This document describes how to install and operate the digital camera adapter for the Canon CR4-45NM. This adapter allows you to use a standard Canon digital camera to take high-quality digital retinal photos and to process them with standard computer hardware and software.

We produce this adapter using your old Polaroid camera attachment (CR4-PC or CR4-PC DUAL, see Figure 1 below). You must send this attachment to us for refurbishment and retrofitting for digital camera use. The retrofit includes mechanical, optical, and electronic components. We will also clean, lubricate, align, recushion, and make minor repairs to your submitted attachment as needed.

ADAPTER COMPONENTS SUPPLIED IN THE KIT

• Main digital adapter attachment (see Figure 4 below).
• Lens adapter tube for Canon SLR lens (see Figure 2 below) (see required 28mm lens below). This tube is attached to the main adapter when shipped.
• Canon body cap for shipping or storing the attachment off the instrument. This cap is also shipped on the adapter.

Depending on which digital camera type you will be using, your adapter kit provides the following electronic adapters:

• Remote cord adapter, E3 to N3 (only if you will be using non-Rebel Canon models such as the Canon 50D or 7D).

COMPONENTS AND TOOLS REQUIRED

The following digital camera components are required to complete the installation, and not included with the digital adapter. Obtain them separately from a retail camera dealer or electronics retailer:

• Canon digital SLR camera. You may use any Canon Rebel model including the following currently available:

  Model	Features
  Canon Rebel XS (buy now)	Still photos
  Canon Rebel XSi (buy now)	Still photos, live view
  Canon Rebel T1i (buy now)	Still photos, live view, HD video out, HD video recording

• Canon EF 28mm f/2.8 autofocus wide angle lens (buy now).
• Canon EF 12 II macro extender. (buy now).

Upgraded camera models: More expensive Canon models include the mid-range Canon 40D, 50D, or 7D. High-end models such as the Canon 5D Mark II will work but with an 0.6X crop factor. Photo quality is excellent with any current model, including the less-expensive Rebel types above, so choose a more expensive model only if you want to use the digital camera for conventional photography off the retinal camera instrument.

Familiarize yourself with the digital camera: If the digital SLR camera is new to you, be sure the learn about the following features which will be used for retinal photography: On/off switch, mode switch for manual settings, setting manual exposure time, setting manual lens aperture, attaching and removing lenses, remote shutter release connector, flash bracket and hot shoe, viewing photos on the camera, transferring photos to a computer. If you will be tethering the camera to a computer for live display of photos, you may wish to connect the camera and computer, and shoot some ordinary photos in tethered mode, to familiarize yourself with the procedure.

No tools are required to assemble or install the adapter and digital camera.

Optional components you may wish to obtain separately:

• Camera AC adapter (buy now for Canon Rebel models) (if you do not wish to depend on the rechargeable camera battery).
• Computer and software for viewing and post-processing digital photos. You may shoot and review photos using only the camera and its memory card, but a computer will provide much more detailed views and the ability to edit and enhance your photos. Since the digital adapter works with standard digital cameras, all the best standard applications for digital photography, such as Adobe Photoshop, are available for use with your upgraded retinal camera. Canon SLR cameras include software applications for photo cataloging and editing.
• HD video display: If your digital camera provides a HDMI high-definition video-out connection, you may wish to install an HD video display for photo review during the patient exam.
• A photo printer if you wish to produce paper photo prints, instead of just video display.

