July 7, 2016 at 11:15AM

0

Correctly Exposing

Hello nofilmschool community! I have what should be a relatively simple question. What is the best way to go about correctly exposing an image? I've seen the article on nfs, and I understand the different methods (and their creative application) used to change exposure i.e. iso, shutter speed, aperture. But it didn't really explain how to adjust the settings so the image is correctly exposed.

I've been told by a previous mentor told that for narrative or doco work, highlights should be at 70% (zebras) on a talent's face, but what about landscapes or establishing shots? I've looked at grey cards and spot metering, but many forums have discussed it's not preferable.

Thoughts? Thanks :)

16 Comments

It all depends on the recording format and image profile you are shooting with.

For example with some LOG formats you want a 90 percent reflectance white target ( essentially a plain matte white object ) to be exposed between 60-70 percent IRE, so you would set your Zebra indicator to these levels.

If you are using a standard gamma profile like "Standard" or "Natural" on a Panasonic mirrorless camera, you want that 90 percent reflectance target to be 100 IRE. This is how I shoot and expose much of the time, where I am making sure that I don't over expose the hilights of my subject, because once they are over-exposed the detail is gone forever.

Shooting in RAW format, your exposure can be off by 1-2 stops ( either over or under exposed ) and be able to correct for this when you process your footage. This is one of the reasons why it's so nice to work in RAW if your camera offers this feature.

The other big feature of RAW footage is that you can set the color-balance in post. With non-RAW formats you have to set your color-balance when you shoot because the color balance will be "baked in" when you shoot, with not much room for correction in post. ( small changes are possible, but big changes are not )

July 7, 2016 at 12:53PM

2
Reply
Guy McLoughlin
Video Producer
32223

Thanks for responding Guy! So I shoot on an a7s in slog 2 - if i want correct exposure then i could use a white balance card with zebras peaking at about 70% IRE? Thanks

Matthew Roper

July 7, 2016 at 10:32PM

There's nothing like using a Waveform monitor to understand where everything sits in a video image. If you have a camera that doesn't have one, you can easily acquire external monitors that do have them. Waveform monitors help you understand not only where your whites and blacks are, but more importantly, whether your scene's overall contrast is too large or not, and how the lights you are using are helping or hurting your cause.

July 7, 2016 at 1:08PM

3
Reply

What Guy says about correcting RAW is true, but it's only half of the truth. The other half is that some people like to be creative in the coloring/grading process. Every stop of exposure you need to use for basic exposure correction is a stop of latitude you lose for creative grading. If you can really nail exposure (which is more complicated than just using a WB card to read 60-70 IRE), then you have room to really make the images look great.

Waveform monitors, histograms, and vector scopes all have their role to play in bringing the best possible images into your edit suite. If you use RAW as a crutch, you will never run with the champions.

July 8, 2016 at 7:51AM

0
Reply

Yes, correct exposure is always best, but RAW is very forgiving if you screw-up, where you could be S-O-L if you mess up when shooting with a non-RAW format.

Guy McLoughlin

July 8, 2016 at 9:07AM

>>> So I shoot on an a7s in slog 2 - if i want correct exposure then i could use a white balance card with zebras peaking at about 70% IRE?

Sony recommends exposing a bright matte white target at 59 percent IRE for S-Log2, so I would set your zebra to 59 percent if possible or 60 percent.

July 8, 2016 at 9:03AM

6
Reply
Guy McLoughlin
Video Producer
32223

You have three primary options for exposing an image:

1) Visual: Seems the most obvious. But the more you become familiar with an imaging system, it is possible to train your eye to “see” a correct exposure. Downside? A large room for error.

2) Signal Based Metering (Wave Forms, Histograms, Zebras, and False Color): These refer to metering tools that measure the sensor data and interprets them to luminance levels. This is “technically” accurate but provides little information as regards what' something really looks like.

3) Light Meter: This is metering the measures the actual light present in a environment then provides a setting, typically aperture, that once set on the camera should render a properly exposed image.

Of the three, exposing with a light meter is my favorite. Some may say that light meters are relics of the past (analogue/film based imaging). I don't personally agree with that. Why?

1) Light, which is what truly determines exposure, is analogue no matter what's capturing it - film or digital.
2) Using a Light Meter is not device dependent ... its a skillset. Like any skillset, it takes time to understand, but once you've mastered the use of a light meter, you can use it with any camera.
2) It's fast. You simply meter the light you want to expose to, set the proper settings, and shoot away!
3) It predictable and repeatable. At some point, your concern over exposure will move beyond just wanting to "expose" a frame, you'll move on to wanting to know contrast ratios, Back-light to fill ratio, etc. Only a light meter will let you know that!
4) It’s promotes creativeness. Unlike signal-based tools, a light meter trains you to use your eye. Unlike a purely visual approach, a light meter will get you 90% percent of the way (technical), then let your eye create the remaining 10% (creative). Percentages purely illustrative, but you get the point ;)
5) It's compact. Most meters are small. You can even get a metering app on you phone that is quite accurate. No need to drag around a dedicated Waveform monitor.

