Exposing correctly [Archive]

Jamie Havill

12-19-2009, 07:28 AM

Hey guys,

I recorded my first ever Red footage recently (in prep for my short in February), and have got around to looking at it just now. We only recorded a few minutes and we were limited to 2K @ 2:1 as we only had a Sony 306x CF card with us.

We were given the Red Pro 18-85mm and the room was quite dark. After all my time spent on the forums and such I exposed as best I could given the light conditions. I left the camera at 320 ISO with the lens wide open at T2.9.

This is a frame grab from one of the clips. It's taken in Premiere Pro CS4 from the R3D and is accompnied by the histogram/RGB parade/vectorscope etc.

It was my understanding (from reading and watching a video with Tod explaining exposure) that when exposing for Red, it's best to keep the majority of the detail around the lower mid section of the histogram (darker than you would expose for video) to preserve highlights. This would give you more latitude in post and give a nice organic image when grading.

From what you can see, does this look correct? The image is straight off the mag, loaded into Premiere and a screenshot taken with no grading, no adjustments of any kind.

Your thoughts are appreciated.

Jamie.

http://i45.tinypic.com/qqof8i.png

XiaoSu Han

12-19-2009, 07:40 AM

Did you meter the light?

If not, you should!

Even if it's a digital camera, a light meter shouldn't be missed!

Jamie Havill

12-19-2009, 07:41 AM

XiaoSu Han

12-19-2009, 07:55 AM

Hey Jamie,

it looks correct, but you missunderstood the exposure advice a bit.

What you should do is expose as much as possible to the light side of the sensor (histogramm), because then you can pull down and get rich blacks and a low noise floor.

You should stop down though to avoid clipping highlights (check traffic lights/false colors). The advice is rather have a bit of a darker image than overexposed (GONE) highlights.

There's a very informative thread going on in Recon at the moment about exposure. Follow it!

Joel Kaye

12-19-2009, 07:55 AM

You've got an underexposed shot. Just needed a faster lens or more light. A colorist could get something usable out of it, but it's still underexposed.

Check this thread out. Grab a coffee first :-)

http://reduser.net/forum/showthread.php?t=38946

David Mullen ASC

12-19-2009, 08:31 AM

The thing to remember about protecting highlights is that it's OK to let small areas clip if they are unimportant -- for example, you would not bias an exposure to hold detail in the filament of a flashlight in a night scene where someone was going through a dark room with a flashlight.

So in your example, you have two types of highlights -- there are the highlights of the objects in the room including the face, and there's that really hot window in the background. What's out that small window is not important enough to cause you to underexpose everything else to achieve some sort of balance, so in this case, I'd ignore that hot spot and expose for everything else in the frame.

But all of this assumes you have enough light or a fast enough lens to make a choice in exposing the shot. It seems in this case, you were just setting the lens wide-open and hoping you had enough light.

On the other hand, it may be correctible without too much noise being introduced.

My suggestion is to light a test subject and a chart (something with black, white, and 18% grey) to the middle of the lens, like f/5.6, and then shoot some over and underexposure versions in one-stop increments and look at the waveforms and histograms to see how it plots out.

Jannard

12-19-2009, 08:43 AM

We didn't have a meter unfortunately. This was a get in, get it done, and then get the hell out kind of deal. I had absolutely no control over anything except trying my best to expose with what I was given.

Edit after David's post... agree.

Try some quick grading to see what you have. You might be surprised with this one. Open in REDAlert! (or REDCINE-X). Set Color Space to CameraRGB, Gamma to REDlog and you will see pretty quickly what's there as the shadows will be opened up quite a bit and all noise exposed. You can either pull down the blacks with a curve here or try a quick grade in REDspace or REC 709.

Exposure is a learning experience with RED. What you can do with what you have in post confirms (or not) your exposure/lighting decision. Lots of practice here will only be a good thing. Shoot... grade. Just make sure you do your footage justice by getting to know one of the apps well... or hand it over to someone that does.

Jim

Jamie Havill

12-19-2009, 08:45 AM

Thanks guys.

@ Joel - I'm checking out that thread now.

@ David - I genuinly thought I was exposing that shot OK. There was a Zeiss T1.3 I could of switched to pretty quickly, but I thought the exposure with the Red Pro looked OK. Would you say that shot is definitely underexposed? If so, severely?

