aperture size and shutter speed?

Question by dEviL: aperture size and shutter speed?
How do they work? I get the basic idea. Longer the shutter speed, the more the light will enter and hence the pic is brighter. Larger the aperture size, again more light will enter and make the pic brighter. So my real question is this. Take 2 cases.
Case 1. I set a small aperture size and leave the shutter open for a long time and
Case 2. I set a large aperture size and increase the shutter speed.
Now both the images should look pretty similar right? since same amount of light is entering into the lens? If so, how to decide which option to go for, (case1 or case 2)..?(I’m also guessing that this is what is called aperture priority and shutter priority? I could be wrong)..

Best answer:

Answer by selina_555
You’re getting pretty close in understanding.

As far as light/exposure is concerned, yes, they will look quite similar.

The BIG difference is in DOF- depth of field. If you have a DSLR and a fast lens, you’ll see the biggest difference – not so much in a small P&S camera – and it is one of the most important aspects of using camera settings creatively (as opposed to AUTO).

ETA to explain further:

DOF – Depth Of Field
DOF is the area (plane) of the photo that is in sharp focus. For landscapes, we usually want a a very deep DOF, so that everything in it is in focus. For portraits, we usually like to have the person in focus, while the background is blurred.
So you have a plane that is in focus – and it can be either in the foreground (so the background is blurry) or in the background (so the foreground is blurry).

For the most part, this is achieved via a lens with a large aperture (that’s the small f/stop number), but a longer focal length – i.e. zoom – increases the effect. Often people ask how to achieve with a small P&S camera, but unfortunately that is not something those little things are very good at.

If you have manual controls, use the biggest aperture. If you don’t, try setting it to the portrait setting which makes the camera choose the biggest aperture it is capable of. Make sure there is some distance between you, the subject, and the background. You can also attempt it on Macro setting – that may work to a certain extent.

For further reading, check out this Wikipedia article: http://en.wikipedia.org/wiki/Depth_of_field

Give your answer to this question below!

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5 Responses to aperture size and shutter speed?

  1. Ashley T says:

    It doesn’t actually work out like your suggestion. A long time ago I used to use a view camera that had negatives about 4X5 inches. Sometimes I would take pictures at night, with a large aperture and a long shutter speed, perhaps ( for that lens ) F8 and 40 minutes. Using a tripod of course. The buildings would be in fine detail but the traffic would be blurs.

    Generally your subject matter determines your settings. F8 and 1/60 is the approximate equivalent of F16 and !/15 th if I can still do math in my head. But the latter setting is what you might want to use to capture a waterfall while showing the flow, all blurry, against a detailed rock and fern setting. If you want to capture a person in midleap over a stream, you probably would want at least a shutter speed of 1/60th, more likely 1/200 or faster.

    Yes, you articulate the relationship of light to aperture and shutter as I understand it too. The only way to fix it in your eyes and head though is to shoot pictures, lots and lots of them. Some subjects need fast shutter speeds, some need slow. Wide open lenses suit some light conditions and subjects better than closed down lenses. Find out for yourself by shooting lots of pictures and EVALUATING EACH ROLL. Your self critique is the best guide to growing brain and eye cells.

    To really learn what the question means, find someplace teaching a course in Zone system, which was invented by Ansel Adams. Probably one is offered by your local technical college’s photo department. A semester shooting and processing images done with the zone system will put great control into your hands and eyes and head. Photos probably aren’t made by cameras but rather are shot first in the brain, which evaluates things like light and texture and aspects of complexity, before you pick up the camera.

  2. EDWIN says:

    You are somewhat confused about the Exposure Triangle which consists of Aperture, Shutter Speed and ISO.

    The Aperture is the opening formed by the movable blades of the diaphragm inside the lens. It controls how much light is admitted. The larger the opening (f1.4, f2) the more light admitted. The smaller the opening (f8, f11, f16) the less light admitted.

    ISO is a measurement of the sensitivity to light of a light sensitive surface, either film or digital sensor. A low ISO (50, 100) is insensitive and requires more light. It also gives the best results since grain (film) or noise (digital) is minimized. A higher ISO (400, 800, 1600) is more sensitive and requires less light. It also increases the possibility of grain or noise.

    The Shutter Speed controls how long the light admitted by the Aperture used is allowed to expose our film or sensor based on the ISO used. Using a low ISO and a small aperture will give a slower shutter speed while using a higher ISO and/or a larger aperture will give a faster shutter speed.

