There's more to background blur than aperture!
Sometimes it seems like the amount of background blur that you get in a given shot is completely random. I mean, the guideline that the larger the aperture (or the lower the aperture value), the more blur you get is a good one, but it doesn't always work, does it? ...or when it does work, you get varying amounts of background blur, even when using the same aperture value!
The reason for the variation is: There's more to background blur than aperture.
Your distance from the subject (the point of focus) as well as the focal length of your lens makes a big difference in how much background blur you'll get on a given shot.
* NOTE: (Focal length just means how much you're "zoomed in" -it's measured in millimeters, like "100mm".)
So, whitout further delay...
Here's a table to help you determine DOF:
(Click on the tables to view a less crowded and more printable version of the tables.)
These are actually just screenshots of my tables because the ones I made on Google Spreadsheets won't print in color. If you want to view the actual spreadsheet, click here.
Using the spreadsheet:
Print it out (preferably in color), and keep it in your camera bag.
Note that there are 4 tables, each for subjects at different distances from the camera. Use the first table when focusing on a subject that's about 10 feet away, the 2nd for a subject @ 20 feet, etc...
Similar tools, links:
There's a free DOF calculator for Palm OS available. If you have a Palm Pilot, it may be more convenient for you: Click here to go to the program's site. -I've never downloaded or used this software, so this is not an endorsement, use at your own risk.
Alternatively, you can search for online calculators (this is the one I used) or other DOF calculators that you can download for various portable devices. There are also cards you can buy with this information on them, but I find it easier to just print it out myself, study it and refer to it as necessary.
Questions? Comments? Email me on the Photography_Beginner'syahoogroup or use my info on this site's homepage.