Filters Deep Dive

Filters transform how film captures light. Unlike digital post-processing, optical filtration happens at the moment of capture—affecting the light before it reaches the emulsion. This creates effects that can't be fully replicated later.

This guide covers filters in depth: types, applications, and practical usage for film photography.

Your First Filters

Don't buy everything at once. Here's what to start with:

For B&W photography: Yellow filter (cuts haze, darkens blue skies). This one filter handles 80% of common needs.

For colour photography: UV/haze filter (lens protection, cuts distant haze). Polariser if you shoot outdoors frequently.

For long exposures: ND1000 (10-stop) for daylight long exposures.

Your first filter should be: A yellow filter for B&W work, or a UV filter for colour. Master one before adding more.

Read on for the complete guide to filters, or stop here and start shooting.

Neutral Density (ND) Filters

ND filters reduce light without affecting colour. They enable wider apertures or longer shutter speeds in bright conditions.

ND Filter Strengths

ND filters are measured in stops or optical density:

When to Use ND Filters

Wide apertures in bright light:

• Shoot f/1.4 in daylight
• Shallow depth of field portraits outdoors
• Eliminates need for very fast shutter speeds

Long exposures in daylight:

• Smooth water effects
• Cloud movement
• Removing moving people from scenes
• Creative blur effects

Film-specific applications:

• Match slow film (ISO 50) to conditions
• Extend exposures for reciprocity testing
• Motion blur with flash (drag the shutter)

Choosing ND Strength

General use: 3-stop (ND8) covers most needs.

Long exposure work: 6-10 stops for multi-second daytime exposures.

Variable ND filters: Adjustable, convenient, but can cause colour casts and cross-pattern artefacts at extreme settings. Better for video than stills.

ND Filter Quality

Optical concerns:

• Colour cast (cheap filters often add warmth or magenta)
• Sharpness loss (poor glass degrades resolution)
• Vignetting (thick filter rings on wide angles)

Quality brands: Lee, NiSi, B+W, Formatt-Hitech, Breakthrough Photography.

Graduated ND Filters

Graduated ND filters are dark on one half, clear on the other, with a graduated transition.

Types of Graduation

Hard edge:

• Sharp transition between dark and clear
• Best for flat horizons (seascapes)
• Visible line if misplaced

Soft edge:

• Gentle transition zone
• More forgiving placement
• Works with uneven horizons

Reverse grad:

• Darkest at horizon line, lighter toward top
• For sunrise/sunset when sky is brightest near horizon

Using Graduated ND

Purpose: Balance exposure between bright sky and darker foreground.

Technique:

Limitations:

• Doesn't work with irregular horizons (mountains, trees)
• Visible darkening on anything crossing the transition
• Less flexible than digital HDR

Square vs Screw-in Grads

Square/rectangular (holder system):

• Adjustable position
• Can rotate and slide
• Preferred for serious use

Round screw-in:

• Fixed transition position
• Less versatile
• More compact

Polarising Filters

Polarisers control reflected light and atmospheric haze. Effects can't be replicated in post-processing.

How Polarisers Work

Light becomes polarised when reflected or scattered. A polarising filter blocks light vibrating in specific orientations, controlled by rotating the filter.

Polariser Effects

Sky darkening:

• Maximum effect 90° from sun
• Deepens blue sky dramatically
• Can look unnatural at extreme settings or with wide angles

Reflection control:

• Reduces reflections from water, glass, foliage
• Allows seeing through water surfaces
• Can eliminate window reflections

Haze reduction:

• Cuts atmospheric scatter
• Improves distant clarity
• More saturated colours in landscapes

Colour saturation:

• Removes surface reflections from leaves and surfaces
• Results in deeper, more saturated colours

Polariser Exposure Factor

Typical filter factor: 1.5-2 stops.

Metering through the polariser: TTL meters compensate automatically.

Handheld metering: Add 1.5-2 stops to reading.

Circular vs Linear Polarisers

Linear polarisers:

• Simpler construction
• Can interfere with autofocus and metering in some cameras
• Fine for manual cameras

Circular polarisers (CPL):

• Include depolarising layer
• Compatible with all cameras
• Standard recommendation for modern use

Polariser Technique

Colour Correction Filters

Colour correction filters adjust the colour temperature of light to match film balance.

Film Colour Balance

Daylight-balanced film: Approximately 5500K (sunny daylight).

Tungsten-balanced film: Approximately 3200K (incandescent light).

Warming and Cooling Filters

81 series (warming):

82 series (cooling):

Conversion Filters

For using wrong-balanced film under different light:

80A (blue):

• Converts tungsten film for use in daylight
• Strong blue filter
• Significant exposure compensation (~2 stops)

85B (orange):

• Converts daylight film for use under tungsten
• Strong amber filter
• Exposure compensation (~2/3 stop)

Fluorescent Correction

Fluorescent lights emit discontinuous spectrum, causing green cast on daylight film.