You have two options for Light Meters. Incident and Reflected Meters. The most commonly used type is an Incident Light Meter. The meter I primarily use is the Spectra-CINE lV-A. It's an investment (if you want to save a lil', you can get the Cine Meter App which is quite accurate, it's my backup), but one that will last you a career. How do you use it? Here’s a basic tutorial: http://www.premiumbeat.com/blog/how-to-use-light-meters-in-videos/.

Hope this helps!

https://acinematographersjournal.wordpress.com/2016/06/13/whats-in-my-ge...

July 8, 2016 at 9:32AM, Edited July 8, 9:56AM

0
Reply
avatar
John Dimalanta
Freelance Photographer/Cinematographer
448

>>>2) Using a Light Meter is not device dependent

But correct exposure may be device dependent.

For example when shooting with a standard gamma profile a 90 percent reflectance white target is normally rated at an exposure of 100 IRE, and an 18 percent reflectance "grey card" is rated at an exposure of 45 IRE.

Now if you want to shoot the same scene using Sony S-Log2, Sony says correct exposure for this profile is 59 IRE for the 90 percent reflectance target and 35 IRE for the 18 percent reflectance "grey card" target.

These are completely different exposures, but they are correct exposures for each unique shooting profile.

>>>3) It's fast. You simply meter the light you want to expose to, set the proper settings, and shoot away!

Only if you understand what the correct exposure is for the device/imaging profile that you are shooting with.

>>>3) It predictable and repeatable.

Again it will depend on you understanding what correct exposure is for the device/imaging profile you are shooting with, and how to correctly interpret the results of your light meter.

There is also the issue of incident vs reflectance light meters. Reflectance light meters take into account the reflectance of your subject and it's evironment, where an incidence light meter has no clue about the reflectance of the subject you are shooting.

While I like light meters and have owned about a dozen of them over the past 30 years ( I still own and use: Sekon L-308DC, Pentax Digital Spotmeter, Minolta Spotmeter F ) most of the time I'm using a combination of Zebra indicators and an IRE waveform display. These tools factor in my lenses, my filters, my lighting, the reflectance of my subject, and the shooting profile I am using. Where it would be harder to apply all of these factors to a light meter reading. ( not impossible, but it's definitely more work )

>>>4) It’s promotes creativeness.

Personally I feel that mastering all of the technology you use to shoot with makes you more creative because you won't have to spend time dealing with these things if you know them like the back of your hand, and you will know exactly how to create any kind of image you can imagine. It's equivalent to looking at a great magazine photo and instantly knowing what you would have to do to create the same look. This is why I recommend beginners to try and replicate a scene that they really like, so that they learn what is essential to creating that scene and perhaps how things are often much harder to create than you think they are. What first looks like simple lighting might not be that simple when you try and do the same thing yourself.

July 8, 2016 at 12:06PM, Edited July 8, 12:07PM

6
Reply
Guy McLoughlin
Video Producer
32223

Thank for your comments...all valid points.

I believe that you've emphasized the point that using a meter requires a depth of understanding - gray scale/zone system, reflectance, ratios, etc.

This level of understanding forms the foundation of imaging. While it may be a deeper subject for a beginner, taking the time to understand these basics will go a long way further in their growth.

John Dimalanta

July 8, 2016 at 12:19PM

Just wanted to clarify, as regards to...

1) "correct exposure may be device dependent." Sort of true. An object that is 50% reflective is 50% reflective no matter how your device chooses to place that on an IRE scale. Using a meter means that you will always place said reference where it needs to be in order for your sensor to properly translate that to the values it needs to according to the gamma being applied. That will work for any device!

Take a SLog2 image that is "properly exposed", Middle Grey at 32IRE (as recommended by Sony), set with a light meter. Then apply a rec709 LUT. What happens to middle grey? It moves up to 45IRE. What changed? Exposure? Gamma, yes. Exposure, no.

2) "Only if you understand what the correct exposure is for the device/imaging profile that you are shooting with." Again, it's fast in the sense that you set the reference to where it needs to be.

3) "incidence light meter has no clue about the reflectance of the subject you are shooting." Correct. And yet it doesn't need to, it just needs to make sure a known reference is correctly set, nature takes care of the rest...thank you Ansel Adams!

4) "mastering all of the technology you use to shoot with makes you more creative" True and couldn't agree more! Yet at some point you need to start somewhere, correct? Why not start with the primary way exposure has been set for years?

John Dimalanta

July 8, 2016 at 9:31PM

Well said!

