Wenqi Wei Posted October 30 Share Posted October 30 I'm reading somewhere that all ProRes footage shot on the Alexa is only legal/video range? How is it possible on such an expensive&professional industry standard camera? https://forum.arri.com/viewtopic.php?t=1595 To my knowledge there're many other less expensive 'cinema' camera that shoots full range footage internally. I just don't get it, or am I missing anything here? Thanks. Link to comment Share on other sites More sharing options...
Brian Drysdale Posted October 30 Share Posted October 30 You would shoot log if using ProRes as a recording format, which the way the other cameras also make full use of their dynamic range when using it. ProRes is for recording video, so will fulfil the technical standards for video. 1 Link to comment Share on other sites More sharing options...
Premium Member David Mullen ASC Posted October 30 Premium Member Share Posted October 30 Log-C provides all the dynamic range of the sensor within legal video for ProRes recording. 1 Link to comment Share on other sites More sharing options...
Wenqi Wei Posted October 30 Author Share Posted October 30 31 minutes ago, David Mullen ASC said: Log-C provides all the dynamic range of the sensor within legal video for ProRes recording. Hi David, but I don't understand why it's not able to shoot full/data range 0-255 but 16-235? For example my much cheaper $7k 2017 Panasonic EVA1 can shoot internal full range/10bit/422 V-Log V-Gamut footage...But why the 6x more expensive model can't? I understand the rest(DR, Color Science...) is different but I believe having full range is fairly important? I do see the video/legal is being crushed sometimes. Link to comment Share on other sites More sharing options...
Wenqi Wei Posted October 30 Author Share Posted October 30 Or do you mean you manually extend the range in post, maybe in certain NLE like Resolve? (Media page > Clip Attribute > Select Level??) I've read somewhere that Apple specifies that ProRes should be Legal? But also some source claims ProRes is not range-specific? Link to comment Share on other sites More sharing options...
Brian Drysdale Posted October 30 Share Posted October 30 This video will explain the use of log in a Panasonic camera. When shooting on an Alexa ProRes 4444 is often used, using Log-C. If you require the full uncompressed data from the sensor, ArriRAW can be used. Link to comment Share on other sites More sharing options...
Wenqi Wei Posted October 30 Author Share Posted October 30 2 minutes ago, Brian Drysdale said: This video will explain the use of log in a Panasonic camera. When shooting on an Alexa ProRes 4444 is often used, using Log-C. If you require the full uncompressed data from the sensor, ArriRAW can be used. Hi Brian, thanks for the link I've actually watched this exact video many years ago. I was just wanting to know how the Arri system works. Thanks for the help anyways. Link to comment Share on other sites More sharing options...
Brian Drysdale Posted October 30 Share Posted October 30 This video compares the two Logs: Link to comment Share on other sites More sharing options...
Wenqi Wei Posted October 30 Author Share Posted October 30 (edited) 18 minutes ago, Brian Drysdale said: This video compares the two Logs: Hi Brian, I understand what Log is, and we both know Log has nothing to do with Legal/Full range. I was just expressing my confusion that the industry Alexa can't seem to shoot Full/Data ProRes internally, while these sub $10k Sony/Panasonic 'Cinema' camera (at least the way they are advertised to be) that shoot HDR+Log+RAW+10bit+422+high bit rate (at least as of 2017, the year I went to college and the year I truly learnt what they are) can shoot Full/Data internally(though not in ProRes but their own internal codec). I am aware that English is NOT my 1st language, but I think I made a clear point about this. Edited October 30 by Wenqi Wei Link to comment Share on other sites More sharing options...
Brian Drysdale Posted October 30 Share Posted October 30 I suspect they're both acting in the same way when recording to a video file. Since video is standardized, I wouldn't expect them act differently. However, The Log C offers more options when exporting to different colour spaces: https://www.arri.com/en/learn-help/learn-help-camera-system/image-science/log-c They both use the same method to capture the highlight information so that it fits within the video legal standards and it's available for grading in post production. If you require everything, you should use RAW. Link to comment Share on other sites More sharing options...
Wenqi Wei Posted October 30 Author Share Posted October 30 (edited) 3 minutes ago, Brian Drysdale said: I suspect they're both acting in the same way when recording to a video file. Since video is standardized, I wouldn't expect them act differently. However, The Log C offers more options when exporting to different colour spaces: https://www.arri.com/en/learn-help/learn-help-camera-system/image-science/log-c They both use the same method to capture the highlight information so that it fits within the video legal standards and it's available for grading in post production. If you require everything, you should use RAW. Yes, thanks for the detailed write-up again, RAW is the ultimate one. Edited October 30 by Wenqi Wei Link to comment Share on other sites More sharing options...
Premium Member Sebastian Bock Posted October 30 Premium Member Share Posted October 30 Hi, Wenqi Wei! Arri is building a professional video camera, so they are using the video / SMPTE standards to be compatible with broadcast equipment all over the world. In the video world you have historically "lower than black" and "whiter than white (109%)" values. These is a legacy from the CRT TV era. Over decades, Manufacturers of broadcast and video equipment tried to stay backwards compatible with older standards so they respected the SMPTE guidelines for video levels. Full Range video is for computer monitors and not a standard in broadcast / video universe. Also, the Alexa has 10 bit ProRes recording, so it is not limited to 16-235 as you mentioned but to 64-1000, so it's not a big deal to have a couple values less than full range would offer... If you playback your Alexa footage on a computer monitor, you should have it transformed to full range somewhere in the chain so your blacks are not lifted. If you play back your Alexa footage on a Rec709 broadcast TV, you shouldn't do that because then you would have crushed blacks and blown out highlights. But you are right: all this has nothing to do with log. Some of my above statements might not be 100% technically correct, but they should give you an idea of the principle. Cheers, Sebastian 1 Link to comment Share on other sites More sharing options...
