Using a Light Meter for DV shoots
 

Hi,

I was wondering if anyone in the forum has used a light meter when setting up their manual shots. I've been using the zebra pattern with success but what about a light meter for getting a general f-stop/shutter speed reading?

I have a hand held http://www.bowerusa.com/SP-lightmeters.html light meter that I used with my 35 mm camera and was thinking about putting it to use for DV cam shoots.

Question is, what do you set the ASA at on the light meter dial? Anyone have any ideas?

Regards,

John

...okay you film guys are going to hate this, but forget ASA ratings, f-stops and shutter speeds.

1.) If you want a filmish look you definitely do not want to shoot on anything other than 1/60th for 60i, 1/48th for 24p or 1/50th for 50i (PAL) shutter speeds. Anything else will not allow you to use magic bullet, dvfilmmaker or other post film look softwares incase you have to.

2.) F-stop. For DV you want this as open as your camera will let you go given the light level of your scene. You definitely don't want to use gain in your camera to compensate either so lock this off to -3dB or 0dB.

3.) Depending on the settings in your camera, once you start seeing zebra stripes it could be too late and your highlights might be blown. You will only see this later when you are editing and it will piss you off. If you can adjust your zebra settings in your camera (like the XL1s or XL2) set it to something low like 75 so when you start to see them you don't have to panic too much.

4.) When using a light meter for DV forget film speed setting and work with contrast ratios instead. For DV you should use a contrast ratio of 4:1 whereas in film 8:1 or even higher is prefered. So basically if you meter your background light in your scene and it measures f2.8 you might want the key on your subject to be around f5.6. Your fill light can then be weaker than your key. This is easily accomplished by using a reflector for fill.

But in order to even get some readings on your light meter it might be necessary to put the ISO of your meter to something like 250 or 500. Then once you start taking meter reads, depending on your lighting you will start getting reads between f1.4 and f11. If your camera does not have fps (frame rate) settings just use 1/48th or 1/60th - again it really doesn't matter what you set this too because you're lighting by ratios not actual settings - the point is you want to be able to get some readings in fstops on your meter.

Shutter Speeds
 

Dennis, I'm trying to figure how manually setting my shutter speed in regard to your post. You listed several options and my scenario is not listed for the Canon Gl-2 "1/60th for 60i, 1/48th for 24p or 1/50th for 50i (PAL) shutter speeds" I beleive the GL-2 is close to 30 fps, but not sure.

Okay, so have the f/stop as open as it will go and keep the gain at 0db

Thanks for the tip in locking the Zebra strips near 75

In regards to contrast ratios, I'm still on a learning curve regarding that point. How do I measure contast ratio to know tha I'm at 2:1 for DV?

Overall, I see that the point of your post is that the we are operating by contrast ratios and not settings. Again, how do I obtain a definitive measure of contrast ratios?

I learned quite bit from your post and it gave me more questions than answers, which brings me on the quest for additional knowledge on the subject of photon management. Thanks

John
Santa Fe, Texas

I don't know the GL2 very well, but the default will likely be 1/60th for you. There might be an option to increase it or decrease but definitely stick with 1/60th.

Some light meters have an "ave" button which will do the work for you and show you the constrast ratio. (Check your light meter manual.) If not then you have to do the math yourself using the f-stop ranges ie. f1.4, f2.8, f5.6, f8, f11, f16.

Aren't the ratios kind of subjective? 2:1 is like a sitcom. What if it's supposed to be night? What if things are supposed to almost fall into black? Can't the DV cameras, for the most part, handle about 5 stops?

Sorry I originally confused the AVE value of 2.0 on your meter which really is a 4:1 contrast ratio. My bad - I will edit my original post.

Whether your scene is night or day, for good lighting and capturing the contrast range of the scene on DV you should always ensure your range of contrast is 4:1. Even night scenes should have lighting on the background where the foreground (or subject) is lit "more" than the rest of the scene.

If you want black areas within a scene they should still be lit, relative to your key subject then brought down overall in post. If you shoot your background in the dark because you want it to look black you will have NO detail in the shadows and if anything grain and noise from your camera.

