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Manual Settings

April 14th, 2020

The first thing that needs to be considered when attempting to shoot a series of images for stitching into a panorama are the camera settings. For consistent, quality results everything should be taken off of auto and set manually.  

Most grand vistas are going to have a range of light intensities and light temperatures that will cause the auto settings of your camera to kick in and automatically adjust to compensate. In any single image that’s beneficial but those changes will make it challenging if not impossible to achieve invisible blending in a picture composited from multiple images. 

This picture, which is a composite of five images, of the Hinkley Shoe Tree just outside of Hinkley, Utah illustrates my point. The top and bottom regions are relatively light when compared to the middle of the picture. Had I used auto settings, blending of the five images would have been more difficult than using consistent, manually configured settings. 

(Fujifilm X100T, 23mm, 1/320s, f/9, ISO 200, infrared conversion)

Stitching

April 7th, 2020

The idea with stitching is simple: take multiple, overlapping images and aggregate them into a single larger image. 

This pair of images of the Hajar Mountains in Oman were one of my first (successful) attempts at stitching.

(Canon Rebel XSi, EF70-300 @ 300, 1/500s, f/6.7, ISO 100)

Here’s the final image with appropriate blending, cropping and contrast adjustments.

I suppose achieving such results might seem complicated; trying to align the images properly, get the exposure blending just right, etc. But it’s not; it’s just a couple of mouse clicks in Lightroom, a few more if you’re working in Photoshop, but all-in-all it’s trivial with today’s software options. (Lightroom and Photoshop aren’t your only options, there are a number of others; some free, some for purchase. Google is your friend.)

While the basic idea is simple, there are a number of things that can make the results less than satisfactory. I’ll address a few of those issues in my next few posts. 

Compositional Limits

March 17th, 2020

Sometimes I find myself overly constrained by the frame around the image I’m shooting. Of course the image framing imposed by the camera is always a constraint but here I’m saying overly constrained because I find that sometimes it doesn’t allow me to capture the full scope of my vision. I most often encounter this constraint in landscape photography by it occasionally occurs in other genres as well. 

What to do? There are at least two approaches to the problem: use a wide-angle lens or stitching. 

Let’s consider the choice of lens first. My standard lens, the one that’s mounted on my camera most frequently, is a normal range zoom lens (24-70mm). Since I am shooting with a full-frame sensor (24mm x 36mm) setting the lens at 50mm results in a field of view of 27° x 40°. Zooming the lens out to 24mm expands that field of view to 53° x 74° which opens the possibilities of what I can capture but can still be very limiting. 

Standing on the rim of the Grand Canyon with a horizontal view that literally extends 270° and only having a 24mm lens can be disheartening.  How can you capture the grandeur without capturing the grand view? I could switch to a wider angle, for example my 16mm lens, but that still only expands the view to just over 90°.

Furthermore, using a wide angle lens distorts the relationship between near and far objects, emphasizing (or enlarging) objects close to the lens and shrinking (or deemphasizing) objects farther away. In my opinion this effect in some situations can result in artistically pleasing images but when employed in grand-view landscapes I find the results unappealing. I think the reason for this is that the diminution of far objects and overall scene distortion results in an image that is less impactful than the actual scene. The scene as experienced when standing at the view point, under a normal perspective, is more present and in-your-face than the result from a using wide angle lens. In my images I want to capture that feeling of being-there and the presence of the actual scene as much as possible.

Another consideration is usable bits

My primary landscape camera is a Sony α7RII with an image size of 42MB. This camera shoots in a ratio of 2x3 and results in an image of about 5300 x 7950 pixels.  

Many of the grand-view images that I shoot I plan on cropping to a long horizontal aspect ration suitable for hanging on a big wall over a couch or some such location. A common crop ration that I use for these wide panorama is one frequently used in movies: 1x2.35. 

Taking an image with my 16mm lens might capture a significant portion of the scene and provide a pleasing composition; however once cropped the final pixel count is significantly reduced and results in an image that is unsuitable for massive printing. For example, cropping a 2x3 image to 1x2.35 results in a loss of almost half the original data. The resulting image is 3383 x 7950 pixels, or only 23MB. Assuming a print resolution of 300dpi, the final image would natively be printed at 26.5″ wide. If my goal is to print a very large image (greater than 5 feet), starting with an image that is barely over 2 feet isn’t going to produce superior results. 

