Similaar Foto tutorials
English
- Espaņol
Equipment
recommendations
Flaat
Picture Styles
Lens tests
Sharpness
- Bokeh

Notes on
Depht of Field and Field of View


 
HOME
 


 
Foto tutorial (English)
Foto tutorial (Espaņol)
 


 
Equipment recommendations US-ES
 


 
Flaat for Canon
Flaat for Nikon
Flaat for the BMC
Flaat for NEX-5N
Old Picture Style Tests
 


 
LENS TESTS
a7s stills
a7s video
550D stills
550D video
550D video lineskip
5D2 stills
5D2 video

Conclusions
APS-C vs Full Frame
ND filters
Other filters


BOKEH TESTS
Summary
Alternative scenarios
 


 
Badly assembled lenses and image quality
Lens mount compatibility chart
ISO on different cameras
High ISO on the 5D3
DIY: DR test chart
RGBWK Bayer sensors


DoF/FoV CALCULATOR
Notes on DoF-FoV
Notes on crop-DoF-FoV


Custom Cropmarks for Magic Lantern on the Canon 550D


How many megapixels do I want?
How many megapixels can I see?


Quick Monitor Calibration Chart


MY VIDEOS


Random rants


Search engine


Playing with my DoF/FoV calculator, I've come to realize that what depth of field really depends on is field of view, sensor size and lens aperture: lens lenght and distance to subject don't matter, as long as the field of view, defined as "height and width of image at focus distance", remains constant.
Let's see an example.
Suppose I want to take a head-and-shoulders shot of some friend. He's going to be in focus, and picture height at that distance has to be around 64cm (2 feet).
Besides that, I want my friend to be in focus, over a very-out-of-focus background. I want my depth of field to be around 22cm (9 inches).
My camera is a 1.6x-crop canon, my target aspect ratio is 1.77:1 (16:9), and I have access to any lens I want to use (lucky hypothetical-me).
What I've found is this: no matter which lens I use, in this example I want to set aperture to f/2.8. Choosing different lenses will mean I have to get closer or farther from the subject, and perspective will change, but if I want DoF to be around 22cm, aperture has to be f/2.8.
Any of the following combinations will provide me with an image that is 64cm tall in the focus plane, and has 22cm of DoF:

17 mm at 0.85 m, set at f/2.8
24 mm at 1.20 m, set at f/2.8
28 mm at 1.40 m, set at f/2.8
35 mm at 1.75 m, set at f/2.8
50 mm at 2.50 m, set at f/2.8
80 mm at 2.80 m, set at f/2.8
120 mm at 6.0 m, set at f/2.8
180 mm at 9.0 m, set at f/2.8

DoF is not exactly constant, but at f/2.8 the DoF difference between the 17mm lens and the 180mm lens is less than 4mm, or 2%.
What does change, a lot, is perspective: the size of stuff on your background will change dramatically if you go from 17mm to 180mm. And that affects bokeh big time: at 17mm, you'll see a whole building behind your subject, and it will be out of focus but you'll know it's a building, and recognize its features; at 180mm lens, with the background at the same distance, all you see behind your subject is a small patch of wall, so it will not be just out of focus, it will be blurred beyond recognition. So depth of field is the same, but the background will be a lot softer on longer lenses.
You probably knew all this already, but I didn't. I'm happy I now know.
And so, here's my simplified DoF/FoV calculator.




please visit my equipment recommendations


















Copyright Similaar 2011 -- similaar.feedback@gmail.com -- @Similaar
Similaar is a participant in the Amazon Services LLC Associates Program and the Amazon EU Associates Programme, two affiliate advertising programs designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com and amazon.es.