Category Archives: Photography Word of the Week

Critical Focus and Depth of Field – Photography Word of the Week 5

While many photographers, both professional and enthusiasts, know the rule of thumb of focusing on someone’s eye for portraits in order to achieve “critical focus”, not everyone understands the difference between critical focus and depth of field, two very related but very different terms. Critical focus is the part of the photo which is optically in focus. It is based on a simple formula which takes only two variables in consideration: the focal length of the lens, and the distance between the back of the lens and the film/sensor. The result is the distance at which critical focus is achieved, and anything on that plane is called critically in focus, while something even 0.0001mm in front or behind that distance might still be extremely sharp, but we wouldn’t be able to call it critically in focus.

In contrast, the depth of field adds a few other important factors: aperture, which affects how much of the image is in focus, and the circle of confusion, which defines what we consider as adequately in focus.

So the depth of field applies to a range of distances, for example with a Canon T5i with a 18mm lens focused at 1m at f/8, the area which is acceptably in focus is everything between 0.696m and 1.774m. In contrast, only something which is exactly at 1m distance would be considered in critical focus.

To find out more about depth of field, try our free online Depth of Field calculator or download our Camera Calculators App for Android app.

Talking about Hardware, Firmware, and Software, oh my!? – Photography Word of the Week 4

This week we will be talking about a different aspect of photography: the equipment we love and loathe. A lot of cameras, recording devices, and even lenses have version numbers, and sometimes it can get confusing getting all those hardware, firmware, and software updates in order. In this blog post, we’ll try to make sense of it all, and see why it matters to you, the person behind the camera!

Hardware, Firmware, and Software, oh my!?

First up, lets make the distinction between Hardware, Firmware, and Software.

Hardware normally refers to the physical device, including sensors, processors, batteries, etc. It could be a camera, computer, laptop, tablet, phone, flash, lens, or even a remote. They can be extremely complex, or the simplest of devices. In order to get the new version of a hardware, you typically have to purchase it. For example, the Canon 5D mark III camera is the version 3 of the Canon 5D series. You cannot just download something to turn your 5D mark II into a 5D mark III, since the cameras are physically different, including new chips, processors, sensors, etc.

Software and Applications (Apps) are the other pieces of the puzzle we are usually very familiar with. They are the programs which run on your hardware, such as the web browser you’re using to read this blog. When it comes to photography, software is usually what runs on your computer, not your camera, such as Adobe Photoshop, Canon Photo Professional, etc. However, there are some third party groups such as Magic Lantern and Nikonhacker who build specialized software which you can install on your camera in order to teach it new tricks.

Firmware is often misunderstood, but plays a very vital role. Firmware is a special category of software which normally comes already installed on a chip within your camera or other device. Firmware is what makes your device able to do something, anything. Without firmware, your camera wouldn’t know what to do when you press the shutter or any other button, turn knobs, etc. Depending on the make and model of your camera or other equipment, some manufacturers are very generous in offering frequent free firmware upgrades full of new features, while others only provide minor bug fixes. In either case, it’s usually best to upgrade the firmware to ensure you get access to all the features which are available for your camera. One example would be a camera which can only record video in 720p resolution might get a firmware upgrade to allow it to record in 1080p. All you need to do is download the firmware, install it in your camera, and you can take advantage of the new features or bug fixes.

Version Numbers
Version numbers are usually a combination of 1 to 4 numbers, such as version 1, version 1.2, version 1.2.3 or version

  1. Major Revision – The first number represents a major revision, which usually includes multiple new features, or a fundamental change in the way the software or firmware works
  2. Minor Revision – The second number represents a minor revision, which would typically add one new feature and maybe fix a few bugs
  3. Bug Fix – The third number represents a bug fix, usually something which can’t wait until the next Minor Revision.
  4. Build Number – Finally, the fourth number is a build number, which is mostly an internal reference used to identify which version of the code was used to build the software or firmware. Some companies do builds every night (nightly builds) with extra builds during the day as needed to test out something, so the build numbers can climb up very quickly.

