Understanding Your Camera's Semi-Automatic Modes

Yesterday we talked about the exposure triangle, and understanding exactly what happens in the camera when you make an image. Today we are going to talk about the different automatic modes that come on most cameras. Each manufacture is a little bit different in their labeling of the three automatic shooting modes, so for this example I will stick to the big three companies: Canon/Nikon/Sony. Nikon and Sony share the same markings, while Canon is a little different. If your camera is a different brand, refer to your manual to verify which of the modes matches the descriptions listed below.


On your mode selection wheel, you will likely see several different options for choosing how you want to take your pictures. All cameras will have a full automatic mode, where you simply point the camera and press the shutter button. A lot of people refer to this as “Green Box Mode” because on most cameras the icon for this mode is, well, a green box. Sometimes it will simply say auto in green lettering. Most DSLR/Mirrorless cameras will also include a few more semi-automatic modes, where you lock in one or two parts of the exposure triangle, and the camera picks the remaining settings to round out the exposure correctly. Two of the three semi-automatic modes (Aperture Priority/Shutter Priority) are very good for every day shooting, and there are many pros that use these modes almost exclusively. Lets look at these modes a little more closely to understand what each of them do.


Auto – This mode is on all cameras and is as basic of a mode as you can get. A 5 year old who accidentally presses the shutter button could take a technically correct exposure, because the camera selects all of the settings necessary to make the exposure right. However, you do lose almost all of the creative aspect of the shot, because you are unable to select any of the settings on your own. The camera sees your scene, meters the light and tells you what the settings will be. There is nothing wrong with shooting in Auto mode, especially when first learning how to shoot. Just know that once you get a little bit more experienced you will outgrow this mode very quickly and be ready for more manual type settings.


Program (P) – Program is a lot like full Auto mode, but does allow for adjustments to things like exposure compensation and flash. The exposure itself is still chosen in the camera.

Aperture Priority (Av/A) – Aperture Priority mode is probably the most popular shooting mode outside of full manual, and many full time working professionals use this mode almost exclusively. This setting allows you to lock in an aperture at a set value and the camera will automatically select the shutter speed needed to provide a correct exposure. This ensures that you always get the depth-of-field that you want in the shot, at the expense of being able to select your exact shutter speed. This mode is an all around good mode to shoot in for most every day photos, but excels at things like portraits where you want to be sure you are isolating your subject to your liking.


Shutter Priority (Tv/S) –  Shutter Priority, or Time Value mode, is just the opposite of Aperture Priority. You set the shutter speed and the camera will select the aperture needed to make a correct exposure. This mode is very popular for sports and wildlife where you need to make sure you are freezing any motion.


Manual (M) – In Manual mode you control every aspect of the image yourself and the camera does not make any changes for you. The only exception to that would be if you have your ISO set to Auto.


So why exactly would  you choose to shoot in one of these modes over either full Auto or full Manual? They each have their strengths and I’ll touch on those a little now.


I don’t really recommend Program mode all that often, because in my opinion it’s just not different enough from full Auto to justify NOT going to Aperture Priority or Shutter Priority if you are ready to move away from full Auto. I do like Program mode for people that are wanting to learn how to shoot in full Manual but don’t know where to start as far as their exposure settings are concerned. The best thing to do is to put the camera in Program, half press the shutter and take note of the settings (aperture, shutter speed, ISO) that the camera recommends for that scene. Now, flip over to Manual mode and input those settings and it should result in the same exposure, but now you can use the exposure triangle to make the image look the way YOU want it to look. If you need more depth of field than what Auto or Program recommends, you just dial down the aperture to your liking and compensate for that change with another setting. Program mode will at least get you a baseline exposure to start from though, and that can be very helpful in the learning process.


For a lot of images, the photographer has one particular aspect of the image that they prioritize. A portrait photographer will almost always prioritize how much of the background is blurred around the subject, and won’t necessarily care what the shutter speed is at (assuming the shutter is at least fast enough to not pickup motion blur or camera shake). For example, a person shooting a portrait outside in good lighting would likely want to lock in an aperture of somewhere around f/4 to make sure the background gets nice an blurry. They don’t really care if the shutter speed is automatically selected at 1/500 or 1/2000, because either way the subject will be frozen and clear since they are not *usually* moving. So setting the camera to Av/A would make a lot of sense because the camera will choose the shutter speed for you to make sure the exposure is correct. That is just one less thing you need to be concentrating on. I personally shoot most of my work in Aperture Priority because more often than not the depth of field is my main concern. The biggest exception is if I’m shooting anything at all with Flashes. If there is any flash/lighting involved then 100% of the time I move over to Manual because you are the one controlling the light. I lock in the Aperture/ISO/Shutter and adjust the power of the lights to conform to my chosen settings.


Another example of a time to use a semi-automatic mode would be shooting sports or wildlife. Most of the time those subjects will be in motion, so there is a very good chance that your primary concern will be making sure your subject is frozen in the picture with no motion blur. You may not necessarily care as much about the background of the scene. I will say that in most cases that you will be using Shutter Priority it will be for the sake of locking in a fast shutter speed (as opposed to a slow one), so most of the time the camera will select a large aperture, which is great for isolating your subject. If your camera is not able to automatically select a large enough aperture to achieve a correct exposure with the shutter speed you have chosen then you will need to raise the ISO sensitivity as well in order to get to a proper exposure.


One big thing about the semi-automatic modes is that as long as you are only prioritizing one element (depth-of-field/shutter speed) the camera does a very good job of getting the exposure correct with the less important setting. The camera can detect the slightest change in lighting much better than our eyes, especially since it changes so gradually throughout the day. If you were to shoot an outdoor portrait in full manual mode, set your aperture and shutter and just leave it as is throughout the shoot, you would see that there are all kinds of variances in exposure, even over just a 10 minute shoot. If a cloud passes overhead it will effect the light. If you’re shooting at sunset/sunrise, the light is changing even quicker usually, but can still be hard to detect exactly how much. If you stayed in full manual you would constantly be changing either your aperture or shutter speed to compensate for any small changes in light. The semi-automatic modes take that worry away and just let you concentrate on getting the shot you want at a good exposure.


I definitely recommend everyone play around with these modes and see exactly how the changes that you make in the settings effect the outcome of your photos. I normally tell almost all new photographers to just skip full Auto and instead start out in Aperture Priority after giving a short lesson on the way that aperture effects your image. Many people that are just getting their hands on a DSLR/Mirrorless camera are simply after that shallow depth of field, “professional look” anyway!