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In over 30 years of making optical filters, Ira Tiffen created the Pro-Mist, Soft/FX, Ultra Contrast, GlimmerGlass, and others, netting him both a Technical Achievement Award from the Academy of Motion Picture Arts and Sciences and a Prime-Time Emmy Award. Elected a Fellow of the SMPTE in 2002, he is also an Associate member of the ASC, and the author of the filter section of the American Cinematographer Manual.

Telling a story visually involves many layers of �reality.� Very little is actually what it seems. The goal is to get the audience to buy in to the story, to become absorbed in what�s going on. And stay absorbed. You don�t want to �jar� them out of their ability to believe in what they�re seeing. A key component to this is continuity.

Continuity issues abound in filmmaking. Making sure that, chronologically, everything makes sense. Nothing is to be where or as it shouldn�t be at that time. Where was that pencil when it last appeared on the desk? Is that a dent-free car after the accident happened that, story-wise, put a dent in it? And so on. However, other, less intuitive elements enter the picture when you apply imaging effects.

Like everything else, effects alter what the audience sees and you will want to keep track of and maintain consistency in what you are showing them. What we�re talking about here is really fine-tuning, and getting these details right shouldn�t be allowed to get in the way of capturing an otherwise great scene. Being sensitive to the relevant issues will make it easier. Here�s what you want to be sensitive to�

Polarization:

Polarizers offer special opportunities for continuity issues. Using one to deepen a blue sky will make the clouds stand out more, and if the patterns appear to alter more frequently than they should, that could be problematic. If you keep cutting back to a talking head with sharply delineated clouds behind it, it helps not to draw attention to the fact that the cloud patterns may not match the timeline. This is really nit-picking; usually the action will get the attention, but in some cases, being aware of this detail can help. In addition, the amount of sky-darkening is dependent on the shooting angle relative to the sun. If you pan, the effect will change. If you edit together two scenes where the angle is different, the sky brightness may not match. When editing scenes together, it is best not to deepen the sky in any of them to maximum effect as it will be harder to maintain throughout. Rotate the filter to get just enough effect to enhance the image and it�ll leave more latitude to make suitable adjustments to later scenes for consistency.

Reflections from water and windows are also reduced by polarizers. Eliminating all reflections from such surfaces may not be best for the story. Rotate the polarizer so as to retain a minimal amount of reflection and you will make it easier for the audience to know what they�re seeing, and still provide greater clarity through the surface. As before, continuitally speaking, shot to shot, it is easier to match a modest degree of reflectivity than none, as the angle changes, since there is only one angle, thirty-three degrees to the reflecting surface, where you can remove all of it. And then just rotate the filter to keep it as similar as you can from there.

Contrast:

A typical situation: a wide angle location-establishing shot, say, a cityscape from a distance at dawn. Next scene is a long-lens enlarged detail of the same cityscape. In the initial shot, the wide field-of-view places the far-distant city in the background, a small part of the overall image. What is at the edges is closer and makes up more of the scene. Now, in most exterior locations, there is a certain level of atmospheric haze that builds up so that far-distant objects are more obscured and of lower contrast. What�s closer-in is less affected. The result is that the wide angle scene is largely of higher contrast than the long lens distance shot. Blending them Tiffentogether requires subtly toning down the contrast of the first scene to blend in better with the second. You can use a contrast control filter such as a Low Contrast, to make this adjustment. Using an UltraContrast filter will tone it down without creating highlight flare from streetlamps and car headlights, which, not being similarly visible in the second scene, could also disturb the continuity.

Other situations: sunlit exteriors where bright light and deep shadows may not be controllable in a wide shot, but may be toned down in a close-up (because it can); use a contrast reduction filter to blend the former into the latter.

Diffusion:

Soften the image with diffusion and you can reduce �her� age by years. However, if �he� is also in the scene with �her,� what to do? You don�t want to unnecessarily impair his rugged looks with diffusion. Well, there are a couple of ways to deal with this. When both appear together, you can use a half-diffusion filter, half clear and half effect. Position the diffusion, of course, on her and the clear half on him. Then maintain the same diffusion effect on her when she is alone.

An alternative, when a half-diffusion filter isn�t available, or the action won�t allow its use, is to modify the diffusion strength as follows. For the close-up on her use the best diffusion filter grade for the circumstance, or something slightly weaker. For the close-up on him use a weak version of the same effect. Put them both together using a moderate strength grade that falls in-between. That way, there won�t be as much difference between him alone and her alone to when they are both together, yet he will be less diffused and she more. It will also reduce the audience�s attention to the use of diffusion on her, for which she will be most thankful to you. Better that they should think she still looks that good�naturally!

Flare:

Using a Mist or Fog filter to flare highlights can be most effective in creating �atmosphere.� Let�s look at what happens with these effects when changing focal lengths. In a wide shot, a grade 2 effect may look just right. At a longer focal length the same filter may be too strong and disturb the continuity. Why? Let�s see how this works.

Using a flare-producing filter on a lamp will cause the light to extend outward from its surface a certain distance. Let�s say that the particular filter grade you are using flares out a distance equal to the diameter of the lamp. What happens when you go to a longer focal length? For our purposes, this just changes the magnification, enlarging everything within the image equally. If the lamp diameter is one-twentieth of the image width to start, zooming in will make it relatively larger, say one-tenth of the image width. What happens to the flare? Well, with the same filter grade, the ratio of the lamp diameter to the flare distance remains the same. To prove this, just try it. However, the flare, like the lamp, becomes a larger portion of the overall scene, and may become too predominant to retain similarity in appearance to the wider shot. Thus, you may decide to use a weaker filter grade when at a longer focal length. There is no standard reduction in grade that correlates to a particular increase in focal length, but you�ll generally find a suitable grade easily- none of this is rocket science.

Color:

As the sun travels through the sky, dawn to dusk, the color temperature of the light it produces changes as well. Shooting various exterior sequences through the day that, in the film, are to take place over a short period of time may require color temperature adjustments to maintain consistent appearance. Optically, Coral filters were originally designed to accommodate this change when using tungsten-corrected film in daylight. Offering a range of densities of an orange daylight-to-tungsten conversion filter, it provides room to handle most any alteration. The same concept can apply to any other format; use the tools, from optical filters to color grading, to match your production needs.

Whether you create the above effects optically or digitally, the concern here is the same: be aware of what you�re doing to the image and keep in mind how it fits in to what the audience is expecting to see. It�ll help you to attain what you�re expecting to see as well.

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Check out this article in the June 2007 print edition of StudentFilmmakers magazine, page 14.