Difference in depth of field when cropping or using a teleconverter

Friday 22 May 2026, 20:10 by Nando Harmsen | 1,557 views | 0 comments

This article was translated from Dutch with the help of AI. Read the original.

What is the difference in depth of field when cropping or using a teleconverter? You can reason it out, or calculate it if you are good at maths. Or you can test it. That is what I did, and you can see the results in this article.

Discussions can sometimes arise about the effect on depth of field when using a teleconverter or cropping. Is there a difference, and if so, what is the difference? Instead of theory, a real-world test is best.

For this, I used a 45-megapixel camera with a 400mm f/2.8 lens and a 2x teleconverter. I used it to take a photo of a little owl that was happy to pose. Of course, I made sure there was a pleasant background.

A photo with 400mm and f/5.6. This photo was not cropped, and no teleconverter was used.
A few facts in a row.
When using the 2x teleconverter, the maximum aperture is reduced to f/5.6.
The resolution with the 2x teleconverter remains unchanged at 45 megapixels.
When cropping, the maximum aperture remains f/2.8.
The resolution when cropping is reduced by a factor of 4. The 45 megapixels therefore becomes 11.12 megapixels.

I am not going to do any pixel peeping. I reduced both the 45-megapixel and 11.12-megapixel photos to 960 pixels, the size of photos on this web page. The difference you see is therefore how a photo is normally viewed.

400mm and f/2.8, cropped
When the same aperture is used, f/5.6, the photo with the teleconverter will produce softer bokeh than the uncropped photo without the teleconverter.

If you compare the photos when both were taken at the maximum aperture, there is no noticeable difference in bokeh.

The conclusion is clear. As long as you use the maximum aperture, a teleconverter makes no difference to the bokeh. It is simply the same.

The only difference with and without a teleconverter is a loss of resolution when cropping, or a small reduction in sharpness and autofocus speed with a teleconverter.

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