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Sigma Fp review and interview / Cinema DNG RAW


Andrew Reid
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24 minutes ago, Chris Whitten said:

Even just two of my 10 second clips is 6gb (zipped). My computer is telling me it will take 7 hours to upload to Dropbox, so I don't think I can stand to do that, you'll just have to take my word for it. I will test other sub-ISO400 conditions later or tomorrow.

Oh man, definitely don't want to upload that, haha. I bet money if it's happening at 200, it's happening at the thirds-ISOs below 400. Very odd behavior. 

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Yea, the first frame brighter happens at ISO's in between 100-400...everything else is fine. Just weird. 

My 2 big grips are the flickering blacks and the audio sync issue...if those 2 issues were fixed...it would be an amazing cam! I still love the IQ out of it...so amazing...even 1080P CDNG's up-rez to 4K beautifully...and it knocks the digital sharpness down a bit do by shooting this way which helps it look more organic. 

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I haven't had a chance to do more tests but ISO200 saw the first frame brighter. And it was 320 ISO at 10 bit for me, none of the others. But consistency is a question - is it *always* the same ISOs?

So i think if we can all test then we need to post our results here and list ISO/BitDepth/ShutterSpeed and whether the first frame was overexposed or whether it flickered.

I should get a chance tomorrow i hope

cheers
Paul

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Yes, it is happening....

I shot ISO 125, 160, 250 and 320 4K UHD 10 Bit.

The first frame of every clip is about one stop brighter than the clip as a whole. This can be seen visually and with the scopes in Resolve.

I can add ISO 200 from yesterday as also having this issue. But ISO400 and 640 were clear of the issue.

I noticed when filming, the on screen histogram blanks out for a fraction (perhaps a frame) when you hit record, but when you hit the record button to stop it doesn't blank out.

 

Can someone collate all these test results (from various members) and forward them to Sigma? I'm not on Twitter or Facebook

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Thank you Chris! That makes three (4 when Paul confirms) of us so far with a 100% repeatable first frame issue. 

The flickering will be weirder to group nicely between us, but with that all we can do is send Sigma samples of what we're seeing to let them figure it out on their end. 

Picking 24 consecutive frames from a sequence that flickers should be enough as sample footage, and would be much smaller to upload for hosting. 

 

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1 hour ago, Chris Whitten said:

Can someone collate all these test results (from various members) and forward them to Sigma? I'm not on Twitter or Facebook

I'm happy to do this as i've been emailing for quite a while now but also once we have them collated then we should reach out on twitter as well?

I will probably get a chance tomorrow to do all the tests.

Too busy fixing up bikes for a quick escape to the countryside for some fresh air!

Out of curiosity for those doing very low light 10 bit tests are you very bottom shadow stops quite green? I want to know if this is universal or whether it's just me. It's only 10 bit this happens to.

cheers
Paul

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I've cycled through all my settings, on 8, 10 and 12 bit. 180 degree shutter. My findings are consistent across bit depths, so that's something solid. I flicked at 400ISO and i think 320 but it might just be an odd flicker at the start. The flash frames seem to be an ISO setting incorrect. Flash frames happen for me 125, 160, 200 and 250 but seems solid after that.

What i was talking about was whether everyone sees a skew towards green in 8 and 10 bit modes at the bottom end? I have reported this and mentioned on this thread.

This is a side effect of reduced shadow bit depth you can see clearly below. But i still think it's a bug because there's no need for it to be green. 

Shoot at a low ISO and push the exposure up 3 in Resolve, it's very clear then (as below), these are ISO 160

So firstly if we're going to report this

1) Are we all happy that the depth setting doesn't change things?
2) Can we confirm what our own flicker ISOs are (and include shutter speed and frame rate)

Screenshot 2020-03-23 at 12.07.36.png

Screenshot 2020-03-23 at 12.08.22.png

Screenshot 2020-03-23 at 12.08.11.png

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That green shift is weird indeed.

1. Bit depth doesn't seem to affect flicker behavior from what I've seen.
2. All with 4K 12bit capture at 23.98fps and 180 degree (1/50th according to DNG files) shutter:
100-400 = fine
500-2000 = flicker
2500 = fine
3200-4000 = flicker
5000-6400 = fine

3. Overexposed first frames happen on ISO 125, 160, 250, 320

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I'm still not seeing any flickering. Certainly not the low end of my scope image bouncing around. This is shooting 180 degree, 50 shutter speed at 25fps.

I've filmed at all ISO's up to 640 now.

I'm not sure about the green tinge either. This is my least well exposed (dark) frame, ungraded other than the camera settings, at ISO125. The scope looks about ok. I guess the image looks slightly green if I push the exposure 3 stops, but the rest of the image also looks rubbish. In a normally exposed and graded version, this image looks normal (and nice) to me.

When I shot some stills outside, I did find the camera really highlighted green. My grass was vibrant and saturated, whereas my Leica Q version of the same shot was a lot less hyped in the green. But this was also with a vintage Pentax lens.

Screen Shot 2020-03-23 at 12.57.49.png

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2 hours ago, Scott_Warren said:

That green shift is weird indeed.

1. Bit depth doesn't seem to affect flicker behavior from what I've seen.
2. All with 4K 12bit capture at 23.98fps and 180 degree (1/50th according to DNG files) shutter:
100-400 = fine
500-2000 = flicker
2500 = fine
3200-4000 = flicker
5000-6400 = fine

3. Overexposed first frames happen on ISO 125, 160, 250, 320

I'm hoping for consistency! Exposure issue on first frames seems the same as me. So can anyone else confirm that it is just this range?

But the flicker is different and that's infuriating! What else might affect the flicker that we're not taking into account.

@Chris Whitten so you not seeing any flicker is important too - unless we find a reason why. On the green issue would it be possible to upload a single DNG from something done at low ISO, like 100, in 10 bit so i can compare?

@Lars Steenhoff It's not black level, i can adjust that but that affects higher tones as well and also 12 bit is fine.

cheers
Paul

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