Species: Canine   |   Classification: Miscellaneous

General faults


  • Generalized:
    • Chemical fogging.
    • Heat.
    • Film beyond 'shelf life'.
    • Safelight intensity too high (should be <25 W) or safelight too close to bench.
    • Safelight filter damaged or does not correspond to sensitivity of film.
  • Localized:
    • Film storage box not closed properly before switching on white light or opening darkroom door.
    • Pressure on films during storage.
    • Light switched on before film fully fed into automatic processor.
    • Cassette damaged so that light leaks in.
    • Damp storage conditions.
    • Cassette stored near x-ray machine or left on table during another exposure.


  • Store films in cool dry conditions.
  • Ensure darkroom is light proof and safelighting appropriate.
  • Check cassettes are light proof and discard any which are damaged.

Static electricity marks

  • Black forked lightning marks Film faults static electricity on the film.


  • Build up of static electricity.
  • Exacerbated by low humidity.


  • Handle film carefully to minimize static build up.
  • Clean screens regularly to avoid static build up.

Crimp marks

  • Usually small black crescent shaped marks Film faults crimp marks on film.
  • May be white if made before exposure.


  • Rough handling of film when transferring in or out of cassette.


  • Avoid creasing film.
    Tip film out of cassette rather than pushing at corners.

Screen marks

  • White marks on the film.


  • Dust or dirt on the screen, or foreign bodies in the cassette, preventing light from screen from reaching the film at a particular point.


  • Clean screens regularly.


  • Damage causing removal of areas of emulsion from film.
  • Finger prints Film faults poor washing caused by dirty or greasy fingers, eg handcream contacting undeveloped film.
  • Roller marks - linear marks on the film.
  • Scratches in film emulsion Film faults scratched emulsion caused by hangers, hopper, cassette and careless handling.
    Emulsion is particularly susceptible to damage when wet.


  • Build up of dirt or gelatine on rollers.


  • Use care when handling film.
  • Clean rollers regularly and service processor periodically.

Exposure faults


  • Movement blur Film faults image unsharpness - movement blur.
  • Poor film-screen contact.
  • Geometric unsharpness from large object-film distance.
  • Sedate patients where necessary.
  • Ensure x-ray table is stable.
  • Do not use damaged cassettes.
Poor positioning and centering
  • Area of interest not in the center of film Film faults mis-centered exposure (or missed completely!).
  • Poor positioning may prohibit diagnosis from radiograph.
  • Poor knowledge of anatomy.
  • Animal is resistant to appropriate positioning or moves before exposure.
  • Sedation.
  • Immobilization.
  • Familiarity with anatomy.
  • Knowledge of correct positioning and centring points.
Patient artifacts
  • Artifacts on image due to radio-opaque material on the body surface.
  • Dirty or wet coat (particular problem in large animal radiography.
  • Artifact overlying area of interest.
  • Ensure coat is clean.
  • Remove radio-opaque objects, eg leads and harnesses from field.
Double exposure
  • Two radiographic exposures made on same film.
  • Improve working pratices.
Inadequate identification
  • Radiographs should always be labeled with correct anatomical marker as well as patient details and date.
  • It is useful to include practice name too.

Image density faults

Film too pale
  • Image too pale but background exposed area of film, where no tissue penetration by x-ray beam, black.
  • Underexposure:
    • kV too low.
    • mAs too low.
    • Exposure time too short.
    • Focal-film distance too great.
    • Grid cut-off (vignetting), ie loss of density and emphasis of grid lines, usually worse towards the edge of the film:
      • Focussed grid upside down.
      • Focussed grid used at wrong focal-film distance.
      • Beam not centered to middle of focussed grid.
      • Beam angled across grid.
    • Black exposed areas of film not dark enough (able to see finger held behind film).


  • Underdevelopment Film faults under development :
    • Developer too weakly constituted.
    • Developer exhausted.
    • Developer temperature too low.
    • Development time too short.
  • May also be due to underexposure - modern films respond to a limited range of kVs.

Film too dark

  • Exposed area of film too dark but clear emulsion in non-exposed areas.


  • Overexposure Film faults over exposure :
    • kV too high.
    • mAs too high.
    • Exposure time too long.
    • Focal-film distance too short.
  • Entire film too dark (image and unexposed edges of film).


  • Fogging:
    • Film exposed to heat.
    • Film exposed to light.
    • Chemical fogging.
    • Film exposed to background radiation.
    • Film out of date.
  • Overdevelopment:
    • Anything which speeds the development process or increased exposure to developer:
      • Developer over concentrated.
      • Developer temperature too high.
      • Development time too long.

Film lacks contrast


  • kV too high.
  • Grid required.
  • Closer collimation required.
  • Film underdeveloped.
  • Film overdeveloped.

Quantum mottle

  • Grainy appearance to film.


  • Insufficient exposure to affect all phosphor crystals in the intensifying screen.
  • Occurs in fast rare-earth film-screen combinations.


  • Use a slower film-screen combination for selected examinations.

Processing faults

Chemical marks
  • Fixer splashes Film faults fixer splashes 01 appear as white patches on the film.
  • Developer splashesappear as black patches on the film.
  • Water splashes Film faults water splashes are gray.
  • Untidy darkroom.
  • Incorrect darkroom procedures.
  • Improve darkroom protocol.
  • Film hangers should be clean and dry before films are put in them to avoid edges of films being marked.
  • Films should be removed from hangers for drying.
  • Streaking results from poor developer agitation or from lifting film out of developer to view.
Generalized chemical stainingCause
  • Insufficient washing.
Dichroic fog
  • Causes brown discoloration Film faults poor washing.
  • Development continuing during fixation.
  • Increase rinsing time to remove more developer, or consider adding acetic acid to rinse.
  • Change fixer as it may be exhausted.