One way to overcome these limitations is through image stitching, which I’ll discuss in my next post. 

(From Sublime to Grand, Sony α7RII, FE 24x70mm @ 70mm, 1/200s, f/6.3, ISO 400, Image Size: 15148 x 6446)

Composition Games

March 10th, 2020

The technical aspects of creating a photograph are relatively simple. It takes some knowledge and experience to craft a properly exposed image with appropriate depth of field to express your mood. But those details are not the challenging part of photography; the real challenge is composition. 

It’s easy to fall into a photography rut, sometimes a game is the perfect way to bounce out and into new realms. Here are some that I use to get me thinking out of my own self-imposed box. 

Limitations

Most of my pictures are taken with similar settings; I tend to shoot with a 24-70mm lens, use a fairly small aperture and set the shutter speed to ensure no motion. One game that I occasionally play to force me into new territory is to choose something outside those standard parameters and try and make successful images with that alternate configuration. 

For example, I might try and shoot a series of images with the lens aperture wide open (small f-number) or swap out my standard lens for a wide angle (16mm) or telephoto (300mm) lens. These exercises force me to look at scenes from a different and new perspective that stretches my creativity into new realms.

Another somewhat popular self-imposed limitation is the disposable camera challenge. (A quick google search for those three words will provide you with plenty of details.) As photographers we’re usually shooting with the best gear we can afford with all possible artistic options (a focusable zoom lens, aperture choices, shutter speed settings, etc.). The disposable camera challenge takes away all those camera settings and forces us to just point and shoot. And true to the name it can be a challenge, albeit a good one. After shooting with a DSLR for a while using my cell phone with some of its inherent limitations can feel a bit like a disposable camera

Creativity

I often find myself with an interesting subject of which I shoot an image or two and then I quickly move on. Sometimes I realize I’m not exploring all the options for a given subject and I’ll challenge myself to shoot 20 different and distinct images of it. I quickly exhaust all the angles (front, back, side, top and bottom) and I’m left stretching my imagination in order to get out of my mental box. I have to delve into areas I normally wouldn’t venture (shallow depth of field, long shutter speed, camera panning, etc.). Getting to 15 is hard but I can still do it fairly rapidly. Getting those last five though… whew, yea; that’s a challenge. Give it a try, let me know how it goes.

When I’m trying to capture a preconceived image I frequently find myself waiting for the optimal conditions to arrive (sunset, blue hour, etc.). I’ll get all set up for the shot and then have an hour or more to kill before I press the button for the money-shot. Often, to kill time I’ll play the 20x20 game. 

The rules of the 20x20 game are that from the moment of inception you have to take 20 distinct images within 20 feet of your current location. They can be of anything, selfies, sidewalk cracks, tree bark, whatever. The idea is that since I’m there for the one preconceived image, I’ve devalued the rest of the scene. So the challenge is to make 20 images of the devalued mess, i.e. create something of visual interest out of nothing interesting. Play this game often enough and you’ll be surprised at what you start to see. 

On my way home from a trip to San Francisco, CA I got to the airport a few hours early. To kill the time before my flight I played 20x20 (well, I fudged a bit on the 20 feet) and spent some time in one of the parking garages taking 20 pictures. This is one of them. 

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(Fujifilm X100T, 1/125s, f/8, ISO 200, infrared conversion) 

Theme

The last game that I want to mention is shooting to a theme. The theme can literally be anything: strength, blue, taste, sound, movement, etc.). The idea is that you take a photograph that conveys or expresses that theme

One theme is the alphabet. The challenge is to take a photograph that expresses ‘A’, then another that screams ‘B’, and so on through ‘Z’. 

Other theme based photography challenges are available on the Internet. One that was quite active for a few years but now appears to be defunct is the Mission 24 flickr discussion group. (https://www.flickr.com/groups/mission24/) You should be able to find others that are currently active or you could just browse the Mission 24 archives for ideas to explore on your own. 

Composition is the holy grail of photography. Playing these games helps me keep my photography fresh and forces me to explore new realms. 

Inspiration

March 3rd, 2020

I spent a few minutes today browsing through the Top 101 Landscape Photographs from 2019.  

