1 post tagged “filter”

With some inspiration from Sam Noyoun's article at diyphotography.net, I decided to try to make some ghetto inexpensive infrared filters for use with my SLR's lenses. Be sure to check out the results at the bottom of this tutorial.

Apparently most point and shoot digital cameras are extremely sensitive to the IR spectrum and some D-SLRs are. You can test if your camera is sensitive by setting your camera to shoot a long exposure and pointing a remote control at the camera, pressing buttons on the remote during your exposure. If your image reveals a "light" coming from the front of the remote you are in business.

Getting started:

Basically what we will do is try to simulate (not exact) the spectral transmission of a Wratten 87 or 88 filter by starting with some unexposed 120 or 4x5 sheet film (for larger than 67mm filters). You may choose E-6 or C-41 film.

For E-6: Do not shoot or expose the film, simply have a lab develop it and let them know that it will be blank and that you want the film back. Make sure that they sleeve your film and they do not fingerprint it up! Most labs will not charge you for a blank roll or sheet.

For C-41: Completely expose the film by unwrapping the paper backing to daylight (120 film) or pulling out the sheet  of film in daylight (4x5). Have it processed and tell the lab you want the black negs back. Make sure that they sleeve your film and they do not fingerprint it up!

The rest of the items you will need:

• Scissors
• Box knife or razor cutter
• Gaffers Tape (preferred) or black, electric tape
• A black marker (with lots of ink)
• A pen
• Medium thickness cardboard
• A lens
  

Start by cutting out a thin, long strip of cardboard that will fit snug (but not too tight) around the barrel of your lens.

Make the outside of the "ring" with your gaffers or electric tape.

Paint the whole thing black with your marker.

Put the ring on your lens, make sure it fits correctly and goes on and off smoothly, but snug with no major light gaps (this is important). Also, test the setup for vignetting (if it does vignette, cut the ring thinner so that it won't).

Next cut another long, thin strip of cardboard to make a tight fitting inner ring. If possible, use a thinner piece of cardboard for this because a thick piece will cause some vignetting (esp on wider lenses). Once the inner ring is placed inside the outer ring, mark and cut off the excess to make both rings sit on the lens flat and level on top.

Don't forget to paint the inner ring black. (try to do a better job than my crappy illustration)

Next, trace the outside of the big ring

 

Then remove the the rings (leaving the inner ring inside the outer ring) and trace the INSIDE of the inner ring to make a donut.

 
It doesn't have to be perfect, here is mine. Cut the donut out with your xacto knife or box cutter. Don't forget to paint it black!

Place the new cap on top of your assembled rings (try to line it up as best as possible) now tape it on, making sure to cover all holes and potential light leaks. Gaffers tape is light tight and would work best here.

Now using the outer diameter of the INSIDE ring as a rough template, cut out two equal size/shape pieces of film and place them inside your ring against your cap as flat as possible without any light leaking in on the corners. Note that I used negative film for mine which required two pieces for the proper opaqueness. I've read that a single sheet of unexposed, developed Kodak E-6 film has the same spectral transmission of a wratten 87 filter.