How to determine you're aperture and shutter speed?


TPF Noob!
Nov 8, 2011
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Hello y'all,

I've been shooting for about 2 months now, still learning the basics of photography/DSLR, but I wanted some clarifications on aperture and shutter speed. I've been using Aperture-priority and Manual majority of them time and hardly ever use Shutter-priority or Program mode, is that a "bad" thing? I feel that A and M are the only really important ones.

Anyways, what aperture would you suggest is a good "overall"? I know its really depends on your camera/environment/lighting/etc. but I was told that f8 - f11 is what you should use when shooting outside during the day. I tend to only use a small aperture (f1.8 - f5.6) when I'm going for the blurry background-clear foreground/subject look or in poor lighted areas. Also for landscape photography is it a good idea to use a large aperture for a shallow depth of field (maybe f15 - f20ish) or just stick with f8 - f11?

As for shutter speed I tend to use this to balance my exposure-compensation metering rather than changing my aperture. I tend to use the fastest shutter speed that I'm allowed for the pointer on the exposure-compensation meter to remain at 0, is that correct? Because I feel that a faster shutter speed will decrease the potential of motion blur. I only use a slow shutter speed (about 1/5" or longer) when I have a tripod and long exposure photography (usually landscape/skyline).

Overall, I just wanted to see if my way of determining aperture/shutter speed is correct. I know it really depends on the lighting of what I'm trying to shoot and it differs every time, but any advice/help would be much appreciated!

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Using the camera on A is the same as using the camera on S which is the same as using the camera on M and bringing the meter to zero. They all produce the same result as does using the camera on P; the camera's metered exposure.

If you pick the f/stop and let the camera pick the shutter, you're still responsible to validate the camera's shutter choice.

If you pick the shutter speed and let the camera pick the f/stop, you're still responsible to validate the camera's f/stop choice.

If you pick both the shutter speed and f/stop on M, you're still responsible to validate the camera's meter reading.

If you set the camera to P, you're still responsible to validate the shutter & f/stop pair the camera selects.

IF YOU RELY ON the camera meter, you're still responsible to validate the meter's choice and the most efficient way to modifiy that choice is with the camera's built-in EC control.

The most important modes to know are shutter priority, aperture priority and manual.

Have a read of the Shutterspeed, aperture and ISO tutorial in my signature.
Another way to determine is a Sekonic 358 or a like product
I feel that A and M are the only really important ones.
shutter priority is indeed important if your priority is time, i.e., when subjects are dynamic.

Also for landscape photography is it a good idea to use a large aperture for a shallow depth of field (maybe f15 - f20ish) or just stick with f8 - f11?
f/15-f/20 is a small aperture, not large, and help in avoiding shallow depth of field. f/8-f/11 is larger and gives some shallowerr DoF. Ideally you would use smaller apertures, but in practice over f/8-f/11 there is some diffraction problem so that sharpness is lower.

The overall suggestion is: since there are many details, read an introductory book, like the often mentioned Understanding exposure by B.Peterson.
Determining which mode and settings to use really depends on where you are and what you're taking a picture of. Based on the exposure triangle you have to decide which trade-offs you want to make to get the best possible picture. I'm not really sure how to answer your questions, so I'll just throw some info at you and hope it relates and helps your problem somehow, haha.

Choosing a Mode:

I'll get the easy one out of the way: Auto. It's useless for anything other than snapshots. If you don't care about the picture or you need to snap something REALLY fast, go ahead and use this setting knowing full well that your picture may come out with motion blur, grain, small DoF, etc. because you don't have control over any of the three in the triangle.

Program gives you control over the ISO, and is just barely better than Auto. Usually the only time Auto mode bumps the ISO high enough to cause a noticeable amount of grain is when you're in an extreme low-light situation, and most of the time your aperture or shutter speed wont be able to compensate for the lower ISO speed, rendering Program mode useless unless you don't mind the picture being underexposed.

Aperture and Shutter modes are where things start to interesting, letting you control the aperture or shutter speed respectively along with the control of the ISO in both modes. Let's say you want to take a photo of something that's not going to be moving at all, but you want the picture to have a high DoF and you don't want to have to worry about the exposure being correct (ex. taking a portrait in a place where there's no wind to blow the subject's hair around). Well, that would be the perfect situation for Aperture Priority; just set it to a narrow aperture for your high DoF, and just start shooting away (you can also adjust your ISO as needed if you don't want your shutter speed too slow). The same works for shutter priority. Let's say you want to take a picture of something that's moving fast, but you don't really mind if the DoF is fairly shallow (ex. a street scene with some cars in it that are moving fairly fast). Just set it to Shutter Priority and put it at your preferred speed then start shooting away (again, you can also adjust ISO as needed).