They’re all pretty amazing; you’ll find one of my favorites here…

https://www.internationallandscapephotographer.com/index.php/food/159-2019-top-101-landscape-photographs?786

These images were selected as finalists in The International Landscape Photographer of the Year contest. 

Of course they all exhibit technical mastery of exposure and depth of field which is to be expected in submissions to a Photographer-of-the-Year competition. (Notice the tack-sharp rendering in https://www.internationallandscapephotographer.com/index.php/food/159-2019-top-101-landscape-photographs?800.) 

What I was most captivated by in all of the images was the simplicity of the subject matters. Take the one I linked to above as one of my favorites (#786 by Stas Bartnikas). This image of a snow-melt pond on a glacier could hardly be more plain but the composition, with the pond placed just right of center and the raking light accentuating the texture in the surface of the snow, I find exquisite. The image is minimalistic in theme but maximalistic in texture and visual interest. Another amazingly simplistic yet exquisite image is #755 by Lazar Ovidiu, just a collection of humps of snow, which is made captivating through the use of contrast and color. 

If you have a minute or two, take a look, you won’t be disappointed. Hopefully, you’ll also find some inspiration for your own practice. I know I have. 

Summary

February 25th, 2020

I started this discussion about photography clear back in June, 2019 and I’ve covered a lot of ground. There’s more I want to cover but before I do I think it will be useful to summarize what I’ve discussed up to now. 

I started this series discussing light and defined photography as the act of capturing light interacting with a subject. As photographic artists we need to understand and use the attributes of light (point source/diffuse, color/temperature, front/side/back) to best express our view, interpretation or feelings about the subject.  Furthermore, understanding the intensity of light, the limitations of our camera being able to capture its intensity and adjusting our camera’s settings to accommodate that intensity are basic knowledge that we must grasp. 

After discussing light, I moved through the design/decision process I use when shooting. The process follows the alphabetical sequence CDE: composition, depth of field and exposure.  

With regard to composition there’s a lot to think about: subject matter, focal points, prominence, figure/ground separation, distractions, tension, flow and contrast (focal, tonal, textural and color). I also discussed lenses and the effect the choice of lens length can have on the image. 

The discussion of lenses led us into the concept of acceptable focus and how to control the depth of field using aperture. 

Lastly, I discussed exposure.  I presented the use of shutter speed to both achieve proper exposure and express artistic vision. I also talked about ISO (film speed) to accommodate low light conditions and control noise. 

This is a lot to think about every time I push the button on my camera. Using the initialism CDE helps me remember each of the important aspects of photography and encourages me to use an ordered process to ensure my images express my vision to the best of my abilities. 

image

(Sony α7RII, FE 24-70 @ 70mm, 0.5s, f/6.7, ISO 1600)

The concepts that I’ve presented up to now are what I consider the fundamentals of photography. With a bit of thought and practice they can be understood and integrated into a shooting routine but to truly master them could take years. Occasionally I fail to achieve an objective for a shoot and find myself having to go back and remind myself to follow the CDE process.  

Exposure Triangle

February 18th, 2020

Back on January 14, 2020 I introduced the exposure triangle. Since then I’ve discussed the relationship between aperture and shutter speed; now I’ll expand the discussion to include ISO. 

image

I mentioned that there are numerous aperture/shutter speed combinations that will produce a properly exposed image. Adding ISO to the mix allows even more combinations, as is represented by the green plane in the graphic above. 

ISO settings have a direct and noticeable effect on the noise (or grainy-ness) of an image, therefore a specific ISO setting is most often chosen to adjust for the available light, with low ISO values being favored. I generally leave my ISO set on a low value, usually 100, and only increase it when needed to accommodate low light conditions. 

This image from the Oakley Rodeo, which I presented last week, was shot at night using the stadium’s lights. I needed to use a relatively fast shutter speed (1/250s) to freeze the action and stabilize the camera. (I was shooting hand-held using an approximately 200mm image stabilized lens.) I wanted to stop down the aperture slightly (to f/6.7) to provide me with a decent depth of field. Therefore, to achieve proper exposure, I needed to boost the ISO significantly, to 12800.

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(Canon 5DMII, EF70-300 DO @ 210mm, f/6.7, 1/250s, ISO 12800)

As an artist working in the photographic medium it is important to have a solid understanding the exposure triangle and the relationship between aperture, shutter speed and film speed (ISO). 

