To get a correctly exposed picture, you need a certain amount of light to get to the sensor. By adjusting one of the above, it also makes the at least one of others need to change in order to get the correct exposure..
So really, for the sake of argument lets say your ISO is fixed for the time being. If thats the case, if you make your shutter speed faster, your aperture will have to become wider in order to still get the same amount of light. So to ask if you should change shutter speed or aperture is a bit of a question with no answer since if you change one, the other will change anyway... So you will change both in either case..
The 3rd parameter, ISO makes this a little bit more complicated, because it makes your sensor more light sensitive, so you no longer need the same amount of light in order to get the correct exposure. The price you pay however is that your shots will have more "noise" at a higher ISO than at a lower ISO..
So when shooting in poor light you really just have to ask yourself how important is it to you to have low noise in your pictures? If it's very important you are unfortunately stuck with a low ISO. If some noise is OK, then a medium ISO is probably OK. If you don't care about noise then crank the ISO up..
The next step after you figure out your ISO is to figure out whats more important, having a deep depth of field, or having a fast shutter speed. In the case of low light photos I can guarantee almost always you will want a fast shutter speed and depth of field is much less important. So you set your aperture to as wide as it can go (if max shutter speed is more important)..
Once you have set your ISO and aperture, the shutter speed is no longer a variable, it will be figured out for you by the camera in order to give you the correct exposure. You can always tweak it up or down a bit to overexpose or underexpose the shot..
If by that stage your pics are still blurred due to camera shake or subject movement, all you can do is a) increase the ISO further (if possible), b) open the aperture wider (if possible), c) use a tripod to avoid camera shake, d) get a camera with shake reduction, e) ask your subject to stop moving. .
If you start at the other end instead, and adjust your shutter speed first then your camera will try to intelligently set the ISO and aperture in such a way as to try and allow your selected shutter speed to have the correct exposure. Note that in very low light conditions, your camera might not be able to get the correct exposure if you set a reasonably high shutter speed because you could get to a point where your ISO is at max, and your aperture is wide open, and yet there still isn't enough light getting in to the sensor for a correct exposure. Which is why personally I prefer to set the ISO and aperture myself and let the camera figure out what shutter speed I need...
To get a proper exposure you have to expose a sensor with a given sensitivity to a specific amount of light for a specific amount of time..
ISO adjusts the sensitivity of the sensor. More sensitive means you need less light or less time but at the cost of more noise or noise reduction artifacts. Less sensitive means you need more light but will get less noise. Normally the lowest ISO setting on a camera will give the highest quality results but one or two stops more still gives good results, more than one or two stops and quality may noticeably suffer. The smaller the sensor the more quickly quality will suffer..
Aperture adjusts the amount of light that can pass to the sensor in a given amount of time. Smaller apertures (higher F numbers) mean less light and more depth of field. Larger apertures mean more light and less depth of field. Many lenses work best at medium apertures not producing images of maximum clarity near their max or min apertures..
Shutter speed adjusts the length of time light passes to the sensor. Higher shutter speed means less light but freezes both camera and subject motion better. Lower shutter speeds means more light but camera or subject motion may cause blurring. Any shutter speed below about 1/focal length (for instance a 50mm lens used below 1/50 of a second shutter speed) may introduce some blur from camera shake if handheld without image stabilization. Slow moving objects may be clear at 1/60, medium sped objects (cars) may need 1/500 and very fast objects (baseballs) may need 1/1000.
If you are taking an image of a fast moving subject, often Shutter speed is your priority any you will set a shutter speed you need to freeze the subjects motion then balance the DOF you want against the amount of noise you are willing to accept and set the ISO and Aperture at an acceptable comprimize to get a good shot..
If you are taking macro or portrait shots where you want all of a subject in focus but everything else blurred, or landscapes where you want everything in focus, then Aperture will be your priority and you will set your Aperature to get the DOF you need, then balance the amount of motion you can accept against the amount of noise you can accept and set Shutter speed and ISO at an acceptable compromise to get a good shot..
In a third case Aperture and Shutter Speed will be equally important so you will select them both and only be able to adjust ISO to arrive at an acceptable exposure. Some cameras offer an auto ISO mode that allows you to adjust Aperature and Shutter speed and the camera adjusts ISO to get the correct exposure..
Typically cameras offer priority modes where you set the one thing most important to you and let the camera do the rest. Or for complete control use a full manual mode and you get to make all the decisions..
Hope this helps.
Step 1 ... set ISO to "minimum".
Step 2 ... compose/ZOOM your image and determine what your FOCAL LENGTH is.
Step 3 ... in "MANUAL" mode: set shutter-speed to 2X the "focal length" you just set..
Step 4 ... set aperture to where your camera says your exposure is "correct"..
Step 5 ... IF ... your aperture is wide open (ala f/2.8) and your camera indicates there is still not enough light ... INCREASE ISO until exposure is "correct".
Step 6 ... IF ... still not enough light ... set shutter-speed LOWER (and put camera on tripod) until exposure is "correct"..
Note: this is assuming you are photographing a "gray" object, (not black or shiny white). IF subject is WHITE .... adjust so camera indicates either one/two stops OVEREXPOSED. (or set "exposure-compensation" to one/two stop overexposed and adjust until says exposure is "correct).
IF subject is BLACK .... adjust so camera indicates one stop "under" exposure. (or set exposure-compensation to one-stop under exposure and adjust until "correct").
ISO, Shutter, and Aperture..
I always find it somewhat confusing which one to adjust to get thebest lighting. I understand what each one does but it is stilldifficult..
When it's somewhat dark, should I adjust the ISO or the Shutterspeed? I know there is no one answer to this question but would liketo know how you determine what to adjust..
As a beginner, this is one of the most challenging aspects of theDSLR camera..
Thanks for reading .... JoePhoto.
( Do You Ever STOP to THINK and FORGET to START Again ??? )..
Thanks for the detailed explanation. This is really helpful. I will try all the tips you guys suggested..
Thanks for the detailed explanation. This is really helpful. I willtry all the tips you guys suggested..
If you are interested to know more... I suggest you to visit some basic photography website or tutorials. I learned most of my basics here:.
"Learn/Glossary" section of DPReviewhttp://digital-photography-school.com/blog/http://www.cambridgeincolour.com/tutorials.htm.
Try to spend a few days and read all the topics. The few days spent will give you useful knowledge for the rest of the life...
Great job explaining that. very helpful for a novice. thx!..
Increase the thing that would have the least effect on your picture (in your opinion) - for example, if you want a smaller DOF, change the shutter as long as you won't have camera shake (or subject movement) or ISO if there might be some shake...
ISO - Shutter - Aperture..
Noise - Blurrrrr - Depth of Field.
Each according to your needs!.