GuerillaBeam slide holder

Prints (0)


GuerillaBeam is a modular flashlight image projector.

A gBeam projector consists of this slide holder (holding slides and add-ons) and screw-in adapters for lenses and lights. Thus, this slide holder is compatible with virtually any lens and most LED lights.

What to expect:

With a 1000 Lumen (10W) flashlight, the brightness will be  comparable to a 100W classic slide projector.

Depending on the lens used, projection range is between 0.1m and 150m. Image quality is usually worse than with conventional projectors, but good enough  (using slides printed on overhead transparencies). 

Compatible devices:
  • current SLR camera lenses (Canon, Nikon, Pentax and compatible)
  • old SLR lenses (M42*, T2*, Canon FD**, Minolta SR, Praktica B, Rollei QBM, Contax, and many more)
  • projector lenses with (standard) tube diameters of 42, 52 and 62mm
  • TrustFire X8 flashlights (most recommended)
  • many other LED flashlights, MR16 and GU10 LED spotlights
How to make:

Firstly, determine the thickness of your 35mm slide mounts. There's one version for slides with up to 2.00mm thickness (i.e. Agfa CS), and another one for thick slides  up to 2.5mm.  (Other sizes available on request).

1. Print the slide holder.
  • Wall thickness of 0.8mm and layer height <0.2mm is recommended. Assuming there are no major defects in your print, this will suffice to support lenses up to 2kg.
  • Recommended infill percentage is 23%. With greater wall strengths, it can also be zero.
  • This part (only) absolutely needs support material. Its only a minimal amount at the slide slot, but it's crucial. Using Cura, automatic support generation for overhangs >51% will work perfectly. With other slicers you might have to try something else. Inspect the support material generated by your slicer carefully, because otherwise you might not be able to remove it.
  • If you have trouble printing, I give support..
  • If you'd like a finished slide holder you can order it here.
2. Install a fresnel condensor lens:

For optimal brightness and FOV the slide holder has to be equipped with a fresnel lens. Such a lens can be obtained by inserting a credit card magnifier lens  into the slide holder. Cut the lens to the size of 38x48mm and insert them to the corresponding slots on the inside of the slide holder (use rubber gloves).

Select lens and light: 1. Lights

A good basic light can be any focused Cree XM-L flashlight. Those are sold from $10 upwards and typically use 18650 batteries. Especially suited is the TrustFire X8 (or the UltraFire X8 but the latter has annoying electronics). Lights with multiple LEDs (like ThruNite TN30 or Sky Ray King) can give even brighter images, but yield lower efficiency and can cause heat problems.

2. Lenses

Any lens with an  f-number of 2.8 or less will work fine, provided there's an adapter for it. Slower lenses (f/3.5, f/4, etc.)  will work too, but only with significantly reduced brightness and image quality.

Recommended focal lengths are between 85mm (short range, most affordable) and 200mm (long range, costly).

Last words:

If you have any question, you can contact me at [email protected]

For more information or buying finished projectors please refer to

Design Files

File Size

2.34 MB
2.43 MB


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