Film Speed (ISO)

February 11th, 2020

Film speed is a term that’s not used much any more but I feel it better describes the concept we need to discuss than the more common, current term ISO. Film speed refers to how sensitive the film, or digital sensor, is to light. 

Back in the day, film was manufactured with silver halide grains which are light sensitive. Film with large grains was called fast film because it would expose quickly; or to state it another way, it would work well in low-light. Slow film, with small silver halide grains, would take more time to expose properly and could therefore be used in bright-light (daylight) conditions.  

Over the decades there have been many ranking systems that provided a relative assessment of how fast film would expose. Two of the more common ones were ASA and DIN. These various rating systems were combined and superseded in 1974 by a collection of ISO standards. (ISO is the acronym for the International Organization for Standardization which addresses not just photography but provides standards on a huge range of topics.) 

The size of the light sensing pixels in a digital sensor is set when the sensor is created/built and can’t easily be swapped out like with a roll of film. Therefore manufacturers of digital cameras have come up with other creative ways to mimic or emulate film speed within a digital camera. Some of the ways include altering the sensor’s voltage, analog and digital amplification. All of these ways have benefits and limitations; there is no panacea. 

The detailed complexities of how these methods work aren’t critical for our discussion but suffice it to say that in general terms they all decrease the signal to noise ration. The result is an increase in the signal (our picture) but also an increase in the noise. 

Consider this picture shot at the Oakley, UT 4th of July rodeo. 

image

(Canon 5DMII, EF70-300 DO @ 210mm, f/6.7, 1/250s, ISO 12800)

I boosted the ISO to 12800 to adjust for the conditions, which allowed me to take the shot, but doing so resulted in significant noise in the final image. 

By zooming in on the rodeo clown’s face we can clearly see the noise.

image

Signal to Noise Ratio

February 4th, 2020

Signal to noise ratio is a measure that compares the strength of the desired signal, or useful information, to the background noise, or irrelevant information. 

To illustrate these concepts consider two scenarios. 

Imagine your hiking in a forest on a foggy day, miles from the nearest road. You and your hiking partner stop for a break and while resting you have a quiet conversation. You have no trouble hearing each other even though you’re both talking in library-voices. 

Now imagine you’re at a rip-roaring New Years Eve party; the music is loud and everyone is whooping it up, having a good time. You’re shouting into the ear of the person beside you trying to have a conversation but you’re only catching half of what they’re saying. 

In the forest you have a dramatic difference between the signal (your voice) and the background noise (the deadened sounds of the forest in fog). It is easy to pick out the sounds that make up words and you can easily carry on your conversation in hushed tones. 

The party is a radically different situation. The background noise is so loud that even shouting, it’s hard to pick out the signal from the noise. 

Electricity is noisy. The electricity that powers the digital sensor in your camera causes noise. When that noise is significant as compared to the signal (the scene we’re shooting) it can cause problems. An easy way to visualize the noise in your camera is to take a picture with the lens cap on. The resultant image should be a uniform field of black, but it’s not. When zoomed in you should see speckles of color and light that were triggered by the background noise in the sensor. Here’s an example shot with my Canon 5DMII. 

image

Using Shutter Speed

January 28th, 2020

Often our choice of shutter speed is dependent on available light, but that’s not what I want to talk about in this post. I want to discuss the use of shutter speed to express artistic choice in our images. Usually, this relates to capturing or expressing movement of some sort. Let’s look at a couple of examples of movement of water. 

In this image (taken at Kilauea Point National Wildlife Refuge, Hawaii) I wanted to capture the potential energy of the wave suspended in motion. I chose a relatively fast shutter speed (1/320s) in order to freeze the motion and capture the crash at the peak of it’s height. I was fortunate in that the bird, a frigate I think, flew through the frame just at the right moment to provide a focal point for the image. 

image

(Canon EOS XSi, EF-S55-250 @ 116mm, f/9, 1/320s, ISO 100)

In this next image (of a small waterfall in Kanarra Canyon, Utah) I wanted to capture the motion of the falling water. To accomplish that I used a slow shutter speed (1/2s) which succeeded in blurring the individual water drops and giving a suggestion of motion in the still frame. 

