*Freebie Photography 101, the Exposure Trifecta Part 1 : Aperture

exposure trifecta aperture part 1

Welcome to a new series on the blog, FREEBIE PHOTOGRAPHY 101 where we will explore both technical and artistic aspects of photography and our cameras.  The aim with the Exposure Trifecta (the relationship between Aperture, Shutter Speed and ISO value) is to learn how to better understand and control our exposure manually through examples and exercises to gain a better grasp on some of the seemingly daunting exposure modes and tools involved.  I’ll add articles about metering, exposure compensation, white balance and other often automated, yet powerful to understand settings that our cameras provide us the ability to control as time goes on as well.  It doesn’t matter if you’re shooting with a phone camera or a fifty thousand dollar medium format machine, understanding how an exposure is created, how a camera works while perhaps overwhelming at first, is easy, it really is.  With just a little time and effort, you’ll be understanding the hows and whys of different photographic effects and how to apply them in different situations.

When starting this blog 5 years ago, I did it to help friends and family who were interested in photography, to share techniques, and help answer questions I’d field to better understand basic photographic principals.  The site has grown and evolved into what you see today, chalk full of camera, lens and software reviews, gear-centric comparison pieces, lighting explanations or post processing tutorials, travel ramblings and editorial articles for the design collective I work with.

As is the cyclical nature of life, I’ve recently been having more and more conversations lately with friends and friends of friends who have shown interest in better understanding these powerful image creation tools and I thought it would be a good opportunity to refresh my original Exposure Trifecta article, written over 5 years ago.  Getting back to the roots as it were, and perhaps act as an introduction to some new friends we’ve gathered along the way here on the site.  So, grab your camera and a cup of coffee, we’re gonna have some fun.

If you feel like you could use a refresher, would like to add your input, or know someone just starting out or looking to better understand the Exposure Trifecta of Aperture, Shutter Speed and ISO sensitivity, come one, come all.  Through my amazing ability to ramble on, and the community we’ve built through this site, we’ll get you sorted and knowing how, and when to adjust these exposure variables to understand how to completely control your photographic vision. C’mon in…

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This will be the first installment in a new category on the blog.  We’ll call it “Freebie Photography 101” and it will live in the side bar for anyone to use and refer to.  I’ll continue to add content, and if you have particular questions, feel free to Contact Me, or post comments in these articles.

If you’re getting a bit overwhelmed, feel free to jump ahead to the recap “Lightning Round” for a simplified bullet point layout of what we cover in this article.

Aperture priority

FREEBIE PHOTOGRAPHY 101 – THE EXPOSURE TRIFECTA PART 1 – APERTURE

Think of this as a condensed photography class.  I’ll walk you through, and explain the how’s and why’s of manual photography so that we all can better understand how to manipulate our settings and control our cameras to not just capture, but create images in any condition.  I’ll also throw in some “intermediate” tidbits for each section so that when you get the basics down, you can revisit the article to both take it further, and impress your friends and fellow camera forum chums with your remarkable knowledge on the capturing and manipulating of light.  We’ll finish with some exercises so that we can put into practice what we’re explaining here.

Photography, digital or analog (it makes absolutely no difference) is merely the capturing and recording of light over a fraction of time onto a light sensitive medium.  When we push that little button, we are exposing a light sensitive device (or material) to the light in that scene.  I find that if you can train yourself to assess the scene, and the light before hand, you can easily prepare yourself and your camera to do what you want it to do.  A pre-visualization with the knowledge of how to get that shot, can set us up to avoid frustration when wanting to capture any one of the many fleeting moments a day may throw at us, or better prepare us to problem solve if and when our camera isn’t doing what we want it to.

There are three main components involved in exposure, hence the trifecta.  ISO, Shutter Speed and Aperture.  Adjusting all three of these in concert allows us to gain different effects while achieving the same exposure when we adjust them certain ways.  All three of these are also intertwined and entirely dependent on one another.  The first of these three components that we’ll talk about today is your lens’ aperture.

