Original BMPCC | Is The Native ISO Really 800?

[@shueibdahir]

One problem with what you just said @ 5:20 . The BM cameras of this era had a thing where once the image was overexposed, zebras showed up and if you tried to lower the ISO the image would still clip. You had to physically lower the amount of light reaching the sensor instead through the iso. This camera uses a dual gain sensor much like the arri alexa where two different gain levels are combined into a single image for more DR. I have a feeling that after the dual analog gai, the signal is fed into the ADC and the ISO is applied after this conversion. Meaning that the ISO is doesn't actually control the analog signal amplifier. So for best results control the exposure by manipulating the light reaching the sensor.

[@carlscinema7086]

I'm not sure how you interpreted what I said as you should use ISO to expose the image. For sure manipulate the light reaching the sensor. I actually have a video covering the relationship between ISO and dynamic range on the BMPCC4K, but the same principles apply for the Original BMPCC, just ignore the second ISO base. kzbin.info/www/bejne/o16tk5ykbamCo68

[@shueibdahir]

@@carlscinema7086 i'm having a hard time expressing what I meant but i wasn't talking about the p4k or the way it shifts it's middle grey according to each iso. What i meant was that I think the og bmpcc had a single level of sensitivity. Any ISO adjustment was simply a gain or pull after the ADC/ Quantization of the analog signal. Meaning if your pixel was already fully saturated aka clipping at some points of the the image, the lowering the iso was like pulling the entire image down like with the exposure slider on lightroom on an already clipped image or pushing the image up with the exposure slider. So to get the best result with this camera you have to control the amount of light actually touching the sensor using ISO 800 as the reference point. If the exposure is nailed at ISO 800 then you have the best possible image as a starting point in post

[@KekeLauda]

@@carlscinema7086 I'm a bit late to the party, but @shueibdahir is 100% correct... Changing the iso on the BMPCC 1st gen doesn't actually change the voltage/gain on the sensor, it is a digital post-processing effect... The Pocket 4K does change the gain on the physical sensor, thus the dynamic range distribution changes as you change the iso... As commented above, if your image is just about clipping @iso 800, lowering the iso on the Pocket 1st will not prevent this clipping as it should if there was an actual gain drop on the sensor... Another commenter also pointed out the iso invariance of the Pocket 1st gen...

[@maxb5529]

Thanks as always this is very helpful, especially when using the OG and 4K. I’ll do a test and drop a comment.

[@carlscinema7086]

Awesome!

[@jimmyzjam]

Great info, So if I meter for 400, do I still need to ETTR or does this work in replace of that?

[@fodsonmedia]

Intressant, tack för att du delar dina findings! Hojta om du vill låna min BMPCC och testa med. Ser fram emot nästa video. /Fredrik

[@carlscinema7086]

👍👍

[@somearsehole]

I really appreciate your videos on this camera.

[@michialharris1850]

I shoot 400 on this camera during the day and 800 at night or inside a building

[@shueibdahir]

Video camera's are not meant to be exposed like photo cameras. ISO is not an exposure tool not is the shutter speed

[@ГеоргийКалошин-ц6ъ]

I think it's just because the super 16 sensor is smaller than mft and catches less light

[@carlscinema7086]

ISO is a standard across cameras, regardless of sensor size. And when shooting ProRes the camera is adhering to the standard.

[@seifenhasedreizehn4077]

​@@carlscinema7086 not true, ISO depends on the sensor size. For lens equivalence, you have to multiply iso with the crop factor to get the same light. ISO 400 on fullframe is iso 800 on m43 in terms of exposure. Google lens equivalence and you'll see I am right

[@carlscinema7086]

In terms of light gathered, yes, but not in terms of exposure. A smaller sensor will gather less light therefore have more noise at a given ISO (assuming the same sensor technology), so a higher ISO on a bigger sensor will be equivalent to a lower ISO on a smaller sensor. But ISO is a standard for exposure, not gathered light. Take an alexa mini lf, a mini and a pocket 4k, all different sensor sizes and set them to the same ISO, aperture and shutter and their exposures will match (even though they've collected different amounts of light due to the different sensor sizes).

[@seifenhasedreizehn4077]

@@carlscinema7086 I think you are right actually :) Still I think Iso is not "natural" but set to be a specific value by the manufactures to be comparable, right? Anyway, I still love your videos in any case :D

[@carlscinema7086]

Yes, ISO stands for the International Organization for Standardization - an organization that sets international standards for all different kinds of measurements. So the whole point of it is that a given ISO should be comparable across cameras. Even more important if you're shooting analog film and expose with a meter. ISO is a neccessary standard so that you can match your meter to the films ISO rating.

[@anttiheik]

No, simply because modern ISO invariant sensors do not have a native ISO. BM’s own employee that goes by the name Captain Hook on bmcforums has confirmed this. The ”native” ISO is simply a balance between noise and highlight detail that the development team has chosen as suitable for most shooting situations. The cinematographer can decide the ISO rating of the camera based on the needed highlight DR and what they consider an acceptable level of noise. 😊

[@carlscinema7086]

That's pretty much exactly what I said in the video. The video isn't debating whether the ISO 800 setting is the native or not, it's about 800 not actually being 800.

[@anttiheik]

@@carlscinema7086 Ah, I see. I marked the video to watch later since I was commuting at the time but I couldn’t help myself answering the question in the title before watching.

[@shueibdahir]

First time in a long time i've seen anyone talking about iso invariance on a video about video cameras. You know your stuff my friend

[@clayz8098]

When it comes to the bmpcc 6K should I mostly try to keep the ISO at 800 too pretty much in all situations?

[@carlscinema7086]

The BMPCC6K and 4K have dual native iso, but for the lower base, that is ISO 400.