Ed Schlotzhauer

An artists journey

Tag: photographic technology

The Color Is…
Color is one of the major considerations in our photo processing. And it can be hard. Have you ever considered how many tools and settings there are to control color in Lightroom and Photoshop?
But where are you on the color concern spectrum? For you, is color:
1. Critical. It must exactly match
2. Important
3. An annoyance
4. Just a design variable
5. Don’t care
Why do we need to change it?
Despite all of the great technology we have, color is still an imprecise and slippery thing to deal with. Different camera manufacturers often create their own unique ‘look”. Fuji, for instance, has profiles built in for some of their famous films (remember Velvia?). But because of different technology and processing tradeoffs, there are subtle differences between, say, Nikon and Canon. There are even small variations between samples of the same camera model,
The color variations are magnified as we move further along the processing chain. What we see is greatly influenced by the decision to shoot RAW or JPEG, and if JPEG, what color balance is chosen. And is our monitor calibrated to ensure it correctly represents the colors in the digital file?
Finally, when we make a print everything can change drastically. The print is strongly influenced by the paper we choose and the printer’s ink set. Using good profiles for the printer and paper combination helps to produce an output that is “similar” to what we edited on screen, but it will never be the same. Just the move from illuminated pixels in RGB space to reflected light from a paper substrate in CMYK space means they can never be exactly the same. The physics is completely different.
The variations along the way are the process of color correcting the image.
Most of us do not see or pay much attention to these differences. The importance to us depends on our application.
©Ed Schlotzhauer
Tools
The color correction tool chain starts back in our camera. Specifically, the color balance setting.
The color of the light on our scene varies greatly in different conditions. Bright sunlight is completely different from open shade, as is a cloudy, overcast day. Indoors under tungsten or fluorescent lighting and. even LED’s give different color casts.
Out eye/brain automatically adjusts for most of these differences, but the camera does not. The color balance setting in the camera is a means to dial out the color casts. But this is only useful for JPEG images and the preview we see in camera. Color balance has no effect on RAW images. Those compensations are made in our image editing software.
My camera stays set to Auto White Balance. I only shoot RAW, so it has little effect on my processing or results.
Lightroom
When I say “Lightroom” that is a shorthand for “Lightroom Classic”. That is the only version I care about. But I”m pretty sure everything I say about it applies to both applications. There are differences in color representations in other RAW image processors like Capture One, but I do not have enough experience with them to say much.
Lightroom is packed full of ways to change the color of our image. In the Develop module you are never far from something that can modify color.
Some of the controls change color globally, that is, for the whole image. Just scanning down from top to bottom (I think my controls are still in the default order), we start with profile. This can be a simple selection of default balance or you can set any of the many provided color effects, including black & white toning.
Next there is the white balance adjustment to allow us to adapt the image to a color that should be neutral. Next to that is the color balance selection to partially compensate for lighting conditions.
Right under them is the Temp and Tint sliders. Vibrance and saturation do not actually alter colors much, but they have a strong effect on the look of colors.
Then there is the Tone Curve, where we can adjust red, green, and blue channel properties directly, followed by Color Mixer and Color Grading. Finally there is the Calibration group where we can control hue and saturation of each channel.
All of these are only the control that affect the whole image. We have many of the same controls to perform selective adjust color in regions (like a linear gradient) or spots (e.g the brush tool).
©Ed Schlotzhauer
Partly driven by the application
Hopefully, you get the impression that Lightroom gives us a lot of control of color. It must be important. I won’t even go into Photoshop with its many adjustments. I trust the point is made. This is not a “how to”.
Color adjustment is a large part of what we may deal with in post processing.
Maybe.
It depends on our application and needs.
If you are doing product photography, the customer is very concerned that the color of their logo or product absolutely matches their specification. Portrait customers have a fairly narrow tolerance for off colors in people’s faces. Or you may have a self-imposed rule that the final color must exactly match the original scene.
In these cases you are probably using gray cards or Color Checker swatches to ensure you faithfully match the original. You may even be calibrating your camera to minimize discrepancies. You will probably be using many of these Lightroom controls to adjust the colors to balance out shifts or color casts.
I’m a Fine Art Photographer
But I’m a Fine Art Photographer. I dislike that term and I’m not completely sure what it means, but I do know that what I create is art. Art is not tied to a real scene. Maybe someday I will get into a discussion on indexicality, but not today. By my definition, anything I want to do as art is acceptable.
I may not care at all about the color of the original scene. I’m certainly not fanatical about matching it or balancing color casts. My consideration is how the resulting image looks (to me) and what effect it has for the viewers.
Yet I do use most of the color controls I listed earlier. Except I very rarely use Calibrarion to adjust color, but that’s just me and my thought process. All the other controls, in global and regional and spots, are tools I use frequently.
Color is a subtle thing. Almost imperceptible shifts can create large perceived changes. It can be tricky, or impossible, to achieve an effect I have in mind. But I try.
©Ed Schlotzhauer
Not an absolute
Breaking the assumption that my image must look like the original was difficult for me. Coming from a very technical, engineering background made me think in absolutes. Precision was important. But now that the assumption is broken, it is freeing. The realities I started with no longer hinder my vision (as much).
Even so, I do not usually create comic book-like pop art. Unless I want to for some reason. But, on the other hand, I do often enjoy making images that are so extreme you will think I modified them too much, even if I did little at all.
