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Re: Curves and Bit Depth - was Sigma fp

Re: Curves and Bit Depth - was Sigma fp

Paul Curtis

I've had one of these since it first came out and it is an amazing camera for it's size and cost. I've spent a lot of time ripping apart the RAW and working out where it's limitation are (for me), this is from memory:

- The sensor appears to be one of the Sony ones and like most sensors in this range, movie capture is limited to 12 bit off the sensor. You will never get more than that. Stills are 14 bit. Log is not needed, RAW is better in every way so long as you've got the workflow and pipeline to support it, you'd never use this cam as a wedding videographer. As a B or C cam it's great.

- Remember that in full frame mode it is downsampling 6K to UHD and with that comes softness. There is no OLPF as such and they rely on that downsampling to hide moire. Personally it's not something that has raised it's head for me but i have seen it. If you do DC mode (crop mode) then you get a UHD crop from the centre of the sensor and that is 1:1 pixel, it's noticeably sharper (and more susceptible)

- Like all of these cameras the workflow is paramount - highlight recovery is essential to extending highlight range and soft rolloffs, also careful transforms of colour are needed to roll off highlight colour too. I've been able to match this to Red footage under IPP2 remarkably well.

- But the range really is around 11/12 stops and for me that is the bigger issue because it means as a B cam side by side with a Red for example, that i cannot use the same lighting as sigma can't hold the highlights outside a window for example, where as Red can. But if you want to tape this camera to the ceiling or put it on some weird rig - it's brilliant.

- Rolling shutter is there and it's very average - better than Sony a7sII but nowhere near the sIII. Longer lenses can really show up the issues too and because it is so light that handholding means micro jitters and this can show up easily.

- As a form factor as a hand held camera the lack of EVF is a pain. The OVF is lovely and offers a great 3 points of contact with the eye but it's position is fixed and it adds so much size to what is a tiny package.

- The 8 bit RAW has a custom log curve in it, well an S curve that keeps the full range in just 8 bits - it's amazing quality. The 12 bit holds the shadows better though. In all cases extreme shadows go green. There's no point in having log as 12 bit RAW gets you all you're going to get off the sensor and it's uncompressed so pulling all the details out works well.

- You can whack a tentacle sync into the audio for TC. Audio is ok overall but i assume we don't care about that.

- The native colourspace is neither 709 or P3, it's whatever is native to the camera. There seems to be a slight advantage to working in a P3 project in Resolve but not really enough to make a huge change. I like the colour of it, it seems natural and malleable.

Having said this i'm hoping a Komodo will fit the bill for me, i have one on the way and will see, but that solves the rolling shutter and the range issue... But i will keep the fp as it's also my stills camera at the moment.

If anyone has any specific questions happy to help if i can..


Paul Curtis, VFX & Post | Canterbury, UK

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