1/3 overexposure, and ASA ratings

[Jon Rosenbloom]

I've always been a little curious about this. On the vast majority of filmed projects I've worked on, the DP has always overexposed the film by 1/3 stop, so if 7218 is on the camera, the meters are set to 400 asa, if 7277 is up, the meter is set to 250, and so on. Having shot a handful of films myself, I now do this as a matter of course as well. The footage just looks better. In fact, I haven't done any densitometry, but it seems that w/ that little bit of extra exposure I'm getting a negative that is more optimally dense than what would result w/ going w/ the asa rating on the film can. So why not just label 7218 as 400asa, and 7205 as 200asa, etc.?

[Rachel Oliver]

So why not just label 7218 as 400asa, and 7205 as 200asa, etc.?

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Hi;

 

Because that would be very misleading! Pushing/pulling away from the true asa of the stock are creative decisions but to assume this is what all film makers want would be very, well.... assuming.

 

Olly

[John Pytlak RIP]

I've always been a little curious about this. On the vast majority of filmed projects I've worked on, the DP has always overexposed the film by 1/3 stop, so if 7218 is on the camera, the meters are set to 400 asa, if 7277 is up, the meter is set to 250, and so on. Having shot a handful of films myself, I now do this as a matter of course as well. The footage just looks better. In fact, I haven't done any densitometry, but it seems that w/ that little bit of extra exposure I'm getting a negative that is more optimally dense than what would result w/ going w/ the asa rating on the film can. So why not just label 7218 as 400asa, and 7205 as 200asa, etc.?

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The Exposure Index (EI) is calculated from the sensitometric curve of the film processed in the normal ECN-2 process. It represents the exposure that will give good images having good shadow detail and dense (i.e., not "milky) blacks on a normal release print or telecine transfer. With a color negative film, slight overexposure places the scene information higher up on the sensitometric curve, resulting in even more shadow detail and "richer" blacks. Slight overexposure also reduces graininess, since the slower emulsions (smaller grains) of the film are used. What exposure you choose depends on the "look" you are trying to achieve. Normal is "normal". Underexposure will tend to give less shadow detail, less dense blacks, and a bit more grain. Increasing exposure will give more shadow detail, darker blacks, and tighter grain structure. The rated EI is a good starting point.

[Jon Rosenbloom]

  Slight overexposure also reduces graininess, since the slower emulsions (smaller grains) of the film are used. 

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Very interesting. Can you elaborate on the different emulsions that make up a given stock?

[John Pytlak RIP]

Very interesting. Can you elaborate on the different emulsions that make up a given stock?

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It's been discussed here and elsewhere many times before. In a modern color negative film, the emulsions are often made up of "fast", "mid", and "slow" speed silver halide grains, either blended, or coated as separate layers. The "fast" emulsions form the image in the darker areas of the scene, the "mid" in the midtones, and the "slow" in the highlights. By increasing exposure slightly, you put more of the image onto the smaller grains of the "mid" and "slow" emulsion components.

[Raffinator]

By increasing exposure slightly, you put more of the image onto the smaller grains of the "mid" and "slow" emulsion components.

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John,

Having done a bit of research on this topic in this forum, I have read (or misread) that this method of slight overexposure does not really apply for film that is going straight to telecine. Is this true? I am shooting a short in low light, high contrast situations, so it would help me a great deal to know. Also, what is a better choice for telecine, 7218 or 7229 (other than their inherant differences)?

 

Many thanks,

 

Raffi

[Kevin Zanit]

If anything I find telecine likes a denser negative.

 

In telecine if you have a negative that has a lot of information on it, you can use it or throw it away.

 

The point is with a print finish, a denser negative helps the blacks some (for the above stated reasons), and other than printing on premiere and using a bleach bypass to the print is the only way to effect your blacks (it is much more subtle than the other methods).

 

But in telecine, you can just simply crush your blacks, thus overexposing for better blacks is not critical to getting that look.

 

 

Kevin Zanit

[John Pytlak RIP]

John,

Having done a bit of research on this topic in this forum, I have read (or misread) that this method of slight overexposure does not really apply for film that is going straight to telecine. Is this true?  I am shooting a short in low light, high contrast situations, so it would help me a great deal to know.  Also, what is a better choice for telecine, 7218 or 7229 (other than their inherant differences)?

 

Many thanks,

 

Raffi

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The issue you may have read about is that a really dense negative can require so much gain on some older telecines that the highlights may have electronic "noise" that resembles a grain pattern. It's usually not an issue unless you have several stops of overexposure. Actually, a film with slightly lower contrast like the 7229 helps this situation, as it has very long latitude, and fits all that scene information into a density range more easily accomodated by the telecine or scanner.

 

On a related topic, Kodak is introducing a new VISION2 Film (7299) and Kodak VISION2 HD system at NAB this week, specifically designed for 16mm television production:

 

http://www.kodak.com/US/en/motion/campaign...005/index.jhtml

 

http://www.kodak.com/US/plugins/acrobat/en...05/workflow.pdf

 

http://www.kino-eye.com/archives/2005/03/kodak_to_build.html

 

Kodak to Build on Super 16 HD Film System for Television

 

Kodak will again be presenting a case for using Super-16 film for High Definition at NAB this year. From TV Technology, here's the announcement.