Using a light meter while shooting digitally is a very good idea, but there's no need to guess or fudge the ASA. The following is the method that I use before every shoot:



1. Setup a chip chart with even lighting, and with the color temperature of the light appropriate to any filter you have on the camera. (85, etc).

2. Monitor to a waveform monitor.

3. Set the desired gain, gamma, and filter settings.

4. While balance with auto iris on, then turn auto iris off.

5. Set your incident meter to 24 fps, 180 degree shutter angle (this is just a reference to film).

6. Adjust T-stop so that the brightest chip is at 100 IRE.

7. Measure the light on the chart with your meter.

8. Change the ASA on the meter until the T-stop reads the same as the T-stop on your lens.

9. This is your ASA for this camera setup. Additional evaluations need to be made for different gain, filter, gamma, etc settings.


If the camera I'm using supports scene files, I typically evaluate and record the ASA for each of those files, and then only use those scene files for the rest of the shoot.

I really like using a meter while shooting digitally because it allows me to use the same methodology across both film and video mediums. Lighting to a monitor (or a viewfinder) as an inhibiting factor that prevents you from knowing what's really going on in terms of exposure.


Hope that helps.

John - I'm sorry if I understood your original question incorrectly. I assumed since you wanted to use a light meter for digital video that your intention was for digital filmmaking and thus I wrote completely from that aspect.

If you are in fact shooting DV for filmmaking I don't see any point in taking a meter read in order to know what f-stop to set your lens to on your digital camera. Why? Because if you are shooting on DV with 1/3" CCD's your depth of field is small enough as it is and the only way to open it up and make it as large as possible is to shoot with your lens completely open. Open to the point that if you are outdoor you stack on Neutral Density filters until you're camera says you are near open (ie. f1.4 for f0). Opening up wide indoors can be tough so you need to light your backgrounds with EXTRA fill light, measure it on your light meter... then remember the contrast ratio I mentioned earlier of 4:1 and double that light on your subject! Your indoor scene will look like the sun has parked itself your house, but in camera your darker areas will have detail and your subjects will stand out nicely and properly. Once you put your footage through software like Magic Bullet you will be giving your footage a lot of flexibility to work with and it will be flexible to manipulate properly and get really beautiful and cinematic results. (assuming that's what you're after)

Many great lighting techniques can be learned by reading online what others have done with their projects and also by just trying it out yourself! Study the films you watch, try and guess where the lighting has been placed, look at the shadows on faces or hair lights on people - guess where all these lights have been placed...

Below are some links you can read on lighting, also there is an indie film called "BROKEN" in the DV for the Masses section with 2.5 hours of bonus footage that can be ordered that is helpful to see and learn how some of the lighting and overall look of the film was accomplished - check that out!

http://www.mvwire.com/dynamic/articl....asp?AID=10564
http://zimmer.csufresno.edu/~candace/design1.htm
http://www.film-and-video.com/broadc...les3point.html

Well, a lot of this is indeed subjective. I would hate to tell anyone what a "proper" contrast range is within a scene--generally having a decent highlight somewhere in a low-key, dark scene will make it look less murky but overall ratios should be set for the individual scene, not to a specific formula.

I don't like using light meters for video any more because the cameras don't have a predictable ISO--they tend to be more sensitive at the low end than in the mid-range than film.

I'm not even sure I like universally recommending that people shoot wide open on DV, because the relatively inexpensive lenses are not optimized for that type of shooting and will be sharper a few stops down. Realistically, there's such a great depth of field on a 1/3" camera that at a wide angle lens setting you won't see much of a difference between f2 and f5.6, which is not the case with larger formats. When shooting telephoto, there's always the option of laying in some ND to open up further, which works out because the lenses are less challenged at telephoto settings than full wide anyway.

Finally, it is true that 1/48th is a standard 24 fps film-style shutter speed, but of course a "skinny shutter" look may be desired which would mean a shorter shutter (i.e. the Saving Private Ryan/Gladiator aka now-overused fight scene look) or a long exposure (Requiem for a Dream).

I present all this not to be specifically contrary, but perhaps to point out that there are many philosophies and approaches to achieve similar ends--it all has to do with what one is comfortable with. I could never get through a film shoot without my spot and incident meters but after countless video shoots where I just don't use them, I've finally learned to keep them in the case.

