PDA

View Full Version : creation of light table for macro work



Willie Jan
07-30-2009, 04:57 AM
i want to make a table for macro work with a milk white surface which will allow light to pass through.

Is it possible to use Polystyrene or polycarbonate to heat this up,
bend it and create a table in such as way?

Or is there a better solution for this.

John Koehrer
07-30-2009, 05:57 PM
Sort of like the Calumet table which is like a sweep?
If that's what you're looking for it shouldn't be too difficult, I think they may use plexiglas.

archphoto
07-30-2009, 06:26 PM
Sorry that it is in dutch, but: een objecttafel met een melkglazen pexiglas sheet er op.
I have one in The Hague, but it is over 1m wide.
Foba has them, for a link via NL, click here (Photal site) (http://www.photal.nl)

Peter

Lee L
07-30-2009, 07:14 PM
Many studios use a clear glass, polycarbonate, or plexiglas tabletop and then use translucent material to make a "sweep". The translucent material could vary depending on the size of your subject. With small macro work, Rosco or Lee gels could work well (not sure what brands or sizes are available in NL), and give you a wide choice of diffusion properties and optical density at very reasonable cost.

The "sweep" is made by resting one end of the background material on the tabletop and clipping the other end to a crossbar above the table.

Lee

Rick A
07-30-2009, 08:42 PM
I made a light table years ago. I used PVC pipe for the frame, and a piece of white plastic (I dont recall if it was plexi) it was thin enough that I didnt have too hard a time getting it to bend. I think I got the plans for it from Popular Photo(or similar) The only "problem" encountered was that plastic is petro based, and any light shone through it would be slightly orange. It is still a problem when I shoot macro using a white styro cup around my subject. I cut the bottom of the cup to fit over my lens, and set the cup over my subject for even , non reflective illumination.
Rick

Willie Jan
07-31-2009, 03:26 AM
I wil be using if for b&w shoots. I now use a light box (for slides) but the amount of light is not adjustable and it is flat. I would like to have it curved and going up at the end.

I'm not sure if I heat the plexiglas up and bend it, that it will get wrinkled in the curve that is visible when i want a white background.
Or the curve must be that large that it will not happen...

yellowcat
07-31-2009, 03:47 AM
How big do you need the macro table to be? You can get acrylic in various thickness, the thinner material like 3mm could be forced into a curve if fixed at both ends. that should be ok for smaller items.
Bending thicker material to a curve is not so easy as a large area needs to be evenly heated.
Where I am in the UK there is a plastics fabricator near that can make customised items (and I can sometimes get useful bits of material from their scrap bin)

lxdude
07-31-2009, 04:13 AM
Bending thicker material to a curve is not so easy as a large area needs to be evenly heated.


My best results for even heating have been with a heat gun or large hair dryer. It's important to work both sides and be patient so as to not overheat the surface. Also wait for it to just reach its yield point. Don't try to force it and don't let it heat much beyond its yield point or the curve is less likely to be even.
It's best to not directly heat the entire area to be curved, as the heat will diffuse laterally. Heating the entire radius will mean that the areas you want to keep unbent will be harder to control.
If at all possible practice first on a piece large enough to get a feel for it.

Willie Jan
07-31-2009, 05:05 AM
I can make a wooden part that has the right curve and place the material on top. After that heat it until it has the form of the wooden part.

50cm width and 90cm high would be the dimensions needed.
I will use it for small objects from a few mm until 10 cm high.

richard ide
07-31-2009, 09:04 AM
Acrylic diffuser sheets are available for 24 x 48 fluorescent fixtures made of material about 1mm thickness. This is thin enough that you would not have to heat it, just clamp it to your table.

Willie Jan
07-31-2009, 10:00 AM
Acryl has a name here of "plexiglas". I will have a look where I can get this here local.
Some shops who sell material for modell of ships/airplanes sell this stuff.

Earl Dunbar
07-31-2009, 11:11 AM
I made a large table with sweep using 4'x8' acrylic. I used acrylic that had one side frosted, and placed the frosted side down. I used a heat gun to bend the sweep. The front sweep was kept in place by attaching a 1"x2" firring strip (wood) underneath the front edge, secured to the acrylic by bolts and washers. This strip was then secured to the bottom of the main frame structure by using picture hanging wire, i.e. guy wires to keep the sweep taut.

With this setup I was able to photograph fairly large objects. I used coloured paper behind the surface to change the background colour. This way I didn't have to use gels on lighting equipment, and IMO the background colours were better. Lighting the background paper from below allowed me to photograph objects that appeared to float in space. I could also simply place background paper on top of the sweep if that was better for the subject.

archphoto
07-31-2009, 11:43 AM
Why don't you guide the light to the plexiglass with a mirror ?
In that way the heat of the lamp will be gone before it reaches the plexiglass.........

Peter

John Koehrer
07-31-2009, 01:08 PM
Acrylic diffuser sheets are available for 24 x 48 fluorescent fixtures made of material about 1mm thickness. This is thin enough that you would not have to heat it, just clamp it to your table.

This works OK but the sheets tend to be brittle and aren't very rugged if not treated gently

Willie Jan
08-01-2009, 08:45 AM
Why don't you guide the light to the plexiglass with a mirror ?
In that way the heat of the lamp will be gone before it reaches the plexiglass.........

Peter

I have seen a solution of somebody who did send the light first through water, and after that onto the subject also to cool the light.

Q.G.
08-02-2009, 07:26 AM
Acryl has a name here of "plexiglas". I will have a look where I can get this here local.
Some shops who sell material for modell of ships/airplanes sell this stuff.

Formido, Praxis, Gamma, and most other such shops will have sheets of plexiglass.

jerry lebens
08-03-2009, 07:35 AM
I tend to use 3mm white opal acrylic. You can create a curve using clamps etc, it depends how 'tight' you want your curve to be. Often the sheet can actually be left flat. As long as the sheet remains evenly illuminated and fills the picture frame it doesn't matter whether it's curved or flat : Obtaining a consistently white background depends on the size and shape of the object you're photographing relative to the size of the acrylic sheet and of course the angle of the camera to the background.

As for the acrylic deforming under the heat of lights, it depends whether you're using hot lights or not. With hot lights, you can use mirrors or reflecting panels both to disperse light evenly across the acrylic sheet and avoid overheating. With studio strobes, simply switch off the modeling lights once you've set up, the flash alone shouldn't generate too much heat.

Jerry

Russ Young
11-09-2009, 08:15 AM
I have a small sweep table... have used it for nearly three decades. It has a thin white opal plastic that needed no heat to make the bend (remember, you want a wide radius bend, not an angle)... have always used strobes so no idea bout how it reacts to heat.

Just be careful to not scratch it by scooting objects across it. Pick things up. Dust will also produce scratches if you clean it improperly.

Russ