BetterPhoto Q&A
Category: Focus Problems (Blur)

Jose Alas		More on Blurring Backgrounds I've read all the ways suggested to blur backgrounds, and they applied to film cameras. With a digital camera, I've tried to blur backgrounds by using the "soft" option of the editing software, but I haven't achieved the results one gets when one focuses on the closest object with a traditional camera. To love this question, log in above April 18, 2004

- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery		If this is a digital SLR, just do it the same way: with the biggest aperture the lens has. To love this comment, log in above April 18, 2004

Dave Cross		Hi Jose. Getting the attractive 'out-of-focus' background using a basic digital camera can be a nightmare. Have a look here http://www.wrotniak.net/photo/dof/ for the reasoning and some ideas. In a nutshell:- Use your 'manual' mode to get the lens aperture wide open (smallest 'f' number) Have the (optical) zoom at maximum (longest focal length). Have your subject as far from the background as possible. Take the picure and hope :-) Meanwhile, if you have PhotoShop CS (the expensive one), it has a 'lens blur' filter which can simulate the effect quite well (apparently, I can't afford CS just yet). Note this filter is NOT the 'Gaussian blur' featured in other PhotoShop versions. Have fun experimenting. To love this comment, log in above April 20, 2004

Chris		Unless you have a digital SLR with a sensor size that compares to a standard 35mm frame, it is almost impossible to get the blurred background effect you desire even at the largest aperture. This is due to the short focal length lenses needed, in the non-SLR digital cameras, to cover the very small sensor size. Unfortunately, focal length is the greatest factor in determining depth-of-field generically if you do the maths. So a typical point-and-shoot (P&S) digital camera will have a focal length of say around 6mm. This is due to the fact that the sensor size is only about 4mm x 2.5mm approx compared to a 35mm frame of 36mm x 24mm. Again, if one does the maths, it can be shown that the "effective" aperture (so far as depth-of-field ONLY is concerned)on the P&S camera is the ratio of the sensor sizes x actual aperture. Therefore even at f2.8 on the P&S camera the efective aperture is f23!! Hence no blurred background even at f2.8. To emphasise again, this "effective" aperture is ONLY applicable to depth of field calculations. As an actual aperture for controlling the amount of light that enters, f2.8 on any camera is still f2.8. But it's not f2.8 when one considers depth-of-field. Even the digital SLR's (except the most expensive pro versions) have a sensor size smaller than a 35mm camera. So, for example, my own camera (Canon 300D - a great piece of kit) has a sensor size of approx 23mm x 15mm. So at f2.8 the effective aperture (for DOF calculations) on my 300D as compared to a 35mm camera is about f4.5, so the background won't be quite as blurred as with f2.8 on a 35mm camera. Chris To love this comment, log in above April 20, 2004

Paul M		You have another software option apart from upgrading to Photoshop CS. Andromeda makes a plugin that does an excellent job of blurring and gives you a lot of control over the effect. The plugin is called Varifocus. http://www.andromeda.com/info/varifocus.html You can try it out and buy it if you find it useful. I actually like it better than the CS version. To love this comment, log in above April 21, 2004

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