A Swell Learning curve
 

What is a chip chart,? I googled it and couldn't find it.

This Thread IS a Keeper!!!
 

Great thread! - And so timely for my development.

Charles thanks for the "permissions" too!

Grazie

John-

A chip chart is a precise chart that includes 18% grey as well as a stepped greyscale and some color chips. Besides the obvious colors, some charts include flesh tones. DSC Labs makes some really good (and expensive) charts. Less expensive charts are available from TecNec and Fotokem.

And markertek.com.

Meter question
 

I was wondering the same thing. I have a Minolta autometer 4F and want to use that to get a base reading to set up my lights.

Light meters used to respond to tungsten light differently than daylight, I assume because there is less blue light in the tungsten light. I read somewhere that the film sensitivity is about 1/2, or 1/2 the iso when dealing with tungsten light. The paper charts that used to come with film verify that.

However, with digital still cameras a more accurate reading would be from the histogram in the camera after the photo is taken. You still need to know where to point the camera, but a light meter will get you in the ballpark and the histogram will get you home.

So, it occured to me that in my XH-A1 every time I snap a photo, a histogram appears.

As long as I use the same shutter speed and f-stop settings with the still photos as I do with video, I'm assuming (bad thing to do) that I could use this histogram to measure the exposure for my video settings. The histogram measures the light that actually gets through the lens onto the sensor, so that would be the most accurate way to measure it.

Yes, I could use Zebras, but I shot a bike race outside last weekend and no matter what I did I couldn't make the zebras go away when someone with a white t-shirt was in the photo. It was an overcast day and the images didn't look overexposed in the lcd or through the viewfinder on playback. The zebra setting was default so maybe it never will go away at the lower numerical setting.

So, my next question is what software to use as a vectorscope? I don't want to pay $600 for the Canon software at this point, anyways.

Meter question
 

Sorry..........double post.

Learn more about Zebras. Zebras do not indicate overexposure. In outside shooting with available light a meter isn't going to do more for you than Zebras will, and a light meter is one more piece of equipment to futz with. OTOH, a meter is a handy way to rough-in lighting setups.

1. What reference was your Zebra set to? Depending on the camera, this could be anywhere from 70 to 100 (percent of full white). If you want white jerseys to be white, set Zebra to 100 and expose such that all highlight areas of the jersey show Zebras.

2. "...no matter what I did I couldn't make the zebras go away..." What did you try? Does your camera have ND (Neuteral Density) filters, shutter speed controls, and iris controls? Is it possible that the camera was on auto exposure, or, that one of the above controls was on auto?

Your NLE may have a vectorscope. Usually, you'd want to check exposure with a waveform monitor, a vectorscope is rarely used in the field, but is handy for matching & correcting colors.

For field, I use DVRack on a PC, but there are some other choices out there if all you need is waveform/vector scopes (DVRack does quite a bit more, but there is a less expensive "Express" version as well). scopebox.com on a mac, and others.

Zebras
 

I set the camera on manual and stopped down the iris manually. I did this at several shutter speeds and nd filter settings. I do need to optimize my knowledge in this area, which is why I asked. Canon doesn't supply much info here.

So, if I understand this correctly, at 100% when the zebras are only on white, you get a good detail in the whites without overexposure. If they show up in darker areas, then those areas are going white and the actual white will burn out.

What happens at the lesser settings like 70%?

Scopebox doesn't support HDV yet, are there other Mac solutions similar to DV Rack? I have a Mac and a PC, I let them fight each other late at night.

Something's not right here. I think you must be missing something - on full manual you should be able to get down to no picture at all using shutter speed, iris and ND. Is it possible that gain is still on auto?

Sorry, don't know much about other mac solutions. Depending on the camera you can downconvert on the fly to scopebox or whatever - this is fine if you just want to see exposure.

Almost. White is white, no detail. A "white" t-shirt with any sort of directional lighting will show greys, shadows, and highlights. These are meaningful details. The eye sees all this range, the brain says "white". You need the camera to see all this range, too. If there are 100% zebras across the entire shirt, there won't be grey, there won't be shadows, there won't be much detail. So, what you want is 100% detail in the truely white areas of the "white" shirt, the brighter areas and highlights.

