Installing and Using the Digital Camera Upgrade for the Topcon TRC-NW6 and TRC-NW6S

Updated: December, 2018

Kit contents:

Digital camera mechanical/electronic/optical adapter assembly (see Figure 1 below), consisting of:
- Adapter front plate.
- Topcon bayonet and pogo-pin fitting (removed and reused from your Topcon Polaroid attachment).
- Adapter tube (37mm).
- Front knurled ring for adapter tube.
- Adapter alignment socket (10-32 x 3/8 nylon SHCS).
- Rear 52-37 step-up ring for digital camera lens.
- Remote shutter and flash sync electronic interface connections.
These instructions.

For online pricing and ordering, see http://www.truetex.com/range.htm.

Required camera and lens: The Canon digital SLR camera body and lens may be purchased with the digital upgrade kit at additional cost, or you may obtain them directly from a camera retailer. The adapter works with the standard, unmodified Canon camera body and lens. See Figure 1a below. The specific model Canon lens identified below is a strict requirement; other lenses will not frame or focus properly with this adapter:

Canon digital SLR camera body: any model with EF-S lens mount (Canon Rebel series such as XS, T1i, T2i; Canon 50D; Canon 7D)
Canon EF-S 60mm F/2.8 Macro USM lens

Topcon TRC-NW6 TRC-NW6S digital adapter front

Topcon TRC-NW6 TRC-NW6S digital adapter rear

Figure 1. Adapter front and rear views.

Topcon TRC-NW6 TRC-NW6S adapter with Canon 40D digital SLR camera

Figure 1a. Adapter with Canon 40D digital SLR camera body and Canon lens.

Figure 2. Topcon TRC-NW6 retinal camera, prior to digital upgrade.

Attaching the digital camera to the adapter:

Study the camera manufacturer's user guide so you are familiar with the camera components, assembly, and operation.
See Figure 3 below for a reference to the following assembly.
Attach the camera lens to the camera body.
Assemble and hand-tighten the threaded lens attachments as follows. Hand-tighten only; do not use tools to tighten as this will make loosening for adjustments difficult.
Screw the 52-37 step-up ring firmly into 52mm threads at front of camera lens. This ring may be supplied to you already assembled to the adapter tube.
If not already assembled, screw the adapter tube 37mm rear threads firmly into 52-37 step-up ring.
Loosen the front tube ring and rotate the front adapter plate to be aligned vertically with respect to the digital camera body. Placing the assembly upright on a flat table surface will help align the camera precisely with the bottom of the adapter place.
Hand-tighten the front tube ring. The adapter should now be rigidly aligned on the digital camera.

Attaching the adapted digital camera to the Topcon instrument:

See Figures 3 and 4 below.
Rotate the bayonet locking arm fully to the right to fully loosen the bayonet receptacle lock.
Align and insert adapter bayonet fitting into Topcon camera mount receptacle.
While inserting the bayonet into the instrument receptacle, observe the lower alignment pin and rotate the adapter to fit the nylon alignment socket on the bottom of the adapter over the pin.
While pushing the adapter bayonet into the instrument receptacle, rotate the bayonet locking arm to the left to secure and lock the adapter and the camera to the instrument. This may require some jiggling since the bayonet fit is close and the alignment pin and socket must also be aligned at the same time. You may adjust the nylon screw on the bottom of the adapter, which mates to the lower alignment pin, to provide more or less clearance to the lower alignment pin.
The adapter and camera should now be rigidly attached to and aligned with the Topcon instrument.

Connecting the adapted digital camera electronically to the Topcon instrument:

Connect the flash sync cable from the interpolation cable to the camera's hot-shoe.
Connect the shutter remote cable from the interpolation cable to the camera's remote connector. The cable provides a Canon E3 connector, which fits directly to Canon Rebel model digital SLR camera bodies. See Figure 5. If using another Canon model, use an optional E3/N3 adapter (available from us) on the remote cable connection, which will provide a Canon N3 connection as in Figure 6 below.
Use cable ties to dress any loose cabling to the adapter.

