Jump to content


Photo

Exposure Questions


  • Please log in to reply
19 replies to this topic

#1 Marc Levy

Marc Levy
  • Basic Members
  • PipPipPip
  • 107 posts
  • Cinematographer
  • Los Angeles

Posted 01 November 2007 - 02:20 AM

Hi,

I need advice on exposure. I'm shooting a feature on the HPX500. The film's dark, so I'm lighitng it that way - very little fill, nothing frontal. I'm shooting in Cinelike D with a Master Pedestal of -3. I chose Cinelike D because it gives me the most latitude, and I prefer its response to highlights better than any of the other matrices.

My problem: When I look on both of the HD plasma monitors I have on set, the image looks good (albeit low-con at this point, as I plan to crush blacks and bump contrast in post) but the waveform monitor doesn't look right - much of the time, most of the image reads below 50IRE (even with caucasian skin tones in frame), and there are times when nothing reads over 50IRE. Both monitors are calibrated, both show very similar images. So then I open up the aperture and the waveform looks better - but the image looks overexposed to my eyes. So I go with my eyes and stop back down, worrying that I'm screwing myself.

Oh, and these images seem a bit noisier than I'm used to.

Anybody have similar experiences or any words of wisdom to ease my worries?
  • 0

#2 Adrian Sierkowski

Adrian Sierkowski
  • Sustaining Members
  • 7117 posts
  • Cinematographer
  • Los Angeles, Ca

Posted 01 November 2007 - 02:27 AM

I can't speak for the HPX, but I have noticed on the other panasonic cameras i've worked with that they noise up very quickly as you take light away; i.e. don't respond well to under exposure.
My advice would be to go with the waveform over the monitor. Don't forget, what you see on the monitor will be effected by what's around it regardless of it's calibration; or so my colorist always tells me. I'd err towards over-exposure aside from under, as you can bring things down in post IMHO, easier than bringing them up
  • 0

#3 Bill Totolo

Bill Totolo
  • Sustaining Members
  • 698 posts
  • Cinematographer
  • Los Angeles, CA

Posted 01 November 2007 - 08:26 AM

Keep in mind that Cine D is the noiseist scene file on the Panasonics.
  • 0

#4 Marc Levy

Marc Levy
  • Basic Members
  • PipPipPip
  • 107 posts
  • Cinematographer
  • Los Angeles

Posted 01 November 2007 - 03:35 PM

Keep in mind that Cine D is the noiseist scene file on the Panasonics.


I knew that going in, but I don't like the response to highlights I get from Cinelike V or B. Press - they tend to look more "videoish" sometimes.
  • 0

#5 Jon Rosenbloom

Jon Rosenbloom
  • Basic Members
  • PipPipPipPip
  • 713 posts
  • Cinematographer

Posted 01 November 2007 - 04:08 PM

I've used the varicam and hdx-900 for a couple of shoots, and I've had the same experience: the monitor looks a couple of stops brighter than the waveform. In dark scenes, my skin tones register somewhere bewteen 20 and 30%. It's a little scary, but everything has worked out fine so far. Now, I think something is amiss if the faces get above 50%.

You can probably tweak your monitors closer to your waveform, and you should definitely be aware of the backlight function, and work it in relation to the environment surrounding the monitor. (Meaning, if the monitor's in a dark room, you should turn down the backlight, and vice-versa.) The only way to get more definitive is to get a DIT, a 20" crt monitor, and a black tent. Me, I've always just glanced at the waveform to make sure I had something there, and I've yet to be burned. It's digital video, if it looks good on a monitor on set (and the monitor isn't cranked all the way up or down), it will probably look good later on.
  • 0

#6 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 01 November 2007 - 06:25 PM

If your scene is dark, then it should look that way on the waveform. A dark or low-key scene will have a majority of the waveform filled with luminances well under 50%, punctuated by brighter areas.

