Canon EF 50mm F/1.4 Lens Review – Resolution Tests and Conclusion

Previous assesments of the Canon EF 50mm F/1.4 USM lens’s performance were of a subjective nature. In evaluating any lens it is worth taking some frames to produce results that are of a quantifiable nature. The following photographs are of the typical brick wall variety and are intended to demonstrate the Canon 50mm’s performance when mounted to a full frame digital camera and focused close to infinity.

Lens Test Methodology

I used a Canon EOS 5D camera mounted to a Bogen/Manfrotto gear head plus tripod as the test platform. The exposure mode was configured to aperture priority with no EV correction. A 10 second shutter delay was used to minimize disturbances from the photographer. Test photos were exposed from the maximum aperture of F/1.4 and concluded at the minimum aperture of F/22.  A 100 percent crop was taken from the center and extreme corner of each photograph. The red  square in the below photo represents the center crop area and the blue square represents the corner area.

50mm Center Crops

At the maximum aperture of F/1.4 the Canon EF 50mm F/1.4 USM lens is soft. The frame is underexposed in the center when compared to the remaining photographs in this series. You can touch this up in photoshop but you can’t put back data that wasn’t captured in the first place.

Stopping the Canon lens down to  F/1.8 makes a dramatic difference. The frame is exposed properly and sharpness is much better than what was rendered at F/1.4.

At an aperture value of F/2.8 the Canon EF 50mm F/1.4 USM lens is giving you 90 percent of the resolution it can deliver in the center of the frame. Marginal increases in performance is realized as you continue to close the aperture.

When stopped down to F/5.6 the Canon lens appears to be providing maximum resolution and contrast in the center of the frame. F/8 doesn’t appear to be much better if at all.

At F/11 the effects of diffraction begin to show up in the form of a reduction in contrast. It is not a big deal really.

At F/16 and F/22 the Canon lens can’t fight the effects of diffraction better than its contemporaries. However the Canon EOS 5D, with its large photosites, produces a usable photo at these apertures. Cameras with smaller photosites, such as the EOS 5D MKII and 50D, might not fare as well as the EOS 5D in this scenario.

50mm Corner Crops

The story of the Canon EF 50mm F/1.4 lens is a bit more dramatic when told from the vantage point of the corners. Take a look at the crop from the photograph snapped at F/1.4. The corner  suffers from serious vignetting, low resolution and low contrast.

Stopping down the Canon 50mm lens to F/1.8 helps spread the light out a bit better and improves the exposure of the corner by about 1 stop. Detailed resolved by the Canon at F/1.8 continues to be poor.

Closing the aperture down to F/2.8 improves the corners exposure even more that F/1.8.  Resolution begins to pick up dramatically at F/2.8 as well.

Detail resolved by the Canon EF 50mm USM F/1.4 lens continues to improve in the corner of the frame at F/4 and F/5.6.

Stopping the 50mm down to F/8  produces peak resolution in the corner. The Canon lens begins to look a smidgen soft at F/11.

Closing the aperture down to F/16 and F/22 appear to mirror the performance of the center of the frame. Diffraction is causing a loss of sharpness and contrast. I would consider both frames to be usable with a touch of USM and a level tweak in Photoshop.

Final Thoughts on the Canon EF 50mm F/1.4 USM

In my introduction to the Canon 50mm lens I said that the lens resided in a sweet spot of price and performance. To spite corners that are soft and dark at F/1.4 and a center that is weak at the same aperture I still stand by that statement. When shooting up close to someone or something these things are not as critical. By F/2.8, the lens produces excellent resolution and contrast in most parts. Performance continues to improve until you reach aperture values of F/5.6 to F/8 at which point performance is brilliant.

Is the Canon EF 50mm F/1.4 USM lens due to an update? I think so. While the design is a classic the performance isn’t quite up to snuff with newer and similarly priced lenses from 1st and 2nd tier companies such as Zeiss and Sigma. Would that stop me from buying another one? The answer is no. In the few months that I have owned this lens it has performed for me and I have produced many great pictures with it. I do caution any user who needs superb corner sharpness and contrast. You will probably want to stop the lens down to F/8 to realize its maximum performance in that scenario.