 

    16mm is hardly just for penny-pinching film students anymore. In fact, it hasn't been for quite a while, especially since the advent of Super 16, which can achieve remarkable HD quality these days (as long as it provides that required 16:9 aspect ratio). Upgrades to Kodak's Super 16mm film system--designed for HD and SD television--will be on display at the NAB show. The Kodak Vision2 HD System uses a new type of film with an advanced hybrid motion-imaging processing technology that takes advantage of proprietary Kodak coloring techniques. High-profile Kodak Super 16 HD motion pictures already aired have included "The Dale Earnhardt Story" last December on ESPN, and the mini-series "The Reagans" for CBS (which aired only on Showtime after a political firestorm over its portrayal of the former president).

 

    Kodak said its new HD-worthy film system is designed to take advantage of breakthroughs in emulsion and film scanning technologies, enabling cinematographers to maximize production values and the "superior quality of a film look" with the flexibility of using 16 mm cameras. The system combines the Kodak Vision2 HD Color Scan Film 7299 with Kodak's HD Digital Processor, which is a post production tool used to adjust digital files of scanned film to imitate the imaging of any Kodak negative--including "film elements" of grain, contrast and colors.

 

http://www.tvtechnology.com/tvsp/one.php?id=51

 

Kodak to Showcase Hybrid Post-Production System

 

Eastman Kodak will introduce the Kodak Vision2 HD System, a package of film and hybrid technologies. The system includes a specially designed, scan-only 16mm film for use with the latest transfer technology. The system also includes a Kodak digital processor that uses proprietary color science technology to adjust the scanned images for the designated film speed, color temperatures, as well as compensating for over- and under-exposure. The Kodak Display Manager System, another component, consists of calibration hardware and proprietary software that adjusts electronic display devices to emulate the look of film. Display Manager is also available standalone for Windows, Irix and Mac platforms.

 

The Vision2 HD System can also work with a version of the Kodak Look Manager System, which is available under a pay-per-use licensing model. Producers can buy a license key for the duration of a project. Trial versions are available to directors of photography.

 

The KODAK Telecine Calibration System 1002-V will also be featured in the Kodak booth, along with several types of Kodak film.

 

Kodak will display in Booth C6226.

[Raffinator]

Thanks, guys

 

Raffi

[Dominic Case]

So why not just label 7218 as 400asa

Exposing at the quoted EI rating gives a good all-round balance: shadows are black, and there is plenty of latitude on the over-exposure side. Exposing more than that increases image spread in the brightest of highlights, while less than the recommended exposure results in thin shadows and more apparent graininess.

 

So it's a question of individual priorities as to which side you prefer to stick to. The latitude you have for meter readings also comes into play. Meter readings are about the illumination of mid tones, but the issues with grain and ,milky blacks are about the exposure of shadows.

 

Finally, I suspect there's a little bit of marketing going on there as well. If a stock works at any speed between 320 and 500 (say), who is going to promote it as a 400 stock? When the opposition might promote a comparable stock at 500?

[Sam Wells]

One might as well consider Vision/Vision 2 stocks as variable EI in terms of *working practice*

 

Note the fine print re Exposure Index "recommended starting point"

 

That said, I think some cases overexposure / print down can be less that earth shattering. When 7274 (the first version) I did a test, shooting normal /print normal and shooting one over / print down one. On projection the difference was negligible. Later I did the same from the negative on a Spirit. Same thing, on the calibrated monitor you would not know which was which.

 

Now this was material that had hot highlights, but most of the info was on the straightline. As Dominic points out, if the issue were shadow detail one might want to modify accordingly.

 

Rarely have I ever found a Kodak box rating to be "wrong" -- but at the same time, what you do exposure -wise must be related to purpose (pace Ansel Adams !)

 

So I also agree with Kevin in this sense: in telecine, do you want wiggle room and if so, where ? :)

 

-Sam

Edited April 18, 2005 by SamWells

[David Mullen ASC]

Also, you have to be honest about how you tend to expose scenes... I like mood and tend to expose on the low-key side, so rating the stock slower keeps me from ending up with a thinner negative if I err in my exposure.

 

In other words, while at a certain lab, let's say, rating a 500 ASA film at 320 ASA will get your average printer lights up into the mid to low 30's instead of the high 20's, it doesn't mean that every shot will end up being printed that way because of the way we tend to creatively use a light meter.

 

So rating a stock only 1/3 of a stop slower, for example, may mean that you still end up with an average density IF you tend to err on the side of underexposing slightly. So it all depends on how you use your meter.

 

This explains why sometimes you read an article where the DP claims that he rated the 500 ASA stock at 1000 ASA, developed normally, and yet was printing at normal printer lights -- obviously they are the type of DP who tends to either like his print on the dark side, or tends to expose more fully than he finally prints for, or both.

 

In other words, if you are getting results you like using a particular method of rating or metering, then go ahead and use it.

 

Also, at least in terms of printing, but even in the telecine maybe, an accidental slight overexposure that is corrected darker often looks better than an accidental slight underexposure that is corrected lighter. So, with color negative, if you are going to err, err on the side of overexposure (unless shooting bright objects like snowy landscapes...)