Tag Archives: prores raw

ProRes Raw Over Exposure Magic Tricks – It’s all smoke and mirrors!

There are a lot of videos circulating on the web right now showing what appears to be some kind of magic trick where someone has shot over exposed, recorded the over exposed images using ProRes Raw and then as if by magic made some adjustments to the footage and it goes from being almost nothing but a white out of over exposure to a perfectly exposed image.

This isn’t magic, this isn’t raw suddenly giving you more over exposure range than you have with log, this is nothing more than a quirk of the way FCP-X handles ProRes Raw material.

Before going any further – this isn’t a put-down of raw or ProRes raw. It’s really great to be able to take raw sensor data and record that with only minimal processing. There are a lot of benefits to shooting with raw (see my earlier post showing all the extra data that 12 bit raw can give). But a magic ability to let you over expose by seemingly crazy amounts isn’t something raw does any better than log.

Currently to work with ProRes Raw you have to go through FCP-X. FCP-X applies a default sequence of transforms to the Raw footage to get it from raw data to a viewable image. These all expect the footage to be exposed exactly as per the camera manufacturers recommendations, with no leeway. Inside FCP-X it’s either exposed exactly right, or it isn’t.

The default decode settings include a heavy highlight roll-off. Apple call it “Tone Mapping”. Fancy words used to make it sound special but it’s really no different to a LUT or the transforms and processes that take place in other raw decoders. Like a LUT it maps very specific values in the raw data  to very specific output brightness values. So if you shoot just a bit bright – as you would often do with log to improve the signal to noise ratio – The ProRes raw appears to be heavily over exposed. This is because anything bright ends up crushed into nothing but flat white by the default highlight roll off that is applied by default.

In reality the material is probably only marginally over exposed, maybe just one to 2 stops which is something we have become used to doing with log. When you view brightly exposed log, the log itself doesn’t look over exposed, but if you apply a narrow high contrast 709 LUT to it, it then the footage looks over exposed until you grade it or add an exposure compensated LUT.  This is what is happening by default inside FCP-X, a transform is being applied that makes brightly exposed footage look very bright and possibly over exposed – because thats the way it was shot!

This is why in FCP-X  it is typical to change the color library to WCG (Wide Color Gamut) as this changes the way FCP-X processes the raw, changing the Tone Mapping and most importantly getting rid of the highlight roll off. With no roll-off, highlights and any even slight over exposure will still blow out as you can’t show 14 stops on a conventional 6 stop TV or monitor. Anything beyond the first 6 stops will be lost, the image will look over exposed until you grade or adjust the material to control the brighter parts of the image and bring them back into a viewable range. When you are in WCG mode in FCP-X the there is no longer a highlight roll off crushing the highlights and now because they are not crushed they can be recovered, but there isn’t any more highlight range than you would have if you shot with log on the same camera!

None of this is some kind of Raw over exposure magic trick as is often portrayed. It’s simply not really understanding how the workflow works and appreciating that if you shoot bright – well it’s going to look bright – until you normalise it in post. We do this all the time with log via LUT’s and grading too! It can be a little more straight forward to recover highlights from Linear Raw footage as comes form an FS5 or FS7 compared to log. That’s because of the way log maintains a constant data level in each highlight stop and often normal grading and colour correction tools don’t deal with this correctly. The highlight range is there, but it can be tricky to normalise the log without log grading tools such as the log controls in DaVinci Resolve.

Another problem is the common use of LUT’s on log footage. The vast majority of LUT’s add a highlight roll off, if you try to grade the highlights after adding a LUT with a highlight roll off it’s going to be next to impossible to recover the highlights. You must do the highlight recovery before the LUT is added or use a LUT that has compensation for any over exposure. All of these things can give the impression that log has less highlight range than the raw from the same camera. This is not normally the case, both will be the same as it’s the sensor that limits the range.

The difference in the highlight behaviour is in the workflows and very often both log and raw workflows are miss-understood. This can lead to owners and users of these cameras thinking that one process has more than the other, when in reality there is no difference, it’s appears to be different because the workflow works in a different way.

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Why I Choose To Shoot ProRes Raw with the FS5

This is a much discussed topic right now, so as I promised in my last article about this, I have put together a video. Unfortunately YouTube’s compression masks many of the differences between the UHD XAVC and the ProRes Raw, but you can still see them, especially on the waveform scopes.

