Ursa Broadcast - ISO Specs missing

Hi there,

the new Ursa mini broadcast seems to be the missing camera in BMDs setup. We would instantly buy 8 of this cameras with full SMPTE Fiber support if we would get some information about the lowlight abilitys of this camera. But you can't find anything on the BMD site. Even any info about native ISO is missing.

But there are some more questions:

#1 Does the B4 adapter that comes with the camera lose light like the one from Ursa mini Pro? Is it actually the same adapter as the one for the Ursa mini pro?

#2 At what native ISO does the camera work?

#3 Why is the sensor 1" when you only need 2/3"?

#4 What about rolling shutter issues?

#5 Seems to be a new sensor. BMD had big issues (magenta, black sun, FPN...) with all of their sensors. What about this one?


I think we can only wait until someone can test this camera under real life circumstances until we make a decision. So if anyone buys or rents one please share your experience.


Cheers

Robert

the sensor is .59 in, the B4 adapter is probably different, and specifically designed for it. suspect the sensor is a tad closer from the lens than in a classic .66 in sensor camera

The sensor seems to be closer to 1 inch:

Effective Sensor Size
2/3 inch sensor size when using 4K B4 mount (Actual sensor size 13.056mm x 7.344mm)

https://newatlas.com/camera-sensor-size-guide/26684/

Cheers

Robert

Effective Sensor Size
2/3 inch sensor size when using 4K B4 mount (Actual sensor size 13.056mm x 7.344mm)

I think you should recheck your maths

let's see...
SQRT( 13.056² + 7.344² ) = SQRT ( 170.4591 + 53.9343 ) = SQRT ( 224.3934 ) = 14.9797 mm
which turns out to be... 0.5897 in according to my HP48

ok, guess that needs more explanations, cause pythagore says otherwise...
12.80mm by 9.6mm gives a 16mm diagonal, none of those measurements are close from 25.4mm

Maybe the sensor is the same as the 4k micro studio camera

I thought the same but its not:

Blackmagic Production Camera 4k:

21.12 x 11.88mm


Cheers

Robert

@edit

Sorry didn't read precisely!

You are right:

BMD Micro studio camera 4k sensor size:

13,056 mm x 7,344 mm

That means that this camera is not usable in normal light situations. You will always need controlled studio lighting to make it work. If that is really the same sensor then the low light capabilities are close to zero.

Cheers

Robert

Its just a Studio camera, no good for events or sports if its the same sensor as the 4k micro studio camera, but i hope it’s something different

I don't have experience with the micro studio camera 4k, but I'm thinking with a bigger heat sink and better thermal design, the ursa broadcast could have a little bit of improvement in terms of low light. I don't think it would be a dramatic difference but probably noticeable. The tech specs for the ursa broadcast says the dynamic range is 12 stops+ whereas the micro studio camera has 11 stops.

Raphaël, the 1/2, 2/3rds, 1-inch sensor designations are not based on the diagonal of the actual sensor size, but rather go back to the days when video cameras used a Vidicon tube instead of CCD or CMOS sensors. The size designation used for vidicon tubes was carried over for 1/2, 2/3, and 1-inch sensors. Nothing to do with the actual sensor size measurements. See below:

When the vidicon tube was invented in the early 1950s, the glass tubing used to make the first units had a nominal exterior diameter of one inch. These were referred to as "One-inch tubes". After allowing for the space taken up by the interior metal structures needed to control the electron beam, the portion of the photoconductor on the front glass accessible for scanning had a diameter of about 5/8 inch. Early television used a raster aspect ratio of 4:3 so the corresponding scanned area was 1/2 inch horizontal by 3/8 inch vertical - the canonic 3:4:5 right triangle. After a while, the image size assumed the name of the tube and a 5/8 inch diagonal raster became commonly called the 1-inch size. 5/8 inch is 15.875 mm and so 16 mm became the designated metric diagonal for 1-inch tubes.

Hope this helps to clear the terminology used. BTW, between 2/3rds and 1-inch is 16mm and Super 16mm film gate sizes. Broadcast cameras kept the old vidicon tube designations, while Cinema camera’s used the actual film gate size, based on film sizes, to designate sensor sizes. So a S16 sensor is slightly smaller size diagonal than a 1-inch sensor. The BM Boradcast Cameras use 1-inch sensors, where a 18mm lens gives the normal AOV.
Cheers

OK, a 4K sensor if a given size is going to have less light sensitivity than its HD or SD counterpart, because the pixel cells have to be smaller, and in turn require more light for a given exposure. Sensor sensitivity is useually measured in Luts in Broadcast Camera specifications, to give a base for comparison.

