Casting Shadows

[wdw1992]

Hi all,

 

I am a complete novice to lighting - but I'm currently undertaking a lighting project at Uni.

 

I have created a spherical lampshade that is one huge latticework in the hope it will cast crazy shadows all over the room which it is in.

 

The problem I have is the light source. I have tested with a conventional 60w incandescent bulb, but this just makes the shadows which are cast very blurry. I then put a sample of the latticework material under my desktop lamp, which uses one of those little 12v wedge type bulbs, and hey presto - a really clear and crisp shadow is cast compared to the standard bulb.

 

So what im really asking is, what is the key to achieving a good shadow from a lightsource that can be used in the home as a ceiling light.

 

Thanks for any advice, and sorry if this isnt the sort of thing you normally discuss on here!

 

Will

[timsabre]

For sharp shadows you need the smallest possible source of light - a normal "pearl" (diffused) lightbulb is quite big. The little halogen capsules are good because the filament is quite compact. A normal 60W lightbulb with clear glass will be a lot better than a pearl one - if you can still buy them.

[paulears]

I wonder what it would be like if you took something like a GU50 spot lamp, and carefully broke the reflector and front glass? These have VERY small filaments and are quite bright.

[wdw1992]

Thanks a lot!

 

So the smaller and brighter I go - the crisper the shadow will be.

 

Will have to experiment with some more bulbs to find the best one.

[paulears]

Adolf Linnebach is worth researching - I remember using modified floodlights to do similar things to what you're doing in the 70s. You took the reflector out of a floodlight or other old spotlight, leaving just the lamp, and then put shapes in the colour frame and it sort of projected them. Like yours, the problem was that back then the lamps were pretty big, so you had to make bigger frames and stand them off the front if you wanted to get sharper edges. Then gobos in profile lanterns seemed to gain favour, as the quality and edge sharpness was better. I did a project once with 'an artist in residence' and he spent ages with a 2 feet square frame which contained all sorts of objects that spun and twisted in the heat from the beam, and people watched the patterns change on the wall. I wonder if we were more easily pleased back then?

[wdw1992]

I'll take a look at Adolf Linnebach, nice bit of log book filling!

 

I think ill try a G9 60w halogen bulb - this should meet the criteria for a crisp shadow, no?

 

I cant seem to find a holder for a G9 bulb that is wired directly to a household plug, I presume it would be fine to just use a B22 to G9 converter so it can fit into the existing socket I have?

[david.elsbury]

Use a clear lamp, not frosted. Most g9s I have seen are frosted. B22 to g9 should be fine, the lamps get super hot, watch out!

 

Use a clear lamp, not frosted. Most g9s I have seen are frosted. B22 to g9 should be fine, the lamps get super hot, watch out!

[maeterlinck]

All as above. If you are getting very picky fillament direction towards the item creating the shadow can affect the quality of the shadow.

 

For similicity I would start with some thing like this:

http://www.diy.com/nav/decor/lighting/lightbulbs/halogen_bulbs/-specificproducttype-globe_bulb/Diall-Halogen-Eco-42W-GLS-B22-12418931

It is basically a halogen capsule lamp in a GLS frame.

[wdw1992]

That looks the ticket, would the 70w version create a better shadow than the 48w?

[maeterlinck]

In general the brighter the source the more contrast you can achieve. I would play around as there are lots of factors that will affect the results.

[adam2]

That looks the ticket, would the 70w version create a better shadow than the 48w?

 

Depends on what you mean by better.

The 70 watt lamp will be brighter and therefore give a greater contrast between shadowed and lit areas.

The 48 watt lamp probably has a smaller filamant and will therefore give sharper edged shadows.

 

Of lamps suitable for domestic use, the best option is probably a mains voltage halogen capsule lamp, these have a non standard base, but adapters are readily available to insert them into a standard holder.

 

Halogen lamps with a clear outer envelope will be much better than frosted lamps, but not as good as a bare halogen lamp. In a lamp with an outer enveolpe internal reflections occur and reduce the sharpness of the shadows.

[Jivemaster]

Interesting lamps would be 12v 100w capsule lamps from some old disco lighting or 24v 250w lamps from Kodak carousel projectors. Under run them to 11v or 22v respectively and they should last reasonable for a project. Both will draw about 10amps so good cable and connectors are needed.

 

Small compact filaments make for sharp shadows.

[wdw1992]

I purchased the above bulb from B&Q today, the (G9 hologen bulb inside the conventinal bulb shape). The shadows have been improved from a standard bulb. I have also got just the standard G9 bulb and adaptor to B22 on the way - im hoping that without the glass around the G9 bulb the shadows will improve yet again, as stated above the inernal reflections are probably degrading the crispness of the shadows.