What options are there for a flicker free light low wattage light source?
My experience of (digital) photography using AC driven light sources is poor (due to flicker). So I am wondering if there is anything that gives a constant light source for photography purposes, which I should imagine means a DC driven lamp.
I mostly photograph items using a stand mounted Canon camera, with the image being displayed on the PC screen before taking the picture.
Something with the brightness similar to a 40W GLS (normal household lamp) or an 8W flourescent tube would give me a starting point for exploration. At this stage any pointer to a suitable light source would be appreciated regardless of colour temperature.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember jim saying something like:
There's a whole world of car headlamps, foglamps and driving lamps open to you, with suitable DC sources easily available. In tungsten halogen,
50W-ish is the norm, so more or less matches what you want and if you want more, you could look at the HID 12V conversion kits available from China via ebay.
Depending on your shutter speed a high frequency ballast for a fluorescent could well sort things - approx 30000 Hz rather than 50Hz which gives a
100 Hz flicker. Before these existed we got round the problem in TV by using groups of three fluorescents fed from different sources. On the occasions where fluorescents were needed. But tungsten off one phase didn't cause any problems.
A couple of years ago I needed to do a series of photos indoors and used a pair of good CFLs - 18 or 20W. (They were sold explicitly as suited to photography - and their colour rendering was as good as I have ever seen from CFLs.) Effectively put the CFLs in a box and photographed through a hole on the side. No problems whatsoever with flicker or banding. Slight adjustment to colour in Photoshop and they were fine for purpose. (Selling ceramic objects on ebay.)
I cared more about sharpness than speed so stopped the lens down a bit - and the shutter on my Canon had a minimum exposure of, IIRC 1/1000, yours might be faster. You might not wish to do this for other reasons, but could you slow the shutter down a bit?
Doing it again, we would use some of the 5500K trumpet top CFLs.
When colours change to the eye using a nominal white light it's due to the spectrum output from that light not being continuous. You get a choice of colour temperature with these kits and I chose the same as tungsten.
Even pro HID lamps used in filming don't have a perfect colour spectrum.
A 40W mains filament lamp is probably thin enough that some 100Hz shows up due to low thermal intertia. A low voltage equivalent would have a much thicker filament and over come that.
Photographers traditionally have problems with the low colour temperature of filament lamps (2700K). Photofloods (over-driven) lamps were used to get around that. I still have a 275W GLS photoflood in the cupboard somewhere, but it only has a life of a few hours. What you could do is use something like a 12V 20W lamp and over-run it -- you'll easily get 40W (actually, it's probably equivalent to 40W even when not overrun). It won't last long, but neither did photofloods. Make sure you house it in a fitting which will contain the red-hot pieces of quartz safely if it explodes though, and carry spares with you.
Fluorescents on electronic control gear mostly won't flicker. There's no flicker at the operating frequency because they're all well above 5kHz, and at 5kHz, the discharge becomes becomes continuous anyway. You can still get 100Hz line frequency ripple coming through in some cases though. The main problem is that the colour spectrum is often particularly bad for photography.
CFLs seem to have high-frequency control gear, but is there available domestic high-frequency control gear for traditional fluorescent 'tubes'? I'm looking at doing some re-lighting, and one of the objectives is to replace the kitchen lights which are traditional fluorescents. There are two things I'd like to do: get a better CRI than the 80-odd that is usual for standard fluorescents; and eliminate the flicker, which is most noticeable for me when I have a headache - at which point simply looking around the kitchen makes me nauseous as I keep catching the flicker out of the corner of my eyes.
Ideally, dimmable as well.
As noted by other people in this newsgroups, I'd also like some longevity of supply - there's no point in spending lots of money on specialist fittings to find they are no longer supplied when next season's colours come in.
And while I'm asking for things (it is that season after all), can I have world peace and elimination of hunger and disease?
Yes, but unfortunately it is significantly harder to find at reasonable prices than it should be.
I really doubt 80-something CRI is too low in a kitchen. Higher CRI usually comes also as much higher colour temperature, and that's normally a disaster in a kitchen (does really nasty things to colour of food).
That will at least double the ballast cost, and require some rewiring.
Can't you adjust the while balance in the camera to compensate?
HIDs are very popular in underwater filming - mostly because they are bright, have a long-burn time vs. battery pack size... However there's no such thing as true colour underwater ;-)
My own underwater "torch" is HID. Compact and very bright and with a
4-hour burn-time on the relatively small NiMH battery pack...
Well, yes - it's not in the 'sheds' afaics, or if it is, it's not well advertised.
Well perhaps I'm confusing things with the old halophosphate 'warm white' tubes, which have/had a truly awful colour rendition. Tomato soup goes a mucky brown colour - and it is not my cooking, I promise. There's a nice picture here:
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colour charts photographed under a CRI of 70 and a CRI of
Perhaps I'm just stuck in the habit of expecting colours to be as seen under incandescent tungsten lighting (not halogen). I just find it disconcerting to move from a fluorescent lit kitchen into the tungsten lit dining room and see some of the colour changes in the food. The colour temperature of say, a Philips TL950 is a bit high, as you say.
Since I'd be relighting, that's not necessarily a problem. Finding decent fittings/lampholders is another fun task. I do not want mains voltage halogen, or LED spots or whatever the current in fashion vogue is. What I'm after is dazzle-free and shadow free task lighting for preparing the food, which should be achievable with under-cabinet fluorescent and a wash of dazzle-free separate general room lighting, which might be achievable with above cabinet fluorescents. I'm after both being dimmable (I've used switchbanks, and they irritate me like blazes, as I don't get the level exactly as I want it).
I suppose I'm quite picky as far as lighting goes. I love the Danish PH designed lamp-holders, with the hidden lamp(so no dazzle), but good illumination. Anything with exposed lamps (especially in public lighting) drives me up the wall - there's really no excuse for such poor lighting design - good lighting makes such a big difference to the general environment. There's more to illuminating an area than just sticking a bare bulb in the middle of it!
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