Most people who are just starting out with photography are familiar with this. You have finally bought a DSLR or mirrorless camera and want to take professional-looking photos with a blurred background, but somehow it doesn't work that way and the cell phone photos sometimes even look better. Why are all of my pictures sharp from front to back?
5 factors for background blurring
There are different ways to create this blurring and it depends on four factors:
- Focal length
- Distance to the subject
- Distance to the background
- Sensor size
In this article, we would like to give you 5 tips on how to get a nice, blurred background on your photos.
1. Adjusting the aperture
If you look into a lens from the front, you can see that black lamellas cover the opening in a circle. This is the so-called aperture.
With the aperture, you can regulate how much light you let onto the image sensor. If it is wide open, a lot of light is let through, if it is more closed, less light comes through.
In addition to this function, there is another very important property that is associated with it. Because the more it is open, the blurrier is the background.
In other words, it's actually quite simple, I open the aperture very wide and bang, the background is out of focus. That's true, but unfortunately, not every lens allows such a large aperture that it becomes really blurred.
The f-number is decisive. If you look at your lens you will see this indicated. For lenses with fixed focal lengths e.g. like this: f / 1.4 (sometimes this is also written like this: 1: 1.4 or F1.4 - but everything means the same). With zooms also more often like this: f / 3.5-5.6.
The smaller this number is, the wider the aperture can be opened, i.e. exactly the other way around as one might assume. If there are two numbers on the lens, it means on the one hand that it is a zoom lens and the first number indicates the maximum aperture when the lens is completely retracted. The second number is the maximum aperture when the lens is fully extended.
The aperture of zoom lenses changes with the retraction and extension of the lens. But not with every zoom. High-quality zooms have a constant maximum aperture, and then, as with prime lenses, there is only one number, e.g. f / 2.8. Lenses with a small f-number are also called high-speed lenses.
2. Adjusting the focal length
Another possibility to influence the blurring is via the focal length. If I use a long focal length e.g. from 85mm, 135mm, 200mm, the background becomes more and more blurred. The sports photographers with the huge lenses can therefore photograph the athletes very well against a blurred background.
Note: The longer the focal length, i.e. the larger the number of millimeters, the more blurred the background.
Here you can see three pictures. The first is taken with a focal length of 17mm, the second with 85mm, and the third with 200mm. The background becomes more and more blurred the longer the focal length is.
3. Changing the distance to the object
What do you do if you don't have a fast lens or a long focal length? You just get closer to the subject. You will notice that this also affects the blurring in the background.
Note: The smaller the distance to the subject, i.e. the closer you are, the blurrier the background. Reduce your distance to the subject!
4. Changing the distance from the object to the background
But not only the distance to the subject is decisive for a blurred background. The distance between the subject and the background is also important. Because if the background and the subject are almost on the same level and there is no distance between them, then both are roughly equally sharp.
However, if you increase the distance between the subject and the background, the background becomes blurred.
Note: The greater the distance between the background and the subject, the blurrier the background. So go ahead and increase the distance between the subject and the background!
5. Playing with the image sensor size
Yes, the size of the image sensor also plays a role in blurring. What you need to know is that if you have a camera with a full-frame sensor and one with an APS-C sensor and want to keep the same distance to the object and have exactly the same image section on the photo, then you have to use different focal lengths on both cameras.
Because of the sensor size, the image section is different for full format and APS-C with the same focal length (e.g. both 50mm). So if you want to have the same image section and the position to the object remains the same, and you take a 50mm lens with a full-frame camera, then you would have to use a 31mm lens on the APS-C camera.
And if you then compare the blurring you will find that it is larger in full format, due to the fact that you had to use a smaller focal length with the APS-C camera in order to get the same image section with the same distance to the object.
Note: the larger the image sensor, the blurrier the background with the same image section and unchanged position. So here’s a takeaway: Use a camera with a larger image sensor!
Admittedly, a new camera with a larger image sensor would be a really big investment and therefore comes last in our tips.
What does all this mean for you if you want to have blurred in the background? Set the largest aperture, take the longest focal length, get close to the subject, and buy a camera with a large image sensor, if everything else fails. Then you will have the blurriest background you can imagine.