Posted Imagescreenshot3.jpeg

Posted Imagescreenshot4.jpeg

(Stills from Slow Burn, photographed by Wally Pfister, ASC)

Remember that the display gamma of many monitors (especially CRT's and plasmas) is not linear, but pushed upwards quite a bit. That means that 50% luminance will often look much brighter on the display than you would think, and shadow areas will show much darker on the waveform than you might think based on viewing the monitor image.
  • 0

#7 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 01 November 2007 - 08:47 PM

I realize those pics are perhaps a bit dark to begin with, so here's a more realistic example.

These stills are from the DVD of Dark City, played on my Mac with custom AV settings that make my monitor closely emulate the look of my CRT TV. I screencapped the images and brought those into FCP (there's a slight gamma adjustment applied to images imported into FCP, so these luminances aren't completely accurate, but close enough for demonstration).

Here in this somewhat dim scene the face is about 40%.
screenshot5.jpeg


Note that in this scene because of the dark background, skintone that is close to "properly exposed" actually looks quite bright in the scene. Here it's actually a touch under, between roughly 55%-65%
screenshot6.jpeg

If you go in tight on the keyed part of the face and replace the dark BG with a 50% luminance border, you can see that the skin tone is close to properly exposed, about 1/3 stop or so under, peaking around 65% instead of 70+%
screenshot7.jpeg
  • 0

#8 Marc Levy

Marc Levy
  • Basic Members
  • PipPipPip
  • 107 posts
  • Cinematographer
  • Los Angeles

Posted 02 November 2007 - 12:14 AM

Michael, thanks for the above demo. It's very useful. I feel a cool wave of relief now, as the waveform images you posted are close to what I've been staring at for the last week on this shoot. I just got a frame grab of one of the shots I was concerned about. It's an H264 compressed file from the editor, but here it is:

Attached Images

  • CU.jpg

  • 0

#9 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 02 November 2007 - 12:40 AM

It is a dim scene, and on the waveform it looks about like you would expect. Hand peaking about 45%, face peaking about 35%.

Think of it this way: if the scenic content weren't below 50%, it wouldn't look dark, now would it?

screenshot.jpeg

Looks good. HPX500, you say? How would you compare the images to those of the HVX200?
  • 0

#10 Marc Levy

Marc Levy
  • Basic Members
  • PipPipPip
  • 107 posts
  • Cinematographer
  • Los Angeles

Posted 02 November 2007 - 09:27 AM

Looks good. HPX500, you say? How would you compare the images to those of the HVX200?


Although I have not tested the two cameras side by side, I like the HPX500 better. The most apparent difference is the 2/3" chips which give me more control of DOF. And the lens that I'm using, even thought it's an ENG (non-CAC) lens, seems far superior to me than the fixed lens on the HVX200. And even compared to the HVX200 with the P+S Technik adapter with Zeiss Super Speeds on it, I think I'm liking the HPX better. It seems like I get a sharper, fuller image.

I do think one could intercut the cameras, if necessary.
  • 0

#11 Jon Rosenbloom

Jon Rosenbloom
  • Basic Members
  • PipPipPipPip
  • 713 posts
  • Cinematographer

Posted 02 November 2007 - 10:43 AM

So, what's the difference between the hpx-500 and the hdx-900? Is everything the same except the hpx records to cards? Does the hpx have sdi out?
  • 0

#12 Marc Levy

Marc Levy
  • Basic Members
  • PipPipPip
  • 107 posts
  • Cinematographer
  • Los Angeles

Posted 02 November 2007 - 04:26 PM

So, what's the difference between the hpx-500 and the hdx-900? Is everything the same except the hpx records to cards? Does the hpx have sdi out?