Configuring the digital camera for retinal photography:

Refer to the camera manufacturer's user guide for details on operating and configuring the digital camera in the following particulars.
Maintain the camera battery charge if you are not using an AC power adapter.
Insert a memory card.
Turn on the camera power.
Set the camera mode dial to "M".
Set the camera shutter speed to 1/20 SEC.
Set the lens aperture to f/2.8.
Set the camera ISO speed to ISO 800.
Set the white balance to FLASH, not AWB (automatic white balance), incandescent, fluorescent, or other setting.
Set the switch on the camera lens to MF (manual focus).
Set the initial focus of the camera lens by turning the lens focusing ring to the extreme close position, which indicates 0.2 meters on the range scale. See Figure 7 below. (This is an initial focus setting only; to get sharply-focused images, you must fine-tune the focus in later steps below as part of the adapter parfocal calibration.)
If you are using tethering software for instant transfer and viewing of digital photos on a tethered PC, refer to the software documentation for configuration and test.

Testing and confirming correct digital photography operation with a test target:

Tape a fixed test target, such as a business card, to the headrest, approximately in the subject eye position. Pull the instrument back with the joystick, as if framing to photograph the anterior segment of a subject eye. Pull out the subject diopter correction lever to the plus setting ("+") on the left of the Topcon instrument; this should provide a focusing range to focus the instrument on the test target, as if taking an anterior photo.
Connect the AC power cord and turn on the Topcon instrument.
Frame and focus on the test target using the Topcon LCD display. Pull the instrument carriage in the rearward position, so that the instrument clicks into the anterior framing mode, not the retinal focusing mode.
Verify the digital camera lens focus selection is set to MF, not AF. See Figure 7 below.
Verify the digital camera lens focus is set to 0.2 meters on the distance scale. See Figure 7 below.
When the instrument flash is charged (that is, the lightning bolt on the Topcon display stops flashing), shoot a photo by pressing the joystick button.
Review the photo on the digital camera playback (or tethering software if so configured). Since the digital camera manual fixed focus has not yet been precisely calibrated to the instrument, the image may be out of focus, but should at least be recognizable, confirming the basic operation of the adapter and digital camera.

Calibrating the digital camera lens focus to the Topcon instrumentation optics:

NOTE: Focus calibration is crucial to getting sharply focused photographs.
If you do not properly complete this procedure, your digital photos will likely be blurry.

This procedure requires two steps: First, you must focus the Topcon instrument on the test target using the instrument's infrared light and Topcon LCD video display. Second, without changing the focus knob adjustment or moving the test target relative to the instrument, you must view the test target with white light on the digital camera, setting the focus of the digital camera lens on this test target. You must use infrared light for the Topcon focus and white light for the digital camera focus, since these are the types of light used in the respective sensors, and the differing wavelengths focus differently.

Determine if your digital camera model provides a live-view feature, and if so, how to activate it. Use the live view, if available, to focus in the following steps. If your camera does not provide live view, you will have to look through the normal viewfinder instead.
If you will be using the digital camera viewfinder instead of live view, verify that the digital camera viewfinder diopter adjustment is correct for your eyesight, such that you have a crisply focused view of the viewfinder landmarks. To illuminate the viewfinder, you may momentarily remove the camera body from the camera lens, and aim the lensless camera at a diffuse light source. To adjust the diopter setting, turn the tiny wheel just above and to the right of the viewfinder exit aperture. Refer to the camera manufacturer's user guide for details. Remount the camera body on the lens.
Set up a test target taped to the Topcon headrest, as described above. Do not attempt to use a distant object as a test target, since the focus must first be set using the infrared light of the instrument, not ambient room light.
Darken the room. Do not allow ambient light to illuminate the test target during the next step. Focusing with ambient light instead of the infrared instrument light will not produce a correct calibration point of the instrument focus.
Center and focus on the test target using the Topcon LCD display, as in the initial test procedure above. Pull the carriage back away from the target, so that the instrument is in the anterior segment framing mode, not the retinal focusing mode. Use the plus setting ("+") on the diopter correction lever on the Topcon instrument to allow focusing on a close target. Boost the infrared illumination intensity (using the Topcon console buttons to the left of the joystick) if needed to see the target clearly.
Lock the instrument carriage using the brake knob to the left of the joystick. During the rest of this procedure, it is important that the instrument remains focused on the test target, the carriage does not move from the rearward position used during infrared focusing, and that the target itself does not move. Since the Topcon LCD display will not available to confirm this proper focus while you (in the next step) manually flip the internal mirror, the carriage must remain mechanically locked in place by the brake, and must not move during the following steps.
Turn off the AC power to the instrument.
Have at hand a soft-tipped probe such as a clean pencil with eraser, a swab stick, or a powder-free exam glove.
Swing the bayonet lock arm to release the adapter while holding the digital camera, so that you momentarily remove and hold the digital camera and adapter, revealing the open rear port optical path of the instrument. During these actions, take care to not push and move the instrument carriage location relative to the test target. Leave the Topcon instrument powered off.
Observe the back of the flip-mirror just inside the rear port, which redirects light from the main optical path up to the infrared video camera inside the unit. This mirror is hinged on its upper rear edge. See Figure 9 below. Using a soft-tipped probe or gloved finger, gently push up on the bottom of the hinged mirror just inside the rear port, which will allow the light path from the instrument lens to exit the rear port. See Figure 10 below. The mirror is actuated by stepper motor, and not spring loaded, so it should stay in the raised position.
Reattach the digital camera and adapter to the instrument, swinging the bayonet lock arm to the locked position. But again, be very careful to not push and move the instrument carriage location relative to the test target.
If the carriage does move during the above steps, you must repeat the initial focus procedure: Cycle the instrument power to reset the mirror, and then start again with the instructions above for the focusing step using the Topcon LCD video display.
With the mirror manually flipped up, you should now be able to view the instrument scene through the digital camera live view or viewfinder. It may help to illuminate the test target with an flashlight.
Adjust the manual focus ring on the digital camera lens until the test target scene is crisply in focus in the digital camera's 10X live view, or the digital camera viewfinder. If the instrument carriage has not moved, both the Topcon infrared viewfinder and the digital camera should now be equally in focus.
You should now have established the crucial "parfocal" calibration. That is, establishing focus with infrared light in the Topcon video LCD is calibrated to also produce a focused image in the digital camera in white light. This parfocal setting should be near the close end of the focusing range of the digital camera lens.
You may alternatively use the camera's autofocus mechanism to find the focus on the test target scene. Since the lighting or skewing of the test target may prevent a proper autofocus, it is usually easier to adjust the focus manually as already described. Nevertheless, to attempt an autofocused calibration, First disconnect the remote shutter connector from the left side of the digital camera, as this may interfere with the shutter button half-actuation. Then set the MF-AF switch on the camera lens to AF (autofocus), press the shutter button halfway to activate the autofocus, and observe a red autofocus confirmation light in the viewfinder. Then be sure to set the MF-AF switch back to MF.
As an alternative to the technique of removing the adapter and flipping the mirror, you can instead just shoot and play back a series of digital photos with slight focus adjustments to find the correct focus by trial and error. Zoom in during play back to see the properly detailed focus quality.
The lens itself provides no mechanical focus lock feature. To lock the digital camera lens calibrated focus setting, apply a small square of medical adhesive tape or self-adhesive paper label taped across the margin of the rotating focus ring and the adjacent non-rotating portion of the lens body. See Figure 8.
You may also wish to record the numerical value on the distance scale for parfocality, perhaps on the bit of tape just applied. (Note that since the focus ring slips at the far and near ends of the focus range, placing a mark on the ring itself cannot indicate the proper focus setting.)
Proceed to live photography with a suitable test subject.
It may further improve the focus calibration to make very slight adjustments to the digital camera manual focus ring from the initial calibration, using a cooperative subject for repeated trials. This will accommodate older instruments that might have drifted slightly off the internal infrared calibration.
Of course, careful focusing and exposure-setting on each live retina is crucial to getting good results once the focus calibration is established. High-resolution digital photos must be in sharp focus and properly exposed for the best results.

