One of the world’s top camera makers of today has an 800mm lens with a list price of $13,999; a very fine looking product indeed if you have the cash and/or if your spouse lets you spent it!
Being the combined engineer and cheap-skate that I am, I looked over this state of affairs and decided to set myself the personal challenge of making a telephoto lens for an out-of-pocket cost of approximately $1!
[ SPECIAL WARNING: Don’t attempt a hair-brained project like this until you are first absolutely certain that your spousal-unit and/or significant-other are in a good mood! ]
Below is a step-by-step/blow-by-blow account of this little adventure.
STEP 1. THE OPTICS
For centuries optical engineers have tackled the problem of different color refraction effects and strived to minimize diffraction, lens flair and a host of all sorts of other effects, all while allowing focusing at different distances. Fancy lens coatings, super glass, multiple glass elements, moving elements relative to one another, precision machining and all sorts of other techniques go into the modern commercial products we are fortunate to have available today.
However, I decided to completely ignore centuries of progress. Therefore I proceeded to make a grand tour of all the stores in my area that advertise “Most All Items for $1 or Less”. After visiting these fine establishments, I selected a magnifying glass with a diameter of 96mm from the School-Supply Section as my one and only glass lens element for my telephoto lens. Cost = $1, plus appropriate taxes.
STEP 2. THE DESIGN
At this point I realized I was already over-budget due to ‘taxes’. However, I was bound and determined to forge ahead so I first scoured this house for all sorts junk squirreled away from past projects, ranging from fixing the toilet to rocket-science.
Next, I used instruction on the internet for how to measure the focal length, which in this case turned out to be 325mm for the readily available lens at ~$1. Then, I pondered and poured over my list of junk and then proceed to finalize the design on the back of an envelope.
STEP 3. FABRICATION
To avoid questions like "“What is that smell!?”", "“Why are you doing that!?”", etc., I recommend at this point that you re-confirm that those around you are in a good mood and send them off on a diversionary maneuver like shopping or something like that so you can proceed with the task at hand.
Fig. 1 shows the final result. Along with the primary lens magnifying glass element, a piece of painted 4” PVC pipe is the lens tube. The f-stop is achieved by putting holes of various diameters in approximately 1/16 inch thick sheets of aluminum painted black. A f=51 value, for example, is achieved in this design by using a ¼” hole in the aluminum sheet. Smaller holes produce larger f-values while bigger holes produce smaller f-values. If no f-plates are inserted then this lens is f3.5.
Another sheet of the aluminum without a hole is used as the shutter. The f-stop sheet, the shutter sheet and filters (if any) fit into a slot in the PVC pipe just in front of the primary lens. Pull out the “shutter sheet” of aluminum and the exposure starts. Put this sheet back in its slot and the exposure ends. “Shutter speed” is measured by a stop-watch.
The focus is achieved in this design by moving the lens closer or further away from the film. In this case I mounted the lens to a 4”x5 ”view camera and the bellows are used to focus the lens. For close objects the lens is moved away from the film, while for distant objects the lens is moved closer to the film. Exposure is determined using a hand-held light meter.
Fig. 1 Telephoto Lens for About $1 (Photo by Claudia)
STEP 4. TESTING AND SUMMARY
Fig. 2 shows a sample photo. If a large f-stop number (small aperture opening) is used this will tend to produce a large depth of field and provide somewhat of a pinhole effect. On the other hand, an advantage of using a much smaller f-stop number (large aperture opening) are photos with a “dreamy” effect and less depth of field.
What fun! And, best of all, my wife, Claudia, somehow managed to put up with me throughout the lens-making event!
ISO 400 4”x5” Sheet Film, 4 second exposure at f 51
Fig. 2 Sample Photo Made By a $1 Lens “Claudia’s Doll
|Feature||Commercial Super Telephoto||My Home-Made Lens|
|Fabrication Time||0 - Just supply the cash!||~6 hours|
|f-stop||5.6 to 32||3.5 to 256|
|Glass Elements||18 in 14 groups||1|
|Features||Image stabilization, Auto focus||Manual everything, Shutter is a drop-in plate, f-stop is another drop-in plate|
|Filters||52mm drop-in||96mm drop-in|
|Minimum Focus||19.7 feet||4 feet|
|Weight||9.9 pounds||1.3 pounds|