Micro-photography (5) Medical experimental
Micro-photography (5)- Medical experimental
In the microscopic photography, it is usually used to narrow aperture method to improve the image contrast.
Aperture field with the aperture and change, always outside the cutting aperture.
aperture function Solvay Group
aperture zoom, photo contrast becomes smaller.
aperture diaphragm contraction is too small, photo contrast increased, but the resolution becomes smaller.
aperture diaphragm contraction of not less than 60% of the numerical aperture objective lens.
3. Film choice clinical (1) Film Type: photographic film used in hard-film (transparent glass coated with photographic emulsion formed) and film (film and film). Film specifications used 135 and 120.
(2) Film Performance:
Color film: reversal film and negatives, but also were divided into daylight-type, light-and dual-type fluorescent light.
black and white film:
colorblind film only feel the film is called blue-violet and ultraviolet light (for black and white, blue-violet shade of the photographic image, but not be used to capture red, green, yellow and other colors of the images);
be able to feel the blue-violet color separation films, yellow-green light of the film (other than the red-colored specimens, the can be widely used in micro-photography);
panchromatic film can feel all the visible light spectrum, said film (shades of the scene can be better performance, black and white many levels, and contrast small).
Sensitivity: the sensitivity of the film to light. Sensitivity Unit:
set (DIN) system, every difference of Sanding Speed on the difference between the double, such as the 21 set 18 set twice, and so on.
Medical trial Standard System (ASA), which provides increased value to double to double the speed of light-sensitive, such as ASA 100 for the ASA 50 twice. 21 be the equivalent of ASA 100.
photomicrography film seeks to use a low sensitivity.
(3) The selection and application of the film
Large selection of hard-film micro-video camera, mini-micro-cameras use film.
clinical experimental Minicomputer need to be amplified relative to the film negatives, so use thin film silver grains.
experimental photomicrography asked to select the speed contrast large (17 ~ 19) set, and slow (14 ~ 16) set, and even special slow (9 ~ 13) will film, generally 18 set (ASA 50) The following is appropriate.
Medical color blindness films and color separation films are suitable for micro-photography, in particular, micro-photography to color separation films the best, full-color film can also be used in microscopic photography, but often use the appropriate color filters, in order to increase contrast in order to achieve good results.
clinical use fluorescent lighting type or dual-mode color negative film with a color sample.