Richard J Kinch

February, 2015.

This document describes how to install and operate the digital camera upgrade kit for the Kowa RC-2 and RC-3 portable retinal cameras. These two models are identical with respect to the digital camera upgrade, so we will refer only to the RC-2 in the descriptions below.

Identify the upgrade kit contents:

Kowa RC-2 digital camera adapter
Figure 1. Kowa RC-2 digital camera adapter components (exploded diagram).

Other components you must obtain separately:

The adapter kit works by design with the ordinary, standard, unmodified Canon retail camera, and with the constantly improving standard computer software supporting digital photography. No special version or modifications of hardware or software are required. 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 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, hot shoe, viewing photos on the camera, transferring photos to a computer, using live view to frame photos.



Kowa RC-2 retinal camera with digital adapter
Figure 2. Kowa RC-2 retinal camera with digital adapter.

Further Notes

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.

Lowering resolution on the camera: Since the highest resolution images of the camera are much finer than the optical resolution of the Kowa 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. PS Remote ( 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.

Copyright 2009, 2010, 2012, 2015 Richard J Kinch.