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Lighting advice

This is posted in the hope that it is useful but without any warranty. LED | CFL | Halogen | Pygmy | ESL | Task lighting | Spectrum issues

LED room-light flicker

I did have some notes here about what causes this, how to prove it exists, and my failed strategies of identifying low-flicker bulbs in catalogues, but now I found an excellent discussion of flicker at LEDBenchmark (an Australian site) I'll simply link there. Stroboscopic "phantom array" effects are particularly irritating if you have nystagmus (uncontrolled eye movements) and V5 blindsight (sensitivity to rapid movement in areas outside your normal visual field), and others who are not sensitive, including sales personnel, might confidently deny the flicker that you know exists.

You could consult LEDBenchmark's list of LEDs and consider only lamps that came lower than the incandescent in their flicker measurements, but these lamps can be hard to find in the UK (LEDBenchmark mostly tests Australian shops). You'll want to check for an exact match on the rated wattage etc, because bulbs sold under the same name by the same manufacturer can have wildly different flicker performances across their wattages (and do not assume any given company's newer bulb will be better than its older counterpart---beware of "no but we have a newer version" sales: it might not be the same thing). IKEA's lower-lumen bulbs sometimes flicker less, but they're not suitable when more light is required unless you have room for many of them. (They also require adaptors if you have B22 sockets.)

Other than that, the best advice I have right now is to avoid LED room lights altogether, unless it's done by a professional LED installation with a very good high-frequency driver.

CFL phosphor leakage and degradation

21st-century versions of "energy saving" CFL bulbs (with high-frequency electronic ballasts) give reasonably good light but they have other issues, not least of which is decreased availability when more retailers prefer LED.

Due to concerns about UV leakage, CFLs should not be used at short distances (see task lighting).

Additionally, all CFLs (like any phosphor-based device) gradually dim due to phosphor degradation:

In areas with high humidity and/or short running times (e.g. small kitchens or bathrooms), CFL electronics can cut out early. If this happens often enough to make CFLs uneconomical and unenvironmental (because you "get through them" too quickly) then see below.

Incandescents for humid rooms

If you experience CFLs cutting out very quickly in humid rooms, and you cannot control the humidity, you might be stuck with bulbs that do not include PCBs, which means either flickering non-rectified LEDs or hot power-hungry incandescents (switch off whenever possible).

(These notes assume the room does not have fluorescent tube fittings. If it does then you might have a problem: some high-frequency flicker-free electrical ballasts can take only 85% RH and only for 30-60 days/year; others are more tolerant, but many fittings try to be robust by using a magnetic ballast, which flickers at twice the mains frequency and might also flicker at the mains frequency if the tube's electrodes are bad. You might at least be able to replace the starter with an electronic one for slightly nicer startups.)

ESL unsuitable for UK use?

ESL bulbs use an unfocused electron beam on phosphor. As of 2011 it's difficult to find 240V ones, and they might turn out to be too heavy for the UK---a B22-to-E27 adapter won't overcome the effective weight limit of a Bayonet socket. Also Vu1 haven't yet explained how they've avoided X-rays in their unshielded bulbs (does their phosphor allow the use of lower-energy electrons?)

Task lighting

Spectrum issues

Certain brain disorders, such as Irlen's syndrome (scotopic sensitivity, identifyable if high-contrast symbols on a printed page sometimes seem to move), and possibly some forms of autism, can result in sensitivity to certain wavelengths of light being overly prominent in the spectrum; the exact wavelengths depend on the individual and are typically addressed using customized eye or page filters, but lighting will obviously have an effect.

The spectral pattern (spectral power distribution) of non-incandescent lighting usually depends on the manufacturer's phosphor chemistry and is likely to have "spikes" at frequencies corresponding with each chemical. Higher CRI "soft white" bulbs typically use more chemicals to reduce the prominence of particular spikes, but it's hard to approach incandescent's CRI=100 without using halogen. (It's possible that phosphor-driven bulbs will irritate less if a "main" lamp is halogen and the others merely add "background" ambient light, but this again depends on the individual.)


All material © Silas S. Brown unless otherwise stated.