This is one of the first thing that we all wants when we hold our first DSLR. Some time we also think before we know any thing about photography usually is, blurry background only possible from expensive cameras.
Well if you know a little about photography .... above mentioned assumptions are totally wrong. Blurry BG is depend on the following 3 things,
Let me explain them one by one in detail,
1- Aperture:
This is the first thing which make any BG blur. The unit of the aperture is define in "f/?" means if you have 50mm f/1.4 lens (where f stands for focal length of the lens & 1.4 is the ratio by which aperture will open) So question is .... what "?" is?
"?" is the ratio which divide the "f" (focal length) and gives us the opening of the aperture as an answer. Higher that number means, less aperture will be open & less BG will be blur (more Depth of Field). Smaller that number means, more aperture will open more BG will be blur (less/shallow Depth of Field). Simple one-on-one math ... any number divided by smaller number give higher value and vice versa.
Another question is ... what is Depth of Field. Answer is simple .... it is focal plane/area in which anything will be focus by the camera. Rest will be blur and it will be measure in distance. If you check below image, i adjust the aperture in such a way that I focus the Lamborghini only. Anything before and behind the car is totally out of focus. So the total length of the car is the total focus area. I can very that length by changing the aperture from f/1.2 ~ f/22 in general. f/1.2 means more light will get inside the lens. f/22 means less light will get inside the lens. Check below some more example of the aperture value.
Following are the aperture types depending on the lens you got,
a- Variable aperture lens: These lenses are general "ZOOM Lenses" and their aperture varies from f/3.5~f/5.6. For example you have kit lens which varies the zoom between 18-55mm and its aperture range is between f/3.5~5.6. So what happens is when you set the zoom @ 18mm, by default you lens aperture is f/3.5. Ones you zoom out to 55mm, by default your zoom is f/5.6. You cannot have aperture f/3.5 @ 55mm to get more light thats why these lenses are cheap.
b- Fixed aperture lens: These lens are also "Zoom Lenses" but their aperture remains fix throughout the zoom length. For example there is a famous 3 Nikon trinity lenses as follows,
14-24mm f/2.8
24-70mm f/2.8
70-200mm f/2.8
All above 3 lenses are best of the best but very expensive because there aperture all wide open @ f/2.8 all the time regardless the focal length. Making such lenses is difficult thats why they are very expensive. They range around 1800~2200 USD per piece. Below are the example of some blur BG using all above 3 lenses,
14-24mm f/2.8 lens
24-70mm f/2.8
70-200mm f/2.8
There are also cheap lenses which are from 24-120mm f/4 lens means they can provide f/4 constant aperture at all the zoom range. Reasonable bargain if you cannot afford the famous Nikon Trinity.
c- Prime Lens: These lenses are having "Fixed" focal length (means no zoom). But the biggest advantage is that you can have the widest aperture ever possible in them. For example,
14mm f/2.8
24mm f/1.4
35mm f/1.4
50mm f/1.2
50mm f/1.4
85mm f/1.2
85mm f/1.4 (this focal length is the addition of 35 & 50mm lens)
105mm f/2.8 (macro lens)
200mm f/2
300mm f/2.8
So as you can see, all above examples are having the widest aperture available and they are capable to provide the most blur BG every possible way. Check below examples and see why Prime lens are more used to blur BG.
35mm f/1.4 Samyang/Rokinon lens
50mm f/1.2 Nikon AIS lens
85mm f/1.8 G Nikon lens
So as you can see, prime lenses are the best source to blur BG. The lower the f/? .... the more the BG is going to blur. As there is no zoom feature in them thats why they can produce the maximum optical quality.
2- Distance from the subject/object
It is simple math .... the far you are from the subject, the less BG will going to be blur. The more close you are from the subject/model the more BG is going to blur.
So there is a chances that you will be more BG blur with kit lens of 18-55mm f/3.5~5.6 zoomed all the way to 55mm (f/5.6) close to the subject/model in compared to 50mm f/1.8 prime lens which is 5 meters away.
3- Focal Length
The more wide angle lens you have, the less BG is going to blur. Check above image i shot with 14-24mm f/2.8 lens shot at 14mm f/2.8.
The more zoom lens (telephoto) you have the more BG is going to blur. Check above image i shot with 70-200mm f/2.8 lens shot at 200mm f/2.8.
About Focus Area:
Focus area in Wide angle lens: In wide angle lens, if you are setting aperture between f/5 ~ f/13 .... your focus plane distance will be in tens of meters .... towards the camera
Well if you know a little about photography .... above mentioned assumptions are totally wrong. Blurry BG is depend on the following 3 things,
1- Aperture value
2- Distance from the subject/object
3- Focal Length
Let me explain them one by one in detail,
1- Aperture:
This is the first thing which make any BG blur. The unit of the aperture is define in "f/?" means if you have 50mm f/1.4 lens (where f stands for focal length of the lens & 1.4 is the ratio by which aperture will open) So question is .... what "?" is?
