A lot has been using P mode already and has seen some varying effects without fully understanding. While most may be getting the effect that they want, it will surely help to know how each factor and associated changes affects the photograph.
If you’re someone who’d want more control over your photographs (may they be digital or film), I’m hoping that this attempt at simplifying photography (based on questions from friends who’re still starting in photography) will somehow give you an idea on how to take photographs, your way, and not just by relying solely on automagical and sophisticated camera presets.
For starters, it helps to understand that Photography = Exposure (the Science) + Composition (the Art). Composition, which is how we arrange and frame our subjects or scenes is a very broad topic on its own, and knowing how to visualize and execute a composition is only secondary compared to achieving the right exposure, for if one cannot control or achieve correct exposure, there won’t be any photograph at all. So, before we deal with artistic “rules” and how to break them, let us first tackle the more technical aspect of photography. In this topic, we’ll only be focusing on Exposure and how to achieve control over the different factors that can aid us in our Composition.
So what exactly is exposure? Exposure is what happens when a medium like film or a digital sensor is in the process of capturing the light emitted by a scene. In a nutshell, a Correct or Acceptable Exposure can be achieved using
- a medium (film or digital sensor) with ample sensitivity (ISO Setting) plus
- the appropriate lens aperture or opening (F-Stop, F/n) to allow just the right amount of light through, and
- the right amount of time the medium is exposed to light (Shutter Speed).
And thanks to exposure meters that are built right into the camera and their many features (Center-weighted, Spot, or Matrix), finding the right combination to achieve acceptable exposure has never been easier. However, deviating from this meter reading (which will always attempt to come up with an average Middle Gray) can easily get you either Under-Exposed photos (picture is too dark) or Over-Exposed ones (too bright). So it’s key to pay attention to what the meter says until you’re comfortable enough to “disobey” it. And the only way you can know which is the acceptable exposure is with lots of practice and experimentation.
Factors affecting Exposure.
While different combinations of the control factors listed above will yield the same amount of exposure, you will soon find out that the pictures are really not the same. And understanding these idiosyncracies and knowing how and when to use them will spell the difference between a photo that is only documentary of a scene, or a photo that invites praise. If you have been playing around with your camera’s P Mode to shoot a scene with different combinations, you may already have noticed this. And these idiosyncracies almost always mean there will be compromises that need to be made.
And before we head on to the aspects which control exposure, it helps to know a basic concept which you will also come across a lot: amounts of light are usually referred to as Stops (in reference to how F-stops are related to each other) and each stop above the other is considered “doubling the amount of light.” Conversely, a stop below is considered as “halving.” While the scales/numbers you’ll see below are in 1-stop intervals, cameras/lenses do allow half-stop adjustments, and sometimes, third-stops. This feature allow us to further fine-tune our exposure levels more granularly.
ISO/ASA (Film Speed/Sensitivity). Even though digital cameras technically use sensors (not film), it also uses the same sensitivity rating system that was standardized for film decades ago. The ISO (International Standards Organization) ratings is practically the same as the older ASA (American Standards Association) from which it was derived from, so an ISO 100 film is the same as an ASA 100. The Germans however have a different way of rating their film. They use the DIN (Deutsche Industrie Normen) degree (logarithmic) system. While we may not see any mention of DIN in digital cameras, they are still pretty much in use when it comes to film.
- Usual values: 100 200 400 800 1600 3200
- Each number in the scale above is twice as sensitive (1 stop) as the one before it.
- Lower Number (Slower) = Lesser Sensitivity, Finer Grain (Less Noise)
- Higher Number (Faster) = Higher Sensitivity, Coarser Grain (More Noise)
While it may seem convenient to stick to a faster film rating, it’s almost always best to stay as low as possible to get more detail because as you go up or faster, more noise (digital) or a coarser/grainier texture (film) is introduced into the photo. ISO 800 and up used to be exclusively used by photojournalists, as the main output medium is newsprint which is almost always composed of half-tones anyway. For portraits or scenes requiring recording of fine detail, It’s always best to stay below ISO 400, if the light permits it. However, shooting with coarser grain film than expected can sometimes yield interesting results. But that may not necessarily be the same when it comes to digital as sensor noise is not really that appealing to look at.
