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For Ilford SFX 200, choose a Wratten-equivalent red #25 for a moderate effect or a deep-red #29 for a stronger one. Ilford’s SFX 200 guide gives them filter factors of 2.8 (1½ stops) and 3 (1⅔ stops), respectively. Pick the filter’s physical diameter to match your lens’s filter thread—not the film.
How red filter strength changes the image
SFX 200 has extended red sensitivity and can produce an infrared-style effect; Ilford does not describe it as true infrared film. It says the film can be used with yellow, orange, or red filters and notes, “The redder the filter, the more dramatic the effect.” A deep red filter can render skies nearly black and much green vegetation nearly white, but the result depends on the filter and lighting in the scene.
The practical choice is between #25 and #29. Ilford’s November 2018 technical information lists the following film-specific guidance:
| Filter | Ilford category | Filter factor for SFX 200 | Exposure increase | Typical use |
|---|---|---|---|---|
| Wratten #25 | Red | 2.8 | 1½ stops | Moderate red-filter effect |
| Wratten #29 | Deep red | 3 | 1⅔ stops | Stronger red-filter effect |
| Wratten 89B | Very deep red | 16 | 4 stops | Very strong filtration with a substantial exposure increase |
These are Ilford’s guidance values for SFX 200, not a guarantee that all brands’ filters transmit light identically or that every camera meter will respond the same way. The #29’s stronger effect comes with only a modestly higher listed exposure increase than #25. The 89B is a different commitment: its four-stop factor can mean very long exposures, for which Ilford recommends using a tripod.
#1 Best Overall
- High contrast, well defined highlights
Which should you choose: #25 or #29?
Choose red #25 for a moderate effect
A #25 is the sensible starting point if you want visible red filtration without going as deep as #29. Search for a red #25 camera lens filter after checking your lens’s thread diameter.
Choose deep-red #29 for a stronger effect
A #29 is the stronger option when you want more pronounced separation between red-sensitive areas and other tones. Search for a deep-red #29 camera lens filter in the correct diameter. Do not assume it will make every sky black or every plant white; scene lighting and filter transmission matter.
Rank #2
- Frame: CNC machining, screw thread installation, quick and convenient disassembly and assembly.
- Usage Scenes: For scenes such as maple leaves, sunset, evening clouds, burning clouds or desert dunes in the evening.
- Red Filter: Suitable for enhancing the red tones in the picture, making the scene more vivid and layered.
- Multilayer Coating Process: Lens has oilproof, properties to the lens from dust and scratches.
- Strong Compatibility: There are five kinds of interfaces: 67mm/2.6in, 62mm/2.4in, 58mm/2.3in, 55mm/2.2in, 52mm/2.0in suitable for 67mm, 62mm, 58mm, 55mm, 52mm interface lens.
Consider very deep red only when its exposure cost suits the shot
Ilford’s 89B factor is 16, or four stops—far above the #25 and #29 factors. For this very dark filter, plan for longer exposures and use a tripod as Ilford advises.
How to meter and bracket SFX 200 with a red filter
Ilford warns that some common TTL metering systems can underexpose by up to 1½ stops when deep red or orange filters are fitted. This is a camera-dependent warning, not a correction that applies to every camera or every #25 or #29 exposure.
Rank #3
- High contrast, well defined highlights
- Fit the filter before taking a TTL reading if your camera meters through the lens, and apply the filter factor if using a separate meter.
- Use the meter result as a starting point. Ilford advises bracketing ±2 stops around the TTL reading or around the separate-meter reading with the filter factor applied.
- Keep notes on the camera, filter, lighting, and exposures so you can judge results from your own setup.
Ilford recommends experimentation when first using SFX 200. Its factor figures are manufacturer guidance, not independent comparative-test results.
Focus before fitting a deep-red filter
Ilford notes that red light may focus at a slightly different point from other visible light, and focusing through a deep-red filter can be almost impossible. A practical approach is to focus before attaching the filter. For short to moderate focal lengths, Ilford says stopping down to the smallest working aperture can accommodate the focus difference; some apochromatic lenses may need no correction.
Rank #4
- Good red light speed: Increased versatility and creativity
- Good latitude: Increased first time success
- Medium white light speed (EI 200/24): Can be used without filtration
- Pushes well: Can push up to EI 800/30 (no filter)
- Easy handling: Not as difficult to load as infra-red films
Choose the diameter from your lens
Filter strength and filter size are separate decisions: #25 and #29 describe optical types, not screw-in diameters. Check the filter-thread marking on the lens or lens cap; it is commonly shown as a diameter in millimetres. Buy a filter that matches that thread.
If one filter needs to serve lenses with different thread sizes, a larger filter with a step-up ring may work on a smaller-thread lens. Check the lens and camera combination for vignetting, particularly with wide-angle lenses. SFX 200 documentation does not establish a universal filter diameter.
Best Value
- Good red light speed: Increased versatility and creativity
- Good latitude: Increased first time success
- Medium white light speed (EI 200/24): Can be used without filtration
- Pushes well: Can push up to EI 800/30 (no filter)
- Easy handling: Not as difficult to load as infra-red films
Filter names are not proof of current availability or identical performance
Ilford’s 2007 legacy fact sheet lists historical light-red examples such as B+W 090, Cokin 003, Hitech 25, Hoya 25A, Kodak Wratten 25, Lee 25, and Heliopan 25. Its dark-red examples include B+W 091, Heliopan 29, Kodak Wratten 29, and Rodenstock 29. These are examples of older designations, not confirmation that those products are currently made or stocked, fit a particular lens, or have identical transmission.
Quick Recap
Sources
- HARMAN technology Limited / ILFORD Photo, SFX 200 Technical Information (November 2018)
- ILFORD Photo, SFX 200 120 product page
- ILFORD SFX 200 legacy fact sheet (April 2007), archived by Fotoimpex
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