APERTURE!

Aperture: An opening which light passes through in an optical or photographic instrument. Designated by a numerical setting on the lens, and adjustable (in most all cases) to different settings called “stops” with a particular aperture value designated by its f-number or f-stop with each full stop a doubling or halving of the light let through the lens.

 

Aperture Illustration Chart

 

Here is a partial list of a lens’ possible aperture values in full stops:

f/1  –  f/1.4  –  f/2  –  f/2.8  –  f/4  –  f/5.6  –  f/8  –  f/11  –  f/16  –  f/22 

Not all lenses will be capable of opening up, or stopping down to all these listed aperture values, while some lenses are capable of opening up or stopping down further than those listed above.

Basic breakdown:

The lens’ aperture is the hole, which we (or our camera) control the size of, and its primary function is to allow more or less light to travel through the lens. The larger the hole, the more light and faster the shutter speed will need to be while the smaller the hole, the less light that makes it to the sensor or film which would require a longer shutter speed for proper exposure.  Regulating light is the aperture’s primary function.  It acts as a light valve, controlling the amount of light passing through the lens.

P1000370 - Version 2

If you’re noticing that your shots are blurry, it is likely because the shutter speed needed to properly expose your image is too slow allowing for the subject’s movements and/or your movement, to result in a blurry shot.  To allow for a faster shutter speed, the first thing we want to try and do is to open up our light valve (aperture) to allow more light through enabling a shorter fraction of time that the light needs to hit the sensor in order to properly expose our image.

Now, at some point we max out, and often with our aperture at its widest, largest setting, it still won’t let enough light through to give us a fast enough shutter speed.  This is common when shooting inside and/or in lower light.  Assuming you do not have any more light to add to your scene, you have two immediate options at this point.  First, (and most likely automatically enabled on most cameras) adding light by way of the flash.  Sometimes this is undesirable as it can look like a deer in headlights, introduces red eye or just creates a flat, snapshot look which we may not be going for.  Secondly, this leads us to a sneak peak at another component of our trifecta, the ISO sensitivity.  We will get into more depth regarding ISO in the ISO article, but basically, if you increase your ISO setting (the higher the ISO value numerically), the faster the shutter speed will be able to be with the trade off being a grainier image the higher that you set your ISO to.

kill the kids - ©tyson robichaud

The second function of the aperture, or more accurately a byproduct of this regulating and focusing of light, is the control of the depth of field.  For our purposes here, think of the depth of field (DOF) as a parallel plane in front of your camera that is in acceptable focus.  Realistically, it’s more of an elliptical semi sphere-ish bubble due to distance being the key variable somewhat regardless of which direction from the camera that focus distance may be, but to keep it simple, just picture a slice of your scene parallel to the front of the camera within which you control what is in focus, within that slice.  When your lens focuses on a particular point in your scene, there will be a measurable distance in front of and behind that point of focus that will be acceptably “in focus,” and this is your depth of field (also simply referred to as DOF).  Anything falling outside of that “acceptable” slice will gradually fall further out of focus both in front of, and behind that point of focus.

By stopping your aperture down (adjusting it to a physically smaller diameter), you will increase your depth of field.  By opening up your aperture, you will decrease the area that is in focus in front of and behind your point of initial focus.  See the diagram below for a basic illustration.

DOF

The focal length and focus distance measurements are irrelevant here in this example, what we’re trying to see is how changing our aperture can affect how much of our scene will be in focus (our DOF) if and when we need to either isolate a subject, or include multiple subjects as we would for a group photo for instance.  Here we have three people facing the camera.  Person A is our point of focus.  If we have our lens set to f/4 in this case, person A will be the only one in acceptable focus with person B too close to our camera to be included in our slice of focus, and person C too far behind our point of focus and away from our camera’s position to be included as well.  If we wanted to get persons A and B in focus, but weren’t so into person C, we could adjust to f/5.6 to gain a deeper DOF while still shallow enough to keep C on the fringes of focus limbo.  If we felt bad and didn’t want to exclude person C, we could then adjust to f/8 to include them in our slice of focus as well.

