Understanding Aperture in Photography for beginners
What is Aperture?
In photography terms, when we talk about aperture, we are talking about the opening in the camera lens through which light can pass, inside that bit filled with glass. A lens aperture is made of a series of metal blades, which increase or decrease the size of the hole depending on which aperture value you have selected. This means, more or less light can pass the lens on the way to the camera sensor. Also the size of the aperture drastically changes the look of the picture.
In present day cameras, the aperture is always fully open and electronically closes to the set value only when you press the shutter release or hit the "aperture preview" or "depth of field preview" button. Older camera lenses may have a manual ring to set the aperture, so you could actually see it move.
Aperture Size or The F-number
When you look at your lens, you will notice it's labeled with a lot of numbers, probably something like 24-70mm 1:2.8 or f/2.8 or on if it's a zoom lens even entire ranges of numbers, something like f/3.5-5.6. These values define what aperture your lens is capable of, in the format f/N, where N is the f-number, also called f-stop or focal ratio.
As complicated as it sounds, it is really easy to understand: The "f" is your focal length. If you have a 50mm lens, then your focal length is exactly that: 50mm. This means e. g. a 50mm f/1.8 lens has a maximum aperture diameter of 50mm/1.8, equaling roughly 27.8 mm. That's all there is to it. This also means an f/1.0 lens would have to have the exact same diameter as its focal length. Hence lower aperture lenses are bigger and more expensive.
This also means there is a technical limit to how small an aperture can go. At f/32 there are roughly 1.56mm of an opening left, so most lenses end there.
The f-Stop Scale
With each full stop, the size of the opening is cut in half. This means with each stop, half the amount of light reaches your sensor, hence the exposure time doubles, to get the same image, and vice versa. In low light situations you use an f-number as low as possible to get the biggest aperture opening, whereas in bright situations you do the opposite.
The fastest aperture on a lens will be where the aperture blades don?t close down at all, when you take the picture. Because the Aperture is ?wide open? you need a lot less light, so we call this a ?fast? aperture.
The smallest aperture on the lens will make the aperture close down to a tiny hole. Because you you are letting in a lot less light, this is considered ?slow?
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Here?s a diagram to show you what the apertures look like on a lens as they are opened and closed:
When you buy a lens, it will almost always tell you only the maximum (fastest) aperture of the lens. For instance a Canon 50mm f1.8. On the whole this is because the minimum aperture will have a lot less impact on a picture than the maximum.
The majority of lenses will have a minimum aperture of either f22 or f32. The difference between these two settings is negligible and you would only see a difference if you?re doing close up work, studio product shoots or similar.
If you were shooting a landscape, there?d be no real difference between f22 and f32.
The aperture setting is a key ingredient for exposing your images correctly, so you?ll find the aperture displayed prominently on either the back panel of the camera, the top display of the camera, on the lens, in the display of the viewfinder or quite often all of these.
When displays need to save a little space (especially in the viewfinder) they will drop the ?f?and you?ll just see 2.8, 5.6 etc. As a rule the aperture will always be to the right of the shutter speed.
The two main settings on modern cameras where you?ll directly access the aperture is in ?M? or Manual mode and ?Av? commonly known as Aperture Priority (Although it actually stands for Aperture Value)
In the Manual setting you will have to select both the shutter speed and aperture separately. With aperture priority, you set the aperture and the camera will take care of the shutter speed for you.
If you?ve bought a new digital SLR with a kit zoom lens, you may notice that the lens has a maximum aperture that is variable, say f3.5-5.6. If you look at the expensive zoom lenses, they will have a constant aperture of f2.8 or f4. Why is this?
The actual size of the aperture doesn?t change, but as you zoom in, the lens gets longer and once again, less light gets to the film/sensor.
So, the amount of light reaching the film/sensor while the lens is zoomed out, you have f3.5 worth of light? when you zoom in, you have only f5.6 ( what we call effective aperture) worth of light hitting the film/sensor.
Overcoming this problem requires bigger elements (What we call the glass in the lens) and better lens engineering. In these lenses the zoom part of the lens is all done inside the lens and the front and rear elements don?t move. That?s why they?re significantly more expensive.
When you use your lens at the maximum aperture you are pushing it to its peak performance. You are pushing it to perform at its very best in terms of image quality.
At F8 you would be hard pushed to tell the difference between a very good lens and a fairly cheap lens.
In order to get really good quality and a very fact lens is quite a feat of engineering. This makes the cost of very fast lenses prohibitively expensive for most people! A fast zoom lens like the Canon 24-70 f2.8 will cost in the region of $1400 while a similar zoom lens with and aperture of f3.5-5.6 will be just a couple of hundred dollars.
However, it is a lot cheaper to get a prime lens, such as a 50mm f1.8 and most manufacturers as well as third party manufacturers such as Sigma and Yongnuo also produce these lenses. A ?nifty fifty? is a great way to get involved in fast aperture photography and should be one of your first purchases, after you?ve bought your camera.
