For ISO standard 23mm and 30mm eyepieces, and Zeiss OPMI and slit lamp eyepieces

Richard J Kinch

Description:The eyepiece to digital camera adapter mechanically and optically couples instruments using standard eyepieces to small digital cameras such as the Canon Powershot A-series (see current list of compatible models in the specifications below). Many other brands and models of smaller digital cameras with small lenses and filter thread mountings or adapters may also work with this adapter.

The adapter assembly consists of a cylindrical, custom-machined adapter which provides standard male filter threads (52mm M52x0.75 thread, or 58mm M58x0.75 thread) on one end, which attaches precisely and rigidly to an eyepiece. This eyepiece may be a new one we supply with the adapter for standard sizes (23mm, 25mm, or 30mm eyetubes or phototubes), or it may be an existing eyepiece you have sent to us for custom fitting to our adapter. Other filter thread sizes may be fitted via standard camera step-up or step-down rings. The custom adapter attaches to a stock conversion lens adapter for the Canon camera, which is a thin tube providing a bayonet adapter on one end and female filter threads on the other end. The custom adapter and stock adapter screw together via the threads to complete the assembly. One end then attaches to the camera and the other end with the eyepiece inserts into the microscope eyetube or other instrument.

The conversion lens adapters for certain Canon models provide an additional threaded ring marked "tele" which lengthens the tube by about 11mm. This ring extends the conversion lens adapter to accommodate the longer extension of the Canon camera lens in the mid- to telephoto-range of camera zoom. The adapter assembly is normally used in the widest wide-angle zoom setting, or slightly zoomed in, without the extension ring. Other Canon models, and non-Canon makes, do not provide this ring; instead one adjusts the tube length by threading the adapter further in or out of the conversion lens adapter, or by loosening the thumbscrew and adjusting the eyepiece position relative to the camera.

Removing the Canon ring: Lens accessories attach to the Canon A-series cameras via a conversion lens adapter which in turn attaches to the camera via a bayonet fitting. To expose the bayonet receptacle on the camera at the base of the lens, remove the lens ring from the Canon camera by pushing the release button and turning the ring. Refer to the Canon manual for your camera for further details on removing the ring.

Attaching the adapter to the camera: Insert and lock the bayonet end of the adapter assembly to the camera. A bit of play exists normally with this attachment. Loosen the thumbscrew and slide out the photo eyepiece. Turn on the camera and switch it to picture-taking mode, so that the lens turret of the camera extends in the wide-angle position. Slide the photo eyepiece back into the adapter gently until it just touches the end of the camera lens turret, and then lock the eyepiece in place by tightening the thumbscrew. The LCD display screen of the camera should show a crisp circular field of view from the eyepiece optics. On some cameras and with different zoom settings it may be necessary to loosen the thumbscrew and adjust the eyepiece position in the adapter in and out to remove vignetting.

Attaching and detaching the adapter from the instrument: Insert the eyepiece end of the adapter into the instrument's eyetube. The telescoping fit will not typically be snug enough to fix the rotational alignment of the camera to the instrument, so you may wish to rotate the camera to a "portrait" orientation with the heavy end down.

Several methods of switching from normal viewing through eyepiece(s) to photographing are possible. If you have a binocular pair of eyepieces, it is usually possible to view through one eyepiece while photographing through the other. Or you can switch the camera on and off the photo eyepiece by loosening the thumbscrew. Or you can remove the photo adapter and eyepiece as a unit with the camera, and switch in a normal viewing eyepiece.

Calibrating photo eyepiece axial distance to eliminate vignetting: "Vignetting" refers to darkened edges of the field of view in the camera, instead of even illumination. Vignetting occurs when the exit pupil of the photo eyepiece is not aligned to the entrance pupil of the camera lens. This effect is much like the vignetting you see when your own eye is too close or too far away from a viewing eyepiece. To calibrate this distance and eliminate vignetting: (1) Mount the camera and adapter on the instrument to set up a live view on the camera LCD using a low magnification of the instrument and the widest angle zoom of the camera. (2) Loosen the thumbscrew fixing the photo eyepiece in the adapter, and adjust the eyepiece axial distance in and out slightly while viewing the camera's live view. The closest adjustment, with the eyepiece just touching the camera lens turret, is a good starting adjustment, but not likely to be the best. You should see vignetting appear when the eyepiece is adjusted too close or too far away axially from the camera lens, and a certain distance where vignetting is eliminated. Lock the eyepiece in this axial position with the thumbscrew. (3) Check and repeat this adjustment for higher magnification objectives on the microscope, which will be more vignetting and perhaps require are more careful fine-tuning of the axial adjustment. Typically one permanent adjustment of this distance will eliminate vignetting for all objectives of a given instrument, and the adapter-camera combination may then be said to be "calibrated" to that instrument. The following may require re-calibration of the axial distance to avoid vignetting: (1) Using the adapter on a different instrument, since the instrument exit pupil may differ, (2) Adjusting the camera zoom, which moves the entrance pupil of the camera lens, and (3) Switching the adapter to a different camera model since the camera lens optics may differ.