Without getting too technical, when we focus light through a larger hole (or aperture) the depth of field (or area in focus) is shallower, meaning less of the scene in front of the camera will be in focus.  Conversely, the physically smaller that hole, or aperture setting, the deeper the amount of focus will be.  Easy, right?  The transition between in and out of focus is also not a hard boundary, but rather gradual and the deeper the depth of field, the more gradual that transition will be.  The transition between acceptably in focus and out of focus is described by a concept called the Circle of Confusion.  It’s called that for a reason, and while I absolutely suggest you do some searching around the web if you are interested, for the time being we’re going to let that sleeping dog lie as it arguably deserves an article to itself.  We’ll keep it simple for now.  See below:

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In the first shot (f/2.8) the yellow is obviously our point of focus.  You can see in the wood grain where our slice of focus is more easily with a pretty quick transition, and “shallow” depth of field.  At f/16, green and blue are much closer to being in focus as is the wood grain, but still aren’t quite there entirely.  While they are on the fringes of our acceptably in focus slice, they’re recognizable at least and our overall DOF is much deeper.

There are two other factors, along with our aperture, that will affect our DOF.  Your focal length and your focusing distance.  Don’t get too hung up on this here, but just as a rule of thumb, the closer your camera is to your point of focus, the longer your focal length and the larger your aperture are, will all create shallower depth of field.  Some may bring up sensor or film size, but this is a bit of a red herring, so ignore that for now.  We’re just concerned with understanding what our DOF is, and means.

DOF is not symmetrical in front of and behind your point of focus either.  The amount of area in front of or behind your point of focus will not be identical because, well, math.  You will have more in focus behind your point of focus than in front of it.  Sometimes this measurement is negligible, others it is quite large, and more pronounced the further away your focus point is.  Optical physics aside, just know that depending on how close you are, how long your focal length is and how large or small your aperture is set to, will all affect the DOF.  Understanding, controlling and manipulating this DOF is where we can turn it into a tool.


 

zooms vs primes

Lenses!

All lenses will have an aperture mechanism of some kind.  Some lenses simply have a singular aperture setting which is fixed, but a vast majority of lenses have a variable aperture which may be adjusted via the camera, or in cases the lens itself by way of a physical aperture ring on the lens (see example below), to regulate the amount of light coming through it.

manual lens fd55mm f/1.2 ssc

There are two basic lens types.  A prime lens (aka: fixed focal length lens) or a zoom lens (a lens with an adjustable range of focal lengths).  Focal length is a measurement at which light is properly focused onto our sensor (or film) and provides an angle of view from the camera’s position.   A 50mm lens will always measure 50mm when properly focusing light onto a sensor or film (see the extra credit section later on for more info on focal length) but can “look” different by way of the angle of view (also referred to as field of view), depending on the size of sensor or film it is focusing light onto.

A zoom lens alters the angle of view from your camera’s position where a prime lens provides one singular angle of view.  If desired, the photographer can crop into an image taken from one focal length to achieve the same angle of view as that captured by a longer focal length from that same position.  Assuming all settings were the same and taken from the same location, the cropped image and the image taken with a longer focal length would appear identical aside from total resolution (you’d lose pixels by cropping) or the possibility of any optical distortion that one lens may introduce, but otherwise, you’d have two identical images. The photographer can also physically adjust their position to relatively frame a subject similarly to that of a different focal length.  Doing this though, will alter your location and physical proximity, changing the spacial relationship between you, your subject and elements in your scene, producing two different images.

A zoom lens allows us to alter our angle of view from a fixed position while a prime lens provides a single angle of view to work with.