Brian Drysdale Posted October 30 Share Posted October 30 (edited) I gather, you need to have the whole pipeline set up for full range, otherwise it all falls down. Edited October 30 by Brian Drysdale Link to comment Share on other sites More sharing options...
Premium Member David Mullen ASC Posted October 30 Premium Member Share Posted October 30 There are many major streaming shows and even features that have recorded ProRes on the Alexa -- I shot five seasons of "The Marvelous Mrs. Maisel" in ProRes on the Alexa for Amazon Studios and it had lot of visual effects in it (and I won three Emmys and two ASC awards for it...) Movies like "The Theory of Everything" was shot in ProRes on the Alexa. Sure, ARRIRAW is even better, things like color temp and color matrices are not baked in, there's no compression, etc. So ARRI offers you both options. I don't think they see much of a reason to offer something slightly in between. I've compared and color-corrected ProRes 4444 versus ARRIRAW on a big screen and the differences are minimal, I'd only say that ARRIRAW felt slightly less "electronic", more film-ish, because there's no electronic sharpening baked in. But it was a subtle feeling and it goes away as soon as you start adding the standard amount of sharpening to the footage. But I have been using ARRIRAW for greenscreen lately because there can be artifacts that pop up in the debayering internally to RGB that can affect the edges for keying, but that can even happen with ARRIRAW footage depending on the software used for debayering. I had a greenscreen shot where the VFX people kept complaining about a drop shadow black edge on the red channel subject and I had to remind them that with ARRIRAW, there is no red channel until after it is converted, so the problem had to be downchain, not in the camera or recording. Which turned out to be true, it went away once they tried a different debayering software. 1 Link to comment Share on other sites More sharing options...
Premium Member David Mullen ASC Posted October 30 Premium Member Share Posted October 30 2 hours ago, Sebastian Bock said: Also, the Alexa has 10 bit ProRes recording, so it is not limited to 16-235 as you mentioned but to 64-1000, so it's not a big deal to have a couple values less than full range would offer... ARRI ProRes 4444 Log-C is 12-bit 1 Link to comment Share on other sites More sharing options...
Nicolas POISSON Posted October 30 Share Posted October 30 (edited) Full range has been adopted on many DSLR for 8-bit log, where the difference between 256 vs. 220 quantization steps (16-235) may be more significant, especially for a log signal that is to be heavily processed. The same devices may still output in legal range for 8-bit 709 built-in profiles. As soon as there are enough quantization steps (say 10bit when you target delivery in 8-bit), the loss using legal instead of full range is really small. However the legal vs. data range question has become a real headache. HDMI being common to both computer and video world has not helped. For example (I hope I do not mistake): - my Fuji mirrorless always records and outputs video in full range, whether being configured in log or 709. - the Sony A7sIII outputs "extended" video range over HDMI when in 709 : 16-255 or 64-1023. Yes: neither legal nor full. I own an old Canon camcorder that uses the same extended range. When configured in Log, I think the A7s3 outputs in full range (not sure). - my Atomos NinjaV expects LUTs to output in the legal range. However I think most LUTs provided on manufacturers website output in full range. This is what you need when the LUT is used in an editing software like DaVinci Resolve. - BMD pocket cinema camera 6K outputs log in legal range. The Gen5 color science uses a log curve that is so flat, that the BMPCC6K hardly uses more than half the available code values. The 10-bit log could be coded in 9 bit. The culprit is not the use of legal range, but the choice made by BMD to define a log curve that can handle 20 stops of DR. - and the exact number of code values used depends on the ISO setting. The same is true for an Alexa, or any camera that sets its ISO shifting the log curve and baking in it. Add to this that manufacturers are not always very explicit in their specs, and you end up testing every single piece of hardware you use to check their range. Trust me, this is really no fun. Although this is not the world I am working in, I can easily understand that a higher grade camera manufacturer prefers to stick with the standards. Improving marginally the number of code values is really not worth it considering the mess it brings. Edited October 30 by Nicolas POISSON 1 Link to comment Share on other sites More sharing options...
Wenqi Wei Posted October 30 Author Share Posted October 30 6 hours ago, Sebastian Bock said: Hi, Wenqi Wei! Arri is building a professional video camera, so they are using the video / SMPTE standards to be compatible with broadcast equipment all over the world. In the video world you have historically "lower than black" and "whiter than white (109%)" values. These is a legacy from the CRT TV era. Over decades, Manufacturers of broadcast and video equipment tried to stay backwards compatible with older standards so they respected the SMPTE guidelines for video levels. Full Range video is for computer monitors and not a standard in broadcast / video universe. Also, the Alexa has 10 bit ProRes recording, so it is not limited to 16-235 as you mentioned but to 64-1000, so it's not a big deal to have a couple values less than full range would offer... If you playback your Alexa footage on a computer monitor, you should have it transformed to full range somewhere in the chain so your blacks are not lifted. If you play back your Alexa footage on a Rec709 broadcast TV, you shouldn't do that because then you would have crushed blacks and blown out highlights. But you are right: all this has nothing to do with log. Some of my above statements might not be 100% technically correct, but they should give you an idea of the principle. Cheers, Sebastian Hi Sebastian, thank you for your mini-essay, Will definitley read it a couple of times and check it! Link to comment Share on other sites More sharing options...
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