Right.

70% & other settings on Zebras are usually used to check skin tones.

(Arguably) a caucasian face should be about 75 or 80 units. Some Canon cameras have settings for 70-75-80-etc., up to 100. In this case you might roll through the different settings to see what they tell you about a scene.

Some practices have wide acceptance... but there are still people who say "I do it this way and it works for me". More power to them.

Caucasian faces 75-80. Whites to 100 (note that your camera may show some detail in recordings above 100). The tendency when working without Zebras seems to be to underexpose, but this is generally better than overexposing.

Oh, one more thing... when I'm shooting I let specular highlights burn out if needed. These are, for example, the reflection of the sun off a chrome bumper. If they're small, I say let 'em burn and don't worry. See how it looks to you.

Mostly, do a bunch of shooting, paying attention to what the zebras tell you, take it in to edit, look at your scopes on the editor, try to develop a sense of how the chain of exposure works on your systems from shoot to edit to distribution.

no picture at all
 

That's what was happening, manual iris stopped down until black-no picture. It's been a week and I don't remember all the settings. I'll fool around with this some more; your info is real helpful.

Can you recommend any book that covers this topic? Maybe I should keep asking questions here.

Most of the TV guys I worked with in the era of 3/4" tape with were just point and shoot. One of them was amazed the I actually disassembled the camera and cleaned everything, or set the camera on manual and stopped down a bit to intensify colors.

Hi John,
As a starting point I use a ISO on the lightmeter of 320 for mini DV in my Xl1s and XL2.
If I set the meter to fps thought (running at 25fps (PAL) it usually reads a stop over E.G
At ISO 320 lightmeter could read f5.6 at 1/60
At 25 fps lightmeter would read f4.0 at 1/60
(these could be the wrong way around i'm away from the meter at present).

Basically on a normal meter use ISO 320 as a starting point. Works for me anyway and I only shoot the XL2 on manual settings, with a manual lens.

If you're lucky your camcorder can show you two zebras at once, like 70 to 90% and 100%
I love to use the two zebra display with 70% and 100% - when you're used to it it's giving you so much information you won't need a lightmeter at all. Skin tones at 70% is stripes, everything blown out at above 100% is dots - what more do you need?

Hey John, to find the ASA rating of your camera...

Point your camera at an evenly lit 18% grey card and set your cameras exposure/iris/aperature to auto.

I'll adjust the light until the the camera, in auto, is reading f/4

Now adjust your meter's frame rate to match the frame rate of the camera and finally adjust the ISO of the meter until it reads F/4.

Taaaaadaaaaa. Now you're in the ballpark but you should go shoot some tests before using your meter on set. There is a lot of literature out there about 12%, 13% and 18% grey and their use for calibration. Shoot some tests and you'll see how you like to expose for your camera.

Meters like the Sekonic 508C and 608C are great for bouncing between shooting stills and moving pix as they have both T and f/s modes.

I didn't get to reading the entire thread yet but one thing to keep in mind that has always been handy for me in the field is that if you set your Zebra for 70, in my broadcast days that was generally considered to be the average caucasion skin level. It's also one of the chips in the B&W chip chart so if you just start hitting the zebras on the face of your principal subject and he/she is caucasion, this is a good indicator of what is considered proper level for that skin tone in the broadcast world. Broadcast, as in News that is.

Theatrical lighting is completely different and as wild as your imagination HOWEVER, you must still stay within the contrast ratio boundaries of the medium. If your in film and you have 7 Stops to work with, feel free to use them. In DV, if you have 4, don't make those dark areas as dark as you would in film or there won't be any detail seen in your video, etc.

It's a sad fact that the contrast range in video is so much lower than film. For those that want a film look, there is generally a gama trick or two or a "black stretch" that can be applied in post to simulate a better S-curve and so on. Trouble is, you can't make it have more dynamic range or contrast than the final medium or it's just lost.

If you really want the film look, you're going to have to shoot film. That's just the truth of it. I know you can simulate it convincingly but it's not going to be the same no matter what you shoot with, what frame rate etc. Video just doesn't have the range.

Sean McHenry
http://www.DeepBlueEdit.com