A lens’ largest, or maximum aperture is normally listed on the front of the lens, and when lens shopping will be how a particular lens is designated next to its focal length by way of the f number.

prime olympus 75mm f/1.8 lens

A prime lens, with only one focal length, will have one maximum aperture listed, denoted by way of an f number (like a 75mm 1:1.8 which would be an f/1.8 lens) as seen above.

Panasonic 100-300mm zoom lens

When using a zoom lens, if you have a good amount of money, you can get a constant aperture zoom lens (likely f/4 or f/2.8), but more than likely, you’ll see two different numbers on the front (something like 1:4.0 – 5.6 as seen above).  This shows the maximum aperture at the two ends of your zoom range with the first being the max aperture at your shortest focal length (or widest angle of view), and the second at the longest focal length.

It is more economical to design and manufacture zoom lenses with a variable aperture and is normally reflected in the price.  Constant aperture zooms, one where you can shoot at the same maximum aperture all the way through the zoom range, are traditionally larger, heavier, and quite a bit more expensive.  The larger and heavier parts of that statement are because the aperture is directly related to the physical measurement of the focal length and larger diameter of the lens elements needed to compensate for the measurements of these larger aperture settings (see the Extra Credit portion below for more info on this).  In short, the aperture value is directly tied to the focal length by way of a ratio based on the focal length : diameter of the aperture.

So, why would we want a larger maximum aperture?  Well, as we’ve touched on, a larger aperture allows more light enabling faster shutter speeds in lower light scenarios, and also allows for a shallower DOF, useful when wanting to control our DOF to separate or isolate our subject from fore and background elements in a scene.

Not all lenses are created equal, and to gain access to larger apertures, normally we need to spend a bit of extra money.  The quickest, and most economical way to gain access to faster, larger apertures is by looking at buying a prime lens.  Most all of the fastest, professional zoom lenses max out at f/2.8, which for a zoom is very fast, but those lenses are usually very expensive compared to say a lens with the same focal range but built with a variable aperture, or often a lens with a fixed focal length (prime lens) at or faster than a maximum aperture of f/2.8.

When a lens is described as being “fast” what is being described is the maximum aperture.  “Fast” max apertures will normally fall at or below f/2.8 with opinion varying on what truly constitutes a “fast” lens.  There are also situational and relative inclusions.  A 50mm lens with a maximum aperture of f/4 would, by most, be considered a slow lens.  A 500mm lens with a max aperture of f/4 would be considered a very fast lens (and would also be very expensive).

Prime lenses can be a fraction of the cost of comparably (when possible) quick zoom lenses, and some even offer apertures dipping down into the ridiculous to very fast range (f/0.95, f/1.2, f/1.4 or f/1.8).  Most systems offer at least a couple very affordable f/1.8 or similar optics, and by affordable, I mean around $100 – $200 or so.  Depending on your camera system, you should be able to search for a fairly affordable 50mm f/1.8 lens.  Try going HERE and searching for “your camera’s brand name + 50mm f/1.8″ to see what comes up.  If you’re using a crop frame or mirrorless system camera, divide 50mm by your crop factor, round that number to the closest 5mm increment and search the same way.  Whether this focal length is one that you’d find useful is a different conversation, but if that is a conversation you’re interested in having, please feel free to comment below, or contact me and I’ll do my best to help out.

Our lens’ aperture is one of the most effective, and creative tools we have at our photographic disposal.  The ability to both regulate light through the lens, and control our depth of field provide two useful and important factors in image creation.

If you’re having problems with blurry pictures, more times than not, it will be because your lens isn’t allowing enough light through it to achieve a fast enough shutter speed.  This often results in movement, either by your subject(s) or your self equalling, yep, blurry or at least not very sharp pictures.  If you’ve opened your aperture up as large as it will go and you’re still having problems getting sharp shots in lower light, don’t worry, we will tackle that in the coming articles.

 

EXERCISE BREAK!

Try this.  Assuming your camera has a mode dial (it may live in a menu), it should have a series of letters on it.  P, A, S, M or Av, Sv, maybe Ap or Sp, etc.  If you’re not sure, have a look at your camera’s manual and look for Mode, or Operation. It should be close to the beginning.

