Pinhole Photography Attachment for Micro Four Thirds

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One of the joys of mirrorless interchangeable lens cameras is the ability to experiment with older lenses, bellows, and similar equipment without any tedious record keeping or expense of film.  With a simple attachment, one can readily adapt a mirrorless camera to experiment with one of the earliest photographic techniques, using a pinhole rather than a lens to project the image.

MkII pinhole non-lens on E-P1

Supplies needed:

C-mount to Micro Four Thirds lens adapter (~$10 off eBay)

Large metal washer to fit the recess in the C-mount adapter (~$1 at local hardware store)

Aluminum flashing or similar thin sheet (also at hardware store, or from the peel-off top of a food container (bread crumbs, soft cat food, etc.) )

CA adhesive (“Superglue”)

PVA adhesive (“Elmer’s Glue-All”)

Marking tool (pencil or ultra-fine point Sharpie brand marker)

Scissors (capable of cutting the aluminum)

Center punch, hardwood block, and small hammer

600 grit wet-or-dry sandpaper and flat surface (glass sheet, marble block, etc.)

Needle and softwood block

Ruler marked in millimeters  (for the obsessive)

Flat black spray paint (optional)

 

Parts for first prototype.

1.  Use the inner edge of the washer to trace circles onto the aluminum sheet.  Then, use the C-mount adapter to trace a larger circles around the smaller circles; these circles should be spaced in slightly from the inner edge of the opening in the C-mount adapter.  Cut out the circles.  Note that the metal edges may be sharp enough to cut through skin!

 

2.  Use the punch to make an indent in the center of each cut-out circle.  This should only take a very light tap.  (Note that the photo shows punching disks for the second prototype, in which the dimples are punches first and then the disk cut out around the indent.)

3.  Sand the side of the aluminum circle with the bulge on a flat surface (the photo shows a marble block salvaged from a bowling trophy – $0.50 at a yard sale years ago) until the bulge has been flattened.  (Again, the photo shows disks for the second prototype – cutting the parts crudely (very crudely) to shape and selecting the most promising disk or two before cutting the circle saves effort in cutting.)

4.  Use the needle to poke a small hole in the center of each indent to form aperture disks.  Ideally, the hole should be 0.2mm in diameter for a Four Thirds sized sensor.  Since the ruler likely is not marked finer than millimeters, estimate about 1/5.  The first try, most likely the smallest hole will still be overly large.

No, I don’t really believe that readers really need this step illustrated.
Yes, I should have trimmed my nails.

5.  Select the best-looking of the punched disks and use CA adhesive to attach it onto the washer, with the punched hole centered in the washer opening.

 

6.  Optionally, spray the washer and disk (on the side of the washer onto which the disk is attached) flat black.

 

7.  Position the washer in the recess in the C-mount adapter (with the aperture disk facing inwards toward the camera-mounting side) and move it until the aperture is centered.  Use dots of PVA glue around the washer (applied on the outer lens-mounting side of the adapter) to attach the washer in position, and set aside to let the glue cure.

 

Testing of the Mark I suggested that the aperture was too large, resulting in a blurry image.

The optimal pinhole size calculator at:

http://www.mrpinhole.com/wiz.php?Func=FilmDimension

indicates that, for a Four Thirds sensor (17mm x 13mm), the optimal size would be 0.2mm.  Comparing the aperture to a ruler revealed in an estimated 0.4 mm aperture, rather than the optimal 0.2 mm.

 

Naively believing that a sharper image could be attained with the proper aperture size, the MkI device was modified.

To provide a smaller aperture, and the ability to readily change the aperture disk as needed, the aperture of the Mark I device was drilled out a bit and a new aperture disk added to form the Mark II device.  The new aperture disk is cut smaller than the washer opening and is attached atop old Mark I aperture disk using PVA glue in the same manner as the washer was attached to the C-mount adapter.

The aperture can be readily centered by holding the assembly overhead and holding the disk down while applying the glue; just be sure that the neighbors aren’t watching this spectacle.  The glue allows the new disk to be readily removed for replacement, which facilitates trying different aperture sizes.

Attaching the washer to the C-mount adapter by PVA glue allows it to be removed if it is desired to use the C-mount adapter for its intended purpose, such as after finding that the image is blurry no matter what size aperture is used, due to the diffraction of light.

MkII with estimated 0.25mm aperture

MkII with estimated 0.2mm aperture

 

Filter Bracket for E-P1 14-42mm Kit Zoom

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The E-P1 kit zoom is the first generation Olympus 14-42mm Micro Four Thirds zoom, which does not handle filters well.  The terminal element rotates as the lens focuses, and the petite focusing motor is not happy when torque is applied to the filter threads.  Even rotating a 46mm polarizer needs to be done gently to avoid an irritating and cryptic “Please check the status of a lens” message on the viewscreen.  (Reportedly, the 2nd generation 14-42mm has internal focusing and avoids this problem.)  Clearly, there was no way that the little focusing motor could handle a Cokin A holder and a graduated ND filter for shooting landscapes with the lens at its wide angle setting.

The simplest solution appeared to be to form a bracket to position an empty filter ring around the end of the lens when in its extended wide-angle position (a peculiarity of the lens is that it is shortest in the middle of its zoom range, extending out as it goes either towards the wide angle or telephoto end.)  Accordingly, an L-shaped piece of scrap aluminum was cut to rough size from a salvaged piece of electronic equipment.  Measuring the desired setback of the camera body with the lens extended, a 1/4″ hole was drilled for a screw to attach the bracket onto the base of the camera via the tripod mounting socket.  Note that this screw should have a threaded recess itself to allow the entire ungainly assembly to still be tripod-mounted.  Thin cork gasket material was attached to the top surface of the aluminum with double-sided tape.  The camera was then secured into place, the lens extended and an empty 55mm filter ring placed roughly concentric with the end of the lens.  The filter ring was traced, this outline used as a guide to cut a curve in the aluminum, and the ring attached in place with epoxy.

A second scrap filter ring was added; this second ring not only provided additional surface area for the epoxy bond, but also extends back over the end of the lens to provide some shading, particularly when the lens is retracted in its middle range.  The back of the aluminum was eventually cut so as not to protrude behind the camera as it does in these early views.

Now, any filter system that can adapt to a 55mm thread can be attached, without straining the delicate focus motor of the lens.  This piece of gear, along with a Cokin A holder and 55mm mounting ring, was dutifully stowed away in the center console of my automobile ready for use in my travels.

In practice, I hardly ever pull out this clunker, and instead simply hold a grad ND filter by hand in front of the lens.  This does require a good bit of care to avoid reflections when there is light striking the camera from behind.

Happily, I found that this rig is well suited for shooting in rain and snow (without a filter).  For this use, a 1-gallon plastic bag with one corner cut off is forced over the marrow section os a telescoping rubber 55mm lens hood, and the hood is then screwed onto the ring on the bracket.  The bag covers the camera, with access for the hands from below, and the hood extends to shield the lens from precipitation.