Thread: Blackmagic Pocket 4K, best Iso's for Dynamic Range and Noise

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  1. #11  
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    In practice, it matters more than it should, and not in ways that are immediately obvious. For example, ISO1600 is just, well, wonky, in ProRes. It craps its pants if over-exposed even modestly, and not commensurate to the ISO's on either side.

    I'll always shoot RAW if shooting for myself, but I know I'm going to be required to deliver ProRes often enough that it was worth testing how each ISO responds to scene dynamics that I'm likely to encounter.
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  2. #12  
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    Quote Originally Posted by joe12south View Post
    In practice, it matters more than it should, and not in ways that are immediately obvious. For example, ISO1600 is just, well, wonky, in ProRes. It craps its pants if over-exposed even modestly, and not commensurate to the ISO's on either side.

    I'll always shoot RAW if shooting for myself, but I know I'm going to be required to deliver ProRes often enough that it was worth testing how each ISO responds to scene dynamics that I'm likely to encounter.
    What I'm trying to say is that any advantage from shooting at an ISO at the far end of the range (from native), as in the case of 1000, will not provide a significant benefit in post, and can have downsides which *will* be significant. This is not argument for using any ISO or saying ISO doesn't matter.
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    Quote Originally Posted by jrd View Post
    What I'm trying to say is that any advantage from shooting at an ISO at the far end of the range (from native), as in the case of 1000, will not provide a significant benefit in post, and can have downsides which *will* be significant. This is not argument for using any ISO or saying ISO doesn't matter.
    I agree in theory, but again, there is some strangeness with the P4K. For example, ISO1000 (the very extreme of the low range) should be demonstrably worse than ISO1600 (near the bottom of the high range) but that's not the case in ProRes.

    btw, some UK store, ProAV maybe, has a video on YouTube showcasing them getting bit by the ProRes issue when they tried to do an overexposure test.
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    Sorry I'm late to the convo. This is so confusing. Ok so from what I understand of the chart, at ISO 1000 you would get 5.3 stops of DR above middle-grey vs 4 stops at ISO 400 and 2 stops at ISO 100, with a respective change in shadow DR depending on which ISO you choose. In other words, if you're shooting a daylight scene with a wide variety of highlights and you choose ISO 1000, you'll get more DR in those highlights *at the expense* of less DR in your shadows, which would no doubt introduce noise depending on how dark the shadows are in your shot. Is that correct? I honestly don't see any other way to interpret that chart. There's always the same amount of *total* dynamic range, but where that range lies is dependent on the ISO you shoot at.

    Now maybe that means jack squat when shooting in the Real World. After all, who the hell can tell exactly how much dynamic range is in an outdoor daylight shot at any given time? If you're shooting a sunset and you adjust exposure for your highlights, you're going to lose detail in your shadows, and vice versa. Will you *really* get more detail in your highlights by using ISO 1000? You'd still have to stop down to get a proper exposure, leaving you in the same situation. And is a 1.3 stop difference in DR even noticeable?

    This stuff is all beyond my comprehension. And I'm not a photographer or cinematographer, so my limited knowledge isn't helping the matter.

    I guess it'd be interesting to see a highlight comparison between ISO 400 and ISO 1000 with the f-stop properly adjusted for a similar or matched exposure.
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    Quote Originally Posted by joe12south View Post
    ISO1600 is just, well, wonky, in ProRes. It craps its pants if over-exposed even modestly, and not commensurate to the ISO's on either side.
    ISO1600 is the same log curve as ISO160, just with analog gain applied on the sensor.