F-Stop (Aperture/Lens Opening). When you look at someone looking out the window into bright sunshine, you will notice that the iris of their eyes suddenly contracts to reduce the light hitting the retina. Have the same person look within the relatively dim room and you’ll see that the iris suddenly dilates to compensate for the lack of light. This behavior or reaction to light is the same principle on how lens apertures work. In fact, the camera is actually an emulation of the eye (cornea = lens, iris = aperture, retina = film/sensor), and the dilation of the opening allows more light in and the contraction reduces it. It continuously adjusts itself to ensure that a perfect picture is formed in the retina.
- Usual values: 1.4 2 2.8 4 5.6 8 11 16 22.
- The F in F/n stands for the lens focal length. Divide the lens focal length with the numbers above and you get the relative area of the opening, .e.g, 100mm/4 > 100mm/8, hence,
- Each number in the scale above allows half the amount of light (less 1 stop) as the one before it.
- Lower Number (Faster) = Higher Sensitivity, Shallower Depth of Field of Focus (DoF)
- Higher Number (Slower) = Lesser Sensitivity, Greater Depth of Field
- As the focal length of the lens extends, the DoF also becomes more shallow, i.e., the DoF of a 200mm lens at f/11 is much narrower than that of a 50mm at the same aperture.
- Lenses which allow very wide openings (2.8 or bigger) are usually more expensive due to more complicated optics.
F-stops are key to determining the depth of field (of focus) of a particular photograph. When, for example, photographing a row of trees that extend into the distance, using a narrower aperture ensures that most of these trees (relative to the specific tree in focus) are in better focus, while a wider aperture will restrict focus to that just one tree and throw everything else out of focus. This throwing out is especially useful when shooting a subject in an uninteresting background.
Some lenses (usually older), employ a DoF scale which will give you an estimate, relative to the subject in focus, how much of the foreground and background will be in focus. If this is not available, you can always use your camera body’s DoF preview button to better visualize the field of focus. For best results in getting a deeper DoF, use of the hyperfocal distance is imperative (this will be covered later).
Shutter Speed (Exposure Duration). The third factor to be considered (and usually, the last in priority) in coming up with an acceptable exposure is the Shutter Speed or the duration of time that the film is exposed to light. If a shutter is made open longer, it essentially allows in more light, and any motion that may occur during that period. Consequently, a shorter duration freezes motion and allows for probably more sharper pictures. You may think this boring, but used wisely, a play on slower shutter speeds can yield pretty interesting pictures, especially when done with water, clouds, light streaks on a highway, while faster speeds can be used to freeze subjects suspended in midair.
- Usual values: 2″ 1″ 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 (the numbers after the first two are fractions of a second)
- Each number in the scale above records half the amount of light (less 1 stop) as the one before it.
- To prevent camera-shake, the shutter speed shouldn’t be slower than 1/F where F is the focal length of the lens, but if you have nerves of steel, you can probably go slower than this. For best results, I’d recommend heavily the use of a tripod.
Still there? Okay, to give an example, let’s assume we’re using an ISO 100 film, then let’s frame an outdoor scene (a tree, with a kid a few meters behind it, and with mild wind blowing) in P mode. Assuming the meter is saying that we use a 1/125 shutter speed and an f/8 for the aperture, the following other P combinations will still yield the same amount of exposure:
- 1/250 & f/5.6 = more motion freezing (leaves will tend to be more static despite the wind), but with shallower depth of field, which will make the kid a bit blurred/out of focus.
- 1/60 & f/11 = less motion freezing (leaves will tend to blur because of the wind), but greater depth of field, which will make the kid to be in better focus.
Did you notice how either shutter speed and aperture compensated for the doubling and halving of the other? That’s how it’s supposed to work if we’re talking about exposure. But each combination yields different effects as mentioned above. And having control over these effects is you taking control of your photography.
Well, while all this may seem complicated and too technical, with practice and experimentation, you will soon find these as second nature, like riding a bike, driving a car, or using a mobile phone. We’ll just have to visualize the end result more and know which tool to use in the process of making that photograph. So the next time you bring out your camera, regardless whether you’re in P mode or in any of the other exposure modes (Manual, Aperture-Priority, or Shutter-Priority), try out the different combinations of ISO, Aperture, and Shutter Speeds and see for yourself the different effects that you can get. I do hope you find this useful in your hobby, but I do intend to simplify this further, especially for newbies, by getting more inputs (questions and comments) from both intermediate and seasoned photographers. That will be very much appreciated.