For all of us who love photography, we will find two fundamental groups of photo folks on the Internet. Those who are concerned with becoming the best artists that they can, and those who want to discuss minutiae until the Sun goes nova. Sadly the first group gets influenced by the second group and one topic that keeps coming back like an ugly sore is focus breathing.
To listen to some of the commentary on this, it is a problem on a global scale. To this I say, Toro Poo Poo. Focus breathing is real, it exists and for the vast majority of image makers it matters not at all.
What is Focus Breathing Anyway?
Here's what happens. You bring the camera to the eye and before you focus you note the amount of image in the frame and where the boundaries are. Then you press the focus button thingy and the camera / lens combination focuses, but you note that what is now showing in the frame is slightly different than what was in the frame before you focused. This is focus breathing.
Zoom lenses are awesome because they are many lenses in one, but unless you are spending big $$$$ on cinematic zooms that are what is called PARFOCAL, if you are focused on your subject at a particular focal length and then zoom, the focus may go out a bit. No big deal, you tap the focus button and all is well again. What often happens when the focus sharpens up is that what is showing from an edge perspective in the viewfinder might change, This is focus breathing again and since you had focus once, and then zoomed, you become more aware of it happening.
Quick! Call the Avengers!
Ok, don't bother. Most of us do our composition when we are in focus not when we are not. Thus the apparent change of focal length that could occur going from out of focus to in focus matters not at all. We have become very comfortable that whenever we change subjects, change focal lengths by zooming, or changing our position slightly that we need to refocus. It's fast and it works. Thus focus breathing has no impact on your images.
Why all the hubbub bub?
We see that some folks like to really dive into specifications and engage in what I refer to as religious wars over which lens is best, yada yada yada. If these people actually spent as much time doing photography as they do chattering about nothing, they might actually make some great images. It's like worrying a lot about half stop differences in dynamic range but only ever shooting JPEG. It's irrelevant, a waste of time and downright silly. However, if this kind of thing floats your boat, have at it, fill your boots and enjoy. For the majority, well they could care less.
I want to thank reader Gord for posting the question about focus breathing. I appreciate the query and the opportunity to answer and clear up misconceptions.
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I'm Ross Chevalier, thanks for reading, and until next time, peace.