In conventional radiography, producing a good radiograph does not end with taking the exposure. The film must also be handled, processed, washed and dried correctly. A small mistake at any stage can produce an unwanted mark or change in the appearance of the radiograph.

These unwanted changes are commonly referred to as film defects or radiographic film processing faults. For a radiographer, recognizing the appearance of a defect is important because it can help identify the cause and prevent unnecessary repeat exposures.

Although modern radiology departments mainly use CR and DR systems, knowledge of conventional film defects remains important for radiography students, examinations, and understanding the fundamentals of image processing.

What Are Film Defects?

A film defect is an unwanted change in the appearance or quality of a processed radiographic film.

The defect may be caused by:

• Incorrect exposure technique
• Improper film handling
• Faulty cassette or intensifying screen
• Incorrect darkroom conditions
• Problems with developer or fixer
• Inadequate washing
• Improper drying
• Poor storage of films
• Dust, foreign material or contamination

The appearance of the defect often gives an important clue about its cause.

A useful way to remember the major groups is:

Fog → Stains → Image Errors → Marks & Prints → Spots & Splashes → Drying Faults → Miscellaneous Faults

1. Fog

What is radiographic fog?

Photographic fog is unwanted darkening of a radiographic film caused by factors other than the intended radiation exposure.

Fog may affect the entire film or only a particular area. Generalized fog reduces image contrast and can make anatomical details more difficult to appreciate.

It is important to differentiate fog from simple overexposure. Overexposure results from excessive radiation reaching the film, whereas fog can have several other causes.

Common causes of fog

The major causes include:

1. Exposure to white light
2. Faulty safelight
3. Incorrect safelight filter
4. Excessive safelight bulb power
5. Prolonged safelight exposure
6. Exposure to X-rays or gamma radiation during storage
7. Chemical fog during processing
8. Old or exhausted developer
9. Overdevelopment
10. Poor storage conditions
11. High temperature and excessive humidity
12. Aging of the film

Light Fog

Light fog occurs when the film is exposed to unwanted visible light.

This can happen when:

• The darkroom is not completely lightproof
• The safelight has an incorrect filter
• The safelight bulb is too powerful
• The safelight is positioned too close to the working area
• The film remains exposed to the safelight for too long
• The safelight filter is cracked or damaged

A simple darkroom check can often identify this problem.

X-ray or Radiation Fog

Unexposed films can become fogged if they are exposed to radiation during storage.

Film storage areas should therefore be adequately protected from radiation sources, and film storage conditions should follow appropriate radiation protection and manufacturer requirements.

Chemical Fog

Chemical fog occurs during film processing.

Common causes include:

• Overdevelopment
• Excessively high developer temperature
• Oxidized developer
• Exhausted developer
• Incorrect developer preparation
• Contamination of processing solutions

Proper chemical preparation, temperature control and solution maintenance are essential.

Dichroic Fog

One particularly interesting processing defect is dichroic fog.

The film may appear yellow or orange in transmitted light, while under reflected light it may show a yellowish, greenish or metallic-silver appearance.

It can occur when the fixer is insufficiently acidic or when developer contaminates the fixer.

This is one reason why developer and fixer should never be allowed to contaminate each other.

2. Stains

A stain is a discoloration of the film that can obscure the radiographic image.

Staining is usually associated with problems in processing, rinsing, fixation or washing.

Some common types include:

How can stains be prevented?

Good processing practice is the key.

• Use correctly prepared processing solutions.
• Replace exhausted chemicals.
• Maintain appropriate temperature.
• Rinse films adequately.
• Wash films properly after fixation.
• Keep processing tanks clean.

3. Errors in the Radiographic Image

Not every defective radiograph is caused by film processing. Some errors occur during radiographic exposure or image formation.

Important examples include:

• Thin image
• Contrast error
• Lack of sharpness
• Image reversal
• Missing image at one edge
• Transfer or additional image

The first question when troubleshooting should be:

Is the problem caused by exposure, processing, equipment, or handling?

This simple approach prevents unnecessary repetition of radiographs.

Thin Image

A thin radiographic image has insufficient optical density.

Common causes include:

• Underexposure
• Underdevelopment
• Incorrect processing conditions

A thin image may lack adequate visibility of anatomical structures.

Before repeating the examination, check both the exposure factors and the processing conditions.

