Flash vs Continuous Lighting

The two fundamental approaches to artificial lighting are flash (strobe) and continuous light. Each has distinct characteristics that affect how you work and what results you get.

This guide compares flash and continuous lighting, helping you choose the right approach for your work.

Flash/Strobe Lighting

Flash produces a brief, intense burst of light. The flash duration is typically between 1/500 and 1/10,000 of a second.

How Flash Works

The basics:

1. Capacitor stores electrical charge
2. Trigger signal fires the flash
3. Electricity passes through flash tube (xenon gas)
4. Brief, intense light emission
5. Capacitor recharges (recycle time)

Flash duration: The actual light pulse varies from about 1/500s at full power to 1/10,000s or shorter at low power. Shorter flash duration = more motion-stopping ability.

Guide numbers: Flash power is often specified as a guide number (GN):

• GN = distance (m) × aperture at ISO 100
• Higher GN = more powerful flash
• Example: GN 40 means f/8 at 5 metres, or f/5.6 at 7 metres

Guide numbers are covered in detail in our Flash Photography Basics guide.

Types of Flash Equipment

Speedlights (Hot Shoe Flash):

• Mount on camera hot shoe or stand
• Battery-powered, portable
• GN typically 30-60
• Limited power but very portable
• Good for location work

Monolights:

• Self-contained flash head with power unit
• AC-powered (some have battery options)
• More powerful than speedlights
• Include modelling light
• Standard for small/medium studios

Pack and Head Systems:

• Separate power pack and flash heads
• Multiple heads from one power source
• Highest power output
• Most professional/commercial use
• Asymmetric power distribution possible

Flash Advantages

Motion freezing: Very short flash duration freezes subject motion absolutely. Even at 1/60s shutter speed, the actual exposure is determined by the 1/1000s flash.

Power efficiency: Flash is very efficient—you get a lot of light output from relatively little power. A 500Ws monolight uses less electricity than a 100W continuous light but produces far more peak intensity.

No heat during exposure: The brief pulse doesn't heat your subject. Important for food, products, and comfortable portrait subjects.

Colour consistency: Flash is daylight-balanced (5500-5600K) and consistent from shot to shot. No warm-up drift.

Overpowering ambient: Flash can easily overpower daylight or room light, giving you complete control.

Flash Limitations

You can't see what you get: Flash fires in a split second. You must use modelling lights (weak continuous lights in the flash head) to preview lighting, or review images after capture.

Sync speed limit: Cameras have a maximum sync speed (typically 1/60 to 1/250 for focal plane shutters). If you exceed your camera's sync speed, you'll see a dark band across part of the frame. This is the shutter curtain blocking the flash—it's travelling across the frame faster than the flash can fire.

Recycle time: After firing, the flash needs time to recharge. This ranges from under 1 second to several seconds depending on power and equipment.

Learning curve: Flash requires understanding sync speed, guide numbers, and flash metering. More technical than continuous light.

Modelling lights: Built-in modelling lights are much weaker than the actual flash output. Ratio between modelling light and flash output may not match exactly.

Continuous Lighting

Continuous lights stay on constantly—what you see is what you get.

Types of Continuous Lights

Tungsten/Halogen:

• Traditional "hot lights"
• Very hot (safety concern)
• Colour temperature around 3200K (tungsten-balanced)
• High power output
• Inexpensive
• Dimmable (but colour changes when dimmed)

Fluorescent (Kino Flo style):

• Cool-running
• Daylight or tungsten-balanced tubes available
• Soft, diffused output
• Popular for video
• Can flicker with some shutter speeds

LED Panels:

• Cool-running
• Very efficient
• Daylight, tungsten, or bi-colour options
• Many are dimmable
• Compact and portable
• Quality varies widely
• Some have colour accuracy issues

HMI (Hydrargyrum Medium-arc Iodide):

• Very high output
• Daylight-balanced
• Very efficient (4x tungsten efficiency)
• Expensive
• Professional film/video standard

Continuous Light Advantages

What you see is what you get (WYSIWYG): The lighting you see is exactly what the camera records. No surprises, no review needed, no modelling lights required.

Easy to learn: No sync speeds, guide numbers, or flash-specific concepts. Position light, meter, shoot.

No sync speed limitations: Any shutter speed works. Useful for slow sync effects or when you need fast shutter speeds.

Video capability: Continuous lights work for both stills and video. If you shoot both, continuous lights do double duty.

Long exposures: For intentional motion blur or low ISO landscape work, continuous light maintains your creative options.

Continuous Light Limitations

Heat: Tungsten and halogen lights get extremely hot. Safety hazard, uncomfortable for subjects, can damage heat-sensitive subjects.

Power consumption: Tungsten lights draw significant power. A 1000W head uses serious electricity, and a multi-light setup may need dedicated circuits.

Lower peak output: Continuous lights can't match flash for sheer output. This limits your ability to overpower ambient or use small apertures.

Colour temperature changes: Dimming tungsten changes its colour temperature (gets warmer). LED dimming varies by manufacturer.

LED colour accuracy: Cheap LEDs often have poor colour rendering (low CRI). This causes colour issues that are difficult to correct.

