Ryan E. Walters, Cinematographer

Cinematic Excellence at 24 Frames a Second

Some Like It RAW. Part 03: Overexposure


Welcome to Part 03 of Some Like It RAW, where I am comparing the Arri AlexaBlackmagic Cinema Camera, and the Red Epic. My goal for these tests is to explore how each of these cameras handle real world shooting environments. Part 01 explored how these cameras handle IR pollution. In Part 02, I tested underexposure. And here in Part 03, I'm exploring the world of overexposure and diffusion filtration. Continue on to watch the 10 minute video, read my summary, and get the downloadable RAW frames from each camera.


I'd again like to thank the following people who helped to make this test possible:

Picture This Productions
(Provided the Blackmagic Cinema Camera)
Shawn Nelson
(Provided his Epic)
Patrick Eggert
(Provided his Alexa)
Isaac Marchionna
(Assisted for the shoot)
Laurie Slater
(Was our Talent for the day)
180 Films
(Provided the Cooke 20-100mm Zoom)
Letus
(Provided the cage for the Blackmagic camera)
Schneider Optics
(Provided the IR Tuner Kit)

As I have stated in the previous two tests, my goal in this series is to stress and break these cameras to see how they perform in their extremes. It is not to prove that they can create beautiful images- that has been done. I am also not interested in furthering the religion of any one of these cameras. So if you are looking for material to support your beliefs, or camera purchase, then this test will disappoint you. But if you are interested in seeing how these cameras perform so that you can learn where and how they break in order to push your own creativity, then continue on.

Here is the overhead diagram of how I lit this scene. For the close up I added a frame of 4x4 full grid and left the light in the same position.

Below the 10 minute video you will find details of how I determined the overexposure values, what I think the dynamic range of the cameras is, exposure recommendations, a summary of my observations, and a link to the downloadable RAW frames from each camera.



How I Determined Overexposure Values:
I ran two tests to determine the overexposure values for these cameras. For the first test, I took the Sekonic Profile Target II exposures and loaded them into the Lite version of Resolve. Once there, I pulled up the waveform and looked for the first chip that had reached the clip point. (The point at which the line completely flattens out). This value gave me the maximum overexposure value, or the clip point. Then I counted down a couple of chips to a position where I felt the waveform had enough detail in it that I could record some discernible highlight detail. This is the value that I used for my safe, or conservative readings.
Waveform of Sekonic Chip Chart
Close Up of Waveform of Sekonic Chip Chart
For the second test, I loaded the files into Photoshop, and I selected each patch individually to acquire its Median value. As soon as this number started to decrease in value, I knew I had found the point at which I had found the clip point. These values lined up with the waveform results- which isn't surprising to me, as it is much easier to determine an absolute clip point in digital than it is to determine an underexposure value.
Selected chip of a +8 EV exposed Sekonic chart in Photoshop
Results of Selection
Why didn't you use a DSC Xlya Chart?
Simple - I don't own one, and it is outside the budget I am going to spend on a testing chart. I recognize that the Xyla is THE standard for testing dynamic range- no arguments here. But for practical purposes, I have found the $130 Sekonic Profile Target II chart to suit my needs and applications when it comes to creating camera profiles for my meter. If you are feeling generous and want to donate the Xyla-21 to me, I will gladly use it in future testing :)


Why do you have a safe or conservative value for overexposure?
Although the clip point is an absolute value that it easy to measure, I am not a fan of clipping at the camera level in digital cinema. By being more conservative in my overexposure values, I am allowing for a touch more headroom for highlight roll off. When it comes time to grade the footage, I have found that this small amount of headroom allows for a smoother transition when it is pushed in the grade. If it is all about the numbers for you, then you can ignore my conservative numbers, as they are just my personal preference :)

Why didn't you use HDR-x on the Epic?
HDR-x is a great way to extend the dynamic range of the camera. And although it will allow me to record more information in the highlight, I don't like the way it renders motion. It is all about personal preference. If you like HDR-x and use it in your shooting, then you can extend the the overexposure values I have listed by your preferred HDR-x settings.

What about the Red Dragon Sensor and the Alexa XT?
I'm interested in testing cameras I can actually use and shoot with today, not years from now. When Red finally releases their new sensor and it is available to shoot on by us mere mortals, I'm sure it will be great. (I am looking forward to its extended dynamic range). But in the meantime, I need to explore and use tools that are available to me now. The same goes for the Alexa XT. Here in my market, the Alexa is in high demand and is very rarely seen sitting around the rental shop. That makes me wonder how quickly they will be upgraded.

Blackmagic continues to be slow in shipping their cameras and while they are still not widely available to the public (as of this writing), I can go to my local rental shop and use it today. (Which is what I will have to do until my MFT version finally arrives...).

Observations & Recommendations:
- Smaller screens make it harder to see detail in the highlights, while bigger screens allow for the opportunity to see detail. Nuances in-between the cameras get lost the smaller the viewing screen. I had a harder time telling the cameras apart on my iPhone than I did on my 50" Plasma.

- Combining overexposure and diffusion filtration is a great way to create a glow, or dreamy look in camera. (If you want to see more filter tests, check out this Filter Test I did).

- Diffusion can help to smooth the transition to overexposure. It does not extend the dynamic range of the camera, but the blooming of the highlights does make the roll off more graceful.

- All of these cameras are more than capable of creating beautiful imagery. If you are consistently getting bad results from any of them, it is not the camera that is causing the problem...

