How to Adapt a Door Viewer "Fish-eye Lens" on to a Full-size Camera

We've seen tutorials on this website that show you how an inexpensive door viewer can be used as a fish-eye lens on a simple point and shoot digital camera, but what if you want to try the effect on a camera with a full-size lens? This Instructable shows you how you can use an inexpensive plumbing part to make an adapter for the end of a camera lens with a diameter of approximately 49-55mm (or roughly 2 inches) - such as those on a "bridge" camera (an advanced point & shoot model that has many functions similar to a DSLR, but without a removable lens, mirror, and reflex system) or DSLR camera. This can also be used on manual-focus film cameras.

CAUTION: Even though the final step in making this adapter is to add a felt buffer to reduce the risk of scratching the lens, you will want to be careful when using the adapter. It happens that this particular model of camera has about a 1/8th-inch plastic border around the glass lens and the adapter rests mainly on this border, rather than the lens. Depending on your model of camera, the adapter ring may be seated on the glass. As a precaution, use a UV filter or similar functional filter to protect the lens, especially since a bridge camera cannot have its lens removed. At the very least, do not push the adapter against the lens and slide it around to adjust its position; rather, cap it gently over the lens and keep it in place when taking pictures. (See Step 7 for notes on using this adapter.) I assume no responsibility for damaged equipment.

Step 1: Materials and Tools Required

The basic materials for this project can be obtained at a hardware or department store for under $20.

Materials

- 1 Door viewer, available at any hardware store from about $5 to $12 in cost
- 1 Plastic plumbing reducer coupling (see picture) that will fit on the end of your camera lens and fit the door viewer - in this example, the wide end of the reducer has a 2-inch exterior diameter, while the long, narrow end has an exterior diameter of 3/4 of a inch
- 1 Scrap of felt (or similar soft material) at least 3-inches by 3-inches square
- A strip of cloth (such as flannel) or paper towel for padding

Tools

- 1 hacksaw or coping saw with fine teeth
- An indelible marker with a fine point
- Ruler
- 1 Thick rubber band (such as used for broccoli)
- Scissors
- Contact cement or a similar multi-purpose glue, safe for use on plastic
- Various files, sandpaper, or a sanding block
- Utility knife (optional)

And If You Have Access to Them...

- A bench-mounted vise
- A bench grinder or hand-held power grinder (e.g. Dremel with sanding disc)

Step 2: Assessing and Modifying Your Reducer/Adapter

As shown in the first picture, the narrow portion of the reducer coupling is actually a little bit longer than the barrel length of the door viewer.

The second picture illustrates what this looks like from the wide-end of the reducer, which is also where the end of your camera lens will be resting. As the setup stands right now, there are over two inches in distance from the end of the camera lens to the end of the door viewer lens, which wastes the majority of the picture area with blank space. In order to bring door viewer lens closer to the camera lens, the reducer will have to be shortened on each end.

Begin by sawing off the first thread ring on the narrow end of the reducer, using its ridge as a natural guide. (Picture 3.)

CAUTION! The saw blade gets quite hot from the friction. Avoid touching it right after completing a cut.

Step 3: Further Modifying Your Reducer/Adapter...

Now that the narrow end of the reducer has been shortened, the next step is to shorten the wide end of the reducer. Start by measuring 5/8ths of a inch from the top threading ring on the reducer and mark it with the indelible marker. Using the threading ring as a guide for the edge of the ruler, mark off 5/8ths of an inch around the reducer. (Pictures 1 and 2) If you prefer metric, use 16mm as your guide. Make sure at least three of the marked points are close together in a row.

Tip: If your ruler is a bit faded or it's hard to read where 5/8ths of an inch is, mark a reference point to it on the ruler before marking off the reducer.

Once the points have been marked, give the ink a couple minutes to dry, and then take your rubber band over the top of the reducer and line its edge up just below your reference points. Since the band has a tendency to want to be crooked, use the three dots in row as a guide to line up at least one section of the band as straight as possible. That will be the side where you will start sawing. Make sure all other reference points are just above the rubber band, and the band is fairly even. Draw a line connecting all the points around the reducer using the band as the guide now. (Picture 3)

Step 4: Further Modifying Your Reducer/Adapter (Continued)...

With the rubber band in place, turn the reducer until the straightest section you marked (ideally, the three points closest together) are at the top and start sawing down through the reducer, keeping the blade at a 90-degree angle (as best as possible, especially if you don't have the assistance of a vise). You may end up cutting through some of the rubber band on the way down, but the end result should be a fairly straight edge (Picture2). Keep back the other piece of the reducer for later.