Comparison Summary

Film-Specific Considerations

Flash with Film

Advantages:

• Daylight-balanced flash matches daylight film perfectly
• Colour consistency shot to shot
• No reciprocity concerns (short duration)
• Can overpower ambient for clean colour

Considerations:

• Sync speed limits shutter options
• Leaf shutters (many medium format) sync at any speed
• Must trust modelling light and experience

Continuous Light with Film

With daylight-balanced film:

• Tungsten lights: Need blue (80A) conversion filter, lose about 2 stops
• LED (daylight balanced): Matches, but verify CRI
• HMI: Matches daylight film

With tungsten-balanced film:

• Tungsten lights: Perfect match
• Flash: Need orange (85B) conversion filter
• LED (tungsten balanced): Matches

Reciprocity concerns: Long exposures with continuous light may require reciprocity compensation. Flash avoids this entirely due to short duration.

Mixed Lighting on Film

Flash + ambient (window light, room light):

• Shutter speed controls ambient contribution
• Aperture (primarily) controls flash contribution
• Balance ratio by adjusting shutter and flash power
• Colour matching is critical—filter lights if needed

Example: Shooting indoors with tungsten room light and flash:

• Option 1: Gel flash to match tungsten, use tungsten film
• Option 2: Overpower room light completely with flash, use daylight film
• Option 3: Accept mixed colour temperatures creatively

Mixing Flash and Ambient

One of the most useful techniques is combining flash with existing light.

Drag the Shutter

Concept: Use a slower shutter speed than you normally would, allowing ambient light to contribute while flash freezes the subject.

Technique:

1. Meter the ambient light
2. Set shutter speed for ambient exposure (or 1-2 stops under for mood)
3. Set flash power for subject exposure
4. Flash freezes subject; slow shutter records ambient

Effects:

• Background properly exposed (not black)
• Motion blur in background, sharp subject
• Warm ambient + cool flash creates colour contrast

Balancing Ratios

More flash than ambient:

• Subject clearly flash-lit
• Background darker
• Clean, controlled look

Equal flash and ambient:

• Natural appearance
• Flash fills shadows
• Background visible

More ambient than flash:

• Ambient dominates
• Flash provides subtle fill
• Location/environment emphasized

Technical approach:

• Aperture affects both (but flash more directly)
• Shutter speed affects only ambient
• Flash power affects only flash

Creative Effects

Rear curtain sync: Flash fires at end of exposure instead of beginning. Motion blur trails behind the subject instead of ahead.

Motion trails with frozen subject: Long exposure with flash at end creates blur from movement with sharp flash-frozen moment.

Colour mixing: Gel flash differently than ambient for creative colour contrasts.

Choosing Between Flash and Continuous

Choose Flash When:

• You need to freeze motion absolutely
• Working with heat-sensitive subjects
• Need maximum output (small apertures, large groups)
• Colour consistency is critical
• Shooting in bright ambient conditions you want to overpower
• Working with daylight film in mixed conditions

Choose Continuous When:

• You want WYSIWYG preview
• Learning lighting (easier to see what you're doing)
• Shooting video and stills
• Working with very long exposures intentionally
• Budget is limited (entry LED is cheaper than entry flash)
• Working with subjects who blink at flash

Consider Both When:

• Building a complete kit over time
• Different jobs have different requirements
• Flash for power, continuous for video
• Some subjects benefit from one over the other

Building a Flash Kit for Film

Starter Kit

One monolight (300-500Ws):

• Sufficient for headshots and small setups
• Modelling light for preview
• Choose daylight-balanced

One medium softbox (60-90cm):

• Versatile single modifier
• Good for portraits

One reflector:

• Acts as fill without second light
• White and silver sides useful

One light stand:

• Sturdy enough for softbox weight

Radio trigger:

• Reliable flash triggering
• Frees you from sync cords

Expanded Kit

Second light:

• Hair light, background light, or fill
• Can be less powerful than key

Additional modifiers:

• Umbrella (different quality than softbox)
• Grid for control
• Beauty dish for different character

C-stand:

• More positioning flexibility
• Better for boom positions

Building a Continuous Kit for Film

Starter Kit

LED panel (high CRI):

• Look for CRI 95+ rating
• Daylight balanced (5500-5600K)
• Minimum 100W equivalent output

Modifier options:

• Many LEDs have softbox/diffusion attachments
• Umbrella works too

Stand:

• Continuous lights are lighter than flash
• Standard stand sufficient

Expanded Kit

Second light:

• Fill or rim
• Different colour temp can be creative

Tungsten option:

• If shooting tungsten film
• Very high output per cost
• Hot, but colour rendition excellent

Summary

Flash:

• Brief burst, freezes motion
• High output, low power consumption
• Requires experience to predict results
• Daylight-balanced, consistent colour
• Can't see what you get without test shots

Continuous:

• Always on, WYSIWYG
• Easier to learn
• Heat issues (tungsten) or quality issues (cheap LED)
• Works for video
• More intuitive for beginners

For film photography:

• Flash matches daylight film naturally
• Continuous tungsten matches tungsten film naturally
• Conversion filters allow flexibility but cost light
• Flash avoids reciprocity concerns entirely

Both approaches produce professional results. Many photographers use both, choosing based on the specific needs of each shoot. Start with whichever seems more intuitive, master it, then add the other approach when you're ready.