  1. Let’s set our cameras to that “A” or Aperture priority mode setting.  This means we will be in control of our Aperture setting, and our camera will adjust our shutter speed to whatever it needs to be.
  2. Let’s open our aperture up as much as we can.  You should have a wheel, slider or buttons to adjust your aperture to its largest, maximum setting.
  3. To do so, set your aperture to the smallest actual number (the number denoted on the front of, or somewhere on your lens barrel) which will be the largest aperture setting.  This is what is called “wide open” regarding a lens.  Whatever it is, set it there and try to take a shot focused on something close to you, like holding your hand out in front of you and shooting it.  Try also to keep the background distant and varied (don’t shoot it with a plain wall in the back for this exercise, for visual effect).
  4. Next, close your aperture down to a moderate f stop like f/8 or f/11 and replicate the shot.  Going by the full stop chart earlier on, try to stop down at least 3 full stops (more if light allows).  The bigger difference between settings on the two shots, the more apparent the change in DOF will be.

wideopen

This is wide open at f/0.95, using a 42.5mm Lens focused about two feet away from the camera.

stopped down

 

This second shot is taken, exactly as the first with the lens stopped down to f/8.

Now, one thing that may derail this experiment is that the second, stopped down shot might be much blurrier…  This is an example of that light regulation, and some situations may require a different approach.  If this is the case here though, try to set the camera on a table or steady surface (a tripod would be ideal here) and replicate the exercise.  Assuming we can keep the camera steady enough, and have enough light to properly expose our hand, we should notice that the shot wide open shows a much shallower depth of field meaning the background is more noticeably out of focus while the second shot shows much more of our background either in focus, or more recognizable at any rate.  If you have enough light to get a decently steady shot, try adjusting your aperture to an even smaller setting (f/11, f/16, f22…) to see how much it affects your DOF. This is a quick and dirty example of how our aperture affects the area in focus, or our depth of field when we adjust it, and now you have a basic understanding on how to control that.  See how easy that is?

If you’re at capacity, feel free to skip over the Extra Credit section below, but I’d also suggest trying to come back once you’ve had a little time to play around, to read through it because these little tidbits will help you debate and debunk the misconceptions regarding aperture when interacting with other photographers on line, or in person.


 

EXTRA CREDIT: Here’s a little more information regarding aperture, for those not yet feeling overwhelmed.