Now you will will to smooth off all the rough areas and scrap plastic, as well as level the edge on the wide end of reducer (Picture 3). Use whatever materials you have on hand for this; sandpaper by itself is quite effective. (I cheated and used a bench grinder.) You may want to use a utility knife to trim around the interior of each end of the reducer; just be careful, as the type of plastic used is quite soft and can be carved into (a little too) easily.

Don't try melting off any persistent rough plastic pieces with heat from a lighter, though. I found out that the plastic absorbs the heat and you get black marks on the surface.

Step 5: Fitting on the Door Viewer

Now that the reducer has been shortened and filed off, you can fit the door viewer on and get a feel of what the the adapter is like with a unit.

Take the strip of cloth or paper towel, making sure it is no wider than the length of the door viewer barrel and wrap it around the barrel a couple times. Test to see if barrel will go through the narrow end of the viewer with a little resistance, but not so much that it jams halfway in. The best fit will be when the wrapped barrel goes in to the reducer with some twisting and will not fall out when the unit is turned on end. You should then be able to take out the door viewer again with a little effort.

Since I'm also using my door viewer on compact point and shoot, I don't want to mount it permanently in the adapter. You may want to make yours permanent gluing the barrel to the cloth with contact cement and then gluing it all into the reducer after that.

Tip: Depending on how you want it to fit, the door viewer barrel can be extended by unscrewing the lens portion from rest of the barrel. Just remember that the longer you make the barrel, the further away the lens will be from the lens of your camera.

Step 6: Adding a Felt Buffer for Your Camera Lens

The door viewer adapter is essentially ready for use now. However, before butting it up against your camera lens, add a felt buffer to reduce the risk of scratching the glass. This should also correct any uneven areas that may leak in unwanted light.

Use the leftover piece of the reducer couple to trace out a ring in your scrap of felt (or other cloth), as it provides you both the exterior and interior circumference guides needed. Cut out the felt ring with a sharp pair of scissors, and then apply a layer of contact cement (or your choice of glue) to both the end of your adapter and the "scrap" side of the felt ring.

If you are using contact cement, wait 10 to 15 minutes before joining the two pieces together; otherwise, follow the manufacture guidelines on your choice of glue. Be careful when lining up the pieces for bonding, as the contact cement is essentially a one-shot effort. Once the ring is glued to adapter and set, you're ready to take pictures.

CAUTION: Even though the felt is intended to reduce the risk of scratching the lens, you will want to be careful when using the adapter. It happens that my particular model of camera has about a 1/8th-inch plastic border around the glass lens and the adapter rests mainly on this border, rather than the lens. Depending on your model of camera, the adapter ring may be seated on the glass. As a precaution, I would use a UV filter or similar functional filter to protect the lens, especially since a bridge camera cannot have its lens removed. At the very least, do not push the adapter against the lens and slide it around to adjust its position; rather, cap it gently over the lens and keep it in place when taking pictures. I am not responsible for any damaged equipment.

Step 7: Tips on Using the Adapter

Assuming you have followed safe protocol and are using a protective filter over your lens, or the camera model is one that lets the adapter rest without touching the glass, you are ready to experiment with your budget "fish-eye lens". Here are a few tips for getting started:

- The camera seems to focus best when the lens is extended out to its longest focal length; this also allows the largest area to be filled with the view from the "fish-eye"
- If you have a digital zoom option, you may want experiment with that, too, as certain settings allow for even more viewing area to be filled
- Since you will only be getting about 1/2 to 2/3 of the total area of a frame filled, set your camera to its highest resolution, as you will probably want to crop your images to a better fit later on
- Focusing can be a bit of a challenge, especially in automatic mode; if you have an option to override the auto focus manually, try using it
- If you have a manual setting on your camera, you may find it easier to work with for this
- Depending on how you aim your camera in relation to the sun, the curvature of the door viewer may lead it to picking up more light and creating a white spot where you do not want one; try focusing the camera and setting its light balance without the fish-eye, and then cap the adapter and lens over the shot on those settings
- Always cap the adapter/fish-eye over your lens, rather than slide it up against the glass to reduce the risk of scratching it
- If your camera has a "mosaic" in the middle of the manual focus screen, try to pick a contrasting scene (as in Picture 2) to help you with focusing
- A trip can be helpful, as you may find yourself trying to focus, hold up the adapter, and aim the camera all at the same time in many instances
- Don't try to rush when you are first getting the feel of this

Photo 1: Looking directly up at a satellite dish on a roof corner. I used the camera on "auto" with a 140mm focal length (equivalent to 135mm in film) with no digital magnification. The photo was cropped and rendered a greyscale in GIMP.

Photo 2: Treetops photographed at sunset. This was taken on "manual" at ISO 100 with a 140mm focal length (equivalent to 135mm) with a 1.4X digital magnification. The photo was cropped and brightened in GIMP.