topic Re: Unfocus in Gear Guide

Unfocus

Paulo26 — Sun, 13 Sep 2026 13:31:10 GMT

What´s the best maximum diafragm aperture f? For the effect of unfocusing the backgroud?

Re: Unfocus

shadowsports — Sun, 13 Sep 2026 13:58:02 GMT

Greetings,

The lower the f stop, the wider the aperture is. This creates a shallower depth of field. Meaning that the portions of your image in front of or in back of your subject will be out of focus. In addition, the distance to your subject can affect the degree of blur. Google "depth of field".

Re: Unfocus

johnrmoyer — Sun, 13 Sep 2026 15:10:13 GMT

I suggest https://en.wikipedia.org/wiki/Depth_of_field

As distance or the size of the acceptable circle of confusion increases, the depth of field increases; however, increasing the size of the aperture (i.e., reducing f-number) or increasing the focal length reduces the depth of field. Depth of field changes linearly with f-number and circle of confusion, but changes in proportion to the square of the distance to the subject and inversely in proportion to the square of the focal length. As a result, photos taken at extremely close range (i.e., so small u) have a proportionally much smaller depth of field.

Sometimes depth of field is based upon an ancient standard for print size, viewing distance, and human ability to see.

When viewing on a screen, it might be very different than a standard print size.

In general, a longer focal length will give a shallower depth of field if one does not stand closer or further.

Re: Unfocus

wq9nsc — Tue, 15 Sep 2026 19:44:58 GMT

This is a website that is very useful for both understanding the relationship between sensor size, focal length, aperture, distance to subject, field of view, and the total depth of field that will be within critical focus: https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/#{%22c%22:[{%22f%22:13,%22av%22:%228%22,%22fl%22:50,%22d%22:3048,%22cm%22:%220%22,%22sf%22:%221%22}],%22m%22:0}

You can plug in various combos to see what combination of variables works best for what you are trying to achieve and then do some actual experimentation based upon the results to fine tune and achieve the "look" that you want.

Keep in mind that the depth of field dispersion around the specific focal point/plane is not symmetrical. The depth of field in critical focus is less than half the total DoF in front of the point of focus and more than half to the rear of that point. So keep that in mind when you are shooting for zero margin between desired and actual DoF results.

Rodger