"?" is the ratio which divide the "f" (focal length) and gives us the opening of the aperture as an answer. Higher that number means, less aperture will be open & less BG will be blur (more Depth of Field). Smaller that number means, more aperture will open more BG will be blur (less/shallow Depth of Field). Simple one-on-one math ... any number divided by smaller number give higher value and vice versa.
Another question is ... what is Depth of Field. Answer is simple .... it is focal plane/area in which anything will be focus by the camera. Rest will be blur and it will be measure in distance. If you check below image, i adjust the aperture in such a way that I focus the Lamborghini only. Anything before and behind the car is totally out of focus. So the total length of the car is the total focus area. I can very that length by changing the aperture from f/1.2 ~ f/22 in general. f/1.2 means more light will get inside the lens. f/22 means less light will get inside the lens. Check below some more example of the aperture value.
Following are the aperture types depending on the lens you got,
a- Variable aperture lens: These lenses are general "ZOOM Lenses" and their aperture varies from f/3.5~f/5.6. For example you have kit lens which varies the zoom between 18-55mm and its aperture range is between f/3.5~5.6. So what happens is when you set the zoom @ 18mm, by default you lens aperture is f/3.5. Ones you zoom out to 55mm, by default your zoom is f/5.6. You cannot have aperture f/3.5 @ 55mm to get more light thats why these lenses are cheap.
b- Fixed aperture lens: These lens are also "Zoom Lenses" but their aperture remains fix throughout the zoom length. For example there is a famous 3 Nikon trinity lenses as follows,
14-24mm f/2.8
24-70mm f/2.8
70-200mm f/2.8
All above 3 lenses are best of the best but very expensive because there aperture all wide open @ f/2.8 all the time regardless the focal length. Making such lenses is difficult thats why they are very expensive. They range around 1800~2200 USD per piece. Below are the example of some blur BG using all above 3 lenses,
14-24mm f/2.8 lens
24-70mm f/2.8
70-200mm f/2.8
There are also cheap lenses which are from 24-120mm f/4 lens means they can provide f/4 constant aperture at all the zoom range. Reasonable bargain if you cannot afford the famous Nikon Trinity.
c- Prime Lens: These lenses are having "Fixed" focal length (means no zoom). But the biggest advantage is that you can have the widest aperture ever possible in them. For example,
14mm f/2.8
24mm f/1.4
35mm f/1.4
50mm f/1.2
50mm f/1.4
85mm f/1.2
85mm f/1.4 (this focal length is the addition of 35 & 50mm lens)
105mm f/2.8 (macro lens)
200mm f/2
300mm f/2.8
So as you can see, all above examples are having the widest aperture available and they are capable to provide the most blur BG every possible way. Check below examples and see why Prime lens are more used to blur BG.
35mm f/1.4 Samyang/Rokinon lens
50mm f/1.2 Nikon AIS lens
85mm f/1.8 G Nikon lens
So as you can see, prime lenses are the best source to blur BG. The lower the f/? .... the more the BG is going to blur. As there is no zoom feature in them thats why they can produce the maximum optical quality.
2- Distance from the subject/object
It is simple math .... the far you are from the subject, the less BG will going to be blur. The more close you are from the subject/model the more BG is going to blur.
So there is a chances that you will be more BG blur with kit lens of 18-55mm f/3.5~5.6 zoomed all the way to 55mm (f/5.6) close to the subject/model in compared to 50mm f/1.8 prime lens which is 5 meters away.
3- Focal Length
The more wide angle lens you have, the less BG is going to blur. Check above image i shot with 14-24mm f/2.8 lens shot at 14mm f/2.8.
The more zoom lens (telephoto) you have the more BG is going to blur. Check above image i shot with 70-200mm f/2.8 lens shot at 200mm f/2.8.
About Focus Area:
Focus area in Wide angle lens: In wide angle lens, if you are setting aperture between f/5 ~ f/13 .... your focus plane distance will be in tens of meters .... towards the camera
Focus area in medium angle lens: Lets say 50mm, if you are setting aperture between f/5~f/13 ... your focus plane distance will be in feets .... towards the camera.
Focus are in Telephoto lens: Lets say 85~500mm (or above) ..... if you are setting aperture between f/5~f/13 ... your focus plane distance will be in centimetres (may be in millimetres) .... towards the camera.
Note: The distance range i mentioned above for 3 categories for "Focus Area" can be vary using Point 1, 2 & 3 but the value will be some where near to the range i mentioned. You can use the combination of Point 1, 2 & 3 to get your desire BG blur ....
Happy Learning guys ....
