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class="style10" Enhancing Filters
>Published : 13th January 2006
>Greetings. I am trying to better understand on the usage of enhancing filter ( reddish ). It subtracts the red spectrum of the light enhancing the blue spectrum. Observing its effect on skin tones, it is rather inconsistent maybe due to different lighting situations. At times it makes the skin tone go a bit orange-red and at others doesn't specifically do anything. Combining it with some warming filters can be fatal! Any experience and knowledge will be greatly learned from.
>Does the green enhancer do the opposite? Subtracts the green, enhances the red? Thank you.
>Kamal bou Nassar
>Kamal bou Nassar wrote :
class="style11">>I am trying to better understand on the usage of enhancing filter ( >reddish )...its effect on skin tones...is rather inconsistent maybe due to >different lighting situations."
>This yields the ability to absorb most or all of the light from about 570nm to 620nm, which is the band between green (550nm) and red (650nm). The effect can be understood by the following example:
>Rust red, muddy red, barn red, brick red all have an element of brown or orange in them. In fact, they reflect both red light and light that tends more toward the green. It is as if you mix red and green paint and get brown. When these reddish colours pass through the didymium filter, the wavelengths between green and red are removed, leaving the more scarlet red component to predominate. Colours that are brownish red are affected most; the closer the original colour is to scarlet red, the less the effect.
>That the colour of the filter is reddish in tungsten light, greenish in fluorescent light and more neutral in daylight is a matter of metamerism. This is the result of light having a different colour bias creating new colour relationships upon mixing depending on the alignment of the peaks and valleys in their respective spectral curves.
>This same effect causes the filter to produce somewhat different results depending on the subject, the lighting, and the colour sensitivity of the recording medium. Experimentation is the best way to judge the result of any particular situation.
>Green and blue enhancers each work in a roughly similar manner, by removing a portion of the spectrum enhancing the saturation of what remains.
>IRA TIFFEN wrote:
class="style11">>When these reddish colours pass through the didymium filter, the >wavelengths between green and red are removed, leaving the more >scarlet red component to predominate.
>Great and useful post, Ira. Always wondered exactly how enhancers worked.
>Are there other rare earth elements with different spectral characteristics?
>Jeff "not yet enhanced himself" Kreines
>Jeff Kreines wrote :
class="style11">>Are there other rare earth elements with different spectral >characteristics?"
>Yes, that's how the blue and green enhancers are made, using different elements. While there are a number of materials available, not all are particularly useful for manipulating light.
>Fortunately, some are.
>Great post, Ira. As always, very informative and to the point.
>Is there exposure compensation with these kinds of filters? If so, does it vary in different light sources?
>Can you meter through the filter with a spot meter and get a reliable offset?
Randy Miller, DP in LA
class="style11">>This yields the ability to absorb most or all of the light from about >570nm to 620nm
>Ah! I'd always assumed that enhancers removed wavelengths between the primaries - good to have it explained so clearly - thanks, Ira.
>I have a pair of Maui Jim sunglasses, which in addition to UV and polariser filtering, also enhance colours quite dramatically - especially reds and greens. The world is an amazing place through these lenses.
>Would I be right in guessing that they also use this rare earth filtering?
>If so, (and also with the colour enhancing camera filters), I guess that they would knock out sodium vapour lighting (580nm): probably something to watch for, but also a good way to check out my sunglasses and see if that's what they are. I'll go and try that out. At the price I paid for them, I guess they were at least "rare earth" - maybe more like "endangered earth"
>I used the Tiffen Enhancer for the entire second half of "Big Top Peewee" after the Circus arrives. It's pretty trick.
>We re-mastered in HD last year. But I don't think the new DVD is out yet.
>On another note I am happy with the newly released and re-mastered "Testament." I'm really proud of that movie. Shot in 20 days for about $700,000.
>Steven Poster ASC
>Dominic Case wrote :
class="style11">>I have a pair of Maui Jim sunglasses, which in addition to UV and >polariser filtering, also enhance colours quite dramatically - especially >reds and greens...Would I be right in guessing that they also use this >rare earth filtering?"
>Very likely, Dominic. Typically today, high-end sunglasses use every optical trick there is to provide the best eye enhancer/protector optics-in-a-frame.
>Combining the abilities of various solid optical glass melts, with precise percentages of materials such as the aforementioned "endangered earth" elements (a great term!) usually from one of the big scientific raw-glass makers, with the fine-tuning qualities of multi-layer coatings, there isn't much you can't do. It also appears there isn't much limit to what you can charge for them.
>Of course, our eyes are rather important...
Currently Port Washington, NY
>Randy Miller wrote :
class="style11">>Is there exposure compensation with these kinds of filters? If so, does it >vary in different light sources? Can you meter through the filter with a >spot meter and get a reliable offset?
>Excellent query...The typical enhancer as provided by Tiffen is designed to absorb approximately one stop, or 50% of the light, which will need compensation. In my experience, there should not be a need to vary this depending on the type of lighting.
>The reason for this is the same as the reason the filter works at all. If we were to start from scratch in choosing the logical filter to produce enhanced reds, we might begin with a red filter. After all, this would certainly increase the red-quotient in the image. However, it would also reduce blues and greens in a disproportionate manner that would make everything appear red-tinted.
>The trick that the enhancer pulls off is that it produces an approximately neutral overall coloration while still increasing saturation of reddish objects. This is due to its narrow (at least for a broad-band filter) absorption band between red and green and a fluctuating but generally neutral net effect elsewhere in
the visible spectrum. It is this latter feature that should provide a reasonably accurate result when using a meter through the filter.
>As always (the filter-man's official disclaimer) experimentation is your best assurance of a satisfactory result.
>But it helps to know where to start...
Port Washington, NY