg’s “Saving Private Ryan” is the poster child for narrow shutter angle.

Before color correction…

In my testing, I found the Ursa Mini to be a camera that needs a lot of light.  Even with the shutter angle at 360 degrees, a subject lit with a 650 watt tungsten light in a Chimera from five feet with the lens iris wide open barely got up to 100 percent video. (An aside:  Instead of a histogram, could there maybe be a waveform monitor and vectorscope displayed in the viewfinder? Thanks.)





…after 1 minute with Lumetri. Apple ProRes 422 codec.

Now, it’s not as if I couldn’t get a nice-looking picture out of the Ursa Mini; all it took was a few minutes in Adobe Premiere Pro’s Lumetri color-correction program to make a great looking picture.  However, remember what I was saying a few paragraphs back about being in a hurry?  News shooters can’t often devote that kind of time to a package.  On the other hand, documentary photogs probably can.



If you are going to be color correcting, it is to your advantage to record in a codec that retains as much information as possible.  The Ursa Mini offers a wide variety of RAW and Apple ProRes codecs to record into, depending on your needs.

Transport controls, audio level knobs and C-FAST2.0 slots.

Unfortunately, because of the enormous data rates involved in recording uncompressed RAW, the Ursa Mini requires the use of C-FAST 2.0 recording chips. Street price for a 128Gb C-FAST 2.0 chip is in the $350 US range right now, and at uncompressed RAW rates, that equates to less than ten minutes of recording.  At the HD rates we are exploring here, it’s about 70 minutes, but when you compare the cost of C-FAST 2.0 to an SDHC or SDXC card that costs twenty or thirty bucks, it is a data point that must be considered.  The Ursa Mini can hold two C-FAST 2.0 chips at a time.




When I installed the Ursa Mini’s ENG-style viewfinder, my first reaction was “Wow!  That thing is tiny!”  Truth be told, that was a reaction to the relatively huge viewfinders found on today’s ENG cameras, which usually double as monitors.  I have no complaints with the Ursa Mini’s viewfinder, with a very bright and sharp 1920×1080 OLED monitor inside a metal (!) casing.  Several of my colleagues commented positively on the peaking display in the viewfinder, which is a very thin green line – understated, but obvious enough for you to know just what is in focus.  Another thing that particularly impressed me and all my eyeglass-wearing fellow shooters was the diopter-adjustment ring.  It features a very wide adjustment variance and a lot of drag – it’s hard to move this accidentally.  And while we are on the subject, the fold-out touchscreen monitor on the left side of the Ursa Mini is bright and sharp as well, although it doesn’t take long for the touchscreen to start accumulating fingerprints.

The audio section of the Ursa Mini is basic but usable.  Twin XLR jacks sit on the top-rear of the camera, and there are onboard mics as well.  Audio settings are all menu-based except for the actual level knobs, which live on the panel behind the fold-out monitor.  I understand that software is far less expensive than physical switches, but to have to dive through menus just to make the headphones louder is not great design.




The Ursa Mini with my favorite lens of all time.


So:  Does the Ursa Mini with the B4 lens adapter make sense?  It’s a very mixed bag.  Positives include being able to use that old favorite lens you love, a camera that is complete and functional in every way without needing all kinds of accessories hanging on cheese plates, and being able to move into a more cinematic look in high-definition for a very reasonable price – along with the future-proofing a 4.6k chipset offers.  The downsides?  Expensive media is right up there, along with a camera that needs a lot of light.  So it boils down to a very personal decision, but if you are devoted to the workhorse B4 lenses you already own and don’t need to shoot 4k anytime soon, the Blackmagic Ursa Mini with the B4 Lens Adapter could very well be the bridge between your present and future needs.

Embarrassing addenda:  You’ll notice the title of this article mentions Blackmagic Designs.  This is in error – it’s Blackmagic DESIGN.  Apologies to the good folks at Blackmagic DESIGN, and thanks for the heads-up.  Also thanks to Chad Myers, chief engineer at Wisconsin Public Television, and my fellow photographers Mike Eicher and Mike Baron among others for giving the Ursa Mini a run-through.  And thanks as well to Nick Lampke at Filmtools for the loan of a C-FAST 2.0 card and reader.


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A 1981 graduate of the Boston University College of Communication, Bruce A. Johnson got his first job in broadcast television at WFTV, an ABC affiliate in Orlando, FL. While there, he rose through the ranks…

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Dean HarringtonBruce A JohnsonJoris Recent comment authors
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Hi Bruce,

You mention the projected image circle is much small than the sensor. Did you try to engage the extender of your lens? This would double the projected image circle to almost entirely fill the Super 35 sensor. Disadvantage of the extender is of course that you’ll have less light…


Bruce A Johnson
Bruce A Johnson

Hi Joris. I did try out the extender on both lenses, but there was still very noticeable vignetting which made the image unusable. Thanks for asking!

Dean Harrington

Bruce, have you noticed any chromatic aberrations or other issues in the image with the B4 mount on the 4.6 k camera? I’m mulling over the new broadcast 4k camera and the pro.