That said, broadcast cameras do not normally use ISO settings, but rather a “Gain” system, starting out a 0-Gain (which would be the native ISO), and use video processing circuits to reduce the gain (for bright light situations) or boost the gain, which also boosts the noise threshold. So the actual ISO is going to depend on how much noise yiu can accept in the image, Howie uses 100, I use 200, but the new update resets a new “0” setting, which is closer to ISO 400. So yes, this is not going to be a low light camera. But it should before a little better than the Studio or Micro Studio Cameras.

Hopefully, the new Broadcast campera, with its larger cooling system, and a better video processor, might boost the base line ISO level to 800, and make the sensor readout time faster (which reduces output lag, and rolling shutter issues). Most broadcast cameras went from the vidicon tube to CCDs, and only recently are using single MOS sensors, as it’s technology improves. New dual base gain sensors, like those on the Panasonic Varicam, EVA and the new GH5S can be used to increase light sensitivity when needed in future broadcast cameras.
Cheers

Without signal to noise ratio numbers and sensor sensitivity we cant know how the camera performs in low light condition, all broadcast brands tell those numbers for their cameras

Agreed, the sensor specifications should be given, including Lux, signal to noise, etc. the. An informed decision can be made. That said, how many small broadcast and individual operators know how to evaluate this data, which is often distorted or based on lab conditions, which do not always reflect real world experience with a given camera sensor. The old Panny AF 100, one of the first bridge cameras for broadcasting and cinema production, looked good on paper (its specifications for signal to noise beating out smaller sensor broadcast cameras) but actual shooting conditions was not as well performing as some higher end 3-CCD cameras, due to its original 8-bit output. But still some great work came out of this camera.

A camera is still just a tool in the end, and it’s how (and who) you use sue it, understanding it’s short comings and advantages along the way.
Cheers

The camera will go to a 12db only, from what i see in the website video and the manual, it is just -6db, 0db, 6db and 12db

So that might be, ISO 100 (-6) 200 (0 Gain/ Native or base ISO), 400 and 800, on the Micro Studio Camera.
It will be interesting to see if that works out the same on the new Broadcast Camera.
Cheers

[Tim Schumann]

On the URSA Broadcast -6dB is 200ISO, 0dB is 400ISO, 6dB is 800ISO and 12dB is 1600ISO.

That is the current range. We are driving the sensor differently to how it has been done previously, more similarly to a traditional broadcast camera, and are happy with the results we have been getting out of it at each of these settings.

You will need to update your ATEM switcher and software to 7.3 and the camera to Camera 5.0 Update so that these line up correctly between camera and switcher.

Thanks Tim,

I recently profiled the Micro sensor and got results that are pretty similar to what you're posting here. At -12 if I expose middle grey at 40 IRE I get ISO120 if I put mid grey at 50IRE I get ISO80. It tracks all the way up through the gain settings as you'd expect.

Do the ISO numbers you've posted include the stop loss of the B4 adapter and since you're here, is it the same sensor from the Micro 4K?

wonder if the reason they hold this info back is that then they'd have to admit they're throttling performance?

I do not see BM holding this info back, Tim just provided it. In a Broadcast workflow, ISO is not used on cameras, they use the original “Gain” setting system, that goes back to when actual analog Gain was being added to the camera sensor circuit p, along with Knee settings. ISO is a Cinema thing going back to film production workflow, and was carried over to digital Cinema cameras, the Ursa Broadcast is not a Cinema camera, so Gain is used for sensor sensitive settings instead of ISO.
Cheers

Broadcast camera builders like Sony, Panasonic, GVG and Hitachi declare the sensitivity of the camera with a standardized value like "F8.0 (2000 lx, 89.9% reflection)". This makes the cameras comparable. Blackmagic doesn't give us this specification. So it's impossible to compare the URSA Broadcast with other broadcast cameras and that's annoying.

I will buy that and this would be useful info to have, but the sensor sensitivity rating has nothing to do with ISO values.
Cheers