Why Shoot Aperture Priority?

Since my first SLR film camera, a Minolta X700 purchased on a trip to Germany in 1984, I fell in love with the ease of control offered by shooting in aperture priority mode. In all the cameras since then, save my large format 4×5 cameras, or panoramic medium format cameras, I have always used aperture priority most of the time. Since the X700, I have used a Nikon FE2, Olympus OM-4, Canon T90, Canon EOS Elan, and Nikon F3, and all of those film cameras were left in aperture priority mode 99% of the time. The only exception being when taking night shots on a tripod, when I would used Bulb mode and a cable release for time exposures, or if I was using flash and wanted to put the camera on its flash-sync speed, then I used manual exposure mode.

Since then, the same story goes for all the digital cameras I’ve owned, numerous Canon bodies from the EOS 20D up to the EOS 7D, Canon P&S cameras like the PowerShot Pro1 and S90, Nikon cameras like the CoolPix 990 as well as the D800 DSLR, Panasonic bodies like the GX-1 and GH-2, Fujifilm cameras like the FinePix S100FS and more recently, multiple X-system bodies; the X100, X-E1, X-E2, X100F, X-Pro2, X-H1 and my latest, the X100V… well whew… I guess I’ve owned a lot of cameras over the years, and that is not even a fully comprehensive list! In any case, the thing that they all have in common is that they were left in aperture priority the vast majority of the time.

So what is aperture priory and why do I like it so much? In aperture priority mode (usually marked “A”… or for Canon cameras, “Av” for “aperture variable”), you generally select the f-stop you want to work at, be it f/1.4, f/5.6, f/11 or whatever, and based on the camera’s internal light meter, ISO setting (used to be called ASA back in the day!) and exposure compensation setting, the camera will choose an appropriate shutter speed for you. So unless you are in a very dark or very bright setting and have a generally appropriate ISO setting for your conditions, or are using Auto-ISO on a modern digital camera, then you will always get a reliably accurate exposure without having to think too much. Well, that depends a little on how reliable the light metering is in the camera, but anyway, I think you get the idea: Choose the f-stop and the camera chooses the shutter speed and (mostly) does the rest.

Note that with most of the retro designed Fujifilm bodies, the like the X-T3 shown above, there isn’t a separate mode dial that you set to “A” (or P, S or M), rather to shoot aperture priority, you just take the lens aperture ring off of “A” and choose your aperture manually, then make sure the shutter speed dial is set to “A”, which means the camera will select the shutter speed automatically. That is how you select “A” mode on cameras like the X-E4, X-T3, X-Pro2 etc. On the Fujifilm bodies, setting a control to “A” means the camera chooses that setting automatically, so there is a “A” on aperture rings of lenses, an “A” on the shutter speed dial and an “A” on the ISO dial. This is actually a very smart and consistent way of choosing your exposure mode on a camera with retro controls, much better than having a PASM mode dial, where you might get fooled when glancing at a control dial and seeing a specific setting which might be totally overridden depending on the PASM setting. Yes, I’m looking at you Nikon Df! Note that on most cameras with “modern” control dials and digital displays for settings, like the two DSLRs shown below, there are no consistency issues with a PASM switch.

For completeness, I should also describe the three other common exposure modes that make up the PASM set. As may be obvious, M for manual is when you make the choice of both shutter speed and aperture. The camera’s light meter will generally provide guidance, telling you how much under or overexposed you are based on its meter reading, but it will not mess with your chosen f-stop and shutter speed. Shutter priority (“S”… or for Canon bodies, it’s called “Tv” for “time variable”) could be thought of as the opposite of aperture priority, where the photographer chooses the shutter speed and the camera’s meter selects the f-stop for you.

In “P” mode, jokingly called “Professional mode” by some, which actually stands for Program mode of course, the camera chooses both the f-stop and shutter speed for you. Modern cameras can be quite smart, understanding the focal length of the lens being used, and shooting at a wide open aperture until one gets to roughly one over the lens focal length (1/focal-length) before starting to stop the lens down to smaller apertures, to ensure the best chance of handholding a sharp image. That is an old rule of thumb… let’s say you are shooting with an 85mm lens, then make sure your shutter speed is at 1/85 or faster to ensure a sharp, handheld shot on a full-frame 35mm camera. Of course, if you are on a tripod, you might want a smaller f-stop since handholding is not an issue, or you might be a particularly steady (or shaky) shooter so the 1/focal-length rule does not apply, so this is on reason why P mode is less than optimal at times. Also, with in-body or lens stabilization, you can often handhold far slower shutter speeds too (see photo below). That said, modern cameras will usually allow you to temporarily override the program chosen f-stop and shutter speed, which does offer a bit more flexibility than the P modes of old.

So that covers how aperture priority works. Now to why I like it…

The aperture, or f-stop used, is one of the most important ways of determining the look of your images. Are you shooting a portrait or wanting to isolate a particular subject? Then shoot at a wide aperture for minimal depth of field and maximal background blur. See the two shots below…

Are you photographing a scene and want a deep depth of field to get both foreground and background sharp, then stop your lens down more, maybe to f/8 or f/11 (see photo below). Are you taking a macro shot and need the most depth of field possible? Then take a chance on diffraction softening your photo (a topic for a future article!) and shoot at f/22.

However, and this might seem a bit counterintuitive, shooting in aperture priority also gives you quick control over your shutter speed in helpful ways. If you are trying to freeze action in a sports or wildlife scenario, freeze an ocean wave splash (see below), a flower fluttering in the wind, then leave the lens at a wider aperture and let the camera maximize your shutter speed.

