Main camera controls which effect any image that you take are:
- White Balance
In this tutorial I’m going to concentrate on Aperture, I’ll later cover the other topics in a later tutorial
How Aperture effects your images
Aperture controls the amount of light that reaches the camera sensor and also the amount of DOF (Depth Of Field which in my opinion should be known as Depth Of Focus) as DOF is the area which appears sharp to the human eye. The higher the f stop number, more DOF
From here on I will call DOF Depth Of Focus as it’s easier for beginners to understand
As you can see in the above screenshot at f1.4 the background is out completely out of focus, as we move through the range to higher f stops e.g. f16+ the background comes more into focus, more Depth Of Focus. The higher the number the more in the image will be in focus. For portraiture when we want to separate the subject from the background we shoot with our lens wide open.
The analogy is often made exposure is like the tap and bucket, the wider the tap opening (Aperture) the quicker the bucket will fill up (Faster Shutter Speed). The smaller the tap opening (Aperture), the longer it will take to fill the bucket (Longer Shutter Speed)
A handy way to remember DOF and f-stops, the larger the f-stop number = the larger the DOF
If you go the from f1.4 to f2 the sensor only get half the amount of light. The higher the number, the less light that reaches the cameras sensor
Aperture Values and f/Stops
Aperture openings are measured as fractions of the focal length of a lens. That is what the ‘f’ stands for in the aperture rating, ‘focal length’. Assuming we have the a 50mm, with an aperture of f/2.8, we can determine the actual diameter of the aperture opening like so:
50mm / 2.8 = 17.85mm
If we open the aperture up to its maximum of, say, 1.4, we can measure that as well:
50mm / 1.4 = 35.71mm
The difference between an aperture of f/2.8 and an aperture of f/1.4 is a difference of four times as much light…or two stops. We know this because the area of the aperture opening itself is four times as large at f/1.4 (1001.54mm^2) as it is at f/2.8 (250.25mm^2). A stop in photography nomenclature means a difference of one exposure value, which is the doubling, or halving, of the amount of light reaching the sensor. There are a few standard “full stops” that f-numbers are rated in:
Full Stop Aperture Value Scale
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64
These aperture settings all differ by one full exposure value, or one full “stop”, and create the full f-stop scale. When you close down your 50mm f/1.4 lens from its maximum aperture of f/1.4 to an aperture of f/2.8, you are “stopping down” by two full stops.
It should be noted that most cameras these days offer a two additional f-stop scales beyond the standard full stop scale: a half-stop scale and a third-stop scale. Most cameras default to a fractional scale rather than the full stop scale, so it is important to learn and memorize the full stop scale so that you are making the proper adjustments when you change your aperture setting on your camera.
Half-stop Aperture Value Scale
1, 1.2, 1.4, 1.7, 2, 2.4, 2.8, 3.3, 4, 4.8, 5.6, 6.7, 8, 9.5, 11, 13, 16, 19, 22
Third-stop Aperture Value Scale
1, 1.1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.5, 2.8, 3.2, 3.5, 4, 4.5, 5.0, 5.6, 6.3, 7.1, 8, 9, 10, 11, 13, 14, 16, 18, 20, 22
The maximum aperture is printed on your lens, more expensive professional lenses have ‘faster’ apertures such as f2 – f2.8, the 18-55mm kit lens that comes with the camera has a ‘slower’ maximum aperture of f3.5 at 18mm and 5.6mm at 55mm
Example of How DOF changes from f1.8 – f22, as you scroll through the photos only the amount in focus changes. I have focused on the menu in the middle. As DOF extends more at the back more than the front you will see the Regatta paper at the back come into focus. Both items are the same distance from the menu in the centre. I took these photos with my Canon 50mm f1.8
Scroll though images using the arrows or let it run automatically
Aperture used to blur the background in Portraiture
Have a look on YouTube video showing effects of Aperture for blurring out the background https://www.youtube.com/watch?v=L3GklufNULg
Also use the following link to Bokeh YouTube video of the very expensive Canon f1.0 lens which even on the secondhand market costs around $5,500 or on eBay https://www.youtube.com/watch?v=g-TbXGi9yI0
This lens clearly demonstrates just how little DOF there is at f1 where only the eye nearest the camera is in focus. Remember always focus on the eyes when taking a portrait. If the eyes are out of focus the image will not look right to a viewer.
At the cheaper end of 50mm lens is the affordable 50mm f1.8 which gives great low light images and a very shallow DOF, costs £100.
Remember distance effects Depth Of Focus, the closer you are to your subject the shallower the DOF
For landscapes we usually use a higher f stop e.g. f8 or more, however if we go too high we introduce diffraction which we don’t want.
All lenses have a ‘sweet spot’ which is usually on most lenses when you have to close down by 1 or 2 stops from maximum aperture to get sharpest image. Usually as you stop down the lens the centre and edges get sharper, this is common in cheaper lenses. Very expensive ‘Professional’ lenses are usually sharp from wide open e.g. f2, f2.8
Camera Manufacturers have a range of lenses for everyone’s pocket
- Consumer – the cheapest, basically the kit lens that come with your camera which is fine for majority of photographers
- Prosumer – more expensive than consumer aimed at camera enthusiasts who are will to pay extra for a faster lens, more sharpness and contrast
- Professional – When you are getting paid for taking photos professional photographers go for the top of the line. Their images may be posted on large billboards so they need the very best.
Canon call their’s L lenses and have a red ring around the lens to denote this which if your were being just a tad cynical you would think that it is just a marketing ploy to get more money for expensive fast (f2.8) long range zoom lenses. These large lenses are coloured white so that everyone around you will know you shelled out for this expensive lens. In their defence, as in all things you get what you pay for. If you are at a sports photographer you need the fastest lens possible to give you clean images without loads of digital noise (grain) the faster the lens the better. If you have a slower lens around f5.6 or f6.3 which are common on long telephoto lenses in the Prosumer range at f5.6 your sensor is getting only ¼ the amount of light. That means that you will have to increase your ISO (sensor sensitivity) to be able to shoot at the same shutter speed
- 400mm lens wide open f2.8 @ 1/1000 sec 100 ISO which would be good to freeze most action
- 400mm lens wide open f5.6 @ 1/250 sec 100 ISO may not freeze action and camera shake introduced
- 400mm lens wide open 5.6 @ 1/1000 sec 400, here we’ve increased the ISO to freeze the action
Second Hand Lenses
Second hand lenses much cheaper than new on sites like https://www.mpb.com/en-uk/ where you can also sell your gear that you no longer need.
Camera Lens Aperture Blades
Image from http://www.tested.com/
Apertures are made up of a number of blades which extend or contract when taking the photo. Apertures are not perfectly circular. Nowadays lens manufacturers are keen to show off the lovely out of focus parts of an image which they now call Bokeh. The more expensive lenses have more blades than in the cheaper consumer lenses which is why they get more circular Bokeh
When you get lens flare which will take the shape of the Aperture opening, the above example it’s easy to see that there are 8 blades making up the Aperture.