The thing thats confusing me, is that I watched a video with Tod from Red who advised really going to town on protecting the highlights, and said correct exposure for Red is a lot darker than what you might be used to. I've also read quite a few discussions advising keeping the majority of detail around the 0.4 mark on the histogram. I know I'm probably holding too much weight on these statements. I'm just curious as to say, how many stops over what I did you would go, and exactly how under exposed that specific shot is for a successful clean grade?

Jamie.

Jamie Havill

12-19-2009, 08:48 AM

Edit after David's post... agree.

Try some quick grading to see what you have. You might be surprised with this one. Open in REDAlert! (or REDCINE-X). Set Color Space to CameraRGB, Gamma to REDlog and you will see pretty quickly what's there as the shadows will be opened up quite a bit and all noise exposed. You can either pull down the blacks with a curve here or try a quick grade in REDspace or REC 709.

Cheers Jim, I'll do that right now.

Edit: Do I set both the colour space and gamma space to REC709 for the grade?

David Mullen ASC

12-19-2009, 09:03 AM

@ David - I genuinly thought I was exposing that shot OK. There was a Zeiss T1.3 I could of switched to pretty quickly, but I thought the exposure with the Red Pro looked OK. Would you say that shot is definitely underexposed? If so, severely?

No, just mildly. I can't really say it's a "wrong" exposure either, just that you had more leeway to give your image more exposure if you ignored that window in the background and just let it clip.

Yes, RAW images can sometimes seem a bit on the dim side because of highlight protection, but in this case, ignoring the hot window again, your other highlights were exposed well below any chance of clipping, even that white piece of paper behind the person is hardly close to being clipped. I'm not sure if I'm reading your charts right, but it looks like that white sheet of paper on frame left is only hitting 40 IRE?

But as Jim suggested, it probably will color-correct fine as long as you don't lift the shadows too much, which would reveal noise.

Jannard

12-19-2009, 09:10 AM

Cheers Jim, I'll do that right now.

Edit: Do I set both the colour space and gamma space to REC709 for the grade?

I'd keep the color space set to CameraRGB for now. It will feel a bit under-saturated.

Get to know one of the RED apps as best you can. Experiment with settings, curves, matrices... the more you know, the better decisions you will make going forward. And if you can make the footage look good... a trained professional won't have any problems.

This is simple stuff... if you protect every highlight in every shot, you will run the risk of noise in high contrast. If you always make sure you have no noise whatsoever, you run the risk of clipping some highlights (again depending on contrast). These are the goal posts. Understanding how to stay in between through lighting and exposure is the puzzle to solve. Most of the time it is pretty easy. High contrast scenes are where you have to put on your thinking cap.

Jim

Jamie Havill

12-19-2009, 09:18 AM

I'd keep the color space set to CameraRGB for now. It will feel a bit under-saturated.

Get to know one of the RED apps as best you can. Experiment with settings, curves, matrices... the more you know, the better decisions you will make going forward. And if you can make the footage look good... a trained professional won't have any problems.

This is simple stuff... if you protect every highlight in every shot, you will run the risk of noise. If you always make sure you have no noise whatsoever, you run the risk of clipping some highlights (depending on contrast). These are the goal posts. Understanding how to stay in between through lighting and metering is the puzzle to solve.

Jim

Thanks Jim, I really, really appreciate that.

I understand the difficulties, I'll start learning to navigate them properly.

I'll spend a lot of time with Redcine-X. I've just purchased a HP dreamcolor, grading this was the final straw for my TN panel based samsung.

I'll spend some time doing a grade, don't expect much, but I'd appreciate peoples thoughts later on what I do.

Joel Kaye

12-19-2009, 09:21 AM

Would you say that shot is definitely underexposed? If so, severely?

Odds are that's a usable image with some grading.

As Jim said, get REDCINE and start playing around. I bet you have something decent there. But, having said that I still think it's underexposed for the person in the foreground. That just means a little more noise in the shadow and the likelihood some colors have shifted or won't be as vibrant as they would have been with more exposure.

As David says, exposure is a choice. It's difficult to claim a "right exposure" for any given scene. This is a scene that I probably would set so highlights in the window would blow out in trade for more information in the room.

It's not as simple as hold all the highlights or your histogram should like this etc. Out in the wild it's just not that easy. RED is pretty forgiving to underexposure, but I don't believe it's a best practice to underexpose. It doesn't really show off what the camera is truly capable of.

