This section could use some work on laser-lit transmission holograms and refinement on the instructions for rainbows.
- Use a digital camera. This will allow you to experiment to your hearts content without worrying about burning film.
- Always turn your flash off, it will never help when photographing holograms.
- Use a good steady tripod. Minor shake can cause ugly blurring in what could otherwise be a good photo.
- If your camera has them, experiment with the manual exposure, metering, aperture and ASA controls. If your camera records all these settings in the exif data you won't need to write down what settings go with what picture. If anything is missing, make sure you take good notes so that you'll know what settings give you the best results.
- Take your pictures in a dark room (excepting the single light used to illuminate your hologram) so that you won't see reflections of the room in the surface of your hologram.
- If you can't make your room sufficiently dark and find that reflections of you or your camera are visible in the hologram glass, do the following. Take a large sheet of black cloth and cut a slit in it big enough to pass the lens of your camera through. Place sheet over your camera with the lens sticking through the slit and wrap a rubber band around the slit edges and lens so that the sheet is held in place. When taking your pictures drape the sheet over your head so that you and the camera can't be seen in the hologram glass. You may need a sheet large enough to cover the legs of your tripod if it's highly reflective.
- If your camera has difficulty focusing on the image in the hologram instead of the glass
take the hologram and lean it such that it is shimmed away from a flat surface or wall by an inch or so. Take a piece of white card and lie/lean it next to the hologram at the flat surface or wall (it will be an inch or so further away from the camera then the hologram). Now take the digital camera and point it at the white card and hold the button half way down. This locks in the focus and exposure of the white card. Now without releasing the button, move to the hologram and push the button in the rest of the way which will take the photo. By adjusting the distance separation between the card and the hologram (1/4 inch, 1/2 inch, 1 inch etc.) you should be able to get the hologram to be in focus. By adjusting where you point the camera on the card (edge or middle) and by holding down the button you should be able to lock in different degrees of exposure/aperture as locking on to the hologram itself overexposes the photo.
- For lighting use a single halogen bulb plugged into a dimmer so that you get a clear single source of light and can control the brightness to get the best image.
- Optileds can also be used to provide narrow-band replay light that results in less haze and clearer, deeper hologram reconstruction.
To photograph these, if you want the greatest detail, I would recommend the following:
- Make sure you have a really good point source of light, so the image is as sharp as possible. As you have a camera and tripod, you can use a long exposure, and the image does not have to be bright. So move your reconstruction light as far away as convenient from the hologram. The image will get dimmer but sharper. I am assuming the hologram is designed to be viewed with a collimated or near-collimated beam.
- Now move your camera towards or away from the hologram till the image is a single color. Now you are in the projected 'slit' of the rainbow hologram.
- Move the camera up and down till the center of the image is the color you want the image to be.
- Move camera towards or away till the entire image is in that color.
- Switch off flash; put camera ASA setting to minimum, e.g. 50
- Focus the image. Simple digital cameras don't normally allow manual focusing these days, but try different things till the image looks as sharp as possible.
- If you have any control, keep the aperture as wide as possible, i.e. f/2 is better than f/16. This will minimize speckle.
- To minimize shake you could put on timer and the camera will shoot a few seconds after you press the button.
All would be so much simpler with an old fashioned manual camera, or else a pro digital camera with full control. Good luck.