How the filter works in the story

The ‘special filter’ that Jan uses in the story is a selective colour filter technique (similar to a notch filter or a very narrow bandpass/block filter). Here are the details:

Basic principle – selective absorption or interference

Normal colour filters (e.g. a red filter) only allow light of a specific wavelength to pass through and absorb or reflect the others.

In the story, it is the other way round: the filter is designed to block or greatly attenuate precisely the wavelength range of the bright red (or later other coloured) bikini fabric. Everything else is allowed to pass through.

The fabric primarily reflects red light (approx. 620–700 nm).

When the filter removes almost all of this red light, the fabric appears dark, grey or transparent in the photo or video – depending on the lighting and post-processing.

The rest of the image (skin, background) retains a warm, vintage-like look.

Why it works with ‘normal’ swimsuits

The story uses special fabrics that have a very narrow, intense colour reflection (e.g. certain synthetic fibres with a high red content).

Such fabrics really do exist – they are often found in sportswear or swimwear. A well-tuned filter can then ‘erase’ almost only this colour, whilst skin tones and other colours are largely preserved.

The result looks like an ‘invisible’ bikini, even though the person is actually fully clothed.

Realistic technical implementation

Optical filter on the lens: A bespoke interference filter (dichroic filter) or a very narrow notch filter that precisely blocks the red spectrum of the fabric. Such filters are available commercially (e.g. for microscopy or spectroscopy), but they are expensive and must be tailored to the exact colour of the fabric.

Digital post-processing: In practice, one would also significantly reduce or set the saturation of the exact red tones to zero in-camera or in post-production (e.g. using DaVinci Resolve or Photoshop). This creates the ‘vintage look’ because only this colour channel is missing. Therefore, the images are saved in RAW format so that the red channel can be removed later.

The great thing about RAW: we can switch the filter on and off at any time later.

• With the filter = Lisa looks completely naked in the picture.
• Without the filter = Lisa looks perfectly normal in her turquoise tankini.

This gives us enormous flexibility. For example, we can:

• Upload the filtered (naked) version to OnlyFans.
• Keep the unfiltered (clothed) version for you or as ‘proof’.
• Later, we can even try out different filter strengths or apply the effect only partially.”

Combination with fabric: The fabric must have as pure and intense a colour as possible (no red mixed with other tones), otherwise the effect will not work cleanly.

Limitations & why it isn’t perfectly ‘invisible’

It works best with highly saturated, uniform colours (bright red, bright yellow, bright blue). It works less well with pastel shades or patterned fabrics.

Skin tones can be slightly distorted (becoming warmer or paler).

In reality, you would often need a combination of a filter + targeted lighting + post-processing to achieve the effect as cleanly as in the story.

It is not ‘true invisibility’ as in science fiction, but an optical trick that only works on camera – not to the naked eye.