Last, but definitely not least, there's Manual. As assumed, this has control over all 3 aspects of the exposure triangle: Aperture, ISO, and Shutter Speed. Your camera will still tell you whether or not your picture is "properly" exposed, but you have the power to make your picture whatever exposure you want if you think the camera is wrong, along with being able to get the best possible picture possible by maximizing the exposure triangle's performance. Once you get more experienced in figuring out what settings will give you the correct exposure and the best picture, this is what you will be using the majority of the time.

Managing the Exposure Triangle:

Aperture controls the exposure along with the depth of field, and is probably the most confusing of the three. The wider the aperture, the brighter the image and the shallower the DoF. The aperture also slightly controls how sharp an image is, due to fuzziness when wide, and diffraction when narrow. Most lenses are the sharpest at around f/4 to f/8. Wider apertures (f/2.8 to f/5.6) are mainly used for singling out a subject with the shallow DoF to create a nice bokeh (think portraits) while still retaining a very sharp image; usually the only time you shoot wide open is when you don't have enough light and your shutter speed or ISO are already pushed to their limits, because the DoF is way too shallow most of the time and it makes the image less sharp. Narrower apertures (f/16 and higher) are mainly used for images where you really want the entire thing in focus and there are no moving, or slow moving, subjects (like landscapes), because unless you're in direct sunlight you most likely will need to use a slow shutter speed when using those smaller apertures. The middle apertures (f/5.6 to f/11) are just for general use when you want a decent depth of field while still retaining a good amount of light coming into the camera (for example street photography, where you want a decent depth of field but also a fast enough shutter to keep cars on the street from getting blurred).

Next is shutter speed, which controls how long the exposure lasts. This is pretty straight-forward; the longer the exposure, the brighter the image and the more motion blur you get. Determining how fast your shutter should be is mostly just practice and learning how fast objects move. Depending on how steady your hands are, you'll start to notice motion blur from yourself around 1/30th to 1/60th of a second; if you need it to be slower than that then get a tripod. You'll stop getting motion blur from people walking at around 1/125th of a second. Bicyclists and slower cars (20-30mph) will freeze at around 1/300th or 1/400th of a second. Sports photography and fast-paced wildlife photography it starts getting into the thousandths of seconds. But sometimes, you want that motion blur effect (ex. setting your camera on a tripod and "painting with light"). Learning which shutter speed is right will come naturally.

Lastly is ISO, which is the most simple. The higher the number, the brighter the image and the more noise you get. It really depends on the camera, but usually you can pull off bumping the ISO up to 1600 without noticing any problems. If you don't want to open the aperture any wider, or if you don't want to slow down the shutter anymore, then bump up the ISO.

I'll try to give an example on the thought process of adding all of these together: Let's say it's the afternoon and I want to shoot a portrait of a friend of mine. I'll set it to manual mode and determine the a starting point for the exposure with the Sunny 16 Rule (in bright sunlight, your ISO and shutter speed will be the same at f/16), which I'll say is f/11 at 1/400th of a second with an ISO of 400 since it's a little darker in the afternoon. But since it's a portrait, I want a shallower depth of field, so I'm going to set it to f/5.6, which is 2 stops brighter. So I'm going to lower my ISO to 200, which darkens it by one stop, and then make my shutter speed 1/800th of a second, which darkens it by another stop. Now our exposure is the same as it originally was, but we're now shooting f/5.6 at 1/800th of a second with an ISO of 200, giving me a shallower DoF for the portrait and also lowering the amount of noise in the picture because of the lower ISO.

You don't need to change the aperture or the shutter speed or the ISO for every single picture you take. Just leave it at something general (like f/8 to f/16 for decent DoF, 1/200th of a second or higher to keep away from motion blur, and under 1600 ISO for least amount of noise) and quickly adjust it if you decide a picture really needs it. The more you shoot in manual mode, the quicker and easier you'll be able to decide which of the three parts of the exposure triangle you need to change and how to do it while still retaining the proper exposure.

Here are some websites that might help a little on the subject:
Exposure Triangle Camera Exposure: Aperture, ISO & Shutter Speed (all of the articles on this website are amazing)
Sunny 16 Rule Sunny 16 rule - Wikipedia, the free encyclopedia
Learning how to expose correctly Ultimate Exposure Computer
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How to determine you're aperture and shutter speed?
The range of shutter speeds are those that will control the motion stopping capability I need, the approximate distance my focus point is from the camera, which along with considering the depth-of-field I want the shot to have leas me to a good estimate of the lens aperture, both balanced against the reflected light meter reading I see in the viewfinder that shows the chosen settings actually provide enough light for a good exposure.

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