I don't know much about the HDX900, but I do know it doesn't have variable frame rate as does the HPX500, which goes from 12FPS - 60FPS. This capability is a major factor in my camera choices. Also, the HPX500 does have SDI out.
  • 0

#13 Clint Nitkiewicz Hernandez

Clint Nitkiewicz Hernandez
  • Basic Members
  • PipPip
  • 23 posts
  • Director

Posted 02 November 2007 - 07:26 PM

Waveform? How can you see this? On the camera in the settings? On a separate in field monitor? In post? What is the best in field monitor to deliver the most close to the actual image as possible? There are many 800x480 field monitors, though for shooting on the hvx-200 at 1080pa would that make sense, do i really need a 1920x1080 true line resolution monitor to really see what im getting? Thanks. What are some of your workflows for this, the 20" crt monitor and a tent is a great idea, are there any other solutions? Specific brands ? Links?
  • 0

#14 Marc Levy

Marc Levy
  • Basic Members
  • PipPipPip
  • 107 posts
  • Cinematographer
  • Los Angeles

Posted 02 November 2007 - 11:45 PM

Waveform? How can you see this? On the camera in the settings? On a separate in field monitor? In post? What is the best in field monitor to deliver the most close to the actual image as possible? There are many 800x480 field monitors, though for shooting on the hvx-200 at 1080pa would that make sense, do i really need a 1920x1080 true line resolution monitor to really see what im getting? Thanks. What are some of your workflows for this, the 20" crt monitor and a tent is a great idea, are there any other solutions? Specific brands ? Links?


Clint,

I've used the Panasonic BT-LH1700W, which is a 17" HD monitor - and it has a waveform monitor function built into it. I've had success with this monitor, and have found that in general it represents (if calibrated properly) what I am actually recording. It's available at most rental houses.

http://catalog2.pana...odel=BT-LH1700W
  • 0

#15 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 03 November 2007 - 01:30 AM

So, what's the difference between the hpx-500 and the hdx-900? Is everything the same except the hpx records to cards? Does the hpx have sdi out?


I'm actually in the middle of an HDX900 shoot right now (with the Panasonic 17" LCD monitor).

The HPX500 and HDX900 are quite different cameras. In a nutshell, the HPX500 is just a 2/3" chip version of the HVX200. Same resolution (540x960 uprezzed), and similar menus and functions. The HDX900 is basically a variant of the Varicam, same chips and image processing (improved to 14bit), but without the variable frame rates. Unlike the Varicam it records to tape in 1080i as well as 720P. The HPX2000 is the P2 version of the HDX900.

You can read about them here.

http://www.cinematog...n...9&hl=hpx500

http://www.cinematog...n...7&hl=hpx500
  • 0

#16 Jon Rosenbloom

Jon Rosenbloom
  • Basic Members
  • PipPipPipPip
  • 713 posts
  • Cinematographer

Posted 03 November 2007 - 12:24 PM

'The HPX500 and HDX900 are quite different cameras. In a nutshell, the HPX500 is just a 2/3" chip version of the HVX200. Same resolution (540x960 uprezzed), and similar menus and functions. The HDX900 is basically a variant of the Varicam, same chips and image processing (improved to 14bit), but without the variable frame rates. Unlike the Varicam it records to tape in 1080i as well as 720P. The HPX2000 is the P2 version of the HDX900."

Too many cameras! I guess they want to cover as many price points as possible.

Random hdx thoughts:
Just finished a 7 day shoot w/ the hdx-900. The rental was a little less than a Varicam's. I found the camera to be "slower" (lower ASA) than the varicam. The rental house sends it out w/ gain options of -3, 0, and +3, and I try to stay at -3. W/ a Varicam, I would set the "sutter angle" to 200 degrees. This option isn't available on the HDX-900, so I turned on the electronic shutter, and set it to 1/40th sec, which seemed to lose us a couple of stops. We had the 17" lcd, and the 8" lcd. The director had the big monitor, so I lit the whole thing off the 8" (w/ - mostly positive - feedback from the folks in "The Village"). Once in a while, I'd use the waveform on the 17", but the director found it distracting.

