# How Much Blur? – A Bokeh Calculator

One of the most returning questions on photography forums is which out of two different lenses has the smallest depth of field (DOF). However, what many people actually mean when they ask this is which lens has the best ability to blur the background in their shots. The answers given are not always very clear. However, they could be just that. All it takes is some simple math. This bokeh calculator will give you the answers you are looking for. Add some lenses, select your subject size, and hit update to see the results in a graph!

I want to take a shot in landscape orientation, which contains someone's head and shoulders (0.9 x 0.6 meters), a full person (3 x 2 meters), or something completely different, which has a width of meters.

Update!

Background blur versus background distance

Theoretical blur disk diameter as percentage of image width [%]

Generated by http://howmuchblur.com

Distance between subject and background

With this nice little slider you can set the distance range of the graph:

It is important to intepret the results correctly. The first obvious observation to make is that the background blur increases when the background is further away, regardless of focal length or aperture settings. In order to give meaning to the results, think about what kind of shot you want to make, and what distance there will be between the subject and the background.

As you probably have seen by now, the relative blurring ability of lenses is very much dependent on the specifics of your shot. As a rule of thumb it can be concluded that a wider aperture is more important for blurring closer backgrounds, whereas the focal length comes more and more into play when the background is further away. Please note that there are two additional effects which determine the amount of background blur in your shot:

1. Each lens has its own bokeh characteristics, which can make background blur appear more or less smooth.
2. A shorter focal length will have a wider field of view, and therefore it is likely that there will be more objects in the background at a closer distance.

You can always link back to this specific comparison by using the following url:

This is version 2.0 of how much blur. Stay tuned for more features and photography greatness. You can always send your suggestions to . And no, I do not support my growing family through this website!

### Related Posts

Why the Nikon 105mm F1.4 is Nikon’s New King... This week Nikon announced the new Nikon 105mm F1.4 lens. This combination of focal length and aperture is a world first. This lens is the brightest 105mm lens. In this post we will discover what that means, and compare the properties with that se...
Five Ways to Take Greats Portraits with Any Camera You have probably all seen lots of beautiful portraits with people posing in front of soft, creamy, blurry backgrounds. For many people this is how professional portaits should be. And indeed, high levels of background blur and soft bokeh are reserve...
All 29 Official Nikon 105mm F1.4 Sample Images Nikon has released some sample images shot with the freshly announced Nikon 105mm F1.4 lens. This world first combination of focal length and aperture makes it the brightest 105mm lens ever. Earlier we have looked at the blurring capabilities of ...
• Having taken over howmuchblur.com, your sidebar has taken what was a pleasant wide screen experience and squeezed it into a miserably small space. You’ve basically ruined half the appeal of the site.

• Malex

Great tool, thanks!

• Malex

how should I enter info for a lens on a micro four third body with a metabone adapter ?
let’s say the x0.71 Ultra adapter with the Sigma 18-35mm f1.8 on the GH5
the crop factor becomes 1.42 (2 x 0.71) but how about the Fstop, should we multiply it also (1.8 x 0.71 = 1.27) ? or should I leave it as f1.8 ?

• I am not familiar with that particular adapter, but if you compensate the crop factor with the 0.71 to 1.41, you should enter the lens characteristics unmodified. Hope that helps.

• Hal Knowles

@Malexirian:disqus as focal reducing adapters, the Metabones Speedboosters add 1 stop of extra light gathering capability to the adapted lens. So using the one quarter f-stop scale, an f-stop of 1.8 would become an f-stop of 1.3 with the Speedbooster. In my personal experience a Canon 50mm f1.8 lens appears in my EXIF data as a 35mm f1.3 when adapted on a GH5 with a Metabones Speedbooster. So on this tool, I would enter the 35mm f1.3 data plus a crop factor of 2 (or conversely, as you suggested I could use the original 50mm plus a crop factor of 1.42).

https://en.wikipedia.org/wiki/F-number

• DanR

Fantastic! I was on the fence about buying the Panasonic 42.5mm F1.7 lens for my G85 camera but this confirmed what everyone is saying about it and I pulled the trigger. Thank you so much!

• John Morgan

This is a GREAT program, and one sorely in need of showing to people.

But, respectfully, your analysis of what most affects bokeh at the end was not correct.
I will use this very program with 9 (made-up) lenses to show what is correct.
First, copy the following line and open a web page with it to start this program with the 9 lenses: