What do you want to control
If you follow the descriptions on exposure, aperture and ISO you will see that you can trade-off one of these and still get the same amount of light to your sensor, resulting in a picture that has the same brightness.
- Increase the aperture by a factor of two and increase the exposure by a factor of four.
- Decrease the exposure by a factor of two and increase the ISO by the same amount
- Increase the ISO by a factor of four and decrease the aperture by a factor of two.
But, all of these settings have different goals:
- ISO is about noise in your picture, the lower the ISO the less noisy it is
- exposure is about how much movement there is. If something is moving quickly, you need to expose it faster in less time.
- aperture is the trickier one. It affects both the speed, and the depth of field allowing you to emphasize what is important and what is not.
- P Program mode: This is the automatic mode. The camera will try to set everything so that you get a nice picture without you worrying about the settings. There is nothing wrong in using it, but if this is how you always use the camera, you definitely paid too much for it as a simpler and cheaper camera would also work for you.
- S Speed priority mode: You determine the exposure speed and the camera determines the aperture (and if allowed ISO).
- A Aperture priority mode: You determine the aperture and the camera determines exposure (and if allowed ISO).
When to use what
- P: more or less when you are frustrated, you need to make a quick picture, when you give your camera to a friend that does not want a lengthy introduction, when you messed around with all the settings, and you finally just want to take a decent picture and be done with it, this is the mode to use.
- S: indoors, especially when it is darker, when you are trying to capture fast moving things like cars, planes, running people, animals. Both are slightly different. In dark places, you would usually know what is the slowest exposure you can have and still keep the image sharpness. So you do not want to go below that. Other applications are where you want to expose for a set time (like dreamy waterfalls).
- A: technically, this should be the mode you use your camera most of the time. Aperture is the most expressive setting, and also determines quite a bit of the quality of the picture. As long as you can maintain the proper exposure for the selected aperture, this will serve you the best.
- M: the torture mode. This is needed when the automatic metering will play tricks on you, when the light around you is changing quickly and when you have the time, to adjust the settings in peace. More or less the total opposite of P.
What about ISO
There is not a direct ISO priority mode. But most cameras actually give you two options.
- Manually adjust ISO during any given mode.
- Use the so called Auto ISO Sensitivity mode. This allows you to set a minimum and maximum ISO that you want to have (more or less your tolerance limit) and the camera will adjust the ISO in P, A or S mode as needed.
These pages are for Amateur Photographers and not really for seasoned photographers and professionals. I have no affiliation or commercial interest with any brand/make. I write from my own experience. I ended up using mainly Nikon, so I am more familiar with this brand than others. See price for notes on pricing as well as photography related links.