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(Samsung Galaxy S10, 4.3mm, f/1.5, 0.5s, ISO 50)

This last image, of the tufas at Mono Lake, CA, I wanted the theme of the image to be the tufas, without other distractions. I used a very long exposure (30s) to ensure that the small waves in the water would be completely averaged out and the surface of the lake rendered flat and still. 

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(Canon 5DMII, EF24-105 @ 50mm, f/6.3, 30s, ISO 500)

These three images represent some of the possibilities that can be expressed using shutter speed creatively. 

Shutter Speed

January 21st, 2020

Shutter speed is the camera setting that controls the length of time that the film or sensor is exposed to light. Standard shutter speeds are: 1, ½, ¼, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500 and 1/1000 of a second. Like the standard aperture settings these values roughly correspond to a change of one stop of light between each adjacent value.

In my last post I presented the exposure triad (aperture, shutter speed and film speed) which I’ll get to soon but to start off I’m going to ignore film speed and just discuss aperture and shutter speed.

In the following graphic the shutter speed is represented on the vertical axis with long shutter speeds (1/2s) close to the bottom and short speeds (1/500s) toward the top. Aperture is depicted along the horizontal axis with small f-number (f/1.4, large aperture) toward the left side and large f-numbers (f/16, small apertures) on the right.

image

A properly exposed image is represented by the blue line which can be achieved using a variety of aperture/shutter speed combinations; two of which are show by the green and red dashed lines.

The green dashed lines represent a small f-stop (perhaps f/4) and a fast shutter speed (perhaps 1/125s) while the red dashed lines represent a large f-stop (perhaps f/11) and a slow shutter speed (perhaps 1/15s).

These two options will both result in a properly exposed image. In the first we have a small f-stop, i.e. large opening, that allows a lot of light into the lens (this is like filling the exposure cup with the faucet on full) which in turn requires a short shutter speed (to prevent the cup from overflowing). By comparison the other option uses a small opening (large f-stop) which allows only a trickle of light through the lens, therefore a longer shutter speed needs to be selected to allow sufficient light to pass through for full exposure.

These two combinations of settings will both produce similarly exposed images but will the images be the same? No, they won’t. As we discussed in previous posts the change in the aperture setting from f/4 to f/11 will provide significantly different depths of field.

So, which combination is correct? The answer is neither and both and it depends. It depends on what you, as the artist, consider most important to express as your vision.

Exposure

January 14th, 2020

Exposure is a measure of the amount of light reaching the image sensor during a single shutter cycle. Exposure can be thought of as water filling a cup; a properly exposed image fills the cup to the brim. An image that is under exposed hasn’t received enough light (i.e. the cup is only partially full) and an image that is over exposed has received too much light (i.e. the cup is overflowing). 

In my post of August 13, 2019 I introduced the concept of exposure and discussed how by default in auto mode the camera attempts to evaluate the light over the scene and adjust the settings to achieve middle grey, which is for most situations a properly exposed image (i.e. a full cup of water). That’s not always what we want so we can use the exposure compensation setting to override the default action to force proper exposure of lighter than average scenes (i.e. a snow field) or darker than average scenes. 

The problem with auto mode is that the camera choses settings to achieve proper exposure and we have little or no control over what settings are used. Taking the camera out of auto mode allows us to assume control of the exposure and chose specific settings to achieve our artistic view.

One of the settings that effects exposure is aperture. Opening the aperture (smaller f-number) allows more light into the camera and can brighten a dark scene to an acceptable level to properly expose the image. However, using a smaller aperture directly effects the depth of field and may not be compatible with our artistic vision. 

The key to understanding exposure is the exposure triad; which is comprised of aperture, shutter speed, and film speed (or ISO). 

image

I’ve already discussed aperture so next I’ll discuss shutter speed and then film speed.  

Artistic use of Depth of Field

January 7th, 2020

Now that we have a basic understanding of depth of field let’s talk briefly about how to use it to express your artistic vision. 

I’ve written before (October 15, 2019) about focal contrast and how our eyes are drawn to areas in an image that are contrasty, sharp and in focus. We can use that to direct the viewer’s attention within the image. 

In a portrait the area of highest importance is the subject’s eyes, which should be tack-sharp. Other areas of the image, especially the background, should be deemphasized so as to not distract from the subject. This can be accomplished by using a backdrop that is plain, in shadow or blurred. Blurring a background is trivial through the use of a large aperture (small f-number) and adequate distance between the background and the subject. 