Jannard

12-19-2009, 09:21 AM

BTW... it is great to have David around here. Having a trained professional share his knowledge is a luxury that shouldn't be taken for granted. All of us at RED appreciate the unselfish effort...

Thanks David.

Jim

David Mullen ASC

12-19-2009, 09:25 AM

You're welcome!

David Mullen ASC

12-19-2009, 09:35 AM

I shot one of the first F900 features in Los Angeles back in 2000, and the post house had never handled a 24P HDCAM project yet, so they were helping us out as a learning experience for themselves too.

Well, the movie was about karaoke bars and I got a note from the post house that my first day's work had clipping going on -- I looked at the shots they were talking about and the were of a karaoke singer with stage lights (actually some Dedolights) behind his head, flaring the lens intentionally. The post house was concerned because the bulbs inside the stage lights were clipping!

My point is that often something gets clipped in a shot unless it is completely devoid of bright areas and specular highlights. If a car drives by in the shot and the sun momentarily glances off of the windshield, well, that sun flare will be clipped. A flashlight pointed into the lens will be clipped. Even in this underexposed test that Jamie posted, parts of the window are clipping.

Clipping just means that the object is so overexposed that it becomes white and featureless, without detail. In small amounts, that's OK, especially if the viewer is not expecting to see detail in that area anyway. It's only distracting when the clipped area looks unnaturally devoid of texture and detail. A clipped white shirt collar on someone wearing a dark suit, no problem generally, but someone wearing a white shirt with no jacket in a medium shot, well, it can get ugly if the whole shirt is clipped and you lose texture in the fabric and even some of the folds and wrinkles disappear in the overexposure.

Jamie Havill

12-19-2009, 12:54 PM

I tinkered for a while and got this. I used CameraRGB for the colourspace and RedLOG for the gamma space. I crushed the blacks. Things are a bit dark, but I don't want to bring the image up anymore because of noise.

Any input is appreciated as usual.

http://i48.tinypic.com/289zm95.png

Liam Hall

12-19-2009, 01:19 PM

Jamie, I remember that thread. I think mine was the first reply, I said the video was junk and should be ignored. I remember you saying how much you had learned and thought this would be the outcome. That is both the benefit and the problem with internet forums.

Anyhow, you've had some great advice in this thread from people far better qualified than me to offer help, but here's a tutorial that should get you in the right direction:

http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml

Also, look at the tutorial on curves.

Your shot is by no means beyond saving - that's the beauty of RED. To improve it, you need to adjust the mid-tones. The node in the middle of the gamma curve should be higher than the linear line, this will have the effect of "pushing" the exposure in the right direction. Have a good play with all the settings, I'm sure you'll get something out of it.

Steve Sherrick

12-19-2009, 01:34 PM

When I was first getting used to exposing the RED and working with DPs who hadn't shot with it much, there would tend to be some panic about highlights clipping. But then you realize, that a lot of times those areas clipping are not necessarily important to the shot, perhaps because they are specular or just not very important information when the better option is to just let them go and get a better overall exposure. Of course, with a much more controlled set, and tools that allow you to control every last pixel of the frame, you can start to alleviate these hot spots a lot of the time. This is the art, knowing when to let something go for the better of the shot. Sometimes meters alone can't tell you the whole story. You need your eyes too, and you need to make decisions based on what's important to you. If that window was an important part of your shot, then it would be necessary to light your subject appropriately to balance the scene.

I know it's been said a million times on here before, but as of right now it's the most important piece of advice. Test as much as you can to learn how this camera reacts to various kinds of light and what the color/gamma spaces do to affect your images. Once you get a feel for it, you'll be much more confident in your lighting decisions and exposure will become second nature. I've had the opportunity to see some great imagery shot with the RED. That's had a lot to do with the talent behind the camera, people that know how to light. Once they adapt to the RED's way of reading that light, they can take full advantage of everything the camera has to offer.

Kudos for shooting this test and beginning the process of trying to understand the sensor. Keep shooting. I'm learning new things every time I use the camera.

Jannard

12-19-2009, 03:13 PM

Steve Sherrick

12-19-2009, 04:48 PM

There is certainly more to be found in this image... a little noise is not the end of the world. Everything is a balance. Take you foot of the brake a bit. If you grade to the look you want and find that you have a bit of noise because of your exposure... use some NR. There are a lot of tools in the bag. Don't be afraid to use them. Using NR is not a sin. If this is the look you want... then ignore everything else. Your call...