  • Also referred to as the “ƒ number” or “ƒ-stop” a lens aperture is denoted as the focal length divided by the effective aperture diameter commonly shown in a ratio printed on the front of a lens 1:1.4, or 1:2.8, etc.  
  • The smaller the number, numerically, the larger the aperture (ƒ/1.2 or ƒ/1.4 or ƒ/2, etc) while conversely, the larger the number numerically, the smaller the physical aperture measurement (ƒ/11, ƒ/16, ƒ/22, etc).
  • The physical measurement of the aperture’s diameter for a 50mm lens for example, with an aperture of ƒ/1 (1:1), would be 50mm.  That same 50mm lens, with an aperture setting of ƒ/2 (or 1:2) would have that aperture’s diameter measure 25mm, so on, etc while the same aperture setting (ƒ/2) on a 100mm lens would measure in at 50mm, but still let the same amount of light in through it as the 50mm lens with the aperture at f/2 measuring 25mm.  
  • The ratio is dependent on both the focal length and its relationship to the diameter of the aperture. The focal length denotes a physical measurement between the rear/back focal plane, and the rear nodal point when that lens is focused to infinity.  That measurement is the focal length.  
  • The size of the lens’ elements will need to be bigger if the lens is designed with larger apertures (larger light valve/larger overall lens elements to accommodate that larger hole which the light passes through) which is why “fast” lenses (those with larger maximum apertures) are heavier, larger, and in most all cases, more expensive than a lens with the same focal length, but smaller maximum aperture.
  • With each full aperture stop, you either half or double the amount of light let through.  For example, from f/2.8 to f/4, you would cut the amount of light traveling through your lens in half while going from f/4 to f/2.8, you’d double the amount of light (as illustrated in the image near the top of the article).
  • An ƒ number for one lens will be equal in light gathering to the same ƒ number for any other lens, for any other format.  Example: If you have a 24mm ƒ/2.8 lens and a 100mm ƒ/2.8 lens, and were to take an image of the same scene with the two different lenses set to that same aperture of ƒ/2.8, under consistent light, at the same ISO and shutter speed settings, you should record the same exposure between the two images of the area captured in each shot (less of course the possibility of transmission differences which in reality, traditionally only affect light transmission by a third or half stop at the most between different lenses).  It’s close enough to call it a wash for this purpose, so we will.  
  • To keep it simple, ƒ/2.8 is ƒ/2.8 when it comes to light gathering and any lens capable of an identical aperture value should be able to allow (near) the exact same amount of light through it, no matter the focal length, or format it is designed for.  You may hear about total light vs density of light, and while scientifically valid, it can over complicate exposure.  Pixel pitch between formats is closer, signal readout is closer, and while there is no replication for physical space, systems now are advanced enough to replicate what I like to call actual exposure, or just “exposure” when looking at how a picture actually looks across formats.  Take two formats, shoot an image with each at the same aperture setting, the same ISO and the same shutter speed (extra extra credit if you match WB and spot meter off of an actual 18% grey mid tone).  For continuity, it would help if the equivalent field of view is the same so that the images include the same stuff, but even this is unnecessary if you are comparing the same elements between the two images in this case.  The result?  Two images that look the same in regards to exposure value and luminance levels. 
  • Where it can get a little complicated as mentioned above, is when we look at a lens’ light transmission.  Most all lenses will contain elements that will “eat” light.  This just means that when set to a particular ƒ stop setting, the lens will transmit less light through it compared to the ƒ stop setting, and it may slightly differ in exposure compared to that of another lens set to that same ƒ stop setting.  The transmission, which is the ACTUAL speed of a lens, is referred to as the T-Stop of a lens.  Most lenses designed for still photography often omit a transmission measure, but often cine or film lenses will be designated by a T-Stop.  This is really the only major factor that will differentiate one f/2.8 lens from another f/2.8 lens in regard to light transmission.  
  • You may hear talk of sensor size and light gathering changing depending on format, but don’t allow this to confuse the math.  Any lens capable of any given aperture (less any T-stop differences which are a reality for all lenses and all formats currently) will have the same ability to allow total light through at that given aperture regardless of the focal length, regardless of the size of sensor or film.  Digital signal to noise amplification, light density and true ISO value may be a different conversation, but the good thing is that it is pretty superfluous in the real world when taking actual pictures.

 

*Sensor size and Depth Of Field – You will, or may have heard people talk about how sensor size affects the depth of field at any given aperture value.  There are a lot of falsehoods out there.  Simply put, the size of the sensor itself does NOT affect the depth of field at all.  Where it all gets confused is when we try to equal what one focal length “looks like” on one format compared to another taking into consideration crop factors. The factors that affect DOF are 1) The aperture, 2) Focus distance, or the measured distance between where the light is focused onto your sensor and the point of focus. 3) Focal length which is a physical measurement regardless of the format.

  • The larger the aperture, the shallower the depth of field.
  • The longer the focal length, the shallower the depth of field.
  • The closer the focusing distance, the shallower the depth of field.
  • If wanting to narrow the depth of field more easily while working with a larger aperture, get as close as you can to the subject you’re focusing on.  The closer you are to your subject at any aperture, the shallower your depth of field will be at that aperture setting compared to shooting from further back at that same aperture setting.  Conversely, if needing more of a scene in focus, without stopping the lens down to a smaller aperture, you can increase your focus distance (either back up, or focus on something further away).
  • With focal length, the shorter the focal length (wider angle), the inherently deeper (greater) the depth of field with longer focal lengths capable of decreasing the DOF more easily from a fixed position.

