The camera focus point for the mannequin photographs was the eye that you are viewing on your left. For resolution comparisons, open separate cropped image windows, and focus your attention on the detail of the eye on your left. Resolution differences are detectable between the images at f/4 for the EF 300 f/4 and the EF 300 f/2.8 taken with the EOS-1Ds (See selected comparison.) Differences in diffuse blurring of background (bokeh) are visible in the first row of thumbnail images without enlargement. No differences in resolution were detectable with the EOS-10D.
All images were processed in a comparable manner from RAW images with cameras set in factory default settings with the exception that the images were converted from RAW in the 1DS by Phase One DSLR software and the 10D RAW images were converted with Canon software. Differences in tone and brightness are variables introduced by different RAW conversion software and flash intensity variability between triggered discharges with the monolight.

	EF 300 f/2.8 @ f/2.8	EF 300 f/2.8 @ f/4	EF 300 f/4 @ f/4
Full Image: EOS-1DS Compare Bokeh: The f/2.8 lens blurs the background slightly better in this test at both f/2.8 and f/4 compared to the f/4 lens at f/4.
Cropped Detail: EOS-1Ds Look at the eyelashes and lower eyeliner in the eye on your left to detect differences in resolution. The f/2.8 lens at f/4 performs better than the f/4 lens at f/4 in resolving eye detail. Click here to see selected crop.
Cropped Detail: EOS-10D Differences in resolution are not apparent between the f/2.8 lens at f/4 and the f/4 lens at f/4 with the 10D.
	EF 300 f/2.8 @ f/2.8	EF 300 f/2.8 @ f/4	EF 300 f/4 @ f/4

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© 2003, William L. Castleman