Jim

For $99, you can use Neat Video. That will do wonders for a lot of shots, just have to find the right balance of noise vs. plastic look. I agree with Jim, as long as the noise is not objectionable, i.e. the pattern doesn't become too apparent, then you may be fine. Everyone has different thresholds for this kind of stuff. Some want ultra clean, some don't mind some noise. But ultimately, you want to be in full control of your image if possible. Know when you'll get noise, and when you won't. That will help a ton.

jimhare

12-19-2009, 05:16 PM

Another recommendation for Neat Video. I had a shot that I thought I would have to throw away. I ran it through Neat Video and it has become an "oh wow" moment from everyone who sees it. Best $99 I ever spent!

As for the topic, I only use in-camera exposure tools and they work very well. Whenever I get an overexposure warning I look for something in the shot that's causing it. As David says, if it's a light or small window, let it go, better to preserve your overall shot. But if it's a highlight on the face of your talent, stop down!

And as Jim says, sometimes a shot will require you to stop down more than you would like, but that's the deal. At least you will only have a few challenging shots in post rather than every one.

Rich Schaefer

12-19-2009, 09:34 PM

Hi Jamie,

Looking at your histogram in the photo, you are underexposed my friend, my guess is around 2 stops. 2 stops under would probably be an issue with just about any format.

But my glass is always half full, because you are a way better shooter and Red tech now than you were that day! Welcome to Cinemotography - where all of the best lessons learned are from f-ing up on shoots! I have learned more screwing up on shoots than I did at 4 years of film school.

Your feature will go much better!

Jamie Havill

12-20-2009, 07:44 AM

Thanks for all the advice guys. I've purchased Neat Video.

I went over to my collegues house tonight and saw this thread on his IPS panel based monitor after trying to grade on my TN based one. Safe to say I'm getting a shiny new HP display for Christmas.

I'll pick up this thread when I've got my new monitor, because this monitor is just useless for grading. There's no detail, and everything has a really plastic artificial feel.

Jim, David, Steve, Rich, Xioasu, Joel, and Liam, thankyou for all your help. The shoot in February is very important to us, and your help is invaluable.
(http://reduser.net/forum/member.php?u=10347)

Jannard

12-20-2009, 09:39 AM

Elsie N

12-20-2009, 09:56 AM

The before and afters should be displayed together. There are so many new objects appearing in the second one that I'm getting dizzy switching back and forth between the two posts.

Jamie Havill

12-20-2009, 09:56 AM

Jamie... this is not intended to be a color grade, just a guess of what we think you can find in the image without needing much (if any) NR. An R3D is pretty flexible... the joy of shooting RAW.

Getting to know what you can do in post certainly helps one make better exposure decisions. Shoot... grade. Shoot... grade. Best on your project.

Jim

http://www.redgrabs.com/up/1261406800.jpg

Thank you Jim. I'm just about to have another crack and that's tremendously helpful. It is incredible how much detail can be pulled up. Like you say (it couldn't really be put better), it's about keeping the balance between nicely preserved highlights and staying away from noise.

Everything is dependent on the scene, what would work best, and trade offs must be made in order to 'hit' the desired exposure. In this particular shot, I certainly would of blown out the window (had I been able to!) and kept things futher away from the noise floor. It has certainly been interesting though, and I'm very glad now that I did preserve all the highlights and started this thread.

Thanks for the kind words about the film, I'll keep people posted if you'd like to see how it goes =]

Blair S. Paulsen

12-21-2009, 03:13 PM

As Jim and others have mentioned - testing is the key. Of course there are real world limitations on testing methodologies so making good guesses in a hurry is often required. Below I will describe one approach, keep in mind that with experience you will learn to reference many exposure indicators in making your choices.

Ignoring format (RedOne, F23, HVX200, whatever) use basic lighting and cinematography practices to stage your elements and set your lighting.

Frame up the shot, switch on false color metering (in view RAW) and spin the iris up and down while looking at where the primary green false color contour lands (this is nominal 18% gray / 50% exposure). Think about your expectations for where elements in the image "should" be in the exposure curve. For example if you have a person with medium skin tone you might want to open up until some of the face reads false color green, and some false color pink. This is your first guess for stop.

Now scan around that false color version of your scene and see what is near, at or over clipping (yellow, orange & red contours). As David and others have mentioned, some items should clip, other elements need to hold detail. If you have placed the most critical elements at the exposure level you desire and nothing you care about is clipping, you're halfway there.

