Daniel Rheaume December 21, 2021 Share December 21, 2021 Hello! I was hoping someone could help shed some light on using the Arri Isabela test chart for me - I've downloaded and have been using the logC Arri Isabela test shot to have a consistent reference when I'm trying to build my looks, specifically in creating contrast curves. The assumption I previously had taken was that this shot was "ready to go" as far as exposure being in the "correct" place and all that jazz. Anyhow, listening to the Masters of Color podcast, I think it was Ian Vertovec who was mentioning how he keeps a neutral 18%gray on his show LUTS. So that got me paying attention to the little gray card in the bottom right of the Isabela test chart - and it looks as though the card is a bit underexposed? In log, it sits at about 35%. In Arri's R.709 Isabela test chart it sits around 27%. Bringing the logC version to 42% on waveform took a significant boost in the offset (11 points in R,G, and B). So my question is - was this chart intended to be have exposure adjusted and color chips brought in line with the vectorscope targets, or did Arri intend for the gray card to sit at the luminance level that it does because skin tones are properly exposed here? Sorry for the muddled question! Still really trying to get the hang of the best way to use a test chart consistently! Thanks in advance for your help! -Daniel Link to comment Share on other sites
Daniel Rheaume December 23, 2021 Author Share December 23, 2021 Seems silly to reply to my own comment, but in case anyone else has been wondering the same things I am, I just came across this comment on a NoFilmSchool post about using gray cards - "This honestly changes based on IRE scales of the camera. If your shooting C-log the middle gray may reside somewhere between 33-35 IRE for middle grey and it can be perfectly exposed. Same with SONY s-log 2; it is meant to be exposed at about 32 IRE for middle grey according to manufacturers , but tends to look better at 55-65 IRE on an 18% grey card." So it sounds like the Isabella chart is probably sitting exactly where the Arri team intended it to sit, as is. Link to comment Share on other sites
Bruno Mansi December 24, 2021 Share December 24, 2021 Not sure about the chart but if you want to see it being used in look development I would recommend you delve into some of Lowepost's courses. The one I'm thinking specifically is LOOK DEVELOPMENT & WORKFLOW IN DAVINCI RESOLVE by Jason Bowdach Take a look at lesson 7 Link to comment Share on other sites
Keidrych wasley December 25, 2021 Share December 25, 2021 From memory I think you are right and well spotted, the Isabella 18% grey card is underexposed. Arri have stated that logC 18% grey should hit 398, or 400 on a 0-1023 10 bit scale and Isabella grey card does not hit this value. Personally I would say that for look development you ideally want to use many more shots across all sorts of lighting environments. One single shot tells you very little about how a show LUT travels. Link to comment Share on other sites
Daniel Rheaume December 27, 2021 Author Share December 27, 2021 On 12/24/2021 at 5:26 AM, Bruno Mansi said: Not sure about the chart but if you want to see it being used in look development I would recommend you delve into some of Lowepost's courses. The one I'm thinking specifically is LOOK DEVELOPMENT & WORKFLOW IN DAVINCI RESOLVE by Jason Bowdach Take a look at lesson 7 Bruno! Yes, I've been through that course and loved it! Of course, there is so much to learn from it that it is indeed probably time for me to revisit it and watch that lesson again in particular! On 12/25/2021 at 3:59 PM, Keidrych wasley said: From memory I think you are right and well spotted, the Isabella 18% grey card is underexposed. Arri have stated that logC 18% grey should hit 398, or 400 on a 0-1023 10 bit scale and Isabella grey card does not hit this value. Personally I would say that for look development you ideally want to use many more shots across all sorts of lighting environments. One single shot tells you very little about how a show LUT travels. Keidrych, Thanks for your reply! Very much agreed. I do have a whole lot of random shots that I have been using to confirm I'm liking where a look is going. The Isabella chart has simply been my "gold standard" - since it's always the same, I can compare it to other looks I've created to see how it's different or the same in that particular chart. But I usually use it to get things looking ballpark, and then refine on a broad range of material. Thanks for your replies and input! Link to comment Share on other sites
