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What lenses do I need in order to achieve the amount of bokeh that's on the image below?
I am quite new to dslr photography, and I want to buy a new lens. My main objective is to get strong bokeh even when the subject is not close (if subject is close, you will get bokeh with pretty much every lens).
Note: I have a Canon 1100D.
What lens to use depends on what effect you want to achieve and how much post-processing you intend to do. The 18-55mm/F3.5-5.6 kit lens is a good general-purpose lens. It is fully capable of producing background blur when appropriate camera-subject-background distances, focal lengths, and apertures are selected.
Since you are relatively new to photography, it may be more beneficial for you to maximize your ability to use your current equipment than to purchase new gear. Try using longer focal lengths with open apertures.
If you feel the 18-55mm range is too limiting, the 18-135mm/F3.5-5.6 IS USM has reasonable quality, performs well, and is fairly inexpensive.
To maximize the amount of blur, modify the following parameters:
Focal Length: Longer (100mm > 50mm).
Aperture Size: Larger, faster (F1 > F22).
Distance Ratio: Subject much closer to camera than to background.
You can determine what focal length (f) and aperture combinations (N) will produce more blur by comparing f/N. For example, using an 18-55mm F3.5-5.6 kit lens. If the subject is 10m away, you want the background to be far, 100m away. If you take a picture zoomed in to 55mm at F5.6, the background will be blurrier than if you take the picture zoomed out to 18mm at F3.5. (55/5.6 = 9.8; 18/3.5 = 5.1)
Since you already have an APS-C sensor, chasing sensor size would be counterproductive. The effect that sensor size has on background blur comes from modifying the above parameters to obtain the same field of view. When distance, focal length, and aperture are kept constant, the crop sensor images a portion of the same scene that the full-frame sensor would have. The amount of blur, relative to frame size is magnified (1.5x for APS-C). Relative to subject size, the amount of blur is the same.
The quality of blur is known as Bokeh. It depends on characteristics of the lens, such as the aperture and number/types of elements. The crop factor can multiplied by the aperture to roughly compare the amount of blur that can be expected in lenses designed for different sensor sizes.
Generally, you want "fast" lenses (ones with a wide aperture). This is denoted by the "f" value; the lower the number, the wider the aperture.
(so f/1.8 is a wider aperture than f/4.0)
The wider the aperture, the more light the lens lets in and the easier shallow depth of field or "bokeh" is to acheive dependant on your composition.
To increase the amount of background blur, you can do a number of different things:
And, of course, some of these are going to be opposed to each other (longer lenses may make you move back or force you to use a smaller aperture setting). And may still only get you so far. But aperture isn't quite as all-powerful in this situation as you might assume.
So, getting a new lens alone may only get you so far, particularly if you're only looking at max. aperture. Just my guess but your example image may have been shot at a smaller aperture than you think with a much longer lens than you think (say, a 70-200 f/2.8 vs. say, an 85/1.8 wide open).
Using a larger sensor may help you get more background blur more easily. The larger sensor itself doesn't decrease DoF simply by usage, but because to get equivalent framing vs. a crop body, you'll probably be closer to your subject or using a longer lens (or both).
I've gotten a good amount of background blur on a crop body using f/5.6 with a 400mm lens, and only a minimal amount of blurring with a 50mm f/1.2 lens wide open on a full-frame body, with a more distant subject. So it does depend on a balance of all four factors.
Another technique you can consider (if your subject isn't moving) is to do a bokeh panorama, also known as "The Brenizer Method". This is where you use a long fast lens on a camera, but shoot with the subject closer in portions, and then stitch it together in a panorama, thus "faking" a larger sensor. A lot of full-frame shooters do this to fake "the medium format" look of thin DoF at longer subject distances.
You need to create a shallow depth of field. You do this by: 1) Using a long focal length - The longer the focal length, the shallower the DOF.
2) Use a large aperture such as f/2.8 or f/1.8 - The larger the size of the aperture (small f/stop numbers) the shallower the DOF.
3) Have the subject further away from the background. Using a long focal length and large aperture will create a shallow depth of field, the trick here is to get the background far away from the area that's within the DOF. The further away the background is from the area that's in the DOF, the blurrier the background will be.
You could be doing all of these and still not achieve the blurred look in the image that you've posted. This happens when you use a camera with a very small sensor. Smaller sensors will require a much shorter focal length than cameras with larger sensors. Because the DOF increases with a shorter focal length, people using cameras with sensors smaller than APS-C will struggle to achieve the blurred background look. This is especially true with bridge cameras and other point-and-shoot cameras that use a 1/2.7 sensor which is a little bit bigger than what's found in a common smartphone.
For profile shoots at 10 meters with a blurry (bokeh) background, if your DSLR is full frame (FX), you will be looking for a 200 mm prime lens with a high aperture lens (f 1:1.8 or below). You are getting into very expensive lenses.
The normal distance for a profile shoot is 2.5 to 4 meters, in that range you will use either a 85 mm or 130 mm prime lens with apertures of f 1:1.8 range. These lenses, although not cheap, they are significantly cheaper than their equivalent in 200 mm.
To get good bokeh you have to shoot with either side/back light or side light, front light will give you mostly blurring, which can easily be mistaken with a post effect (Gaussian or other distribution softening) in photoshop... like in the photo of the dog above, the blurring could easily been done on photoshop because he is front lighted but getting bokeh right on photoshop is quite a challenging task.