The second check is shadow levels. There is a -3 stop false color contour that looks kinda blue. Note your projected stop and then spin the iris to see what is above and below that contour as your ride exposure up and down. AS a general rule (lots of creative exceptions are valid, this is just a rule of thumb) anything below that -3 blue contour is at risk of being noisy. My usual strategy is to add fill to any elements that would look lousy if noisy. This can result in a flatter look on set but a simple tweak of the curve in RedAlert, Scratch, etc can easily restore the intended contrast ratios.

While I consider the Mysterium sensor with Build 20+ a 9 stop+ DR camera, I try and keep elements of interest in a 6 stop window (3 over and 3 under 50% exposure) so there is plenty of noise free detail and pure chroma for grading. YMMV.

Cheers - #19

Meryem Ersoz

12-21-2009, 03:35 PM

a future reference bit of advice...

I find that this is a very light-hungry camera - (not a complaint but an observation)...

...and you'll find that the kicker, rim light, hair light - whatever you want to call - is your friend. Don't leave home without it. Even in quick in-and-out, fast set-ups, it helps a lot to have a litepanels micro or roscoe lightpad or best of all, one of Richard's handy, portable Coollights that can run off a RED battery if you buy the V-lock mount - that's my favorite. It doesn't add a lot of weight, is flexible, and easy to set up, even without a crew.

Documentary-style situations that I may not have lit in the past, when shooting RED - I light them. That separation between the foreground and background helps tremendously, and your lighting setup doesn't have to be heavy or cumbersome. But it's pretty indispensable.

When people with dark hair are underexposed, it's easy to lose detail in the hair - makes 'em look like they're wearing a helmet, not hair. A bit of backlight will cure this. I would say that I almost never shoot humans indoors without it. It just looks good.

Steve Sherrick

12-22-2009, 04:01 PM

I'm about to debut Obscure Knowledge Test Lab. Now before anyone gets too excited, let me say it's going to start off slow, but basically I will provide some R3D test files for people to take a look at under different conditions. I've got a test subject who is very cooperative and I just upgraded my web site hosting account to unlimited bandwith so people can download the R3Ds. With each R3D will be information about lens used, camera settings, F-stop info, filters, type of light, etc. People can then play around with the files, get hands on with the processing. Hopefully this will continue once Epic and Scarlet comes along. The place to find these files and info will be here.

http://www.obscureknowledge.com/MEDIA.html

Look for a test file to appear soon and an official announcement of the site.

Jamie Havill

12-22-2009, 04:03 PM

Steve that's fantastic, it will be so helpful to us. I hope you manage to get some up in the coming weeks. Much respect.

Steve Sherrick

12-22-2009, 04:06 PM

Steve that's fantastic, it will be so helpful to us. I hope you manage to get some up in the coming weeks. Much respect.

Hopefully in the next few days, maybe sooner. At least a test file should be available very soon.

Jamie Havill

12-22-2009, 04:08 PM

Hopefully in the next few days, maybe sooner. At least a test file should be available very soon.

Excellent, it would be an invaluable resource for those who are coming from a video/film background like us. It's very difficult to get hold of a good range of R3D's unless you go out and shoot yourself which is expensive (at least in England) to do.

You should set up a way to donate towards server costs maybe if things really get going.

Steve Sherrick

12-22-2009, 04:20 PM

Excellent, it would be an invaluable resource for those who are coming from a video/film background like us. It's very difficult to get hold of a good range of R3D's unless you go out and shoot yourself which is expensive (at least in England) to do.

You should set up a way to donate towards server costs maybe if things really get going.

There used to be more sites with R3D files but they seem to have gone by the wayside lately. I know Jason H has a site, but otherwise you have to dig deep to find files. What I'm hoping to do is give folks some files with reference information so they can have a chance to play with actual footage without the expense of renting the camera. The key is the reference info. Knowing what stop, what lens, how the lighting was setup (early tests may be crude by the way, I'm not a DP but I know some good ones who will eventually help with these tests) and other information that will be valuable in judging the images.

If I can do a small part to help people who are trying to figure this stuff out I'm happy to do so. If it gets costly or expands to the point where I need to offset the cost somehow, I'll explore donations but for now I'm just trying to help. Having actual R3D files is far more informative than JPEGs or even TIFFs. You need to see what's actually recorded.