Another artistic use of a shallow depth of field is to isolate one object out of a field of repeating objects. In the following image, taken during a Buddhist alms-giving ceremony in Chiang Mai, Thailand, I used a shallow depth of field and tonal contrast to bring the viewer’s attention to rest on the monk who is looking at the camera in the upper-right. He acts as the focal point both literally and figuratively.  

(Canon 5DMII, EF24-105 @ 105mm, 1/100s, f/4, ISO2500)

In this next image, of a group of villagers rescuing a fishing boat that sunk overnight in a storm, I used a large depth of field to help tell the full story; from the sizable anchor on the end of the rope at the right edge of the image up to the swamped boat on the left. 

(Canon 5DMII, EF24-105 @ 24mm, 1/100s, f/11, ISO 400)

I could have made other artistic choices. For example I could have used a large depth of field to emphasis the sea of monks and let the one monk with a lighter colored shawl take a lesser, but still prominent, role in the image. The apertures that I chose serve to convey the mood and message that I felt and wished to share. 

As an artist, depth of field is one of the useful tools that allow us to share our vision and interpretation of the world. 

Hyperfocal

December 31st, 2019

With regard to depth of field I should probably mention hyperfocal distance. There are actually two definitions for hyperfocal distance. 

1. The closest distance at which a lens can be focused and still have objects at infinity acceptably sharp.

2. For a lens focused at infinity, the distance beyond which all objects are acceptably sharp. 

While these two definitions result in almost the same depth of field they’re not identical (only differing by one focal length) but are interchangeable from a practicality perspective for most situations. 

When I was a kid I had a point and shoot camera that didn’t have any configuration capability; there wasn’t any way to focus the lens, change the aperture or adjust the shutter speed. Literally, point and shoot. 

When I got a bit older and starting shooting with my Dad’s full-function cameras I asked him how my no-option camera managed to get anything in focus. He introduced me to the concept of hyperfocal distance and explained that the camera was fixed at a moderate aperture (probably around f/8), had a slight wide angle lens (probably 35mm equivalent) and was permanently focused at infinity. These settings ensure acceptable results for most daylight pictures.

Current disposable cameras probably work on the same principles, though I haven’t played with them at all to verify that. 

Arthur “Weegee” Fellig, a legendary street photographer, is credited with coining the phrase “f/8 and be there”. Using an aperture of f/8 provides a reasonable large depth of field and when coupled with an appropriate focus setting allows shooting rapidly and achieving acceptable results without having to fiddle with the technical camera settings. 

(Canon 5DMII, EF24-105 @ 105mm, 1/80s, f/8, ISO 640)

Depth of Field (finally)

December 24th, 2019

Depth of field is defined as the distance between the nearest and farthest objects that are in acceptable focus. Depth of field depends on four factors: the focal length, the distance to your subject, the aperture and the circle of confusion. 

The circle of confusion is a characteristic of your camera/lens and can’t be altered so although we need to take it into account to determine the depth of field we can effectively ignore it for the rest of this discussion.

Mathematically, the depth of field is directly proportional to the distance to your subject; which means that as the distance to your subject increases so does the depth of field. For example: focusing on a city skyline will have a greater depth of field than will focusing on a flower (assuming other factors remain constant). 

Conversely, the depth of field is inversely proportional to both the size of the aperture and the focal length. Therefore, an increase in the size of the aperture (i.e. smaller f-number) decreases the depth of field and a decrease in the size of the aperture (i.e. larger f-number) increases the depth of field. Also, as the focal length increases, the depth of field shrinks. If you’re using a zoom lens (e.g. 24-70mm) moving from the wide end (24mm) to the telephoto end (70mm) will result in a reduced depth of field. 

While these statements will help you understand the basic fundamentals of depth of field and help you achieve basic goals when shooting, sometimes you need more precision. Rather than carry the mathematical formula and a calculator in your camera bag you can easily determine the depth of field for a particular set of settings using a smart-phone app. A quick search in the app store will list dozens. 

(Canon 5DMII, EF100 Macro, 1s, f/11, ISO 400)

Aperture

December 10th, 2019

An aperture is an opening, hole or gap. 

