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Hi-Con Filters

Published : 29th August 2003


I have a client who would like to shoot color film/video and increase the black level optically. The goal is to drop in a "Hi-Con" filter (maybe in various grades) to increase contrast neutrally (darken shadows) while maintaining all other levels and ideally with a very small amount of T-stop compensation.

Of course a hi-contrast color image can be created 'in-camera' with lighting, and some contrast can be gained outdoors with a Polarizer. However this goal of the 'hi-con filter' would be different, more akin to a yellow, orange or red filter in B&W photography.

Again, the desired effect is darkening shadows (without a color shift) and leaving everything else alone.

Does anyone know if this filter exists, or if this is even a physical possibility?

I spoke with Stan Wallace at "The Filter Gallery" and he hadn't ever heard of such a piece of glass and recommended I send an email to Ira Tiffen (who I've CC: on this post)

Thanks in advance for any suggestions.

Illya Friedman
Senior Camera Rental Agent
Moviola
Hollywood, CA
www.moviola.com



A high contrast filter...

While I like the concept, I don't think that this sort of filter is possible- at least for color film. Video does have that capability in the menu. You mention all the possible ways that contrast actually can be increased with the exception of the haze filter. The "skip bleach" process will increase contrast, and there are filters that will "enhance" certain colors.

Years ago I assisted a DP who insisted that an ND (neutral density) filter would increase contrast. I don't think so. There are subtle things happening there that you could say would actually reduce contrast…hardly noticeable though.

I personally dislike any filter that reduces contrast- low cons and "milky" diffusion filters. However, having said that I almost always use a rear net for video which does reduce contrast. I would tell your client the best place to control contrast is in post. Only there can you fine tune and get exactly what you see.

Edwin Myers, Atlanta dp



Illya Friedman wrote:

>I have a client who would like...to drop in a "Hi-Con" filter

Filters that lower contrast abound. They do the relatively simple job of redirecting light available in the scene in a manner that effectively lightens shadows with minimal effect on highlights. They don't have to distinguish between highlight areas and shadow areas; its just that when the filter adds, say, 1% of the overall luminance to the entire scene, it has a greater effect on shadows than highlights, (because while you won't notice the addition of 1% to 99%, adding 1% to 0% is very noticeable) thus reducing the apparent difference between them and thus "lowering contrast."

Filters that alter grey scale tonality in black-and-white imaging work because while they are intense enough to bias one part of the spectrum at the expense of another, their color is removed as an issue because the recording medium is color-blind and only sees shade of grey. This doesn't really apply well to color imaging.

The filters that under certain circumstances can be said to increase contrast optically like polarisers, color enhancers, and haze filters, work only in very specific situations that may not apply to what you are trying to do.

To truly create a "Hi-Con" filter, it would have to increase the difference between highlight and shadow luminance levels. It could lighten highlights and/or darken shadows. To do so, it would have to be able to intelligently differentiate between highlight and shadow areas, unlike in the low contrast example, because what you do to one has to be the opposite of what you do to the other. To increase contrast, you can't simply add or remove light from everything equally, and this is what makes it harder to do.

As far as I am aware, a filter that does this won't available in time for your current project, so electronic manipulation in post is probably your best bet.

Ira Tiffen
The Tiffen Company
Hauppauge, NY 11788



Regarding a potential Hi-Con filter, Brian Heller wrote :

>Any idea of when it might be ready?"

Unfortunately, I am not in a position to divulge such proprietary information at this time.
Ira Tiffen
The Tiffen Company
Hauppauge, NY 11788



Ira Tiffen wrote :

>Unfortunately, I am not in a position to divulge such proprietary >information at this time.

Still working on how to shift those annoying Laws of Physics?

Ira's just having a little fun but for those that don't realize it, anything that is placed in front of a lens will cause some degree of scattering of light, therefore reducing contrast. This is infinitesimally true even for an optical flat. Due to certain properties under specific conditions, a few filters such as Polarisers, haze filters and Enhancing filters can effectively increase the relative contrast of an image. But in general there is no such thing nor will there ever be such a thing as an optical Hi-Con filter.

Mitch Gross
NYC DP



Ira Tiffen Writes:

>Unfortunately, I am not in a position to divulge such proprietary >information at this time.

Mitch Gross writes in reply :

>Still working on how to shift those annoying Laws of Physics?

I have the highest regard for Ira's abilities and I'm willing to wait. Of course, I'd like to see an adjustable version; you know, the kind with the little knob on the side.

Brian Heller
IA 600 DP



Mitch Gross wrote:

>anything that is placed in front of a lens will cause some degree of >scattering of light, therefore reducing contrast.

As Ira pointed out, lowering contrast is simply a matter of adding exposure across the entire frame to effectively fog the shadow areas of the picture whilst leaving the highlights relatively unaffected. The conceptual Hi-Con filter would need to intelligently distinguish areas of shadow or light in the frame and either suppress exposure (for shadow areas) or augment it (for highlights) to increase the apparent contrast of the image.

