FocusAssist

Fast focus feedback for Canon DSLRs

Purpose

I wrote this program for simple purpose--to assist in manually focusing my Digital Rebel XTi through a telescope. The rationale:

The optical viewfinder is small and difficult to focus accurately.
Reviewing in playback mode is slow and does not show the image at full resolution.

Here's what this program does: Connect your camera to your PC. Take a picture, using either the PC or the camera's own shutter release. FocusAssist will immediately transfer the picture to the PC and display the center of the image at 1:1. It can save photos to the PC, the camera's CF card, both, or neither (useful when you're just trying to acquire focus and don't want to use up any storage space yet).

Note that only JPEG photos will be displayed, although RAW photos will still be saved. If you shoot RAW+JPEG and elect to save photos on the camera alone, only the JPEG will be transferred and displayed on the PC.

Also note, for what it's worth, that FocusAssist will let you adjust the size and quality of the JPEG saved in RAW+JPEG (however, the camera might not like to display a RAW+small JPEG in its playback mode).

One more bonus feature: FocusAssist lets you enable RAW in full auto mode!

Supported cameras

Cameras known to work with FocusAssist:

Canon EOS 400D/Digital Rebel XTi

Cameras that will probably work just fine:

Canon EOS 30D

Possibly supported cameras

The following cameras should work with FocusAssist, but I don't have one to test.

These cameras use what Canon calls "Legacy Protocol" for communication with the PC. This requires you to set your camera in "PC connection" mode and install a driver provided by Canon. You may also have to enable the "Lock camera UI while querying/changing settings" option in FocusAssist.

Please let me know whether FocusAssist works with your camera.

EOS 20D/20Da
EOS 5D
EOS 350D/Digital Rebel XT
EOS-1D Mark II/Mark II N/1Ds Mark II

Unsupported cameras

Canon dropped SDK support for older DSLRs, so there will be no support for the D30, D60, 1D, 1Ds, 10D, or 300D.

Download

FocusAssist v0.1 for Windows 2000/XP
Source code
A Mac version is within the realm of possibility, since both Canon's SDK and the GUI library I used (wxWidgets) support the Mac as well as Windows. If you are a registered Canon SDK developer, have a Mac, and are able to build Mac binaries for FocusAssist, send me your source modifications and binaries so other Mac users can benefit.

Contact

Send feature requests, compatibility reports, bug reports, etc. here.