Midterm 2 Flashcards by Kirsten Sparley

List the darkroom essentials

Film processors
Loading bench
Film bin
Film identification printer
Safelights

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Safelights must not exceed ___ watts

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Safelights must be at least ___ feet away from work area

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Undeveloped film must not be exposed to safelights more than ___ minutes

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Safelights usually only allows light from the ____ end of visible light spectrum?

Red (GBX filter)

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_______ consists of incrementally exposing undeveloped film to dark room conditions in 30 sec intervals for up to 3 minutes.

Safe light test

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What are the steps of film development?

Exposure
Development
Fixing
Washing
Dry

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What part of film development/image creation is when the film is exposed to light?

Exposure

Note: 99% of the image is created by light emanated by screens. 1% or less comes from direct exposure of silver halide crystal by an x-ray photon

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Exposure of the film causes silver bromide crystal to what?

Separate into a silver ion and a bromine ion

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What step of film development is the latent image created?

Exposure

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What does the developer do in film development?

Donates electrons that create elemental silver

Note: black in color

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Between developer and fixer, what happens?

Wash stop bath to remove excess developer

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What does fixer do in film development?

Remove unexposed silver halide crystals from emulsion.

Permanently stops exposure beyond what has been done prior to developer

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What does the final wash do in the film development process?

Clears all chemicals on the film surface and emulsion.

Prevents fixer chemicals from continuing to cause chemical changes to emulsion after the finished product has been produced.

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What happens in the film development process if washing was not good enough?

Overtime the film degrades: brown color, acetic acid smell, etc

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What pH is developer?

pH 10-11.5, strong base

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What is in developer?

Activator
Reducing agents
Preservative
Restrainer

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What does “activator” do in developer solution and what is it?

Sodium carbonate

Softens gelatin protective cover on film, Makes alkaline pH at >7

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What do the “reducing agents” do in developer solution and what is it?

Hydroquinone or Phenidone (Metal or Elon)

Reduces EXPOSED silver halide to black metallic silver

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What does the “preservative” do in developer solution and what is it?

Sodium sulfite

Prevents oxidation

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What does the “restrainer” do in developer solution and what is it?

Potassium bromide, acetic acid

Prevents chemical fog in new developer

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What is in the fixer solution?

Clearing agent
Tanning agent
Activator

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What does the “clearing agent” do in fixer solution and what is it?

Ammonium thiosulfate

Dissolves undeveloped silver halide, removes it from emulsion

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What does the “tanning agent” do in fixer solution and what is it?

Potassium alum

Shrinks, hardens, preserves emulsion

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What does the “activator” do in fixer solution and what is it?

Acetic acid Neutralizes developer, stops the development process, maintains acid pH

Processing is a function of 3 T’s

Time Temp Titration (chemicals)

What causes film overdevelopment?

Increased time, temp or titration. Note: overdevelopment = darker film

Film overdevelopment is caused by processor-induced fog which is the forced development of

unexposed silver halide crystals by too much processing

Manual processing: ___˚F, and list time for development, fixer, wash, dry

``` 68˚ F 5 min development 10 min fixer 20 min washing 20-40 min drying ``` Summary: estimated 1 hour total for each film in manual processing

Automatic processing: temp ____ ˚F and ave. time ____ mins

92-96˚F | 1.5-3 mins

Benefit of automatic developer vs manual

Faster, constant agitation, consistency

If you don’t take many films, but you keep your processor running all day, your machine requires [more/less] chemical replenishment

More Because chemicals degrade more quickly when they are sitting at higher temps

Under-replenishment of automatic developer chemicals causes (in regards to contrast and film density)

Loss of contrast (appears gray) | Loss of film density

Over-replenishment of automatic developer chemicals causes (in regards to contrast and film density)

Loss of contrast (increased fog) | Chemical waste

Every 1-2 months you should do what to your developer system (4)

- Completely change chemicals - Clean tank - Check replenished rates - Check cycle time

Causes of lower contrast on a film is caused by these (5) adverse conditions in the dark room:

- safe light fog - night room temp/humidity - chemical fog from processor too hot - chemical fog from chemicals too concentrated - film past expiration date

How does penumbra increase most rapidly?

Increasing OID

How do you get shape distortion?

When x-ray tub is angled and object and film are parallel... unequal magnification creates shape distortion: e.g. increase OID of one end of a bone, it appears fatter and shortened.

What is the machine that exposes film to a step wedge of known densities?

Sensitometer

The sensitometric (H&D) curve is a graphic measure of how a film records density over a range of exposures. What is the vertical/Y axis measuring and what is the horizontal/X axis measuring?

Y axis — optical density X axis — log relative exposure Note: the Y axis goes from 0 to 4.0. 0 means 100% light transmission and 0 absorption of light (which isn’t truly possible)

The H&D curve consists of 3 parts of the curve named

Toe, body, shoulder

The toe of the H&D curve measures what

Light absorbed by the film base, plus any fog

The length of toe indicates

Sensitivity of film to fog

The body of the H&D curve is the straight line component of the curve. It determines

The latitude of the film

Short latitude vs. long latitude (body of the H&D curve)

Short lat has vertical rise and higher contrast film Long lat has lower slope and lower contrast film, more shades of gray

What does the shoulder of the H&D curve represent

The “D-max” or maximum optical density the film will achieve no matter how much mAs or kVp you throw at it

What is a density meter?

Measures optical density of each step on a step wedge. Scale from 0 to 4

What do the numbers on the densitometer represent?

0 means 0% absorption of light through the film. So the film transmits 100% of light through itself. 4 means 100% absorption of light. The film is black and lets 0 light through it.

What is the significance of the densitometer?

Measurements obtained track processor performance over time

________ is established by finding the step on the sensitometric step wedge strip that has the closest optical density to 1.0

Speed index

___________ is the difference in optical density between the Speed Index step and the optical density reading of the step that is 2 steps darker on the sensimetric strip

Contrast index

Contrast index step should be between what 2 values for films used for skeletons

1.4 to 1.7

Gross fog index is

Base plus Fog It’s the optical density of a film when its not been exposed and was run through processor blank. In a perfect world, it’d be clear. However there is no such thing so the usual value for optical density of fresh, unexposed film is 0.15-0.20

What is the usual value for optical density of fresh, unexposed film

0.15-0.20

Faster films have a higher/lower gross fog index

Higher Fast films = high gross fog index

The longer the toe, the more/less sensitive to fog the film is

Less Big toe = less sensitive to fog

You should not see fluctuations greater than (3) on serial readings for speed, contrast, gross fog index

+/- 0.15 speed and contrast index | +/- 0.03 gross fog index

What kind of crystals give you the slowest speed film but the best detail?

Small crystals in thin layers And so: fast speed/lowest detail are large crystals in thick layers

Term used to describe range of densities that can be recorded on the film

Latitude - Wide is best for low contrast e.g. chest - Short is best for high contrast

How are contrast and latitude related (for film)?

Inversely As contrast decreases, latitude increases.

Double mAs, double

Density