There are occasions when you can achieve this effect without any additional gizmos:
- Longer than standard focal length (eg 100mm+ on full frame - wide-angle lenses tend to give the 'string-of-pearls' effect not the flaring you desire). PLUS
- Main light source JUST out of frame or even in shot - ie strong backlighting. PLUS
- SMALL aperture eg f/11 or smaller. Larger apertures tend to give you a slash of flare across the image rather than an overall veiling.
With this scenario, you do need all three of the above elements to get the effect, not always possible.
An alternative is, as foodguy says, nylon stocking/pantyhose. This is the classic 'Hollywood Glamour' look of the 1930s/40s
(not 1980s as mentioned in the link
). Here, you have more variations possible:
- BLACK legwear will give the least effect, all other things being equal. Depending on stretch, you may require exposure compensation.
- WHITE legwear will give the greatest effect.
- You can vary each legwear effect by the amount by which you stretch the material. More stretch increases the size of each hole (the yarn remaining virtually the same diameter irrespective of stretch) hence
- More stretch reduces the effect.
- Less stretch increases the effect as more light passes through the yarn than through the holes.
- The amount of stretch changes the ratio of light passing through the holes to light passing through the yarn of the legwear. The yarn itself doesn't stretch by very much, stretching simply opens up the holes in the knit of the material relative to the diameter of the yarn.
- In addition to stretch you have to consider that he lower the denier of legwear, the smaller the effect.
- This technique brings with it a softening of overall sharpness as the image-forming light is passing through the nylon/polyester yarn and is marginally distorted by it.
Hoya/Kenko, Tiffen, Cokin, Lee & Fformat all still make 'Fog filters' which have the desired effect to some degree but much depends on your
controlled use of ambient light direction in addition to your OCF.
It's
vaguely possible to get the effect you want simply by breathing on the front of your lens and
immediately taking the shot through the condensation formed. However, this tends to be completely unrepeatable so probably would cause you more frustration than success!

Good luck!