July 8, 2016 at 6:44PM

0
Reply

Getting proper exposure every time is like getting a new camera. You'll be surprised how much better your footage looks and how much more you can do in post with it properly exposed. It sounds like you and I are in roughly the same place experience-wise. I recently got a field monitor with false color. Not only has it helped me nail exposure, it's training my eye. I'm starting to see the underlit and overexposed spots before I even power up the monitor.

I prefer false color because it shows me exactly where a problem is. Other people prefer waveform because they say it is more accurate. Get a monitor or external recorder/monitor that has one or both. Your camera may have waveform, but working off a 3 inch screen you'll miss problem areas. I got an Aputure VS-2 FineHD for $279. It's a little contrasty, but for focus and exposure it is great.

July 9, 2016 at 12:29PM

1
Reply
avatar
Robert Schmeltzer
Cinematographer
117

Alright - i've concluded that exposure is a more lengthy subject than originally thought. At this stage I'm looking at the blackmagic video assist as a field monitor/recorder. Seeing it doesn't have false colour - only zebras, should I be looking at light meters? The Lumu for iphone seems like a good budget option.

Matthew Roper

July 9, 2016 at 9:57PM, Edited July 9, 9:57PM

The Ninja Assassin (https://www.atomos.com/ninja-assassin/) is presently offered at a reduced price as there are newer models with more features. At that price, it's only $100 more than the Video Assist and has all the monitoring features you need that the Video Assist lacks. eBay may offer even less expensive options as people upgrade to Ninja Flame.

July 10, 2016 at 6:32AM

6
Reply

Hi Matthew. I wanted to mention a few more ideas:

-- ETTR can work well: https://en.wikipedia.org/wiki/Exposing_to_the_right

-- Normally expose for skin tones, right? But you might want to vary the rule depending on the image and circumstances. For instance, you might really want to see some detail out of that window over there, but that would mean underexposing the skin (and you don't have any other options like ND gels on the window or extra lighting on the person). Well, maybe you can bring up the skin acceptably in post.

-- For a controlled shoot, sure, pull out the zebras and look for 70% IRE on the highlights on the skin (or whatever seems to look good on your camera), or look at a waveform/histogram to see how much detail you're losing at high and low end and whether you should brighten/darken the image for safety's sake. But personally I reckon a good camera operator should learn to eyeball it. For many types of shooting, you don't have the time to look at a waveform, let alone pull out a light meter. If you're doing a documentary/wedding/news recording/whatever and the action is happening NOW, then you've just got to get the shot -- no focus aids, no exposure aids, just your eye (and maybe autofocus/autoexposure/auto white balance :)).

A good training device is practising with a black and white viewfinder, and looking for zone VI for Caucasian skin (https://en.wikipedia.org/wiki/Zone_System). Older camera guys will have had no choice but to learn this sort of method (zebras have been around for a while, but I think built-in waveform monitors are fairly new... even colour viewfinders are fairly new).

-- DSLRs usually come with an exposure meter needle in the viewfinder. I think it's a great tool for uncontrolled shoots or photos or times when you need to act fast. The key thing to bear in mind is that the metering is usually set to do a centre-weighted average of the scene, and can be biased to under or overexpose skin tones by the presence of a lot of dark or a lot of light elements in frame. So you have to compensate; and if you're shooting on the fly, without any other sort of exposure aid, how much you should compensate kind of comes with practice, especially for photos. Good photographers will look at what the exposure needle is telling them, factor in the brightness, and think to themselves, "OK, I need to go 1 stop higher", etc without needing to chimp the image.

-- People talk about "correct" exposure, but personally I believe there's subjectivity here. For instance: consider any sort of silhouette image -- maybe it looks good with no detail and just black shapes, or maybe a certain amount of detail looks good. It all depends.

Or consider any night time image. With DSLRs, you have the capacity to show that image brighter than it would look to the human eye. So, what is the correct exposure? Do you make it look comfortable and pleasing, or do you try to convey a sense of what it's actually like? I remember a John Brawley test shoot with one of the BM cameras. Someone in the comments section accused his image of being "underexposed". John replied, "I wouldn't call it underexposed. Dark, maybe, but not underexposed."

Even for normal daytime images, you can look at someone's skin tones and genuinely be in doubt and spend a while stressing over it. "Do I go 1/3 of a stop up? Do I go 1/3 down? Not quite sure."

In your avatar image, one side of the face is dark and one side is light. Is the light side underexposed? To my taste, yes. But if you bumped up the exposure, maybe you'd see too much detail on the darker side. -- I think it's subjective.

-- As for landscapes... Well, you do have a bit of flexibility. Does depend a lot on what mood you're trying to convey and what looks good to your eye. Or if you're trying to capture as much detail as possible, then, sure, use a waveform or whatever tools you have to get most of the pixels falling within a safe range, and then adjust to taste depending on how good/bad the highlights in the image look, and whether you're willing to sacrifice information at low or high end.

January 3, 2017 at 9:24PM, Edited January 3, 9:49PM

0
Reply
Adrian Tan
Videographer
867

Your Comment