To really appreciate the difference you should watch the video on a large screen at at high quality, preferably 4K.

What are the benefits of ProRes Raw with the PXW-FS5?

There has been a lot of discussion recently and few videos posted that perhaps give the impression that if you shoot with S-Log2 on an FS5 and compare it to raw shot on the FS5 there is very little difference.

Many of the points raised in the videos are correct. ProRes raw won’t give you any more dynamic range. It won’t improve the cameras low light performance. There are features such as automatic lens aberration correction applied when shooting internally which isn’t applied when shooting raw.  Plus it’s true that shooting ProRes raw requires an external recorder that makes the diminutive little FS5 much more bulky.

So why in that case shoot ProRes Raw?

Frankly, if all you are doing is producing videos that will be compressed to within an inch of their life for YouTube, S-Log2 can do an excellent job when exposed well, it can be graded and can produce a nice image.

But if you are trying to produce the highest quality images possible then well shot ProRes raw will give you more data to work with in post production with fewer compression artefacts than the internal 8 bit UHD XAVC.

I was looking at some shots that I did in preparation for my recent webinar on ProRes raw earlier today and at first glance there isn’t perhaps much difference between the UHD 8 bit XAVC S-Log2 files and the ProRes raw files that were shot within seconds of each other. But look more closely and there are some important differences, especially if skin tones are important too you.

Skin tones sit half way between middle grey and white and typically span around 2 to 3 stops. So with S-Log 2 and an 8 bit recording a face would span around 24 to 34 IRE and have a somewhere between 24 and 35 code values – Yes, that’s right, maybe as few as 24 shades in each of the R, G and B channels. If you apply a basic LUT to this and then view it on a typical 8 bit monitor it will probably look OK.

But compare that to 12 bit linear raw recording and the same face with 2 to 3 stops across it will have anywhere up to 10 to 20 times as many code values ( somewhere around 250 – 500 code values depending on exactly how it’s exposed) . Apply the same LUT as for the S-Log2 and on the surface it looks pretty much the same – or does it?

Look closely and you will see more texture in the 12 bit raw. If you are lucky enough to have a 10 bit monitor the differences are even more apparent. Sure, it isn’t an in-your-face night and day difference but the 12 bit skin tones look less like plastic and much more real, they just look nicer, especially if it’s someone with a good complexion.

In addition looking at my test material I am also seeing some mpeg compression artefacts on the skin tones in the 8 bit XAVC that has a smoothing effect on the skin tones, reducing some of the subtle textures and adding to the slightly un-real, video look.

The other deal with a lack of code values and H624 compression  is banding. Take 8 bit S-Log2 and start boosting the contrast in a sky scene, perhaps to bring out some cloud details and you will start to see banding and stair stepping if you are not very careful. You will also see it across wall and other textureless surfaces. You can even see this on your grading suite waveform scopes in many cases. You won’t get this with well exposed 12 bit linear raw (for any normal grading at least).

None of these are huge deals perhaps. But what is it that makes a great picture? Take Sony’s Venice or the Arri Alexa as examples. We know these to be great cameras that produce excellent images. But what is it that makes the images so good? The short answer is that it is a combination of a wide range of factors, each done as well as is possible. Good DR, good colour, good skin tones etc. So what you want to record is whatever the sensor in your camera can deliver as well as you can. 8 bit UHD compressed to only 100Mb/s is not really that great. 12 bit raw will give you more textures in the mid range and highlights. It does have some limitations in the shadows, but that is easily overcome with a nice bright exposure and printing down in post.

And it’s not just about image quality.

Don’t forget that ProRes Raw makes shooting at 4K DCI possible. If you hope to ever release your work for cinema display, perhaps on the festival circuit, you are going to be much better off shooting in the cinema DCI 4K standard rather than the UHD TV standard. It also allows you to shoot 60fps in 4K (I’m in the middle of a very big 4K 60p project right now). Want to shoot even faster – well with ProRes Raw you can, you can shoot at up to 120fps in 4K. So there are many other benefits to the raw option on the FS5 and recording to ProRes raw on a Shogun Inferno.

There is also the acceptability of 8 bit UHD. No broadcaster that I know of will ever consider 8 bit UHD unless there is absolutely no other way to get the material. You are far more likely to be able to get them to accept 12 bit raw.

