Sensitivity bug? Underexposed footage

[Dave Sanders]

I recently worked on a shoot with the Red One (build 21) and toward the end of the day when we were shooting a scene it suddenly seemed as if the camera was not as light sensitive as it should be. The DP was metering rating the camera at 200 ASA and while exposure should have been a 2.8, it looked about 2 stops underexposed on the waveform even at a 2. The scene looked pretty brightly lit to the eye so I don't think it was a malfunction with the lights.

Shutter, sensitivity, and look settings were the same as they had been all day and there were no filters (1/60, 320, default). Has anyone else had an issue like this?

I tried searching this forum, but as you can imagine it was difficult to search for this particular issue with so many related threads. Thanks for any help.

[Tim Sutherland]

Did someone adjust the parameters in the video settings, such as gain or contrast? Or did you switch from Redspace to Raw view? They can look pretty dramatically different.

If your shutter and lens stop/filter combination were correct, the info should be there and you should be able to see it in post by resetting the metadata.

Tim

[Dave Sanders]

Hi Tim,

Thanks for your reply. It wouldn't be the gain or contrast. I checked that and even reset the look settings to default just to be sure. We were viewing on an HD monitor in rec 709.
I haven't been involved with post, I'll recommend they try resetting the metadata.

[Jannard]

I recently worked on a shoot with the Red One (build 21) and toward the end of the day when we were shooting a scene it suddenly seemed as if the camera was not as light sensitive as it should be. The DP was metering rating the camera at 200 ASA and while exposure should have been a 2.8, it looked about 2 stops underexposed on the waveform even at a 2. The scene looked pretty brightly lit to the eye so I don't think it was a malfunction with the lights.

Shutter, sensitivity, and look settings were the same as they had been all day and there were no filters (1/60, 320, default). Has anyone else had an issue like this?

I tried searching this forum, but as you can imagine it was difficult to search for this particular issue with so many related threads. Thanks for any help.

It sounds to me like the most telling comment is "toward the end of the day when we were shooting a scene it suddenly seemed as if the camera was not as light sensitive as it should be". It sounds like it was fine early in the day and then changed? If this is the case, it really does point to someone monkeying with camera settings... what does the footage look like at full res in REDCINE-X?

Jim

[Dave Sanders]

Hi Jim,

I heard from the DP that in post they found the footage was unusably underexposed. But like I said the look settings were at default. I cleared them just to be sure.

[Jannard]

Hi Jim,

I heard from the DP that in post they found the footage was unusably underexposed. But like I said the look settings were at default. I cleared them just to be sure.

Was all of the footage unusable or just the late afternoon stuff?

It is always a good idea to check footage in REDCINE-X right after making your backups (on set).

Jim

[Dan Hudgins]

Since the camera shoots "RAW" in as much as the data is recorded without any change no mater what buttons you push other than the shutter and fps (and "open gate"), always rember the cameraman's Mnemonic,

1) Focus

2) Aperture

3) Shutter

4) Tachometer

or F.A.S.T.,

http://www.saccard.com/edited-pages/FOCUSING.HTM

Since nothing other than the Shutter angle or wrong fps (Tachometer) reading can change the exposure, all other camera settings are not relevant if you use a good light meter in the right way and set the lens iris and ND or other optical filter right. ("open gate" is part of the shutter angle control)

The is no excuse for bad exposure, you always check your lighting ratios with your light meter. The old kind of meter that does not have a battery are better since the meter will not read unless you have enough light to shoot with.

Also you know how many kw of light you have plugged in, so you just need to addup the kw and see if your exposure is at the same stop it was last time you used that stop.

Before you push the run button say F.A.S.T. in your mind and look to see that the lens is at 6 feet, f/5.6, your camera at 144 degrees & 24.000fps.

And always before you do that walk around with your light meter with the incident dome pointed AT the camera and see if the needle points to f/5.6 with the EI 320 for M or EI 800 for M-X slide in place.

Bad footage is NEVER the camera's fault, well unless its broken in some way, nor is there any reason to have it turn out bad since its not hard to make it turn out well if you can tell the director you need more kw of light. To many DP in fear of not getting another job I think are afraid to tell the director and producer in pre production what it will actualy take to get good results, and hope that some miracle of digital image generation will compensate for not doing things right in the first place.

To protect yourself from people goofing with the camera, always use your light meter and the FAST checks before you push the run button. You should be able to trust that the "RAW" recording will be gradable if your light meter was in range even if the camera monitor display is off. If you work from the camera displays you CAN mess up the sensor and "RAW"' exposure since the monitor changes but the sensor does not, better to ignore the monitor and histograms that go though various curves, and stick with the fixed exposure point that is best for the sensor and "RAW" recording. The solar cell in the light meter is fixed like the sensor, all you need to do is match the iris to the meter, and keep the other settings for shutter and fps constant. And stand near the camera and look at your subject and its lighting ratios, develop an understanding of how the "RAW" data looks with various ratios of rim light to fill light.

The EI/ISO and K value settings on the camera do not change anything recorded, and I think just cause confusion. If you don't use them and expose the sensor like you would Daylight film of the same fixed ISO speed (320 for M or 800 for M-X) you will get cleaner signals and overall better results, and yes that means using 80 series and other optical filters. If you tried exposing film 3 stops down and 2000K off I think it would look messed up as well...