In photography the aperture is the opening in the lens that controls the amount of light passed through the lens to the sensor. The aperture, or lens opening, is  analogous to the iris in an eye; which adapts to the amount of light present in our environment.

The size of the aperture is stated as an f-number which is the ratio of the lens’s focal length to the diameter of the opening. So, a 50mm lens with a 50mm opening would have an f-number of 1, that same lens with a 25mm opening would have an f-number of 2 and with a 6.25mm opening it would have an f-number of 8. 

The use of a ratio to express the aperture is good in that it allows comparisons between apertures on lenses of different focal lengths but it also can be a source of some confusion in that the smaller numbers indicate bigger openings while the larger numbers represent smaller ones; which is somewhat counter-intuitive. 

Standard f-numbers are 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16 and 22. These values represent full stop values for a lens and are written as f/1.4, f/8, etc.

I introduced the concept of a stop as a measurement of light intensity in my blog post on July 30, 2019. In that post I explained that a stop of light is a halving or doubling of light. So altering the lens by one full stop from f/2.8 to f/4 is going to make a smaller opening and let in half as much light; adjusting from f/11 to f/8 is going to open the aperture letting in twice as much light. 

Most modern cameras allow opening or closing down the lens in more granular increments than full stops, some allowing half, third and even quarter stop increments. 

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(Lava and Ferns, Canon 5DMII, EF24-105 @ 82mm, 1/400s, f/5.6, ISO 1000)

As I mentioned in my post on November 19, ensuring proper focus across the full plane of the sensor is not a trivial task. This challenge is amplified by the need to accommodate varying apertures and is most difficult at the extremes of the aperture range of the lens. 

For example, the lens I have on my Sony a7RII is the FE 4/24-70. The 4 before the slash (/) represents the widest aperture (f/4) while the narrowest aperture is f/22. (The 24-70 is the focal length range: 24mm through 70mm). 

Lenses performs best and achieve maximum focal sharpness at the middle of their aperture range–in this example about f/8 or f/11–while it will be least sharp at the extremes. In a high-quality lens the fall-off will be minimal and perhaps even unnoticeable to the naked eye. 

There are times when using an extreme aperture (e.g. f/22) is desirable or necessary but knowing and shooting in the sweet-spot for your lens will help ensure tack sharp images.

Circle of Confusion

December 3rd, 2019

As I’ve stated, a lens can only focus on one distance and everything at other distances will be out of focus. There are regions close to the focal plane that are so close to being in focus that we can’t tell that they’re not. 

Suppose that I focus on a point-subject 20 feet away and that my camera settings are rendering everything farther than 30 feet away as completely blurry. In this situation a point 1/8th inch past 20 feet is mathematically going to be out of focus but not by much. In fact, even if I inspect the photo at high magnification I might not be able to tell that the spot, which is just slightly out of focus, is any more out of focus than the spot 1/8th inch closer at the plane of focus. This is due to the optical abilities of the lens, the resolution offered by the sensor and the resolution capabilities of my print/display medium. 

All of these factor contribute to slightly distort a perfect dot/point and fuzzy-it-up a bit making it indistinguishable from an adjacent dot that is fuzzyed-up by being slightly out of focus. The fuzzing-up of in focus dots as compared to truly out of focus dots is the basis of the circle of confusion.  

The circle of confusion is defined as the largest blur spot that will still be perceived as a point by the human eye. As photographers we can take advantage of the circle of confusion and use it to make our images appear to be more in focus than they are. 

We do this by adjusting the lens aperture to achieve the desired depth of field that gives us acceptable focus over the range in the scene that we want sharp.  

image

(Fujifilm X100T, 1/125s, f/11, ISO 200, IR Conversion)

Acceptable Focus

November 26th, 2019

Let’s assume our lens provides a focal plane that is free from edge distortion and achieves even focus across the entire sensor (which is what I discussed in my last post). That’s all good and fine and we’ll get great pictures if the subject we’re photographing is a flat object. For example, if we’re taking a picture of a painting it’s a simple matter to square up the camera/lens in front of the painting, focus the lens, push the button and get an image that’s in focus from edge to edge. 

However, the focal plane applies to both sides of the lens: both the inside of the camera and outside of it, looking forward toward the subject. 