    The old “Sunny 16 Rule” can be used to show this relationship. Invented before cameras had built-in light meters it states: “On a sunny day set your aperture to f16 and your shutter speed to 1/ISO.”
    So if we’re using ISO 100 and go out on a sunny day here is what an exposure chart would look like:

    ISO 100

    f16 @ 1/100 sec.
    f11 @ 1/200 sec.
    f8 @ 1/400 sec.
    f5.6 @ 1/800 sec.
    f4 @ 1/1600 sec.
    f2.8 @ 1/3200 sec.
    f2 @ 1/6400 sec.
    f1.4 @ 1/12800 sec.

    As you can see, your assumptions in Case 1 & 2 are correct. All of the exposures shown above would be identical except for the depth of field.

    When you’re using Aperture Priority you select an aperture and the camera selects a shutter speed.

    When you’re using Shutter Priority you select a shutter speed and the camera selects an aperture.

    Another way of seeing the ISO/Aperture/Shutter Speed relationship is by referring to this site which I use and recommend for low-light/night exposures:

    http://www.calculator.org/exposure.aspx If you use the Scene ‘Domestic interiors at night, subject lit by campfire or bonfire’ and choose ISO 100, 200, 400, 800, 1600, 3200 and 6400 you can see the effect on the shutter speed using the different ISO settings at the same f-stop – from 1/15 sec. at f1.4 using ISO 100 to 1/1000 sec. at f1.4 using ISO 6400.

    I consider the site to be fairly accurate. I chose the Scene ‘Distant view of city skyline or floodlit buildings’ and ISO 200 for these pictures:

    http://www.flickr.com/photos/drifter45h/4048051455/ 100mm @ f11, exposure of 30 seconds.

    http://www.flickr.com/photos/drifter45h/4048796836/ 200mm @ f11, exposure of 30 seconds.

    You might consider reading these books by Bryan Peterson: “Understanding Exposure” and “Understanding Shutter Speed”.

  3. Eric Lefebvre says:

    In your 2 examples they will be pretty close as far as proper exposure but:

    1- due to light dispersion (how light id affected as it enters the lens), your Depth of Field will be affected … your DoF is how “thick” the are of focus is. The larger the aperture, the smaller/shallower the DoF.

    In this pic, notice that the DoF is pretty think … the subject is in focus but not the bride or the background.

    2- longer shutter speeds can lead to blurriness caused by your subject moving or “camera shake” if the shutter is quite slow.

    3- Lenses have what’s called a sweet spot … a aperture at which the sharpness of detail is optimal … usually it’s one or two stops from maximum aperture (so f1.8 would be better at f2.5 normally as far as crispness of the image within the field of focus)

    As far as deciding what option to use, it depends on what you are trying to achieve but normally you want a sharp and well exposed picture so you would try to keep a decent shutter speed (1/60th for most scenarios unless there is fast movement in the scene) so you would adjust your Aperture, ISO and Shutter Speed to achieve the shot your are trying to get … in that order.

  4. MendozaTJ says:

    Case 1 would have a very large (or depth) Depth of Field which means everything would be in focus. This would work for an environmental or landscape picture but for a portrait the background would too defined and too distracting
    Case 2 would give you more Bokeh or background separation and you might even be able to freeze moving objects. This would work great for portraits or taking pictures of children at play for instance
    Deciding what to use would be determined by the intended use of the picture. Is the picture about the playground being full of children or is it a portrait of a particular child?

  5. deep blue2 says:

    Yes you’re right in the understanding of Case 1 & Case 2. If the same amount of light is entering the lens in both cases, then the images will be similarly exposed.

    Case 1 & Case 2 would be manual settings if YOU set both aperture & shutter speed. If you set the aperture & the CAMERA sets shutter speed that is aperture priority. If you set the shutter speed & the CAMERA sets aperture, that is shutter priority.

    Which option you go for depends on the effect you’re after. If aperture is important to you (because you want to control depth of field) then you’d set the aperture to what you want (narrow for deep dof, wide for shallow dof) and then set shutter speed (or have camera do it) for the correct exposure.

    If shutter speed is important to you (because you want to freeze or blur motion), then you’d set the shutter speed appropriately (fast to freeze motion, slow to blur it) and then set aperture (or have camera do it) for the correct exposure.

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