Starting the camera and setting the zoom: When first turned on, the Canon camera will set the camera lens in the widest angle zoom setting. This maximum wide-angle setting is the normal setting for photography with the adapter, because the circular instrument field just fills the camera field up to the top and bottom of the rectangular edges ("inscribed" crop), and the corners are dark. Thus you need take no action to adjust the camera for this choice of image cropping. You may also zoom the camera's lens just a bit from the widest angle, to obtain an "outscribed" crop, where the corners of the image are just inside the circular instrument field, the entire camera frame is imaged, and crescent portions of the instrument field are cropped out of the camera image.

To zoom in slightly with the camera lens, you must first loosen the thumbscrew and move the eyepiece out to prevent the camera lens turret from bumping into the adapter as the turret extends from zooming. If you attempt to zoom too far without this adjustment, the camera will shut down while displaying a "lens error" message. To correct this error, you must restart the camera (that is, turn it off and back on). For extreme zoom positions, the range of adjustment of the eyepiece alone is not enough, and you must insert the extension ring to lengthen the tube, followed by adjusting the eyepiece back near the end of the lens turret.

Using the automatic camera focus, aperture, and exposure time: Typically the automatic mode of the camera works well when photographing through optical instruments with our afocal adapter, which makes everything very easy. In this case, the camera will automatically focus on the instrument image, and select an appropriate aperture and exposure time. Many instruments are compatible with this "point and shoot" convenience.

Setting manual focus, aperture, and/or exposure time: If the automatic mode of the camera does not produce suitable results, or you want precise and repeatable control of photographic conditions, use the manual settings to set the camera properly. The adapter optics should provide an image that appears to the camera to be at infinity, not close up, so you should normally be using a fixed manual focus at infinity. Different manual settings of aperture may improve or degrade resolution, contrast, and vignetting of your instrument's image, and may require that you adjust the adapter photo eyepiece position relative to the camera lens using the thumbscrew.

Consult the Canon manual for using the custom "C" mode of the camera, which will allow you to save a manual setup of the camera for quick and consistent use.

Microscopy is as much about light as magnification, and photomicrography is critically dependent on sufficient light for the best quality photographs. This is especially true of the small digital sensors in most digital cameras, which produce noisy images if not supplied with many photons per pixel.

Adjusting and calibrating for parfocality: The adapter is designed and delivered for "parfocal" operation. In practice, this means that the camera will take a well-focused photograph whenever a trained operator sees a properly calibrated and focused instrument view through the normal eyepiece view. That is, one need not be concerned about adjusting a different focus for photographing with the camera versus the normal visual view of the instrument. Furthermore, the autofocusing capability of the camera (if you have not set the camera to a manual-focus mode) can typically compensate for a slight mis-focusing of the instrument, both inside of and "beyond" infinity.

Cleaning the optics: Cleaning the optics should not normally be necessary, as they are protected within the adapter. The exposed lens face nearest the camera can be cleaned without disassembly. If cleaning of the internal optical surfaces should become necessary, the eyepiece may be disassembled by unscrewing the body end from the eyetube end. Unscrew these two parts of the eyepiece cylinder, a narrower and wider end, from each other. Remove the two lenses and one spacer ring. Take care to note the orientation of the lenses and spacer ring in the assembly so that you do not reassemble them backwards, which would degrade image quality. Carefully clean the lenses and remove any dust, as you would for a microscopic instrument.

Warranty: We manufacture these adapters to high mechanical and optical standards, and guarantee the performance will be in accord with the specifications. Please contact me via email ( should you have any difficulties we can correct.

Specifications (January, 2009)

Input interfaceISO standard eyepiece (23mm or 30mm) or Zeiss OPMI eyepiece (25mm)
Output interface37 degree circular afocal image
M52x0.75 or M58x0.75 male thread
(52mm or 58mm camera filter thread)
(Step-down rings to 46mm and 37mm available)
19mm exit aperture
18mm exit pupil relief
Field number18mm (with 23mm or Zeiss eyepiece, or 23mm eyepiece with 30mm adapter bushing)
22mm (with true 30mm eyepiece)
WeightApproximately 110 grams
(52mm version, varies slightly with eyepiece tube size)
(Includes unextended conversion lens adapter)
Overall length53mm (eyetube shoulder to front of camera)
Canon camera models compatibilityCanon A510, A520, A540, A570, A580, A590IS,
A610, A620, A630, A640, A650IS,
A710IS, A720IS,
G7, G9
Optical elements3 elements in 2 groups, fully coated
ManufactureCustom made and assembled in USA