I didn't really care about having sd out, until we put the camera on the steadi-cam, and the operator asked us if we had a down-converter.

We used the Fujinon HD Cine Zoom, 7.3mm-110mm, which is an ok lens. I think our Gamma setting prevented the blacks from looking very crisp. Our issues w/ this lens were: close focus is 4', which isn't vey close. Also, the barrel is quite big, so the pulls are tough for the AC's and the steadi-op couldn't fit his remote motors ... (We switched to the wide eng lens.)

One thing that bugs me is that the daylight preset on the filter wheel is 6300K, which renders daylight a little warm.
  • 0

#17 Clément Brewer

Clément Brewer

    New

  • Basic Members
  • Pip
  • 8 posts
  • Student

Posted 03 November 2007 - 12:57 PM

Hi all,
I'd like your advice on oscilloscopes and vectorscopes : do you guys rely on renting or would it be wise to buy this equipement (2nd hand) ?
I'm a student so when I get the chance to Dp it's mostly on indie projects that's why I thought having my own gear could be useful (like gaffers with their own lighting packages).

Thanks.
  • 0

#18 Jon Rosenbloom

Jon Rosenbloom
  • Basic Members
  • PipPipPipPip
  • 713 posts
  • Cinematographer

Posted 03 November 2007 - 04:11 PM

It all depends on what you want to do. If you want to be an owner/operator, then I suppose you could buy that stuff ... I'm pretty sure any PC can be equipped w/ waveform and vector-scope software. If you're DPing a film w/ a half-way decent budget, a Digital Image Technician should be on the staff.
  • 0

#19 Chris Keth

Chris Keth
  • Sustaining Members
  • 4427 posts
  • 1st Assistant Camera
  • Los Angeles

Posted 03 November 2007 - 08:23 PM

It all depends on what you want to do. If you want to be an owner/operator, then I suppose you could buy that stuff ... I'm pretty sure any PC can be equipped w/ waveform and vector-scope software. If you're DPing a film w/ a half-way decent budget, a Digital Image Technician should be on the staff.


Even if you don't have a DIT on staff many monitors can display a waveform. The last thing I wa on we had the 17 inch monitor nentioned above that had a waveform function as well as a little 7-inch onboard that could display a waveform.
  • 0

#20 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 04 November 2007 - 03:32 AM

Random hdx thoughts:
Just finished a 7 day shoot w/ the hdx-900. The rental was a little less than a Varicam's. I found the camera to be "slower" (lower ASA) than the varicam. The rental house sends it out w/ gain options of -3, 0, and +3, and I try to stay at -3. W/ a Varicam, I would set the "sutter angle" to 200 degrees. This option isn't available on the HDX-900, so I turned on the electronic shutter, and set it to 1/40th sec, which seemed to lose us a couple of stops.


The effective ASA is strongly influenced by the gamma settings:
http://www.bbc.co.uk...onic_hdx900.pdf

I didn't meter it but the 640-ish ASA range seems consistent with the lighting and shooting stops of the project I just finished with the HDX.
  • 0


Media Blackout - Custom Cables and AKS

Tai Audio

CineTape

FJS International, LLC

Aerial Filmworks

Metropolis Post

Opal

Wooden Camera

Technodolly

CineLab

Visual Products

Rig Wheels Passport

rebotnix Technologies

Abel Cine

Glidecam

The Slider

Ritter Battery

Willys Widgets

Paralinx LLC

Gamma Ray Digital Inc

Broadcast Solutions Inc

Aerial Filmworks

Rig Wheels Passport

Opal

Metropolis Post

CineTape

CineLab

Visual Products

Gamma Ray Digital Inc

Media Blackout - Custom Cables and AKS

Technodolly

Willys Widgets

Wooden Camera

FJS International, LLC

rebotnix Technologies

Tai Audio

Broadcast Solutions Inc

Abel Cine

Ritter Battery

The Slider

Glidecam

Paralinx LLC