Richard J Kinch

October, 2017.

This document describes how to install and operate the digital camera upgrade kit for the Topcon TRC-50XF retinal camera.

Identify the upgrade kit contents:

Other components you must obtain separately:

The adapter kit works by design with the ordinary, standard, unmodified Canon retail camera body, and with the constantly improving standard computer software supporting digital photography. No special version or modifications of hardware or software are required. New Canon camera models in the future should also be compatible, as should advances in Canon and third-party computer software support. You may process the standard RAW or JPEG images using industry standard software such as Adobe Photoshop or Corel PhotoPaint.

Optional components you may wish to obtain separately:

Familiarize yourself with the digital camera and lens: If the digital SLR camera is new to you, study at least the following features which will be used for retinal photography: On/off switch, mode switch "M" setting for manual operation, setting manual exposure time, attaching and removing lenses, remote shutter release connector, hot shoe, viewing photos on the camera, transferring photos to a computer, enabling and using live view mode.



Analyzing exposures for optimal exposure: Viewing the image exposure histogram in the digital camera is the only sure way to evaluate a proper exposure. The histogram provides a quantitative analysis of your retinal images for proper exposure level and degree of contrast. The goal is to have a histogram spread roughly in the middle third of the dynamic range. Observe the green histogram rather than the white, since for a retinal image most of the diagnostic information is represented in the green portion of the color spectrum. The position of the hump in the histogram indicates the exposure level, which should be around the middle of the range, and the width of the hump indicates the contrast

Correcting exposures and improving contrast with digital post-processing: Simple post-processing of your digital images on a computer will correct any mis-exposures and improve correct exposures. Retinal images are by nature limited in contrast, and by digitally stretching the contrast, the visual impression of the photographic is much improved. Filtering enhancements such as red-free images are available via digital post-processing, even though the original instrument may lack the physical filters.

Establish your practice routine: After completing the above, you will have a powerful digital facility for retinal photography. You must now handle digital data where you used to handle 35mm film slides or Polaroid prints. It most regards the digital methods are quicker, easier, and cheaper than film, but do require an initial investment in careful design and training. Your digital system is based on standard digital cameras, and so is compatible with ordinary software for capturing, post-processing, and cataloging digital photographs. Your upgraded digital retinal camera should, with occasional maintenance, provide decades of reliable service.

Further Notes

Lowering resolution on the camera: Since the highest resolution images of the camera are much finer than the optical resolution of the Topcon instrument, you may wish to set the camera to record lower-resolution images. This will decrease storage space and improve tethered transfer times. These settings are found on the camera's "Quality" menu.

Tethering software: If you want to have live previewing and capture of photos on a computer while shooting with the Canon camera, consider using "tethering" software. This type of application uses a "tether" from the camera to the computer via a USB cable. A simple version is included with the Canon camera software support disc. DSLR Remote Pro ( is one popular aftermarket package sold for this application. Tethering to a computer with a large display is the best way to instantly review your photos for proper focus and exposure while you still have a chance to retake a missed shot. The small display on the camera does not adequately reveal the quality of the image focus.

Instruments without accessory ports: The Topcon TRC-50XF retinal camera is similar to the TRC-50X model, except that the TRC-50XF omits the upper port for a second camera as provided on the TRC-50X. On the TRC-50X it is preferable to install the digital camera on the upper port and retain the original film camera (and its better viewfinder) on the rear port. This method is not available to upgrade the TRC-50XF since it does not provide an upper port. A similar situation applies to upgrading the previous Topcon models TRC-50VT and TRC-50V (both upper and rear ports like the TRC-50X) versus the TRC-50F and TRC-50FT (upper port only).

Digital upgrade components for the Topcon TRC-50XF retinal camera
Figure 1. Digital upgrade components for the Topcon TRC-50XF retinal camera.

Components of the digital upgrade include the viewfinder magnifier-inverter for the Canon digital camera, the bayonet adapter ring, and the electronic interface cable.

Rear port of the Topcon TRC-50XF retinal camera
Figure 2. Rear port of the Topcon TRC-50XF retinal camera.

This is the rear port of the instrument with the film camera removed, where the digital camera will be attached. Observe the electronic interface round receptacle above and to the right of the camera attachment. This will receive the new electronic interface cable.

Canon 5D Mark II digital SLR camera body with bayonet adapter ring for the Topcon TRC-50XF attached
Figure 3. Canon 5D Mark II digital SLR camera body with bayonet adapter ring for the Topcon TRC-50XF attached.

The adapter ring inserts, turns, and locks, like the rear of a standard camera lens. Observe that the Topcon side of the adapter ring has a small slot at the top.

Canon 5D Mark II digital SLR camera body with adapter ring and viewfinder magnifier-inverter
Figure 4. Canon 5D Mark II digital SLR camera body with adapter ring and viewfinder magnifier-inverter.

This shows the Canon digital camera as adapted for the Topcon TRC-50XF.

Canon digital camera attached to Topcon TRC-50XF
Figure 5. Canon digital camera attached to Topcon TRC-50XF.

This shows the close fit of the digital camera body to the rear of the Topcon instrument. Electronic interface cable is connected to the Topcon connector, and wrapped around the camera to connect to the camera's hot shoe on top and shutter remote on the left. The cord from the hot shoe connector may exit to either the right or left of the camera.

Overall view of the digitally upgraded Topcon TRC-50XF
Figure 6. Overall view of the digitally upgraded Topcon TRC-50XF.

This shows the compact arrangement of the digital upgrade. Not shown are an optional tethered PC for instant transfer and review of the digital photos, and an optional HDTV for live viewfinder HD video and instant photo review. Instrument headrest has been removed for this photo.

Copyright 2009, 2010, 2012, 2013, 2017 Richard J Kinch.