So now you understand that a Canon 5D Mark III with firmware 1.2.3 is the third version of the Canon 5D camera running firmware version 1.2.3 which added new features and fixed some bugs compared to when the Canon 5D Mark III first came out.

Talking about Blur, Shake, Bokeh, Movement, and Panning – Photography Word of the Week 3

This week’s mission: Making blur-related concepts clear.

Blur refers to the elements in the photo which do not have enough clarity to see details. It could be only one or multiple subjects in the photo, or it could be the entire photo. Blur can sometimes be intentional improving the photo, or can be unwanted and make an image unusable.

Blur in a photo can have multiple causes.
1) Blur can be caused by blurring out the foreground and background in a photo to make the main subject stand out more. In the example below, the bird is in focus, but the background is out-of-focus. This type of blur is usually controlled by using a different sensor size, focal length, or aperture. The quality of such blur is called bokeh, which we go in further details down below. When talking of the quantity of such out-of-focus blur, we usually talk about depth of field, which represents how much of the image is in focus.

Red Winged Blackbird

Red Winged Blackbird

2) A blur which is normally not wanted is caused by camera shake, where the whole image becomes blurry, and is usually unusable, except for some art forms where blur is intentional. Camera shake can be prevented by using a faster shutter speed, or using a camera or lens with some form of Image Stabilization, which can have different names depending on the manufacturer (Vibration Reduction, Vibration Compensation, etc). One rule of thumb to prevent camera shake blur is to use a shutter speed at least as fast as your focal length. So if you’re using a 300mm lens, your shutter speed should be at least 1/300s or faster. If you use Image Stabilization with 4 stops compensation on that same 300mm, you could use that same 300mm lens at around 1/(300/(2^4))s = 1/(300/16) = 1/18.75s instead of 1/300s.

Red Winged Blackbird camera shake

Red Winged Blackbird camera shake

3) A blur which can sometimes be used artistically is called movement blur, where an object going fast in front of the camera becomes blurry, with the foreground and background still sharp. You can do this artistically by using a slower shutter speed, or you can prevent it by using a faster shutter speed. Which shutter speeds to use mostly depends on how fast the object is moving, focal length, and how far it is from the camera.

Red Winged Blackbird movement blur

Red Winged Blackbird movement blur in back leg

4) Panning blur is where you have a fast moving object as in 3), but you pan the camera to follow the movement, so the object stays sharp, and the foreground and background instead become blurry.

5) While technically not blur, some noise can be caused by using a high ISO film or setting which makes the image unsharp, or by modifying the exposure value in post production by a large amount. We usually refer to it as a noisy image.

Red Winged Blackbird ISO noise

Red Winged Blackbird ISO noise

Bokeh is probably one of the most used catch phrases of Photography, but unfortunately it is rarely used correctly both gramatically and phonetically. The Japanese would pronounce the ‘eh’ like the ‘a’ in “a rock (as opposed to the ‘a’ in Ale). However it is oftenly incorrectly pronounced as rhyming with “O-Kay”.

Lets start by what isn’t bokeh to understand some key terms. If you look at a photo or video (which is basically a series of photos anyways), you may notice some blur coming from out-of-focus elements. A common mistake is calling that bokeh, for instance: “The 400mm f/2.8 lens produces a lot of bokeh.” A correct way of saying it would be “The 400mm f/2.8 lens causes a lot of foreground and background blur.” or “The 400mm f/2.8 lens causes a lot of the elements to be out of focus.”

As we saw, bokeh has nothing to do with the quantity of the blur. So what is bokeh? It has everything to do with the QUALITY of the blur. Lets say you have two lenses, a Canon 70-200mm f/2.8 and a Nikon 70-200mm f/2.8 You both extend them at 200mm, and you both select an aperture of 2.8. The images will look very similar, but one major difference could be the quality of the blur. While it wouldn’t change how much of the image is blurry, you might notice that one blur is more pleasant to the eyes than the other. THAT is what we call bokeh! So the correct use of bokeh would have “This lens offers very pleasant bokeh”. Bokeh is also very debatable, some people might prefer the bokeh of the Canon 70-200, while some prefer the bokeh of the Nikon 70-200.