So, why all the confusion? I will use a full frame digital and a Micro 4/3 (cropped frame) digital camera for comparison here.  Keep in mind that the Micro 4/3 sensor is physically 1/4 of the size of a full frame sensor, and has an effective crop value of 2x (meaning that to equal the field of view as it would roughly appear if captured on a full frame camera, you need to multiply the focal length by 2).  

If you use the same exact lens, at the same exact focal length and aperture setting, focused on the exact same point a fixed distance away, (where the sensor size is the ONLY variable), while the image captured on the m4/3 sensor will be captured at a tighter angle due to the image circle being cropped into, and while the subject will appear closer, the actual depth of field will not change.

See below.  The setup was using the same exact 100mm lens adapted to both a full frame camera, and a micro 4/3 camera from a fixed distance, and focused from a tripod onto a ruler at the same exact point, using the same exact aperture, and exposure settings.  Aside from a white balance difference, the images when cropped into as seen below, show that the actual depth of field are identical.

IMG_7125 - Version 2 P1110343 - Version 2

 

Where the DOF is altered, is when we try to equal the angle of view on one format compared to another which requires us to decrease the focal length on smaller sensors to equal the same angle of view which WILL affect the DOF because we change the focal length, or increase the focal length on larger sensors which also affects the DOF.  This goes for any and all formats as DOF is a mathematical equation that doesn’t care how large or small the capture medium is, and is affected by focal length, focus distance and aperture only.

Now, the original images, from that fixed location, using the same exact lens and exposure settings, focused onto the ruler at the same point will “look” different regarding the angle of view that the original, full sized files look like.  See below:

IMG_7125 P1110343

 

Of course, the field of view changes substantially between the two formats evident when looking at how the images from that fixed position were originally captured, with the m4/3 image effectively equal to cropping into 1/4 the space of the FF image, one thing that does not change is the DOF.  To equal the same field of view, we’d either have to double the physical distance between the camera and subject in the case of the m4/3 sensor image, or cut the distance in half in terms of the Full Frame camera, either of which would alter the DOF, but from a fixed location, there is no difference in the DOF when everything else is equal.

Some argue that we need to discuss this in terms of equivalent angle or field of view.  I disagree on the whole here.  Why?  Well, there are times that we cannot replicate the field of view by way of a lens compared to another format.  The equivalence argument, while valid it its own right, is a different discussion.  If you shoot multiple formats and want to know how one focal length affects your DOF and angle of view on those various formats, then it is pretty easy.  Keeping with the m4/3 and FF comparison, a FF camera with a 50mm lens set to f/4 would produce the same DOF and angle of view (but with a different physical relationship between elements in the scene from the cameras position) as a 50mm lens on a micro 4/3 camera, twice the distance away at f/2.  We tend to use the 135mm (Full frame) format as our benchmark and reference, but do we need to?  Where it gets shady is, what if we want to shoot that 50mm lens on a smaller format at that initial focus distance?  Well, it will crop into the image circle, producing an image similar to that of a 100mm lens on a full frame, but will then need to be looked at either as an actual focal length (50mm which will have the same DOF at f/4 as the 50mm on the FF at f/4 from that position) or compared to an entirely different focal length in an attempt to replicate the angle of view, which will affect the DOF.