The focal plane on the inside of the camera (i.e. the sensor) is always flat. The focal plane on the outside, the subject, rarely is. When you focus the lens on a subject 20 feet away, that same point on the sensor will be in focus but… every other point in the scene, that’s not 20 feet away, will be out of focus. 

Consider this image of my nephew, Cody, performing at Kilby Court in Salt Lake City, Utah. The narrow depth of field is apparent as the microphone and his face are sharp and in focus while the head of his guitar and the backdrop are very out of focus.  

image

(Canon 5DMII, 50mm, 1/60s, f/4, ISO 1600)

Mathematically lenses can only focus at one focal length but we can use other characteristics of the lens to achieve acceptable focus across a depth. 

Now consider this image of salt encrusted posts in a pond adjacent to the Great Salt Lake in Utah. This image has a much more extensive focal depth. Notice the reflection of the nearest post is reasonably sharp all the way down its length and the salt layers at the base of the post are quite sharp well into the upper third of the image. 

image

(Canon 5DMII, EF24-105 @ 65 mm, 1/320s, f/16, ISO 400)

(Neither of these images look very sharp as rendered in low resolution through this blog, but trust me, they are as described.)

Notice in both of these images that the focus fades slowly from sharp to semi-blurry to blurry, although at different rates. The rate of fading allows us to achieve acceptable focus over the critical or important part of the image. 

Focal Plane

November 19th, 2019

We’ve been talking about composition and, in the last few posts, about lenses as they relate to composition. Now we need to expand our discussion of lenses and talk about lenses as they relate to depth of field

In previous posts I’ve mentioned focal length, which is the distance over which a lens converges light rays. In these previous discussions, though I didn’t explicitly state it, we assumed that the light was being focused to a single point. But that’s not realistic. Since the sensor in your camera is flat and occupies an area something larger than a single point, in some cases quite a bit larger, it follows that the lens needs to achieve not just a single point of focus on the sensor but an entire plane of focus that covers the entire surface area of the sensor. This is the focal plane

Lenses are typically constructed from multiple layers of glass (or some other translucent material) where each surface of each layer is ground to an either concave or convex shape to promote and achieve proper focusing. The objective is to ensure that light rays of varying wave lengths passing through both the center and edges of the lens all arrive and focus at the flat plane of the sensor. This is not a trivial task. 

Viewing an image shot through a cheap, poorly constructed lens might reveal a variety of defects including blurry edges and fringing (where different colors of light don’t focus on the same plane). In a quality lens these effects should be minimized or non-existent. 

Zoom, Zoom

November 12th, 2019

When standing in front of a scene you’d like to capture photographically an early decision that needs to be made is how to frame the image. 

If you’re using a fixed lens (single focal length) you have to move your physical position relative to the subject in order to adjust the framing of the composition. This is kind of a human-zoom; you walk forward to zoom in or backward to zoom out. 

When using a camera that has a zoom lens you have the capability to adjust the framing of the scene without physically moving yourself. This series of images illustrates the effect of zooming in on a subject. 

image

(Published by Nikon in Understanding Focal Lengthhttps://www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/understanding-focal-length.html)

Optical vs Digital

Digital cameras use a image sensor to capture the viewed image. Light from the subject passes through the lens and falls upon the sensor which interprets the light and captures the image. The sensor is comprised of thousands of pixels, each capable capturing a single point of light and color to be used in the rendered image. The size and density of the pixels on the sensor have a direct effect on the quality of the resultant image.

Many lower-end cameras offer two types of zooming: optical and/or digital. Optical zooming alters the resultant image using the physical capabilities of the lens to optically alter the view area to be captured. If the camera is capable of taking a 12 megapixel (MP) image, all images captured using the optical zoom will be 12 MP in size. 

Digital zoom is different. If you use digital zooming the result is a smaller number of captured pixels and therefore a smaller image, perhaps only 10 or 8 MP. The camera accomplishes digital zoom by excluding pixels on the edge of the sensor and only capturing information from the pixels in the center.  The end result of using digital zoom is as if you took a full sensor image and cropped the result later using image processing software (e.g. Lightroom). 

Some cameras include software that will automatically expand a digitally zoomed image to match the pixel count of a full-size image (in the case discussed here: 12MP). The full-sized image is built off the reduced set of pixels from the center of the sensor and can only provide the resolution/detail available in those pixels. Again, the same results can be achieved post-capture using a full-sized image and image processing software.