Future proofing is another consideration. I am sure that ProRes raw decoders will improve and support in other applications will eventually come. By going back to your raw sensor data with better software you may be able to gain better image quality from your footage in the future. With Log you are already somewhat limited as the bulk of the image processing has already been done and is baked into the footage.

It’s late on Friday afternoon here in the UK and I’ve promised to spend some time with the family this evening. So no videos today. But next week I’ll post some of the examples I’ve been looking at so that you can see where ProRes raw elevates the image quality possible from the FS5.

Free ProRes Raw and Sony Venice Webinars

I will be doing a couple of free interactive Webinars with Visual Impact in July. The first is on ProRes Raw looking at what it is, the equipment you will need and how to shoot with it.

http://www.visuals.co.uk/events/events.php?event=eid11028-839

The second is about my practical experiences shooting with a Sony Venice using the version 2 firmware.

http://www.visuals.co.uk/events/events.php?event=eid14021-841

Both webinars will feature a Q&A session where you will be able to ask questions online. You will find the full details about both webinars by following the links above, including how to register. The webinars are free but registration is required to obtain the login details for the events.

 

ProRes Raw and Atomos Inferno and Sumo – BIG deal for the FS5 and FS7!!

proresraw-logo ProRes Raw and Atomos Inferno and Sumo - BIG deal for the FS5 and FS7!!Over the last few days there have been various rumours and posts coming from Apple about how they intend to get back to providing decent support for professional users of their computers. Apple have openly admitted that the Trash Can Mac Pro has thermal problems and as a result has become a dead end design, which is why there haven’t been any big updates to the flagship workstation from Apple. Apple have hinted that new workstations are on the way, although it would seem that we won’t see these until next year perhaps.
Another announcement came out today, a new version of FCP-X is to be released which includes support for a new ProRes codec called ProRes Raw. This is BIG!

PRORES RAW.

Raw recordings can be made from certain cameras that have bayer sensors such as the Sony FS5 and FS7. Recording the raw data from the sensor maximises your post production flexibility and normally offers the best possible image quality from the camera. Currently if you record 4K raw with these cameras using an Atomos Shogun or similar the bit rate will be close to 3Gb/s at 24p. These are huge files and the cDNG format used to record them is difficult and clunky to work with.  As a result most users take the raw output from the camera and transform it to S-Log2 or S-Log3 and record it as 10 bit ProRes on the external recorder. This is a bit of a shame as going from 12 bit linear raw to 10 bit S-log means you are not getting the full benefit of the raw output.

Enter ProRes Raw:  ProRes Raw will allow users to record the cameras raw output at a much reduced bit rate with no significant of quality. There are two versions, ProRes Raw and ProRes Raw HQ. The HQ bit rate is around 1Gb/s at 24fps. This is not significantly bigger than the ProRes HQ (880Mb/s) that most users are using now to record the raw, yet the full benefit of 12 bit linear will be retained. A 1TB SSD will hold around an hour of ProRes Raw, compare that to uncompressed raw where you only get around 20 mins and you can see that this is a big step forwards for users of the FS5 in particular.

ProRes Raw (the non HQ version) is even smaller! The files are smaller than typical ProRes HQ files. This is possible because recording raw is inherently more efficient than recording component video.

It is claimed by Apple that ProRes Raw will play back in real time on MacBook Pro’s and iMacs without any additional rendering or external graphics cards, so it obviously isn’t terribly processor intensive. This is excellent news! Within FCP-X the playback resolution can be decreased to bring improved playback performance in less powerful systems or mutistream playback.

It looks like you will be able to record from a 4K DCI  from an FS5 or FS7 at up to 60fps continuously. This breaks through the previous limits for the Shogun of 30fps. The FS7 will be able to record 2K raw at up to 240fps and the FS5 will be able to record 4K raw at 100 and 120fps for 4 seconds. Other raw cameras are also supported by the Atomos recorders at differing frame sizes and frame rates.

At the moment the only recorders listed as supporting ProRes Raw are the Atomos Shogun Inferno and the Sumo19 and it looks like it will be a free update. In addition the DJI Inspire 2 drone and Zenmuse X7 Super 35mm camera will also support ProRes Raw.

Whether you will be able to use ProRes Raw in other applications such as Resolve or Premiere is unclear at this time. I hope that you can (or at least will be able to in the near future).

SEE: Apple Press Release.

SEE: Apple ProRes Raw White Paper

SEE: ATOMOS ProRes Raw INFO PAGE.