Alexa:
- Total overexposure = 7 2/3
- Conservative overexposure = 7 1/3
- The extended amount of range in overexposure allows the Alexa to have the most graceful roll off of the three cameras. This is why it has been one of my preferred cameras to shoot with to date.
- Older lenses look great on it, as the imperfections in the lens add a more organic feel to the imagery without degrading it too much.
- This camera doesn't need diffusion filtration, as the images do not feel overly sharp. The choice to use diffusion will be more about making the talent look good than it will be about removing an artifact from the camera.

- Dynamic Range (DR) at EI 800 As Profiled In Log Using the Sekonic Profile Target II [8-Bit Photoshop values]
  • Overexposure (Total) = 7 2/3 [243]
  • Overexposure (Safe) = 7 1/3 [235]
  • At Exposure = 0 [106]
  • Underexposure (Safe) = -5 5/6 [31]
  • Underexposure (Total) = - 8 5/6 [22]
  • Total Measurable DR = 16 1/3
  • Usable DR = 13 1/6
- Exposure Recommendations Based on DR: (YMMV)
I have had the best results when exposing the camera at EI 800 by keeping all important highlight information within 7 stops, and all important underexposure values within 6 stops. Any detail that is recorded beyond these levels is a bonus. As the EI decreases in this camera, the image gets cleaner, and there is less headroom in the highlights. As the EI increases in this camera, the image gets noisier and there is more headroom in the highlights.


Blackmagic Cinema Camera:
- Total overexposure = 5 1/6
- Conservative overexposure = 4 5/6
- It transitions quickly into overexposure, and the overexposure tends toward yellow. So carefully choose what you allow to clip.
- Diffusion is this camera's friend. The lack of an OLPF in this camera causes it to have overly sharp images which is not flattering- especially on a close up. By using diffusion on the camera you can make the image more forgiving on the talent.
- Stay away from Rec 709 for best results, and make sure that the images are handled correctly in post. I shot this test in Film Mode but when the files come into Resolve they show up as Rec709. The Rec709 images looks WAY overexposed. (And made my heart skip a beat, before I realized what was going on). If the files are processed without being changed to BMD Film first, you will NOT be able to get the best imagery out of the camera.

- Dynamic Range (DR) at EI 800 As Profiled In Log Using the Sekonic Profile Target II [8-Bit Photoshop values]
  • Overexposure (Total) = 5 1/6 [251]
  • Overexposure (Safe) = 4 5/6 [245]
  • At Exposure = 0 [96]
  • Underexposure (Safe) = -5 [15]
  • Underexposure (Total) = - 7 1/6 [9]
  • Total Measurable DR = 12 1/3
  • Usable DR = 9 5/6
- Exposure Recommendations Based on DR: (YMMV)
I have not worked with this camera long enough to have any definitive recommendations. Based off of my test results and what I have experienced so far, I recommend that all important highlight information be kept within 5 stops, and all important shadow information be kept within 5 stops. Any detail that is recorded beyond these levels is a bonus. (I have a hunch that there will be some added information in the shadows that will add subtly to the picture). Practically speaking, this means that you will have to expose for your highlights, and then add lighting to compensate for the underexposure areas of the image if needed.

Red Epic: (With MX Sensor without using HDR-x)
- Total overexposure = 5 1/3
- Conservative overexposure = 4 2/3
- It transitions quickly into overexposure, and the overexposure tends toward magenta. So carefully choose what you allow to clip.
- Older lenses look great on it, as the imperfections in the lens add a more organic feel to the imagery without degrading it too much.
- This camera does not require diffusion, but it is helpful to use due to the high resolution that this camera shoots at. If you want to be more forgiving to your talent, then I'd add a touch of diffusion :)

- Dynamic Range (DR) at EI 800 As Profiled In Log Using the Sekonic Profile Target II [8-Bit Photoshop values]
  • Overexposure (Total) = 5 1/3 [237]
  • Overexposure (Safe) = 4 2/3 [228]
  • At Exposure = 0 [100]
  • Underexposure (Safe) = -5 1/6 [16]
  • Underexposure (Total) = - 8 1/3 [11]
  • Total Measurable DR = 13 2/3
  • Usable DR = 9 5/6
- Exposure Recommendations Based on DR: (YMMV)
I have had the best results when exposing the camera at EI 800 by keeping all important highlight information within 5 stops, and all important underexposure values within 5 stops. Any detail that is recorded beyond these levels is a bonus. I have often found that there is extra detail beyond the 5 stops of underexposure, which can add additional subtlety and texture to the image. But if I am counting on this added range, or if I need to pull out information in the shadows I find that I am disappointed with the results. (It gets too noisy for my tastes). I have also found that if I protect my highlights with the Epic, I can get a nice roll off into overexposure. This is why I am more conservative with the overexposure values of this camera. As the EI decreases in this camera, the image gets cleaner, and there is less headroom in the highlights. As the EI increases in this camera, the image gets noisier and there is more headroom in the highlights.

Downloadable RAW Frames (87MB): SLIR-Overexposure.zip

What do you think? Do these results surprise you? Will you be using diffusion filtration with the Blackmagic? If so, what will you use? Do you have any exposure recommendations that you have found helpful when shooting with any of these cameras?

Until Next Time - Get Out There And Shoot!
Ryan E. Walters, Cinematographer

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