Darkroom & Film Processing

Question 1

Safe lights inside dark rooms need to be:

Answer 1

4 feet from work area
Proper bulb wattage
Covered by filter only allowing red end of spectrum
No film exposed more then 3 min

Question 2

Safe light test?

Answer 2

incrementally exposing undeveloped film to dark room conditions in 30 second intervals for 3 min

Question 3

what are the three Ts and what is it used for?

Answer 3

time, temperature, titration

used in processing
increasing these will cause film overdevelopment caused by processor induced fog forcing the development of unexposed SILVER HALIDE CRYSTALS film is darker

Question 4

Manual processing

Answer 4

68 degrees, development for 5 min, fixer for 10min, wash 20min, dry 20-40min

Question 5

image creation: Exposure

Answer 5

the film is exposed to light

99% of image created by light emanated by screen

1% of any visable image comes from direct exposure of a silver halide crystal by an x-ray photon

a small sensitivity crystal consisting of sulfur collects spare electrons formed by this process

in this state we cant see image on film LATENT IMAGE

Question 6

Image creation: Development

Answer 6

developer donates electrons that creates elemental silver (black in color results in black and grey color on film

Question 7

Image creation: Fixing

Answer 7

fixer removes all unexposed silver halidesstopping ant exposure afterwards

Question 8

Image creation: washing

Answer 8

the final wash clears all chemicals on the film surface and in the emulsion

final wash prevents fixer chemicals from continuing to cause chemical changes

when washing is insufficient artifacts emerge over time

Question 9

Developer pH is in what range?

Answer 9

10-11.5 strong base

Question 10

Developer: activator

Answer 10

sodium carbonate- softens gelatonprotective cover on film preserves basic pH

Question 11

Developmenter: Reducing agent

Answer 11

hydroquinone or phenidone reduces EXPOSED silver halide to black metallic silver

Question 12

Developer: preservative

Answer 12

sodium sulfate

Question 13

developer: restrainer

Answer 13

potassium bromide and acetic acid

Question 14

Fixer: pH? and what is it called

Answer 14

acidic pH 4-4.5

known as a clearing agent

ammonium thiosulfate is the key ingredient dissolves silver halide

Question 15

what is the tanning agent used?

Answer 15

potassium alum

Question 16

Activator used is

Answer 16

acetic acid to neutralize the developer

Question 17

What are the characteristics of an automatic developer system?

Answer 17

• Higher temp
• Stronger acid
• Constant agitation of chemicals
• Rapid through put of film
• Chemicals degrade more quickly at higher temp
• underreplenishment= grey appearing
• overdevelopment causes increase in fog and wastes chemicals

Question 18

What are the causes of lowered contrast on a film caused by adverse conditions in the dark room

Answer 18

-safe light fog
room temp
chemical fog from too hot processor
chemical fog from too concentrated chemicals
film past experiation date

Question 19

What needs to be done every 1-2 months

Answer 19

complete chemical chack and tank clean

check replenisher rates

check cycle time

Question 20

Sensitometer is a machine that does what?

Answer 20

exposes the film to a step wedge of known densities

Question 21

H&D curve is a graphic measure of what??

Answer 21

a graphic measure of how a film records density over a range

Question 22

H&D curve graph

Answer 22

graph plots optical density vs log relative exposures

3 components: toe, body, shoulder

Question 23

Toe of curve

Answer 23

starts above zero optical density even in the absense of any exposure as theres always a small amount of light absorbtion & “auto exposure”

Question 24

Body of the curve

Answer 24

straight line component of the curve

short lattitude film has a high slope =high contrast smaller changes in grey density per unit exposure

long latitude film has lower slope and is a lower contrast film small change ingrey densty more shades of grey

Question 25

shoulder of the curve

Answer 25

this represents maximal optimum density the fild will achieve no matter how much mAs or kVp you throw at it

Question 26

if two H&D curves for two different types of film are plotted next to each other which one is faster?

Answer 26

the left one is faster

Question 27

on the densimeter what is the scale? and what is the meaning of the maximum vs minimum value

Answer 27

0-4

0= zero absorbtion of light through the film or the film transmits 100% of inciedent light through the film

4= 100% absorbtion film is entirely black

Question 28

What are the measurements we obtain to track performance of the processer over time?

Answer 28

speed index- finding step on sensitomeric step wedge strip
contrast index- difference in optical density
gross fog index- base plus fog

Question 29

Gross Fog index

Answer 29

base plus fog
inherant optical density of a film when it has not been exposed at all and was just run through blank

the length of the toe of the H&D curve is related to the films sensitivity to fog

therefore, the longer the toe the less sentsitive to fog the film is

Question 30

What are the fluctuations valus you should see for

speed index
contrast index
gross fog index

Answer 30

+/- -0.15 speed idex
+/- -0.15 contrast index
+/- -0.03 gros fog index

Question 31

the spectral sensitivity of film is the bandwhidth of light that is most sensitive to during exposure

Answer 31

should match the spectral emission of the screens that it is paired with

Question 32

speed vs detail film is a function of crystal size and looks like what?

Answer 32

slow speed with best detail: small crystals in thin layers

Medium speed with medium detail:

• medium sized crystals in a medium thick layer of the film
• large crystals in a thin layer
• small crystals in a thick layer

Question 33

slow speed with best detail:

Answer 33

small crystals in thin layers

Question 34

Medium speed with medium detail:

Answer 34

• medium sized crystals in a medium thick layer of the film
• large crystals in a thin layer
• small crystals in a thick layer

Question 35

Fast speed with low detail:

Answer 35

large crystals in thick layers