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Lighting adviceThis 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 flickerI 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 there are excellent discussions of flicker by LEDBenchmark Australia and German consultant Peter Erwin I'd rather link to. 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.
Peter Erwin's Der Lichtpeter test results may be useful in Europe, although less so in the UK because products for the UK's common B22 socket type are not included. There are some B22s on LEDBenchmark's list (consider only lamps that came lower than the incandescent in their flicker measurements) but these lamps can still be hard to find in UK shops (LEDBenchmark mostly tests Australian shops), and you'll want to check for an exact match on the rated wattage etc---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. (These are available in the UK but require adaptors if you have B22 sockets; IKEA usually sell them in their own table lamps.)
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 degradation21st-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).
- UV reduces with greater distance, lower wattage, full-enclosure lampshades, or "globe" bulbs (which cover the tube), but these strategies also reduce the brightness. It's possible that "straight" CFLs leak less UV than "twisted" ones that stretch the phosphor more, but both types are susceptible. (If you have shades/fittings that block UV but are tight, you might want spirals for more brightness in limited space.)
Additionally, all CFLs (like any phosphor-based device) gradually dim due to phosphor degradation:
- Dim CFLs might not be a problem if good task lighting is also available, such as a good desk lamp.
- If bright light is important and task lighting is not available, then you could:
- Replace the bulb before the end of its life
- These bulbs contain mercury (which also makes them unhealthy in an accident). Recycling facilities at large shops etc are now more common (I hope they don't have hidden downsides); if you can't get to one of these then the environmental cost of early replacement is greater.
- Alternatively the dim bulb could be kept as an emergency spare, or moved to a location where brightness is less important (if one exists)
- Run several dim bulbs instead of one bright one (if you have the fittings)
- This uses more power, which might or might not outweigh the cost and environmental impact of early replacement (depending on how often it saves a replacement); it also increases the UV.
- Choose a bulb with higher-quality phosphor that stays bright for longer (lumen maintenance)
- You could pay a review database (Which, Choice, etc) for the results of their stress tests on currently-available bulbs
- Some approval marks carry minimum requirements but these can be lenient (e.g. the American "Energy Star" specification v4.3 allowed the brightness to drop to 80% after 40% of the rated life, with 30% of the sample dropping below 75%, and said nothing about what happens after that time)
- Choose a bulb that is too bright to start with
- Again this uses more power, see above
- If you need to go beyond "100W equivalent", it could mean expensive horticultural lights.
- Replace the bulb before the end of its life
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 roomsIf 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.)
- Clear xenon halogen bulbs (EU energy category B) were not included by the UK's 2009-2012 "phase-out" legislation or the EU's 2016 halogen ban.
- A B22 halogen (e.g. 42W for "60W equivalent") might be the best option for small kitchens that can't take CFLs, but check if it really is equivalent to 60W (i.e. 700 to 900 lumens; calling a 600-lumen bulb "60W" is dubious, and 42W for that is category C).
- While halogens don't save nearly as much as CFLs, a halogen upgrade should still pay for itself in less than an older bulb's lifetime, so anyone who has stockpiled older bulbs should be better off not using them and buying halogens.
- Refrigerator and oven bulbs were also kept on by this legislation
- A clear 15W "Pygmy" refrigerator bulb can dimly light a small bathroom (if it's B22), but don't try this in a work area.
- It might also be useful in small areas where a ceiling-level cupboard door collides with a pendant light due to inappropriate cable length.
- Beware of 25W Pygmy bulbs: clear 15W is typically rated at 90 to 105 lumens, but clear 25W can come as low as 120 lumens (the extra brightness seems hardly worth the wattage); you might be able to get a 190-lumen one but these are not typical stock.
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?)
- A fluorescent desk lamp can be positioned closer to the work than an incandescent (useful in conjuction with a ``Hedgehog'' magnifier).
- Some people put CFLs into old reading lamps (Anglepoise etc), but if the shade is not large enough to cover the CFL then it may glare (especially when positioned closely) and might also lead to UV exposure because CFL safety standards assume ceiling use. (UV is reduced if the desk lamp is placed further away or light is bounced off a wall, but this also reduces light levels.)
- A purpose-designed fluorescent fixture is better, but some of them have ballasts that become annoyingly noisy later (and are also inefficient).
- Flicker-free LED desk lamps with high-frequency drivers are available, but are expensive and tend to have lower lumen ratings than other types of lamp. If buying one then make sure it really is flicker-free---the product literature should claim a driving frequency of kHz or MHz (not just Hz).
Spectrum issuesCertain 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.