What Camera Lens Blurs The Background?

Background Blur And Depth Of Field

background blur is caused by a very shallow depth of field, whereby only a small part of your image is in focus, and the rest is out of focus. using a shallow depth of field allows you to isolate your subject from its background and create a soft, dreamy quality to your images.

the thing you need to understand about those magical blurry backgrounds that we all love so much, is that they are created by controlling something called the depth of field.

depth of field is created via the aperture in your lens by allowing you to control the area of your scene that you want to have in focus from the front all the way to the back. a shallow depth of field means that very little is in focus and will result in a blurrier background, while a deeper depth of field will result in an image that appears in focus all the way from the front to the back of the scene.

you need to understand how depth of field works first, and then you will see how its achieved via a lens and what to look for in a lens or how get the look you want on what you already have.

• larger aperture (lower f number) = narrower depth of field, so blurrier background.
• so an f/1.8 lens will give you a blurrier background than an f/4 lens.
• however if your dof is too narrow then you'll have a hard time keeping yourself in focus when moving around doing your excercises!
• so instead positioning yourself and the camera so the background is further away will let you have a fairly deep depth-of-filed so you remain in focus while still having a blurry background.

Aperture And F-Stop

aperture controls how much light reaches your camera's sensor. it is measured in f-stops. the lower the number of your f-stop, the shallower the depth of field (andthe more light is allowed in; you might hear it referred to as "shooting wide open"). a high f-stop number willcause more of your image to be in focus.

the only camera setting that enables you to control your depth of field is your aperture, and the way that we control this when shooting in manual mode is by adjusting the f-stop of our lens.

• the lower the f-stop number (like f/1.4), the wider the opening in the aperture, and the blurrier the background will be.
• on the flip side, the higher the f-stop number (like f/16), the smaller the opening in the aperture, and the more in-focus your images will be from the front to the back of the scene.
• if you’re having trouble achieving those creamy, blurry backgrounds, try opening up your aperture to your lens’s widest f-stop setting and see what changes.

if you want to achieve a shallow depth of field/blurry background, it is probably best to shoot in aperture priority mode on your camera (av mode), and to choose the lowest number f-stop available to you for the lens you are using. each lens will have a different range of f-stops. i usually shoot somewhere between f1.4 and f2.8 when i'm after a shallow depth of field, but it depends on the other elements below.

you should also be aware that some camera lenses have a tendency to be very soft and not sharp enough when you shoot at the lowest f-stop number. i would recommend taking the same shot using a few different f-stop numbers and then comparing the results afterwards.

your choice of aperture has a big influence on the look of the bokeh in your photos. the wider the aperture (that is, the lower the f-number), the shallower the depth of field, which in turn means the background will become more blurred. so try shooting in either aperture priority (av) mode or manual mode, and select a wide aperture (low f-number).

Focal Length

the focal length of your lens (measured in millimetres) governs the field/angle of view and the magnification of your subject. the shorter the focal length, the wider your view;the longer the focal length, the greater the magnification.

• depth of field gets shalloweras focal length increases.
• conversely, depth of field increases (so more is in focus) as focal length gets shorter.
• so, to achieve blurry backgrounds, choose a longer focal length (and a low f-stop number).
• for example, i would achieve a very shallow depth of field if i was using my 100mm macro lens at f2.8 or my 50mm lens at f1.4.

fast lenses with a focal length of 50mm or more are generally best for bokeh photography as blurring the background can be more challenging with wide-angle lenses. that's because shorter focal lengths produce a larger depth of field at any given focus distance and aperture, so more of the scene from the foreground to the background will be rendered sharply, and you'll get less bokeh.

a longer focal length produces a tighter depth of field, which in turn can result in stronger background blur. this is the reason why telephoto zooms can be used to great effect to isolate a subject and transform the backdrop into detail-less blur.

for example, the canon rf-s 18-150mm f3.5-6.3 is stm lens can produce an excellent bokeh background if you use it towards the long end of its zoom range, even though the aperture is narrower at that length. so if you want to make the blur stronger and enhance the bokeh, take a few steps back and zoom in (or change lenses) to a longer focal length.

Distance Between Camera, Subject And Background

the closer you are to your subject, the shallower the depth of field will be (and the blurrier your background). the further away you get from your subject, the greater the depth of field (and more of your image will be in focus).

all lenses will have a minimum focussing distance, so it is important to check what this is. if you get closer than your minimum focussing distance, your camera will not be able to focus.

• the distance between you and your subject has a big impact on the depth of field that you can achieve.
• the closer you are to your subject, the blurrier your background will appear, and the further away you are from your subject the sharper the background will appear (even with your lens at its widest aperture setting).
• the position of your subject not only matters in relation to you and your camera, but in relation to the background itself.
• the distance between your subject and the background has a big impact on the way dof is captured by your camera.
• the closer your subject is to the background, the sharper it’ll appear, while the further away your subject is from the background, the blurrier it’ll appear.

the further away your background is from your subject, the blurrier it will be (as depth of field is describing what depth of the image is in focus; so if the depth is say 10cm, anything further away than that will be out of focus). the closer your background is to your subject, the more of it will be in focus.

the further away objects in the background are from you, the more out-of-focus they will be! might also be worth considering shooting through a mirror - i'd expect that a gym will have a fair few of those. mirrors let you get more distance between background and foreground than the space physically allows. also it would make the fact you're filming less obtrusive as you're not actively pointing the camera at anyone else sharing the space.

increasing the distance between your subject and the background will blur the background more. another factor is the distance between the subject and your camera. the closer your lens is to the subject, the shallower the depth of field. this means that background areas will fall out of focus more quickly. to blur more of the image, move the subject closer to your camera and further away from the background.