    Also while generally it is true that with RAW ISO is just metadata, you have to be careful as on the Pocket 4K analog gain is used and you can't change that after the fact. You can't shoot ISO400 and then change to ISO3200 and have it look the same as if you shot ISO3200 in camera for example. So the ISOs available in RAW are limited to the valid list for the analog gain that was used at the time of shooting.
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    Quote Originally Posted by vonner View Post
    In other words, if you're shooting a daylight scene with a wide variety of highlights and you choose ISO 1000, you'll get more DR in those highlights *at the expense* of less DR in your shadows, which would no doubt introduce noise depending on how dark the shadows are in your shot. Is that correct?
    No. If you want to make your life simple, shoot at nothing but 400, for the 100-1000 ISO circuit. For the low-light 1250-25600 circuit, you could use 1250 for relatively well lit scenes, and 3200 for most of the rest. I haven't tested it, but I would guess you could get as much detail out of 3200 (in post) as you would shooting 25600 (at the same exposure in both cases), despite the fact that 25600 footage will be much brighter straight of the camera.
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  7. #17  
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    Quote Originally Posted by jrd View Post
    No. If you want to make your life simple, shoot at nothing but 400, for the 100-1000 ISO circuit. For the low-light 1250-25600 circuit, you could use 1250 for relatively well lit scenes, and 3200 for most of the rest. I haven't tested it, but I would guess you could get as much detail out of 3200 (in post) as you would shooting 25600 (at the same exposure in both cases), despite the fact that 25600 footage will be much brighter straight of the camera.
    I'm starting to suspect that you don't own the camera. What your are saying sounds good on paper but in actuality is not how the camera performs.
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  8. #18  
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    Quote Originally Posted by vonner View Post
    Sorry I'm late to the convo. This is so confusing. Ok so from what I understand of the chart, at ISO 1000 you would get 5.3 stops of DR above middle-grey vs 4 stops at ISO 400 and 2 stops at ISO 100, with a respective change in shadow DR depending on which ISO you choose. In other words, if you're shooting a daylight scene with a wide variety of highlights and you choose ISO 1000, you'll get more DR in those highlights *at the expense* of less DR in your shadows, which would no doubt introduce noise depending on how dark the shadows are in your shot. Is that correct? I honestly don't see any other way to interpret that chart. There's always the same amount of *total* dynamic range, but where that range lies is dependent on the ISO you shoot at.

    Now maybe that means jack squat when shooting in the Real World. After all, who the hell can tell exactly how much dynamic range is in an outdoor daylight shot at any given time? If you're shooting a sunset and you adjust exposure for your highlights, you're going to lose detail in your shadows, and vice versa. Will you *really* get more detail in your highlights by using ISO 1000? You'd still have to stop down to get a proper exposure, leaving you in the same situation. And is a 1.3 stop difference in DR even noticeable?

    This stuff is all beyond my comprehension. And I'm not a photographer or cinematographer, so my limited knowledge isn't helping the matter.

    I guess it'd be interesting to see a highlight comparison between ISO 400 and ISO 1000 with the f-stop properly adjusted for a similar or matched exposure.
    You got it correct. I remember it RED MX days people shot 800 for Day exterior and 320 for Night interior. Its a little counter intuitive, but thats how most cameras work.

    Any cinematographer should be able to tell you the average values of day exterior scenes, blue sky and green grass are very close to middle grey for spot reading, theres on average a 3 stop difference between incident readings in direct sun and shade. White objects are on average 2 stops up from middle grey at least. So if you have a grey object in shade and a white object in sun is the same shot there will be at least a 5 stop exposure latitude.

    Does 1.3 stops in the highlights make a difference, its the reason 90% of everything is Alexa Mini now, its the only major difference between the Red/f55/varicam and the Alexa, 1.5 stops of dr.

    There was also a mention of a struggle to expose for 1000 ISO, a 2.1 IRND is 80 bucks in 77mm. I don't think I've ever shot any day exterior at higher than a T2.2 on my p4k.
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  9. #19  
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    Quote Originally Posted by jrd View Post
    That chart shows the allocation of stops above and below middle-grey. But +1 in the highlights, versus a lower ISO setting, doesn't mean a gain of a stop of light you can actually capture, versus the lower iso setting. The iso settings are just shifting how the values are distributed, with relation to where middle-grey is positioned.

    Note here that you clip at exactly the same f-stop from 100 to 1000, so it's hard to see how the roll-off will be smoother at 1000 than it is at 400. Did you actually test it?

    Of course, this is for Prores only. In raw, ISO is just metadata.
    Of course it doesn't, it means the sensor is getting less light. The sensor clips at 400 FC, you don't see how the gradation between middle grey set at 100 FC and middle grey set at 10 FC would make a difference is the transition to the full well capacity. I don't need to test it. Its literally how every camera on the market works other than the C series camera.
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  10. #20  
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    Quote Originally Posted by rze View Post
    Of course it doesn't, it means the sensor is getting less light. The sensor clips at 400 FC, you don't see how the gradation between middle grey set at 100 FC and middle grey set at 10 FC would make a difference is the transition to the full well capacity. I don't need to test it. Its literally how every camera on the market works other than the C series camera.
    If you don't need to test anything, then there's no point in me trying to persuade you that you're mistaken about the function and operation of ISO settings on this camera, and other digital cameras.

    There are still people who, years later and against all evidence, insist that they get better results on the original BMPCC using anything but the native ISO, so this one is clearly a losing battle.
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