This is of course impossible - in front of the lens. However if the filter is positioned behind the lens, sufficiently close to the film plane, then it could 'react' selectively to the areas of shadow and light in the resolved image passing through it.

Then all one would need to do would be to find some phlogiston to add the glass and hey presto! A Hi-Con filter.

I'm thinking of marketing them in fact and if anyone try’s to sue me I'll just tell them that the name derives from, Highly Improbable-Confidence trick.

Tom Townend,
Cinematographer/London.



Has anyone done more testing with the Tiffen Soft Con filter?

This filter is suppose to reduce contrast by adding density to the highlight areas ... rather then the typical adding light to the shadow areas.

By making the highlights darker...it can create an illusion of more contrast...by making everything a bit darker. Of course if one lightened everything back to "normal"...the effect was one of slight diffusion. Supposedly (Ira?) one isn't suppose to compensate for this filter, that definitely has an ND quality to it...varying in density by grade of filter.

The only extended project that I know of that used Soft Cons through out... was "Blue Sky," Dp'ed by Steve Yaconelli. I AC'ed on that film for a few days. We did however compensate for the filter's density...and so the effect was minimized.

I played around using Soft Cons on my home Hi-8 camera years ago...and it could darked highlights...and it did seem to increase apparent contrast.

Perhaps the fellow that was asking about a Hi-Con filter could experiment
with Soft-Cons ...

Mako, Makofoto Images, Glendale, CA



>This filter is suppose to reduce contrast by adding density to the >highlight areas...rather then the typical adding light to the shadow areas.

Couldn't you also use ND grads or attenuator grads to selectively darken bright areas in the frame and increase apparent contrast?

Jessica Gallant
Los Angeles based Director of Photography
West Coast Systems Administrator, Cinematography Mailing List
http://www.cinematography.net



Jessica Gallant writes :

>Couldn't you also use ND grads or attenuator grads to selectively >darken bright areas in the frame and increase apparent contrast?

Hmmm…Darkening light areas would seem to *reduce* apparent contrast, yes? Or am I misunderstanding what you're suggesting?

Dan Drasin
Producer/DP
Marin County, CA



>Hmmm…Darkening light areas would seem to *reduce* apparent >contrast

They would increase the apparent contrast of areas which would otherwise be over-exposed w/out the ND grad.

For example, instead of the sky being blown out and white, it would be blue and white clouds would be visible there by increasing the amount of detail in the frame and the apparent contrast of the image.

Jessica Gallant
Los Angeles based Director of Photography
West Coast Systems Administrator, Cinematography Mailing List



Referring to Soft Contrast filters, Mako wrote:

>By making the highlights darker ... it can create an illusion of more >contrast ... by making everything a bit darker."

In reply, Jessica wrote :


>Couldn't you also use ND grads or attenuator grads to selectively >darken bright areas in the frame and increase apparent contrast?"

Soft Contrast filters are a combination of our standard Low Contrast filter series with an ND 0.3 in each grade. That means there is a consistent one-stop light reduction throughout the Soft-Con range, and only the light scattering component which lowers contrast increases in strength with increasing grade number.

The concept centres around wanting to render highlights darker than they would otherwise appear, to show more highlight detail, and to specifically do so in a manner that fits in with the often-used practice of maintaining a particular T-stop to better maintain lens sharpness and depth-of-field characteristics. Used the way we suggest, not compensating for exposure, the filter will darken highlights by one stop, which, if it were just an ND filter, in darkening everything by one stop you would not see a real change in contrast.

The difference is that the low contrast component will still lighten shadows. The net result is that you have raised shadow luminance AND reduced highlight luminance simultaneously. You could accomplish this by closing down a stop and using a Low Contrast filter, but you would have to make the stop adjustment, which may be undesirable. When you compensate for the one stop of the Soft Con filter, you are effectively taking advantage of it as an ND filter to allow for a larger lens opening while retaining its ability to lighten shadows and reduce contrast.

Think of exposure adjustments as able to either raise or lower luminance levels of everything. Highlights up, shadows up; highlights down, shadows down. The only time this results in an apparent increase in contrast is in parts of the scene that are either black from underexposure or white from overexposure; in either instance, adjusting exposure will bring out more detail and thus more apparent contrast. But contrast is still the difference between the luminance levels of highlights and shadows, and to effectively increase this you may need to be able to treat both differently, as I have written earlier.

Grads and attenuators will allow overly bright areas to come closer to being properly exposed at the same exposure that you would use for getting good detail in otherwise darker areas, such as with an overly bright sky- a ND 0.6 grad will usually be enough to allow good detail in the average bright sky as well as in the darker foreground. However, these filters will not have an increasing or decreasing effect on actual contrast apart from the particular circumstances of apparent contrast changes I refer to above.

Ira Tiffen
The Tiffen Company
Hauppauge, NY 11788