View Full Version : BMPCC 3D LUT appear overexposed


Frank Grygier
March 21st, 2015, 08:39 AM
When I apply a LUT or use FilmConvert in Premiere CC the footage appears way over exposed. I get similar results when using Raw or Prores. Any thoughts.

Gary Huff
March 23rd, 2015, 07:42 AM
How are you exposing your image?

Chris Medico
March 23rd, 2015, 07:58 AM
It could be that you have exposed your image above the design.

I also would like to know what tools you are using to measure exposure and what values you are exposing to.

Frank Grygier
March 23rd, 2015, 11:42 AM
I generally use the histagram on the Pocket Cinema Camera and 100 zebras for the highlights.Is it critical to expose to the right for the best results wen using a LUT. Any thought on VisionColor ImpulZ? - 35mm Film Emulation LUTs (http://www.vision-color.com/impulz/)

Thanks

Chris Medico
March 23rd, 2015, 12:32 PM
Can you post some images that show where you are exposing things?

Do you have a grey card? That is an essential tool to shooting LOG or RAW.

Chris Medico
March 23rd, 2015, 12:56 PM
I just checked out some examples on their website and they are setting skin tones between 40% and 60%.

Where are your skin tones falling on your exposure?

Chris Medico
March 23rd, 2015, 01:01 PM
Here is what I measure.

Frank Grygier
March 24th, 2015, 01:23 PM
Thanks for your guidance. I will get a screen shot for you this evening.

Frank Grygier
March 24th, 2015, 01:24 PM
So skin tones are about middle grey?

Gary Huff
March 24th, 2015, 05:53 PM
So skin tones are about middle grey?

No, they should be around 60IRE.

Frank Grygier
March 24th, 2015, 09:11 PM
Got it.
Thanks for putting me on the right track.

Gary Huff
March 24th, 2015, 09:12 PM
Actually, I should clarify that 60IRE is for Rec.709. So once you de-log the footage, it should ideally be in that range.

Chris Medico
March 25th, 2015, 03:30 AM
The thing to do is to buy a grey card and do some exposure tests. That will allow you to know exactly what you should expose to for the best results with your LUT of choice.

As an example when I shoot S-LOG the design for that curve is for mid grey to be at 38IRE. If I stay close to that my LUT works well. LOG isn't RAW so that exposure won't work for you.

With a $20 grey card and a few hours playing around with your camera you'll be able to get it dialed in just right and have a great method for nailing your exposure on set. Remember to keep the card square to the lens. Don't tilt it up or down. Straight at the lens.

Frank Grygier
March 25th, 2015, 08:38 AM
I do have a grey card but have neglected to use it. I have been relying on zebras and histogram.I will do some testing and get back to you all with the results. I can see now that I am overexposing the footage.

Thanks to you all. It is great to have this forum.

Alex Humphrey
June 16th, 2017, 02:34 PM
I'm on a different camera currently, but I'm finding the same answer for 709 Log as well as raw cameras is an incident light meter. Middle grey 35-40 IRE seems to be the most common middle ground on most cameras, 709, Log, and raw.. so maybe try it out or meter a grey card to read around 35%-38%. My Lumu ($59 at amazon) light meter ball that plugs into my iPod touch and $29 Cine Meter II app work well, though a real light meter that doesn't have a iPod touch running an app would be better, but more expensive.

Ben Johnston
July 19th, 2017, 04:52 PM
Belated response here. I think it's important to point out that LUTs aren't 'intelligent' - they just shift things from one place to another, by a fixed amount.

If you want to use a LUT as a kind of one-click 'look', you'll probably need to make adjustments before the LUT, such as bringing the highlights down.