Contrast Error

Radiographic contrast can be affected by both exposure technique and processing.

Using excessively high kV generally produces a radiograph with lower subject contrast, giving a flatter appearance.

Processing problems can also influence contrast.

Therefore, when a radiograph appears too flat, do not immediately assume that the kV was the only problem. Check the processing conditions as well.

4. Lack of Sharpness

Sharpness refers to the ability of the imaging system to reproduce fine anatomical details.

Loss of sharpness may occur because of:

• Patient movement
• Tube movement
• Film movement
• Poor screen-film contact
• Faulty cassette
• Aging or damaged intensifying screens

Poor screen-film contact

If the film is not in close contact with the intensifying screen, light produced by the screen can spread before reaching the film. This reduces recorded detail.

Cassette and screen condition should therefore be checked regularly.

A wire-mesh screen-contact test can be used to identify areas of poor contact.

5. Image Reversal

Image reversal is traditionally associated with the Sabattier effect.

In this phenomenon, a partially developed photographic image may undergo reversal after inappropriate exposure to light during processing.

The result is an unusual reversal of portions of the image, with dark areas becoming lighter and lighter areas becoming darker.

Possible causes include:

• Brief exposure to white light during processing
• Incorrect safelight conditions
• Improper darkroom practice

This is a classic conventional film-processing phenomenon and is less relevant to modern digital radiography.

6. Pressure Marks

Pressure marks are among the common handling artifacts seen on radiographic films.

They are generally crescent-shaped and occur when the film is bent, buckled or subjected to excessive pressure.

Interestingly, the appearance depends on when the pressure occurs.

Before exposure

A pressure mark occurring before exposure may appear as a white crescent.

After exposure

A pressure mark occurring after exposure may appear as a dark crescent.

The lesson is simple: radiographic film should always be handled gently.

7. Static Marks

Static marks occur because of the discharge of static electricity.

They may have a characteristic:

• Lightning-like appearance
• Branching appearance
• Tree-like pattern
• Irregular black pattern

Static electricity can be generated by friction when film is removed from its packet or cassette.

Static artifacts are more likely under unfavorable environmental conditions, particularly when humidity is low.

Prevention

• Handle film gently.
• Avoid unnecessary friction.
• Maintain suitable environmental conditions.
• Keep the loading area clean.
• Ground appropriate equipment where applicable.

8. Hanger Marks

Hanger marks are generally seen along the edges of processed films.

They may result from:

• Dirty film hangers
• Dried processing chemicals
• Chemical contamination
• Poor cleaning of hangers

Dirty chemically contaminated hangers may produce a characteristic bronzed effect along the film edge.

Prevention

Film hangers should be thoroughly washed and dried before reuse.

Regular cleaning of hangers is a simple but important part of darkroom quality control.

9. Fingerprints, Abrasion and Flow Marks

Careless handling can produce several other film artifacts.

These include:

• Fingerprints
• Abrasion marks
• Flow marks
• Scratches
• Handling marks

Dirty or greasy hands can leave visible marks on the film.

Films should therefore be handled by their edges whenever possible, and unnecessary contact with the emulsion surface should be avoided.

10. Spots and Splashes

Spots can be either dark or light depending on their cause.

Dark spots

Dark spots may result from:

• Pinholes in film packaging
• Defective cassettes
• Developer splashes
• Developer dust or contamination

Developer splashes can sometimes produce a comet-tail appearance.

Light spots

Light spots may occur when:

• Air bubbles stick to the film during development
• Dust or paper is present on the intensifying screen
• Foreign material is present between the cassette and film

The location and shape of the spot can help identify its origin.

11. Air-Bell Marks

An air bubble can stick to the film surface during development.

The bubble prevents the developer from contacting the emulsion beneath it. As a result, that area is not developed normally and appears as a small, clear or light circular spot.

Proper agitation helps prevent air bubbles from remaining attached to the film.

12. Patchiness and Uneven Processing

Patchiness refers to an uneven appearance of the processed film.

Possible causes include:

• Inadequate agitation
• Uneven development
• Short development time
• Incorrect processing temperature
• Chemical contamination
• Incomplete fixation
• Uneven drying

Fresh developer should be mixed appropriately before use, and the film should receive uniform chemical action.

Consistent time, temperature and agitation are fundamental principles of good film processing.