INSTALLING THE ADAPTER

• Remove the body cap from the attachment bayonet.
• Connect the cable with 8-pin round connector to the receptacle on the instrument, and screw snug.
• Attach the unit to the retinal instrument in the usual way, by mating the bayonet to the receptacle, and rotating the locking lever.
• Remove the front lens cap from the Canon EF 28mm lens.
• Adjust the manual focusing ring on the lens so that the range scale on the lens reads all the way on the left end (0.3m, the closest focusing distance).
• Screw the black adapter tube to the front of the lens using the mating filter threads. See Figure 2 below. Take care starting the threads, as the mating parts are plastic. The connection should be only slightly snug, not so much that it is difficult to remove later.
• Set the the MF/AF switch on the lens to MF (manual focus).
• Remove the rear lens cap from the 28mm lens.
• Remove the front and rear caps from the Canon EF 12 II macro extender.
• Attach the macro extender to the back of the Canon lens.
• Remove any cap or lens from the Canon digital SLR camera body.
• Attach the 28mm lens with extender and adapter tube to the Canon digital SLR camera body. See Figure 3 below.
• Hold and align the digital camera so that the black adapter tube slides over the silver extension on the back of the digital adapter attachment. Loosen the white thumbscrew if needed to couple the mating tubes to their complete depths. See Figure 5 and Figure 6 below.
• Align the tilt of the camera body so it is level with the instrument, and tighten the white thumbscrew. See Figure 7 below.
• Connect the camera remote cable (2.5mm plug, Canon "E3" type) from the digital adapter to the camera. The plain cable (ending in a 2.5mm plug) directly fits the Canon Rebel models. If you are using a higher Canon model (Canon 50D or Canon 7D), connect the optional E3-N3 short adapter cord between the plain cord and the camera.
• Connect the camera flash sync cable to the hot shoe receptacle (flash bracket) on top of your digital SLR camera body. To connect, slide the square connector into the rear of the hot shoe receptacle, with the cord pointing to the left.
• Set the digital SLR camera as follows:
  • Use a fully-charged battery or external AC power supply.
  • Insert a memory card, or tether to a PC with USB cable and remote software.
  • Power switch: ON
  • Mode dial: M (manual)
  • Exposure time: 1/20 SEC
  • Aperture: F2.8
  • ISO speed: ISO 100
• Set the Canon CR4-45NM menus as follows using the buttons below the CRT monitor:
  • 35mm film
  • ISO 100 film speed
• Set up and operate the CR4-45NM in the usual way to take a test photo on a test target. Observe that the digital camera shutter operates and that the instrument flash fires. View the digital photo to verify that the photo is in focus when the instrument also carefully focused. The circular field stop of the Canon instrument, with an orientation notch at about the 2 o'clock position, should be clearly visible and sharply focused.
• Take trial photos of subject eyes. Use careful technique for alignment, centering, and especially focus. Use flash intensity adjustments on the instrument to correct over- or under-exposures.

 
Figure 1. The original Polaroid attachment before upgrade.

 
Figure 2. Canon camera, extender, and lens, with black adapter tube.
This shows the Canon model 40D digital SLR body.

 
Figure 3. Camera and lens assembled with black adapter tube.

 
Figure 4. Retrofitted Canon attachment. Old Polaroid film back has been removed by us and replaced with a digital attachment fitting and electronic interface circuitry.

 
Figure 5. Retrofitted attachment assembled with Canon digital SLR lens.

 
Figure 6. Attachment with digital camera on the instrument.

 
Figure 7. Close up of the complete digital attachment.
Canon 40D digital SLR shown, with flash sync connection on left side of camera.
Current adapters provide a hot shoe connector which attaches to the flash bracket on top of the camera.

 
Figure 8. Sample retinal photo.
Somewhat overexposed, and with dust on objective lens at left.
Gray border shows the full image area of the camera.
See also in full-resolution.

Viewfinding with the digital camera live view: If your Canon digital SLR models provides a live view capability (such as the Canon Rebel XSi or T1i models), this can be used for viewfinding on the instrument with the infrared filter out. (Canon digital camera image sensors all contain an infrared blocking filter which prevents the camera from seeing the infrared viewfinding illumination.) Since using a bright and visible exam light for viewfinding defeats the non-mydriatic viewfinding principle of the instrument, digital live viewing will require that patient eyes be dilated to an adequate pupil diameter for successful photography.

All that is necessary in the adapter is to raise the mirror in the attachment and to fix it in the raised position using a bit of tape. Then set the digital camera to live view mode as explained in the camera's user manual. The digital camera can display the live view on the camera's display, or you can connect the camera via a USB cable to and computer and software for live PC preview ("tethering") at higher resolution and larger size.