DOF / Bokeh / Defocused Background

[scootermcq]

There have been quite a few threads about DOF and how to blur backgrounds. I thought I would lay out this tutorial with examples to help illustrate how it works.

1. The longer the focal length, the more defocused the background
2. The larger the aperture (smaller number), the more defocused the background
3. The closer you are to the subject, the more defocused the background
4. The further the subject is from the background, the more defocused the background



When you look at this example, you can see I have kept the aperture at 2.8, but moved up in focal length. Not only does the background defocus more (blur) but it also compresses more so you can fit the model on the small background. The subject did not move from the hedge, I increased the focal length (zoomed) and moved the camera back to keep the same approximate framing.



When you look at this example, I have kept everything the same except for the aperture. When I dropped from 2.8 to 1.4, you can see the background is more blurred. Compression and perspective stay the same.



When you look at this example, I have moved the subject from 10' from the background to 20' from the background. The camera was the same 20' from the subject and the aperture & focal length stayed the same. Obviously, the subject 20' from the background is more blurred than the subject 10' from the background.



When you look at this last example, the amount of blur or defocusing is very similar. What has changed is one is 50mm is at 1.4 and the other 200mm at 2.8

You can see how perspective is changed and the compression of the background. At 50mm the subject does not fit in the hedge, but at 200mm it is fully covered by the background.

I hope this helps illustrate the effects of aperture & focal length affect background defocusing and compression.

[aroonkalandy]

Fine tutorial......Explained well with illustrations......

Great going......

[yulchick]

Great explanation, very simple to understand, wish I could of read it a while ago when I was just getting into photography, would of made it a lot easier.

[Bruce A]

I'm amazed you took your angel doll out into the elements to model for this tutorial

Seriously, well done. This is an important topic and your tutoriaI should prove helpful to many here.

[FlyingKiwiGirl]

Thanks for the tutorial Scooter, I used it to refresh before doing some bokeh today. Although I'm not sure I followed it exactly to achieve this one Cheers!



Exif data
Camera Sony DSLR-A350
Exposure 0.001 sec (1/1250)
Aperture f/6.3
Focal Length 200 mm
ISO Speed 400

[scootermcq]

Thanks for the feedback & kind words guys.

And just so everyone knows, no angels were hurt in the making of this production

[zona5101]

Nicely illustrated Scott. Thanks for putting that together.

[BexJarratt]

Great thread that all new photographers should read.

[scootermcq]

Originally Posted by zona5101

Nicely illustrated Scott. Thanks for putting that together.

Originally Posted by BexJarratt

Great thread that all new photographers should read.

Thanks, Gang. I have learned so much from others, I figured I should give some back.