Lens Choices For Blurry Backgrounds

to capture attractive bokeh, you need a 'fast' lens – that is, one with a wide maximum aperture, ideally f/2.8 or wider (lower f-number). this is one of the main reasons to include a fast prime (fixed focal length) lens in your kitbag, even if the focal length is one covered by your kit zoom.

• a great lens to start out with is the 50mm f1.8 or f1.4, depending on your budget.
• it is probably the cheapest lens you can buy to achieve beautiful blurry backgrounds.
• it is of course a prime lens, of fixed focal length, so there is no zoom, other than your feet!
• it is probably the lens most often used by bloggers.

another lovely lens for background blur is the 85mm f1.8 lens. this works well for portraits (as does the 50mm), although it has a longer focussing distance, so you can't get super close to your subject.

if you want to take close-up images of flowers, you will need a longer lens. my favourite is the 100mm f2.8 macro lens. this allows you to focus very close to your subject for an extremely shallow depth of field. it is heavy, though.

• top choices for cost-effective bokeh lenses include the canon rf 50mm f1.8 stmrf 85mm f2 macro is stmrf 35mm f1.8 macro is stmrf 24mm f1.8 macro is stm work really well for creating a bokeh background in close-up photography as the depth of field shrinks with shorter focus distances.
• with its ultra-wide f/1.2 maximum aperture, the canon rf 45mm f1.2 stm is one of the best canon lenses for background blur and bokeh.
• it’s the first non-l-series lens to offer such a fast aperture, giving smooth, attractive bokeh and strong subject separation.
• it can also focus as close as 45cm, making it easy to create a very shallow depth of field that helps your subject stand out against a soft, blurred background.

you will notice that none of these recommendations include zoom lenses. you can buy zoom lenses with low f-stop numbers that produce very beautiful blurry backgrounds, but they are very expensive and very heavy. the24-70mm f2.8 and 70-200mm f2.8 have been on my wish list for a very long time.

that said, it is possible to achieve some background blur with a zoom lens at a long focal length and a not-quite-so-small aperture. the shot below was taken on my canon 24-105mm lens at 105mm and f4. because the trees in the background were a long way away, they are out of focus.

Canon EOS R, 35mm F1.4 And Focus

is a sigma 35mm f1.4 art good enough?

probably more than good enough!

• 35mm f/1.4
• 2m distance (reasonable for a 35mm lens on full frame to get a decent mcu shot)
• use canon 5d as the format as it's got the same size sensor as your eos-r
• ...you're only going to have a depth-of-field of 27cm. that's absolutely tiny, that's probably about the distance from my spine to my nipples and i'm fairly skinny!

if you take it up to f/2.8, you've got 55cm which is workable but still pretty tight. take it down to f/4, and you're at 80cm which i would feel would probably be about ideal.

here's the trick though... most lenses get best optical performance (in terms of sharpness and abbarations) a few f-stops slower than their maximum rating. f/2.8 -f/4 will be about optimal for that sigma.

granted the eos-r has fantastic dpaf autofocus which might help offset this, but generally i feel for this sort of video you want to make sure that your whole body is in focus.

Sensor Size And Camera Body

very simply speaking, the larger the sensor that your camera has, the greater the background blur. there are huge variations between camera sensors and i am certainly no expert on these. but i thought it was worth mentioning here all the same.

the type of sensor that the iphone camera has, for example, is very different to that of a compact zoom camera, or a dslr. so, with an iphone, although you may be shooting at f2.2, the focal length is very short/wide, and the sensor is so different, that it is hard to get any background blur.

• to achieve significant background blur, you really need to use a dslr or micro four thirds camera with interchangeable lenses.
• with dslrs, you will achieve more background blur with a full frame camera which has a bigger sensor (such as the canon 5d or 6d),than the crop frame sensor cameras (such as the canon 70d or 700d).
• however, all dslrs will produce significant background blur when paired with the right lens.

the size of the sensor also affects the amount of background blur you get. so, if you're very concerned about dof, you need to consider that as well, not just which camera will fit the lens you want.

so moving to a larger-sensored camera inherently means more background blurring. you won't just see it in macro shots any more.

Bokeh Settings And Lens Design

the term bokeh is a japanese word meaning 'blur' that is used to describe the look of the out-of-focus areas of a photo. bokeh – widely pronounced to rhyme with ok – is most obvious in photos with lots of small bright highlights, like street lights at night. but it's not just about bold circular highlights, it refers to the quality of any blurry parts of an image.

bokeh is influenced by several factors, including aperture size, focal length, and the distance between the subject and the background. a larger aperture (lower f-stop number) allows more light to enter the lens, creating a shallower depth of field and enhancing the blur effect in the background.

• in general, a lens with more aperture blades results in more attractively circular bokeh, as each point of defocused light mirrors the shape of the aperture.
• it's not an issue if you're shooting with the lens wide open – that is, at the maximum aperture (lowest f-number), when the opening will be circular anyway – but that won't always be the case.
• seven blades is great for attractive bokeh, but nine is even better.

when you shoot with your lens wide open (at its maximum aperture), you should get round bokeh in your images, because the opening is round. otherwise, the shape of bokeh is determined by the number of aperture blades in the lens – in general, the more blades, the more circular the aperture remains as it opens, and therefore the more circular the bokeh.