13. Drying Faults

Drying is the final stage of conventional film processing, but it is sometimes overlooked.

Incorrect drying can produce several defects.

Reticulation or Frilling

Reticulation occurs when the gelatin emulsion undergoes sudden temperature changes.

For example, a film processed at one temperature and then suddenly exposed to water at a substantially different temperature may develop a network-like appearance.

The gelatin may become damaged or even separate from the film base.

Reticulation can also occur when processed films are stored under unsuitable hot and humid conditions.

Blistering

Blistering occurs when the gelatin layer forms raised areas or blisters.

Possible causes include:

• Excessive heat
• Rapid drying
• Viewing wet film in front of a hot light source
• Excessive heating during drying

Controlled drying is therefore important.

Water Marks and Water Spots

Water droplets remaining on the film during drying can produce spots or streaks.

Water marks may appear as areas of altered density and can interfere with image interpretation.

Proper washing and drying procedures help prevent these defects.

14. Miscellaneous Film Faults

Several other defects may appear on conventional radiographic films.

For example, lines may result from:

• Hair on the intensifying screen
• Cracks in the screen
• Scratches on the film
• Rough handling

The timing of a scratch can also influence its appearance.

A scratch occurring before processing and a scratch occurring after processing may produce different appearances.

Regular cassette and screen inspection is therefore an important component of quality control.

How to Troubleshoot a Defective Radiograph

When you encounter a defective film, avoid immediately repeating the examination.

Instead, follow a systematic approach.

Step 1: Observe the defect

Ask:

What exactly do I see?

Is it generalized darkening, a spot, a line, a crescent, a stain, or loss of sharpness?

Step 2: Determine the distribution

Is the defect:

• Across the entire film?
• On one side?
• Along the edge?
• In a particular area?
• Repeated in the same location?

Step 3: Consider exposure

Check:

• kV
• mAs
• Exposure time
• Positioning
• Motion

Step 4: Check the processing

Evaluate:

• Developer condition
• Fixer condition
• Temperature
• Development time
• Agitation
• Rinsing
• Washing
• Drying

Step 5: Check equipment

Inspect:

• Cassette
• Intensifying screens
• Film hangers
• Safelight
• Darkroom
• Film storage area

Step 6: Look for a pattern

If the same artifact repeatedly appears in the same location, suspect a cassette, screen, hanger or processing equipment problem.

This systematic approach is much more useful than simply repeating the radiograph.

Quick Film Defect Identification Guide

Importance of Quality Control

The study of film defects is not only useful for examinations. It teaches an important principle of radiographic practice:

A good radiograph depends on the entire imaging chain, not just the exposure.

In conventional radiography, quality control should include:

• Darkroom light-leak inspection
• Safelight testing
• Film storage monitoring
• Developer and fixer maintenance
• Processing temperature monitoring
• Cassette inspection
• Screen cleaning
• Screen-film contact testing
• Hanger cleaning
• Proper washing and drying
• Regular analysis of repeat examinations

Good quality control reduces repeat radiographs, saves time and supports radiation protection by avoiding unnecessary patient exposure.

Conclusion

Film defects are an important part of conventional radiographic technique. Fog, stains, pressure marks, static artifacts, spots, processing errors, drying faults and cassette-related artifacts each have characteristic appearances and causes.

For a radiographer, the most valuable skill is not simply memorizing the names of these defects. It is learning to look at the radiograph and ask:

What is the pattern? What caused it? How can I prevent it from happening again?

That approach turns film-defect knowledge into a practical quality-control skill.

Although most departments have moved from film-screen radiography to CR and DR, these principles remain valuable for understanding image quality, troubleshooting, radiographic technique and the history of imaging technology.

RadiologyConnect

This topic is part of the RadiologyConnect learning series for radiography, radiotherapy and nuclear medicine students and professionals.

For students preparing for radiographer examinations, focus particularly on the appearance → cause → prevention relationship of each film defect. This is more effective than memorizing long lists of faults.

Learn the pattern. Find the cause. Prevent the repeat.

Keywords: film defects in radiography, radiographic film faults, film fog, chemical fog, dichroic fog, radiographic stains, pressure marks, static marks, hanger marks, air bell marks, drying faults, reticulation, radiographic artifacts, darkroom techniques, radiography students, conventional radiography.