Talking about light, Luminous Flux, Luminous Intensity, Illuminance, Luminance, Brightness, Exposure, Exposure Value, and Light Stops – Photography Word of the Week 2

This week, we discus various words used to describe and measure light in photography and videography.

Graphic of luminance, illuminance, luminous intensity, and luminous flux

luminance illuminance luminous intensity luminous flux

Luminous Flux is how much light a light source emits, measured in lumens (lm). This could be the sun, a light bulb, a flash, etc.

Luminous Intensity is how much light travels in a certain direction, measured in candelas (cd). For example, the sun sends out light all over the galaxy, but chances are we are only interested in the light hitting around us.

Illuminance is how much of that light is hitting an object, measured in lux.

Luminance is how much light is reflected or emitted by an object or scene, measured in candela per square meter (cd/m²). Luminance can either be measured for the object or scene being photographed, or for the final print photo.

Brightness, on the other hand, is a judgement call made by a subject looking at an object or scene, which can be biased. This is usually made by comparing two objects to determine which is brighter and which is darker.

To better understand the difference, lets look at a cell phone or tablet screen. Ever noticed how bright your cell phone looks inside, but when you take it outside in the sun, you can barely see the screen? A very popular model of cell phones was measured at 536 cd/m². Inside the house, the screen looks very bright. But if you bring it outside on a sunny day at noon time, the sun’s 1.6×10^9 cd/m² luminance will make that same cell phone screen look dark.

Exposure is a measure of how much of that light reaches the camera per area, which is affected by the aperture, the shutter speed, and the luminance of the scene or object. A scene or object can be considered underexposed, if it is too dark, correctly exposed, or over-exposed, if it is too bright.

Exposure Value represents the aperture and shutter speed settings of a camera, and is measured in EV. An EV of 0 represents an aperture of 1 and a shutter speed of 1 second, where 1 EV represents a 1 stop of light difference.

Interestingly, Exposure Value does not mention the ISO light sensitivity of the film or sensor, so it is very typical to describe an Exposure value as 15 EV at ISO 100, which would give a correct exposure for a sunny scene based on the Sunny f/16 rule where in a sunny scene, a correct exposure can be obtained with an aperture of f/16 with the ISO and Shutter speed being equal (f/16, 1/100 secs, ISO 100 would work, as well as f/16, 1/2000 sec, ISO 2000).

Light Stops are used to compare Exposure and Exposure Value, where each stop of light represents double the intensity of light. Stops can be used to describe the aperture, shutter speed, and ISO settings used to take a photo, and are usually used in full stops, half stops, or third stops.

Come back next week for our next Photography Word of the Week!

Photography – Photography Word of the Week 1

Welcome to this new series which I will simply call Photography Word of the Week. Each week I will take a common photography term and explain it’s meaning and why they are important. The goal of this? To enrich our vocabulary, and perhaps learn a thing or two about photography. I believe that the word worthy of the first Word of the Week should be Photography.

From the Ancient Greek words φωτός (phōtos – genitive of the word “light”) and γραφή (graphé – drawing, painting, writing, in this case drawing is the one which interests us), photography is the art of drawing light. While we may think it is a modern art, philosophers Mozi and Aristotle, as well as mathematician Euclid all described pinhole cameras back in the 5th and 4th centuries BCE, but it was only over 1500 years later that the first camera obscuras and pinhole cameras were constructed, and by the 15th century they were used by artists such as Leonardo DaVinci to project an image on a canvas, where the artist would manually draw the image. Over the years, that manual process was replaced by film, and most recently by digital sensors.

The technology might evolve at an exponential rate, but the idea remains the same: light goes through a hole (or lens) and gets focused on something (canvas, film, digital sensor), which allows to immortalize the events, both joyful and sad, for millenniums to come.

Join us next week for the next Photography Word of the Week!