Manual and aperture priority are two of the most common modes photographers use, but when you are new to the craft, it might be difficult to know when to use which. This excellent video tutorial discusses manual and aperture priority modes, including how they work and when each is appropriate.
Coming to you from Saurav Sinha, this awesome video tutorial will show you how to work with manual and aperture priority modes, as well as when to use each. There is a common misconception that professionals only ever use manual mode, but nothing can be further from the truth. It is true that manual mode is a valuable tool for taking total control over the creative process, and without a doubt, it is appropriate for many situations. However, there are situations in which allowing the camera to make some decisions can actually be beneficial. No matter how experienced we are, a computer can read and make adjustments more quickly than we can. This makes semiautomatic modes quite useful for quickly changing situations. For example, wedding photographers, who are often moving in and out of differing lighting situations, often use aperture priority to maintain creative control over depth of field while allowing the camera to take care of balancing out the exposure. Check out the video above for the full rundown from Sinha.
For Canon mirrorless camera uses, there's another camera mode - Fv or flexible priority. It's a very easy way to adjust camera settings without changing modes. After a short learning curve I tend to use this mode most often.
I use FV almost exclusively.
The best thing since Dual Pixel AF.
Can't live without it now.
The modes just control the exposure triangle. There is no single right mode. The mode to select depends on context.
If I want to isolate my subject with a nice blurry background, I need a low aperture. A fast lens that can do f2 or less is best for isolating the subject. So I set my aperture manually and use aperture priority mode (the camera won't concern itself with the possible aperture). I then let the camera tweak the shutter speed or even ISO to get the exposure it thinks is proper.
I also use Aperture Priority of I need to shoot with a higher aperture so that more of the photo is in focus. Landscape or city photography looks great when the whole photo is in focus regardless of the distance differences of each subject I'm the field of view. But a higher aperture reduces the light available, so I need slower shutter or higher ISO to compensate. If I have movement in the field, I only have ISO left to tweak since I may have to try to get the camera to both select a fast shutter speed at a given aperture.
This is still better than shooting in pure manual mode as the camera will be working on the average medium grey over the frame to achieve the best exposure as you slide the ISO up or down. When both the shutter and preset aperture are where I want them, I stop messing with ISO. If I have to go really high on the ISO to get a shutter speed I want, I may need to rethink the aperture. Moving the aperture to a lower number allows in more light at the expense of depth of field.
I use shutter priority when I need to freeze action, like a bird in flight. I would need 1/1000 at a minimum for that. So if I know I'm shooting moving subjects, I lock in a high shutter setting and either use an autofocus lens (so the camera can tweak the aperture automatically) or move the aperture myself to get a good looking exposure.
One key to any mode is capping the max ISO you are willing to let the camera select. More on that later...
On my Sony, the P mode is quite handy. I just rotate a knob and it selects the proper shutter setting for the aperture on a sliding scale. This frees me up to just tweak the ISO. On manual lenses it is less handy since the camera cannot adjust the aperture.
Manual mode is a tedious time consuming mode that I only really use for astrophotography. I mean, modern cameras are really good at getting the exposure right for almost all other photography subjects. But in astro I might want a long exposure (shutter speed) and high ISO (sensitivity) to reveal nebulosity in the Milky Way or maybe I want a short shutter speed and low ISO to capture a bright planet on my telescope. Tweaking all three independently is time consuming but a necessary evil for astro subjects. I was shooting Saturn in a telescope recently and shocked to see how dim I had to make it to get any detail at all. I was able to use my base ISO of 100 and a reasonably fast shutter. But I was shooting the milky way a week ago requiring an ISO of 2000. Otherwise all I would see is stars and not the foggy nebulosity.
I use a lot of manual lenses meaning my camera cannot set the aperture or focus automatically. But in a given shoot I will know ahead of time what aperture will be appropriate and have that already preset. This is basically aperture mode. If it is daytime and bright outside, I preset a lens at f8 or maybe f5.6 and let the camera figure out the rest. After all if the f is too low the focus isn't as sharp and vignetting might be present on some lenses.
Maybe I'll lock in the ISO at 100 too instead of letting that get automatically adjusted if I'm confident the shutter speed and aperture can handle the light.
For my few automatic focus lenses, I don't like the aperture settings my Sony often selects and the shutter speed is often too slow as well. So I use P mode a lot with AF lenses so I can ensure I am maximizing the shutter or aperture depending on my target. For AF lenses that aren't particularly fast (not having a very low max aperture), I give my Cera room to breath by upping the ISO to at least 400. That way I can get higher shutter speeds.
People have been circulating a myth that you aren't supposed to shoot above the base (lowest) ISO. This is nonsense. If you know your sensor well, you know that there are plenty of ISO options that won't look noisy. After all, the ISO isn't the source of noise in most cases. It is the signal to noise ratio. Not enough light AND a high ISO give noisy images.But if the light is good, a high ISO just gives you fast shutter speeds up to a max value that depends on the camera. Anything below ISO 3200 is pretty safe on any camera. And that is the point. Shoot at ISO 1000 in good light and you will have a much faster shutter than shooting at ISO 100. And that makes for vastly sharper images when motion is involved.