Depth of Field
So, we touched on Depth of Field a little earlier. It?s likely you?ll have heard this term, but might not know what it is exactly.
Without getting too technical it?s the amount of the image that?s in focus.
Most likely you?ll have seen pictures of people where the person is pin sharp, but the background is all blurry. This would be a ?shallow depth of field? and is created using a fast lens on it?s maximum aperture, or thereabouts.
An effect like this would be achieved using an 80mm lens and an aperture of about f4
However, if you?re taking pictures of a gorgeous landscape, with mountains off miles in the background, you don?t want a shallow depth of field. You want the grass in the foreground to be in focus AND you want to those gorgeous mountains in the background to be pin sharp too.
This is what we refer to as ?Deep focus? and requires a very small aperture, say around f22 or f32
Aperture and Exposure.
So, we mentioned before that a fast maximum aperture needs a lot less light than your minimum aperture. The amount of light required for an aperture of say f1.4 is significantly less than f32.
To give you an idea of the difference, if your shutter is 1/1000th of a second at f1.4, at f32 that will be a whopping ½ a second! That?s a huge difference! Where as with f1.4 you?ll be able to photograph a fast moving sporting event with a large telephoto lens hand held? At f32 you WILL need to be taking your photograph using a tripod!
This is why you see sports photographers with those huge white lenses at sporting events? they are very large telephoto lenses with very fast maximum apertures? Generally around the f2.8 mark.
It?s also while you?ll also see most landscape photographers carrying around a very sturdy tripod!
Which Aperture to choose
Aperture is probably one of the most difficult aspects of photography to get to grips with, but hopefully by now you?ll have a bit of an understanding of how it all works.
In order to get to grips with aperture, here are some things you can have a go at, that will help you understand how it all works.
For this, ideally you?ll want a big zoom lens. It doesn?t have to be an ultra fast mega expensive affair, something like a 70-200mm or 75-300mm would be a great starting point.
Zoom your lens out to it?s longest telephoto (say 200mm or 300mm)
Now set your camera to Aperture Priority (Av on your camera)
As you wheel the dial of your camera up and down and your aperture changes, you?ll notice that the shutter speed will change alongside it.
We want the aperture to be wide open. Dial it down until it?s the smallest number it can be. This will probably be f5.6 or f6.3. You should be getting a nice, fast shutter speed that will enable you to get fast action shots.
Just to see the difference, while you?re doing this, dial the aperture up, all the way to f22/f32.
You?ll see exactly how slow the shutter becomes and what a disastrous effect it has on sports photography!
If you?ve got a family friend who doesn?t mind modelling, this can be good fun.
The ideal for photographing a person is round 80mm on the lens, about 125th of a second shutter speed and f8 on the aperture.
We need f8 to ensure that whole face is in focus. If you?re not careful and use a maximum aperture of f1.8, then just the eyes can be in focus, not the ears and nose!
You can try opening up to f1.8 to see how it looks!
Once again, you can try closing down to F22 and if you have one, use a tripod. You may find that while the camera is dead steady, the shot is still blurred, because your subject can?t stand still enough!
The key to photographing a great landscape is finding a place that takes your breath away and then try and take a picture of it! If it sort of looks ?quite nice? you?ll only ever end up with a quite nice picture!
Now as we?ve previously discussed, we want to be shooting at around f22 / f32 and unless it is an extraordinarily bright day (If it?s this bright, it?s probably not the best time to take pictures, but we?ll discuss the golden hour at another time) your shutter speed is going to be fairly slow.
If you don?t have a tripod, buy a small camera bean bag and prop it on wall to ensure your camera is dead still.
Now, focus about ? of the way between what you want to be in focus in the foreground and what you want to be in focus in the background. Once you?ve taken your picture,all should be pin sharp. (It?s also worth investing in a cable release, or learn to use the self timer)
Once again, try opening the aperture and just have a look at the difference it makes to the image and the shutter speed.
These are all great ways to really learn about aperture, the effects it has on shutter speed and of course the depth of field.
So, you may have heard of Bokeh in discussions about aperture and it has always been of interest but right now it?s going through a renaissance.
To break it down, Bokeh is all about shooting with your lens wide open on its maximum aperture and looking at the way it handles light in the out of focus background? It really is quite beautiful?
Bokeh is normally (but not exclusively) practised with a 50mm lens. You don?t have to worry about the quality of the lens unduly and many people buy second hand manual lenses specifically for the purpose, using adapter rings.
Aperture probably has the biggest effect on the look of your photograph, more so than shutter speed and ISO.
It?s really important that you have an understanding of what effects all of the different apertures have on your finished image. There?s only one way to make that happen and that is to practice, practice, practice!
Don?t worry about getting it wrong, you can?t. Go out, explore, have fun and enjoy your photography. The more you do the better you?ll get.
If you?re just starting out and want to really get some amazing ?wow? shots you really can have a great time exploring Bokeh with a nice, fairly cheap 50mm ?nifty fifty? lens.
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