Testing and confirming correct digital photography operation with a live subject:

Collimate and focus on the retina in the usual way with the Topcon LCD viewfinder, using the joystick button to take exposures.
Adjust the brightness of the digital photo only with the ISO speed setting of the camera, or the Topcon flash intensity settings. Do not attempt to use the digital camera exposure time or aperture (f/stop) to adjust exposures.
The Topcon flash intensity programmed by the digital camera adapter is a much lower energy than was delivered for Polaroid photography, since the digital camera is much more sensitive. The flash will be much less bright and thus less dazzling to your subjects.
If digital photos are consistently out of focus, but you are properly focusing in the Topcon LCD video display, then you likely have not properly calibrated the digital camera parfocality. Repeat the focus calibration procedure immediately above.

Digital adapter on Topcon TRC-NW6 TRC-NW6S

Figure 3. Assembled adapter and camera mounted and attached to Topcon instrument.

Figure 4. Rear port of Topcon instrument.

Figure 5. Left: Canon E3 remote shutter connector. Right: hot shoe flash sync connector.

Figure 6. Canon N3 remote shutter connector.

Figure 7. Distance scale on Canon 60mm lens.

Locking manual focus on Canon 60mm lens with paper label

Figure 8. Locking manual focus with a bit of self-adhesive paper label.

Lifting TRC-NW6 TRC-NW6 mirror with handheld probe

Figure 9. Lifting mirror with handheld probe.

View through TRC-NW6 TRC-NW6 with mirror lifted

Figure 10. View through instrument with mirror lifted for focus calibration.

Figure 10. Sample retinal image taken with the digital adapter on a Topcon TRC-NW6 retinal camera. See full-resolution image here.

Troubleshooting:

Symptom	Cause	Corrective Action
No response to pushing joystick button.	Digital camera power is off.	Turn on digital camera.
	Digital camera battery (if so equipped) is discharged.	Charge battery. Use digital camera menus to set "Auto Power Off" to an appropriate value to conserve battery power.
	AC power adapter to camera (if so equipped) is off or disconnected.	Turn on or connect AC power adapter.
	Camera remote shutter connector disconnected.	Reconnect the connector. Use cable ties to dress loose cables and avoid inadvertent disconnections.
	Wrong camera settings.	Check camera for correct mode dial ("M") and shutter speed (1/20 SEC) settings.
	Camera lens AF-MF switch set to AF (autofocus) instead of MF (manual focus).	Set switch to MF, and since the autofocus motor will have disturbed the fixed focus setting, also reapply the parfocality adjustment procedure.
	Flash sync cable plugged into wrong socket on camera	Connect the flash sync cable to the hot shoe adapter on the top of the camera. Do not connect to the built-in flash sync connector provided on some models of the camera body.
	Interpolation PC board or cable disconnected from main PC board inside the instrument	Remove covers as in the installation procedure, and check the connections are properly seated and the cable undamaged.
Camera exposes a photograph, but the flash does not fire. Photograph is completely dark.	Flash sync connector not making connection.	Remove and reinsert flash sync connector. Use cable ties to dress loose cables and avoid inadvertent disconnections.
	Insufficient wait time for Topcon flash to charge.	The digital camera will shoot a photo even though the Topcon flash is not fully charged. Wait for the "lightning bolt" flash charge indicator to stop blinking on the Topcon LCD before pressing the joystick button.
	Wrong camera setting for exposure time.	Set camera exposure time to 1/20 SEC. Shorter exposure times will miss the flash entirely.
	Camera mode dial not set to "M" (manual) mode.	Set camera mode dial to "M" (manual) mode. (Automatic exposure modes will attempt to make a time exposure, briefly locking up the camera, since no light is normally entering the camera.) When operating the instrument, or working around it, it is possible to accidentally bump the mode dial, inadvertently switching it to an incorrect setting.
	Flash sync cable plugged into wrong socket on camera	Connect the flash sync cable to the hot shoe adapter on the top of the camera. Do not connect to the built-in flash sync connector provided on some models of the camera body.
Photograph is overexposed.	Camera too sensitive.	Set sensitivity to ISO 100, or lowest setting number available.
	Camera mode dial not set to "M" (manual) mode.	Set camera mode dial to "M" (manual) mode. (Automatic exposure modes cannot meter the external flash.)
	Camera configured for reduced flash energy, but normal flash energy setting was used.	Press button on instrument console to lower the flash energy. The Topcon instrument does not retain this lower flash energy setting when the power is switched off, so you must manually apply it by pressing the console button at the start of every session.
	The subject eye blinked or the eye moved, yielding an overexposed and blurred image of anterior features.	Retake the photograph.
Black photos, although the camera clicked and the instrument flashed.	Wrong exposure time setting.	Set camera mode dial to "M" (manual) mode, and manual exposure time to 1/20 SEC. Shorter exposure times may miss the instrument flash and result in black photos. Longer exposure times may record stray light.
Retinal photographs consistently out of focus.	Improper focusing technique with Topcon LCD display.	Observe proper operational technique and focusing.
	You have not performed the parfocal calibration as part of the installation.	Refer to "Calibrate the digital camera lens focus" above to perform the parfocal calibration. Once calibrated, apply a sticker or tape to the lens focus bearing as described above, which will avoid an accidental disturbance.
	Camera lens parfocal adjustment disturbed from its calibrated setting.	Confirm parfocality with test target shot, and reapply parfocalizing procedure if out of parfocality.
	Camera lens AF-MF switch set to AF (autofocus) instead of MF (manual focus).	Set switch to MF, and since the autofocus motor will have disturbed the fixed focus setting, also reapply the parfocality adjustment procedure.
	Unreasonable expectations of digital photographic resolution.	Expect that the digital photographs on an upgraded film instrument will exceed Polaroid quality and approach or somewhat exceed 35mm film quality. Additional digital resolution will be "empty", and even properly focused images will be somewhat "soft" and not resolved down to single-pixel levels. With the higher quality photos, focus calibration and live focusing technique becomes quite critical, as any out-of-focus picture does not deliver the full resolution available in the optical system.
Consistent dark dust spots or bright lighting flares on every digital photograph.	Dust, fingerprints, or other contamination on the digital camera lens or the Topcon instrumentation optics.	Avoid touching lens surfaces when handling the instrument. The front lens is easily touched by subjects posing for retinal photography; inspect it frequently. Blow off dust with a can duster. Shoot an out-of-focus test photo of a large white card held about a foot from the front instrument lens to locate and map the state of dust contamination for cleaning. Repeat this test photo shoot to see whether cleaning has removed all dust. Distinguish contaminants on the camera versus the instrument by rotating the camera and seeing if the spots move with the rotation. Distinguish contaminants on the camera lens versus camera sensor by removing the lens and shooting a test photo of a brightly lit white wall. Shine a bright penlight obliquely onto lens surfaces to reveal dust and contamination to direct observation. Seemingly minor fingerprints and other filmy contamination on optical surfaces will cause scattering of light which will degrade images with flares or reduced contrast. Persistent or filmy contaminants will require cleaning with an appropriate solvent and tissue. See manufacturer's documentation for proper cleaning techniques to avoid scratching lens surfaces or damaging antireflection coatings. Reaching internal optical elements of the Topcon instrument requires disassembly by a capable technician.
