Telephoto Extenders & Quality

[Jonathan Farmer]

For those of you who may be wondering how much image quality is lost when using teleconverters, I have attached some photos that were taken with the Canon 500 f/4 L IS USM. The first image was taken with no TC attached, the second with a 1.4X TC, the third with a 2X TC and finally the last one taken with the 1.4x and 2x combined. the focal lengths were 500mm, 700mm, 1000mm and 1400mm.

Please note that the 500mm and 700mm images were taken with AF on; the 1000mm and 1400mm images were focused with my 52 year old eyes.

As you can see in the 3" X 3" crops, there is image quality loss with the 1400mm image where the 1.4X and 2X converters were stacked, however this is a tight crop, the full size image (no crop) looks very good considering it is a 3.4X magnified image.

The objective of my test is to show that although image quality is lost using such high magnification, this method is still better than when an image with no magnification is cropped to scale the subject to the same size, eg. if the 2X image is cropped to scale the subject to be the same as the 3.4x image, the 3.4x image is better in resolution.

In each photo, the subject (bird) was further away with the longer focal length.

Click on images to view larger.

Regards

Jonathan Farmer

[Roy C]

Interesting test Jonathan - I did a similar one with my 400mm f5.6 and came to the same conclusion. Attached is a stacked converter shot (1.4x + 2x) which I consider very usable.

[Jonathan Farmer]

What camera were you using?