Teleconverters: Useful? Not always it seems.

Which looks better to your eye?

Is it worth it to use the EF2X II teleconverter at all?

This page contains two images taken in the field of the same subject, at the same time and at the same distance with the same lens and camera. The lens was the Canon EF600 f/4L IS. The camera was the Canon D60 digital SLR body. Incidentally, I have dozens of images of this bird taken with and without the TC. All are indistinguishable from each other focus-wise. I had to use MF with the TC, of course. Still, all were pretty much the same and the reason for the EF2X II faring poorly here can not be attributed to focusing errors.

The image immediately below was one taken using the EF2X II teleconverter: FULL FRAME, resized to 1024 pixel width. NO SHARPENING.

1/500 sec, f8.0, +1/3, ISO 200.

Below this, the same bird, at the same distance taken WITHOUT a teleconverter, using the EF600 f/4L IS lens alone. The image was cropped and resized to match the one above at 1024 pixels in width to give, very approximately, the same image scale to the bird's head. Again, it is stressed, no sharpening was applied to either image. Both were saved as medium quality jpegs at the identical compression factors using Photoshop.

1/400 sec, f8.0, +2/3, ISO 200

Below is a thumbnail showing the full frame from which the the enlarged heron head was cropped. The top image was, to repeat, the full frame with the EF2X II.

So, did I really gain much in using the EF2X II over just enlarging the image from the lens alone to the same scale using Photoshop' bicubic interpolation routine? Is there really that much of a difference in quality?

These results surprised me. In order for the 2X teleconverter to be considered useful, it absolutely must deliver images that are consistently and substantively better than those simply enlarged to the same scale using digital techniques. The results left me wondering whether it was EVER worth using the EF 2X II at all? I shot test images, under controlled circumstances, to try and determine if the EF2X II really offered any significant advantage to just "upressing" in Photoshop. I compared 100% crops of images taken with the EF2X II to crops taken with the lens alone and subsequently enlarged to the same scale using PSCS bicubic smoother. I then also performed the same test with images taken with the EF1.4X. The test results confirmed the feelings my field work had indicated. The EF2X II converter just is not useful! Those test images are presented beginning on the next page.

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