	Dust on the digital SLR sensor chip.	Activate automatic sensor cleaning via camera menus. Activate manual sensor cleaning via camera menus. Append dust-delete data via camera menus. Use care when switching SLR camera lenses to avoid introducing dust into the camera. When storing the camera off-instrument, keep dust caps in place. Blow dust off lenses and caps just before attaching to camera body. In extreme cases of dust accumulated on the sensor, Canon factory service can perform a sensor cleaning.
Consistent purple ring ghost image or lens flare in the center of every image.	Filmy deposit or other degradation of antireflective coating on internal Topcon optics.	The flash illumination light passes coaxially through the same objective lenses which form the image. This would ordinarily cause a lens flare in every photograph, except that the instrument lenses are exquisitely antireflection-coated to minimize this internal reflection. This coating can become degraded by a gradual film buildup on the internal surfaces with age, or as the coating itself slowly loses its quality over the long term. If due to a film contamination, cleaning may help, but this internal surface must be decontaminated in a clean-room environment using scrupulous techniques with molecular clarity, which are not generally available in the field. Disassembling the objective lens in the field with a casual cleaning technique will likely introduce dust or stray films which will actually worsen the flare. If due to coating degradation from age, there is no practical fix other than to replace the lenses themselves. Hence it may be best to accommodate the flare rather than try to remove it casually. This purple lens flare involves a principle of the original Topcon instrument, and does not involve the digital adaptation, although the flaw may be more apparent in high-quality digital photos than in the old Polaroid prints. Digital post-processing can remove much of the flare, since the flare image is essentially superimposed on the desired image, and consists mostly of red and blue colors, not green. Shoot a photo of a black background to get a digital photo containing only the flare image. Then in post-processing, you may subtract this image from a retinal image. Or, in digitally post-processing, you may split the digital image into red-green-blue components, and read just the monochromatic green component. This component is largely free of lens flare. This is similar to the classic red-free retinal imaging technique, which enhances the retinal image contrast, except you will filter the white-light photograph digitally and after-the-fact, instead of photographing with an optically-filtered green light. The purple color of this lens flare is due to the disproportionate effects of antireflective coating inefficiency at the ends of the visible light spectrum, which is to say the red and blue ends, and these two colors in turn combine to produce a purple tint.
Digital photographs slightly rotated when played back.	Camera tilted on adapter tube.	Check that adapter is firmly threaded into the lens. Loosen the adapter tube front ring, rotate camera to be level on adapter tube, and re-tighten front ring. If loosening is a recurring problem, you may apply a dab of nitrocellulose cement (readily available as black nail polish) to the threaded joint. Do not use cyanoacrylate threadlockers (Loctite, etc.), as these substances emit solvent fumes when curing that can damage optical coatings, and the threadlocking is too strong to permit adjustments or disassembly in the future.
At the edges, photographs are consistently overexposed, of low contrast, out-of-focus, or veiled by glare.	Normal effect of the uncropped field of view of the digital adapter.	The digital camera adapter does not mask the edges of the instrument field of view, and instead images all the way to the indistinct edges of the full optical path. This provides a slightly wider view than the Polaroid or 35mm film cameras, which were sharply masked and which cropped the outer edges of the field. You may apply a circular mask in post-processing your photo with a photo editor on a PC if needed, such as for publication purposes.
	Pupil vignetting.	Small subject pupils require precise collimation of the instrument to the eye. Being slightly off-center or too far in or out will cause the brighter iris reflection to overexpose the edges of the photograph. The second pupil will constrict in sympathy once the first eye is flashed; allow a few minutes of recovery time for the subject's second pupil to relax. Recognize that small-pupil photographs, even if successful, will necessarily be of lower resolution and contrast compared to dilated pupil, due to the unavoidably reduced numerical aperture of the optical system.
	Filmy contamination on lens surface(s).	See troubleshooting advice above for inspecting and cleaning lens surfaces.
Photographs show a yellowish cast or other color distortion not seen in the actual subjects.	Incorrect white balance setting in the digital camera.	Use the digital camera menus to set the manual white balance setting to FLASH, which is the best match to the light produced by the xenon flash tube in the Topcon instrument. Other settings such as AWB (automatic), incandescent, or fluorescent will result in distorted colors to FLASH.
Digital photos are vignetted (that is, dark at the edges, as if looking through a keyhole).	Wrong digital camera mode dial setting or wrong lens aperture setting.	Use the "M" mode of the camera's mode dial, and an f/2.8 manual aperture setting. Narrower aperture settings (higher f/numbers) will cause vignetting. Adjust exposure level using the camera's ISO speed setting, not the aperture or exposure time.
Excessive shutter lag on the digital camera. That is, the instrument flash occurs longer than usual after pressing the joystick button, perhaps slow enough to catch the subject's blink reflex.	When the digital camera is left powered on but idle, the "Auto Power Off" setting shuts the camera power off. The first shot triggered by the joystick will then be delayed while the camera powers back on.	Press the playback button on the camera twice to "wake up" the camera before taking the first shot. You may use an AC adapter to power the camera instead of the battery, and set "Auto Power Off" to a long time, or to "Off". Disabling "Auto Power Off" with battery power is not recommended, as inadvertently leaving the camera on will drain the battery, requiring a lengthy battery charge before further shooting may proceed.