Are you trying to generate some motion blur for a shot of a busy city street? Well then stop the lens down to give you a slow shutter speed to blur that fast moving traffic. Of course you need to take some care that the required shutter speed for the given f-stop isn’t beyond the camera’s maximum shutter speed, or way too slow for handholding.

There are certainly cases where precise shutter speed control is important of course. A scenario I recall, when shooting a moving and splashing stream up close, was that I wanted an exact shutter speed to precisely control the length of the individual droplet blurs (I chose a 1/4 second if memory serves), and for that I might use manual mode or maybe shutter priority. Also, to maximize my flash sync speed would be another example where manual mode or shutter priority is better than aperture priority. In addition, if you are using a camera with studio strobes, or with a non-TTL flash, the camera doesn’t “know” when a flash is connected. If you are not careful when shooting in A mode, you might cause the shutter speed to go beyond the camera’s maximum flash sync speed, which will cause part of the frame to be dark. For an example of where I used manual mode, below is a rapid handheld left-to-right sweep blur photo at dusk. I wanted a precise degree of motion blur, not too much, not too little, so specifying a shutter speed gave me the control, and manual exposure gave me consistency in exposure from frame to frame, since I did a bunch of shots with slightly differing starting points…

You might wonder, conversely, why not shoot in shutter priority mode, since changing the shutter speed also gives you control over the aperture used? For a landscape photo as an example, in theory I can set my slowest reliable hand-held shutter speed, and then maximize my depth of field that way; the brighter the conditions, the smaller the aperture I get… good, right? Well, I would suggest that the optimal aperture for the desired result in a photo is usually in a far narrower range than the optimal shutter speed is. For example, if I can handhold a 1/30 second reliably with a wide-angle lens and my camera tops out at 1/8000, then that gives me an 8-stop range of metering at a given ISO and f-stop. However, when it comes to the aperture, on a landscape photo where I want maximal depth of field without stopping the lens down too far that diffraction softens things, on a crop-sensor camera my range might be f/8 to f/11, which is only one stop of latitude. For a full-frame camera, that might be f/11 to f/16, the same one stop of optimal f-stop latitude.

If I want a shallow depth of field for a portrait shot, I might want a lens to be in the f/1.4 to f/2.8 range, which is only a two stop range. Realistically, I might want the most subject isolation possible, which means shooting at f/1.4 (in this example) with no range – the optimal aperture in this case is wide open and that’s it. What I’m getting at, is that for most static shots, the optimal aperture to use for your desired result is in a much narrower range than the optimal shutter speed, which usually spans a wide range of acceptable speeds, so this is why precise aperture control is so important and why aperture priority makes more sense to me most of the time.

So I’ve explained why I don’t recommend shutter priority for most situations, but what about program mode or full manual? Well in program mode, the camera is choosing both the shutter speed and aperture, and while modern cameras are pretty darn smart, I just don’t feel comfortable relinquishing aperture control to the camera in most cases, for the above mentioned reasons. The exception might be handing a camera to a server in a restaurant to take a quick group photo… in that case it is likely the easiest to let the camera make all the decisions. Manual mode is great of course, since I am in full control, but again, usually I want to dial in a specific aperture, and for that there is only one shutter speed that will give me exactly the exposure I want, so why not let the camera choose that shutter speed?

There is however a very compelling reason to shoot manual, and that is to prevent minor changes in composition from significantly changing your exposure. In my film camera days, I often used exposure lock in aperture priority mode, where you either keep your shutter half pressed, or press a separate lock button. I would point my film camera, often with partial metering engaged (large spot where the meter ignores much of the frame), at an area of my scene where I knew from experience the 18% grey metering would give me a good exposure, lock the exposure, reframe and shoot. Had I used manual mode more, then I wouldn’t have needed to do the point, lock and reframe as often, but I was good at it and usually nailed my exposure. It was an action I became very familiar with and it didn’t really take significantly extra time.

I will say that when I was shooting my medium format Pentax 67II, I used spot metering most of the time to explore my scene to check the exposure for highlights and shadows. Since shooting medium format transparency film was a bit expensive, I wanted to make certain every shot counted. I was very careful with my metering and did actually use manual exposure most of the time with that camera. It is the only camera I’ve owned where I metered in that way, which was rather tedious but seemed worthwhile at the time.

Now, with modern mirrorless cameras that feature a live simulation of the resulting exposure in their EVF, things are even easier! I can just set my camera’s f-stop, then twist the exposure compensation dial while framing my shot exactly how I want it, until I have the desired look to the shot. Do I want it brighter, darker… easy, just twist the exposure compensation and get exactly the result I envision! Only when the desired look to the shot is beyond the metering + compensation range (as in a backlit silhouette for example), or if I’m doing long exposures, might I need to resort to manual mode. Of course I do watch the metered shutter speed in the EVF in marginal light, to ensure that it isn’t too slow for reliable handholding for example. Having an EVF with accurate exposure preview has been liberating and now that I am used to that way of metering and shooting, I’d never want to shoot a camera without an EVF again.

So there, more than you probably ever wanted to read about aperture priority mode! In short, I feel it is generally the most powerful and flexible mode to leave a camera in, and especially nowadays with real-time EVF exposure preview, one can get precisely the results one wants with very little fuss. For me, a camera could generally have aperture priority and manual modes and I’d be totally happy. That is why I always liked my Nikon SLRs, the FE2 and F3, since those are the two modes they offered and I never really wanted anything else. Nowadays, that is how I shoot with my Fujifilm bodies; select the f-stop on the lens’ aperture ring and let the camera choose the shutter speed. Twist the exposure compensation dial to get the desired look to the photo. I leave the blinking overexposed highlight warning enabled in the EVF so I can immediately verify that my important highlights are not blown with my chosen exposure. Quick and reliable!