LogC is a storage medium not meant to be viewed directly without a interpretive LUT or color correction placed on top. I call LogC "DBX for video".
On Aug 19, 2016, at 12:41 AM, Tom McD ltr54@sbcglobal.net [Avid-L2] <Avid-L2@yahoogroups.com> wrote:John,For feature work yes shooting logCmakes sense. For a lesser budget show with compressed post time that's a tougher decision. I've seen top DP's shoot both ways with equal success. People monitor and judge exposure by how the LogC signal looks. That by itself should tell you how uninformed people are of and how the LogC signal displays information.LogC is a storage medium not meant to be viewed directly without a interpretive LUT or color correction placed on top. I call LogC "DBX for video".
Tom McDonnell818-675-1501Sent from my iPhoneJohn,LogC today is the fanboy rah rah of "must get every useless stop of unneeded range." Honestly it's made shooting HD or 2k or 4K almost as easy as shooting film neg.Tom McDonnell818-675-1501Sent from my iPhoneWell I am a colorist although my realm is not high end work for the most part. Your gallon of milk analogy is not quite accurate but a good starting point. In my world it's more like the gallon of milk is condensed to fit into a quart container in a manner that isn't always turned back into the original gallon but one with some curds in it. When I see that I have 700 millivolts of range and it's now condensed into 500 to 550 millivolts of range there is clearly some detail being lost. It's simply the fact that there are fewer steps with less range hence less detail. As I said clearly the general consciences is it's more valuable to not clip or lose shadow detail. In my perfect world it would be more effective to expose for the delivery color space. In other words I shoot into the quart container, I color correct in the quart container and I serve in a quart container. Then I'd be getting the full 700 millivolts of detail that Rec 709 affords. At some point it's going to be in a quart container and having done it that way for decades I have a handle on things. Now I get logC from the world of marginal cameras and the LUTs in a generic form or those I get from the field aren't very usable. Like I said the Arri LogC, Panasonic V-Log, Sony S3 Gamut and other Sony incarnations have been pretty reliable but the cannons and God knows what others I will get handed have no consistency and whether that's because of improper exposure or just bad math in the LUTs I don't know. I don't expect the LUT to be the final say but a decent starting point and with the latter cameras I've mentioned I always seem to be starting from scratch without a clear indication of what was intended in the field.
What I do know it using LUTs in Avid in the 4K world is a big performance hog but assume they are more tolerable in the HD realm. Most of my HD LUTed work I pre-process in Resolve so I haven't w! orked with the Avid internal LUTs in HD much.
My experience and opinions are based in the real world I live in where I don't have enough time as it is and adding LUTs has not streamlined my end of the food chain hence I am less of a fan than those with bigger budgets and more time to spend fine tuning. If I want to be theoretical then over all LUTs are great for not clipping things and having more latitude to tweak and correct for errors later but I'll take footage from the Camera people I've worked with for decades shooting without LUTs who know how to expose over LUTs most of the time.
From earlier in this thread:
Pat wrote:
"I'd go even further than Tod and say shooting Log and not adjusting exposure accordingly is worse than straight Rec709.
Log is about trading bit depth in some areas of exposure to gain latitude. Don't need or use the latitude and you are just losing."
This comment speaks to what I'm talking about, especially, "Don't need or use the latitude and you are just losing." So while I may be wrong if I'm trying to make the most pristine possible image given enough time to tweak. I don't think I'm wrong in the arena I work in. When I start getting into Resolve and other higher end color systems I may feel differently but with the turn around time of round tripping I have yet to work on those systems for the color end of things.
---In Avid-L2@yahoogroups.com, <cutandcover@...> wrote :It's almost comical how you are arguing in essence the exact opposite view of what these things are supposed to help you with. Or maybe not help you, but help someone else (like a colorist).Log footage is not losing low/highlight info. It's retaining it! It's great at doing that if properly exposed. Think about it this way:- your shot is a gallon of water- your camera can only hold a quart- linear says pick a quart of the shot and put it in the camera, that's all you can take- log says squish the gallon in, it will fit into the quart container if you do it my way- in post, log says AAAAAAAHHHHH all this room is great I can stretch my quart back out to gallon size!Compare the linear quart to the log gallon and see how much more you actually wound up with - the log is almost always more detailed and a better representation of the available light of the original shot.LUT is a starting point ALWAYS. It is never really designed to be the end. So if you want a quick reconfiguration of the log footage into something reasonably linear, use a LUT - it's like a one-light.Almost any colorist you or I know will either use a LUT and work from there, or abandon the LUT and work from scratch.On Thu, Aug 18, 2016 at 4:44 PM, bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:I am of the opinion that properly shot Rec 709 that is intended to be delivered in Rec 709 is technically superior to shooting LogC. While this may be technically true it is not common practice these days as everyone has opted to shoot LogC under the assumption it's going to give me more to work with in post. When you say it trades big depth in some areas of exposure I would think it trades bit resolution more so than bit depth. In my basic understanding the top and bottom of exposure are rolled off so they have fewer steps or millivolts of data range at the top and bottom. To me that would mean that a gradient would have more banding in the high and low exposure areas. This is how I view it but please correct me if this is wrong.
From the most basic stand point when I get Arri LogC the un lutted range on my scope is typically 100 to 550/600 millivolts. Right away the exposure modification of the sensor data has left a 100 or more millivolts of potential image contrast/detail at the top and bottom lost. I realize the idea behind the LogC is to avoid clipping and try and take the data from the more optimal range of the sensor. So once you've compressed the image contrast using the LogC math when you stretch it back out you are adding noise to some degree and I would assume the quantizing steps are stretched out so some subtlety of detail is being lost. I have just assumed the lack of clipping etc... outways these inherent issue. For me LUTs are pain than gain but I realize I seem to be in the minority in this area. Every time I have to color correct just to get to a square one of the basic look it takes more time and time is not something I get much of. In my experience the whole Log workflows get confused in many ways and as you say when things are not properly exposed in Log things are more work to correct. Arri LogC, Sony S3 Gamut etc..., and Panasonic Vlog seem to play pret! ty nice but I've battled footage from Cannon c300 log that had no consistency so I could not apply a generic LUT to all the footage so it just became easier to drop Luts and color correct each shot. That is where I have the most issue with Luts in my world.
---In Avid-L2@yahoogroups.com, <pat@...> wrote :I'd go even further than Tod and say shooting Log and not adjusting exposure accordingly is worse than straight Rec709.
Log is about trading bit depth in some areas of expisure to gain latitude. Don't need or use the latitude and you are just losing.
Pat from his mobile.
Posted by: Jim Feeley <jfeeley@gmail.com>
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