Electronic flash light.
How we see, color films are produced for daylight, especially sunny, or for photographic lamps significantly revolted. So what should you pay attention to when using electronic flash lamps which are becoming more and more popular?
However, electronic flash light is adapted to color films, however, these devices have very short exposure times and produce flat spots, soft images, just like it happens in black and white materials, so that such pictures on color films need to be developed 20-30% longer. This does not apply to reversible membranes. Therefore, normal and ultra-short exposures should not be taken on the same film, using flash light. When submitting flash-illuminated films for development, the developer should be informed, which will make them last longer. The same applies to reproduction, what will we come back to.
Regardless of the formation of a soft image, due to ultra-short illumination by an electron flash lamp, there is another reason for the softening of the image caused by this, that a reflector mounted on a camera produces a shadow-free image. These circumstances, as we said above, cause, that reversible materials will be slightly underexposed in these conditions, while negative materials exposed under the same conditions will have the correct exposure. Therefore, for reversible materials, lower photosensitivity values than those stated on the packaging should be used. Flat motifs with sufficient exposure for negative film will produce reversible film, with the same light sensitivity according to the DIN standard, invalid images.
Flash photos on color negative material are not difficult, while on reversible material, the only difficulty is the need to use appropriate filters. The spectrum of light emitted by an electron flash lamp is very similar to daylight, so that for materials adapted to daylight marked with the letter T, we do not need to use any filters.
If the flash gives a slightly blue haze to the daylight reversible T material, use a very weak yellow filter, has an example of a K filter 32. Flash lamps containing magnesium or aluminum wires or foils inside (RFT-Fotoblitz, Osram Vacublitz, Philips Photoflux) they give a more yellowish light. There are special flash units for color films -- with blue tinted glass for T daylight materials and yellow for K artificial light materials. White glass bulbs can always be used for artificial light negatives, while with approximately double the exposure time, they can also be used for materials intended only for daylight. Reversible materials intended for artificial light, however, require the use of non-tinted lamps, however, in these cases, a filter should be used in front of the camera, e.g. K 32.