When is this even relatively useful in the real world as most times, we’d be looking to compare a similar field or angle of view when talking about the differences between formats?  Well, if you cannot get physically closer to your subject, the same focal length on two different sized formats will “look” different in that the smaller the format, the closer your subject(s) will appear, being that they occupy more space in your frame.  The two images will in fact have the same DOF from that fixed position at any given aperture compared to a larger (or smaller) format at the same focal length and aperture setting.  Think sideline sports, safaris or situations where to get a more highly magnified image of your subject(s) you’ll need more optical reach, or will need to crop into your image to do so.  In this sense, one could argue that a smaller format enables the shooter to produce an image with a higher possible resolution in most cases as opposed to shooting and cropping later from an image captured on a larger sensor which will essentially throw away pixels decreasing the total resolution of the image.  Coupled with the fact that an aperture setting, regardless of the format, will enable a level of light gathering and in turn faster shutter speeds at like settings, it can be beneficial when shooting from a fixed location with a smaller format if maintaining resolution and getting closer by way of that crop, to your subject(s) is important.  While yes, doubling the focal length on a FF compared to a m4/3 sensor would provide the same angle of view, assuming you could acquire (and afford) a lens with the same maximum aperture, you would in fact decrease the DOF if shot at that same f stop because you’ve changed your physical focal length.


LIGHTNING ROUND!!!  A quick, simple and concise recap…

  • The Aperture is a hole that can be opened or closed within our lens, adjusted in “stops.”
  • The aperture regulates the amount of light that is let through our lens.  The more light through the lens, the less time that the shutter needs to be open making for a faster shutter speed helping freeze, or account for subject or camera movement.
  • Setting your camera on A or Aperture Priority mode allows you to control your lens’ aperture while the camera will automate your shutter speed, and in cases your ISO to compensate for proper exposure.  It’s kinda like full Auto mode, but you have full control of one key feature!
  • The larger our aperture means the more light let through and the shallower our Depth of Field (DOF) or area in focus.  If you want to isolate a subject with an out of focus fore or background, a larger aperture is an important factor.  If you want your entire scene in focus when shooting a beautiful landscape or the like, you will likely need to stop down your aperture to a smaller setting which will increase your DOF, but also require a slower shutter speed for proper exposure (big hole = more light + shallower DOF, small hole = less light + deeper DOF).
  • Think of aperture as a ratio (because it is = focal length:aperture diameter) 1:1 is larger than 1:8, as 1:2.8 is a larger value than 1:5.6 is.  To translate this to your f-stop, just change the first 1 to f and the colon to a “/” and you have your f number (f/2.8, f/4, f/5.6, f/8, f/11, f/16, etc) easy!

I challenge those that are new to shooting in aperture priority to try shooting in that mode for a while.  Get used to controlling and adjusting your aperture.  Manipulate your DOF and play with your images by way of both shallow and deep depth of field.

Feel free to wander around the site.  I’ve spent years compiling various reviews, tidbits and freebies and much of what I have written and found is linked all the way at the top of the page.  Check Free-sources for great sites, forums and content, the Tutorials page for, well, various shooting, lighting and post processing tutorials, or the Review page to see my take on many photographic instruments or photography related software.  You can always contact me via the link at the top of the page too.

I’m always game to network and collaborate, and I’m happy to try and answer questions, so feel free to hit me up. I’d love to connect via Facebook, Twitter, Flickr or Instagram and to stay posted on new articles, feel free to add your email address at the top right of the page here.  You’ll get email alerts as new articles are released.  As new Freebie Photography 101 articles are published, they’ll live HERE.

Read Part 2 – Shutter Speed HERE

Read Part 3 – ISO HERE

Thank you for the read, and if you’re new here, welcome.  We have built quite an awesome group of regulars that share insight, comment and contribute.  Learning is always boosted by a greater spectrum of experience and point of view, so please don’t be shy.  If you have a question, ask away.  I’m sure someone else has the same question.  If you have some insight to contribute, please do so as well, and stay tuned for more freebie photography 101 articles.

Happy shooting,

Tyson

9 thoughts on “*Freebie Photography 101, the Exposure Trifecta Part 1 : Aperture

  1. Pingback: In the News: 2015-01-17 | Klaus' Korner

  2. Pingback: *Freebie Photography 101, the Exposure Trifecta Part 2 : Shutter Speed | Tyson Robichaud Photo-blography

  3. Pingback: *Freebie Photography 101, the Exposure Trifecta Part 3 : ISO | Tyson Robichaud Photo-blography

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