My original intention in running these tests was to see if resolution differences at 300mm detected on film were visible in digital images with the EOS-1Ds and to evaluate reflection patterns. Mannequin tests were run with an EOS-1Ds on tripod left at one location for all lenses tested. There is a mirror on the back wall that reflects light from the slanted ceiling that the monolight is pointed at. Focus point was the mannequin's right eye. Other data: ISO 200, custom white balance from grey card, single monolight bounced off ceiling, exposure adjusted with flash meter. Tungsten filament light bulb lit in background. Images were shot in manual mode at 1/250th as RAW files and converted to large jpg's with Capture One DSLR 1.2. No adjustments were made except addition of slight unsharp mask. Slightly higher image brightness for the EF 300 f/4 exposure is the result of monolight flash variation. The top images are full frame reduced in size. The eye detail is enlarged roughly 2x from the converted RAW file.

The diffractive optics lens flared under relatively modest background lighting conditions. I have never seen even the cheapest consumer lens flare under these conditions before. Upon observing the flare with the diffractive optics lens, exposures were shot from f/5.6 to f/16, but did not remove flare.

Full Frame	EF 70-300mm f/4.5-5.6 DO IS USM 300mm @ f/8 Marked flare to lighting reflection from mirror in background	EF 75-300mm f/4-5.6 III USM 300mm @ f/8	EF 100-400mm f/4.5-5.6 L IS USM 300mm @ f/8	EF 300mm f/4 L IS USM 300mm @ f/5.6
Crop	Detail of Above Photograph EF 70-300mm f/4.5-5.6 DO IS USM 300mm @ f/8	Detail of Above Photograph EF 75-300mm f/4-5.6 III USM 300mm @ f/8	Detail of Above Photograph EF 100-400mm f/4.5-5.6 L IS USM 300mm @ f/8	Detail of Above Photograph EF 300mm f/4 L IS USM 300mm @ f/5.6