FL-D (Fluorescent to Daylight):

• Magenta filter
• Corrects for standard cool white fluorescent

Challenge: Different fluorescent types have different spectra. Perfect correction is difficult.

When Digital Has Advantage

Colour correction filters are less critical with scanning workflows:

• Scan can correct colour casts
• Raw adjustments in conversion software
• Greater flexibility than filter at capture

When filters still matter:

• Slide film (no scanning correction)
• Hybrid printing (printing from negative directly)
• Getting it right in camera

Black and White Contrast Filters

Coloured filters dramatically alter how black and white film renders tones.

The Principle

Filters lighten their own colour and darken complementary colours.

Standard B&W Filters

Yellow (K2/Y2):

• Subtle sky darkening
• Natural-looking tonal separation
• Good starting filter
• Filter factor: ~2× (1 stop)

Orange (G):

• Moderate sky darkening
• Good contrast enhancement
• Classic landscape choice
• Filter factor: ~3× (1.5 stops)

Red (25A):

• Dramatic sky darkening (nearly black)
• Strong contrast
• Can create surreal effects
• Filter factor: ~8× (3 stops)

Green (X1):

• Lightens foliage
• Natural skin tones in portraits
• Separates similar green tones
• Filter factor: ~4× (2 stops)

B&W Filter Technique

Example:

• Scene: green foliage against blue sky
• Without filter: similar grey tones
• With orange filter: sky darkens, foliage separates
• With red filter: sky goes very dark, dramatic

Visualising Filter Effects

Some photographers use coloured viewing filters (made by Tiffen and others) to preview the effect before shooting. Look through the coloured glass to approximate tonal rendering.

UV and Haze Filters

UV Filters

Purpose: Block ultraviolet light that can cause haze and slight colour shift at high altitudes or over water.

Modern relevance:

• Modern lenses often have UV coating
• Effect is subtle
• Often used primarily as lens protection

As lens protection:

• Prevents scratches on front element
• Easy to replace if damaged
• Some image quality purists avoid them

Haze Filters

Skylight filters (1A, 1B):

• Slight warming
• Mild haze reduction
• Often used as protection with warming benefit

For high altitude/aerial:

• Stronger UV/haze filters available
• More relevant for mountain and aviation photography

Filter Systems

Screw-In Filters

Advantages:

• Simple, compact
• No holder needed
• Rotating polarisers

Disadvantages:

• One size per lens
• Stacking can cause vignetting
• Grads can't be positioned

Step-up rings: Use larger filters with adapters to fit smaller lenses. Buy filters for your largest lens, adapt down.

Square/Rectangular Filter Systems

Advantages:

• One filter fits multiple lenses (via adapter rings)
• Grads can be positioned
• Easy to stack
• Remove quickly

Disadvantages:

• More bulk
• Additional cost (holder + adapter rings)
• Can be affected by wind

Systems: Lee Filters, NiSi, Formatt-Hitech, Cokin (budget).

Sizes

Common square/rectangular:

• 100mm: Standard for most lenses
• 150mm: For ultra-wide angles
• 85mm (Cokin P): Budget option

Filter Factors and Metering

What Is Filter Factor?

Filter factor indicates how much light the filter absorbs. Expressed as multiplication factor or stops.

Metering with Filters

Through-the-lens (TTL) metering:

• Automatically compensates for filter
• Usually accurate
• May be fooled by strong colour filters

Handheld metering:

• Meter without filter
• Add filter factor to exposure

Testing recommendation: With any new filter, bracket exposures to verify your metering/compensation is accurate.

Summary

ND filters:

• Reduce light without colour change
• Enable wide apertures and long exposures in bright light
• Quality matters—cheap NDs cause colour casts

Graduated ND:

• Balance bright skies with darker foregrounds
• Soft grad for uneven horizons, hard grad for flat horizons
• Less necessary with scanning workflows

Polarisers:

• Darken skies, reduce reflections, increase saturation
• Effects can't be replicated in post
• Use circular polariser (CPL) for compatibility

Colour correction:

• Match film balance to light source
• Less critical with scanning (can correct later)
• Essential for slide film under mixed lighting

B&W contrast filters:

• Transform tonal rendering dramatically
• Yellow for subtle, red for dramatic
• Require filter factor compensation

Protection filters:

• UV filters offer minimal optical benefit
• Some photographers use them for lens protection
• Quality matters if using

Filters are tools for optical control at capture. While digital scanning provides flexibility, many filter effects—especially polarisation and long-exposure motion blur—can't be replicated later. Invest in quality filters for the effects you use regularly.