Sometimes color is the subject. Sometimes an image “needs” to be a different color than the original. An extreme use of color modification is black & white. Yes, taking away all color and just leaving tonality is extreme color manipulation.
In the questions I posed at the start, I’m usually operating at about 4 or 5. It is a tool I can apply to accomplish my vision. Not something I am stuck with because that’s what the original was.
©Ed Schlotzhauer
Do what you need to do
Color perception is one aspect of a visual image. But it is a powerful one. With our technology, we are blessed with extreme ability to control or modify color. Don’t be afraid to use it creatively.
Unless you are working in an application that demands absolute fidelity to the original, color becomes just another design element to be used for art.
Make your art. The color is… what you need it to be.
Today’s feature image
Is this the “right” color? I don’t know. First, I didn’t have a gray card with me. Second, even if I did, I couldn’t have held it out the window at 40,000 ft. Third and most important, I don’t care.
This is what I remember seeing at the time. It is the way I chose to make the image look. It is art. I like it like that.
March 26, 2025
It’s Just a Camera
That piece of technology we use to make images, it’s just a camera. Not magic or sentient or automatic. It still needs someone to take the picture.
Brushes
I really like my camera. It is a good tool to use to make images I like. When I’m in the field, my camera is the vehicle for my creative expression.
Have you ever had someone look at one of your pictures and say “Wow, you must have a great camera”? Or see you taking pictures and say “You must be a professional, since you have a big camera.” I have. Many times. Now, I basically just smile and go on.
But if you see a painting hanging in a gallery, who looks for the artist and tells them “Man, those must be some great brushes you have.” Or, seeing a nice wood carving, tell the sculptor “you must have some really sharp chisels”.
The public has a tendency to attribute a good photograph to the camera more than to the photographer. Being a piece of technology, somehow there is the implication that the camera somehow made the picture.
As artists, we should not encourage this attitude.
©Ed Schlotzhauer
A box
At it’s most basic, a camera is a box that keeps out light. The name comes from “camera obscura”, which was a dark space, often a room, with a small opening to let in light. This caused an inverted and reversed image to be projected on the back wall. It is believed this technique has been used since 500 BC.
The first “modern” cameras were wooden boxes that had a lens on one end and a holder for coated glass plates on the other. This is how many great historical photographs were exposed.
They have certainly become much more sophisticated now, with auto focus, camera shake compensation, exposure measurement, ability to automatically set exposure parameters, etc. Too much to list. The user manual for my Nikon Z7 II is 823 pages. Astounding, but it still doesn’t take the pictures. At it’s most basic, it is still a closed box to keep light off the sensor until time to record the image.
I appreciate many of the features in modern cameras. They make my art easier and extend the range I can operate in. It is great to have our little “dark spaces” getting smaller all the time. Even to becoming little flat things we can put in our pocket (phone).
I fear there will come a point where we will face some major decisions.
It’s still a tool
Right now our cameras and phones have amazing capabilities. Some of them are just basic technological advances. Some are deemed “AI”. Many of the best features are appearing first in our phones.
The ability to “sweep” our phone across a scene and have it automatically stitch together a panorama is very useful. Face detection is common now and can be useful for some types of work. An interesting feature I have seen is where, when taking a group shot, some cameras actually take many images and pick out and merge together the “best” look for everyone. At least, ones when they are smiling and their eyes are open.
Features like these make shooting pictures less technical and less stressful. Anyone can get “professional” level results. That is probably a good thing. It is an aid.©Ed Schlotzhauer
A coming “revolution”
There are still some of us who want to make the artistic decisions ourselves. Even if it is difficult and requires lots of training. Even if we make mistakes and bad choices. Those don’t matter. It is our art, our decisions, our responsibility. The technology is likely to get a lot more intrusive.
Probably right now most major camera manufacturers and all phone makers have teams of smart people trying to go all in with AI. People who actually believe in it and confidently think AI actually is or will become intelligent. Some who actually think AI can do art.
I can imagine one of the user stories they are working from: “(Camera speaking) Attach the 24-70 lens. It is best for this shot. Move me 34.7 inches left and lower me 9.3 inches. I detect a glare. Attach the lens hood. Place the subject at the Rule of Thirds point I am illuminating in the viewfinder. I will shoot it now and remove the non-subject person traversing the frame. I am also correcting the 3° tilt to the right and the overall color. Done. “
To me, this is a dystopian scene. I do not want to relinquish my artistic vision to anything, especially a machine. I am very willing to use smart tools to assist my work. In-camera features like eye identification and focus tracking can be very handy. On the computer, making it easier to make selections or to remove distractions is useful. But I do not plan to give control over to the camera to make it’s own decisions
Plasticity.
In The Interior Landscape, Guy Tal states
For any medium to be useful to an artist, it must allow a generous degree of plasticity. It must lend itself readily to subjective expression of concepts and feelings originating in the artist’s mind and not just those inherent in or commonly associated with the subject.
Mr. Tal was not referring to AI here, but I believe it applies. An AI controlled camera could probably expose images that would be regarded by most consumers as pleasing. The pictures would be a faithful and well exposed depiction of the subject. Most users would be happy. Unfortunately, the AI could not know the subjective expressions that are in my mind. It cannot know my vision and intent.
Again in The Interior Landscape, Guy Tal states
There are well-established compositional templates knows to impress viewers, requiring only mechanical skills but no expressive intent. Art raises the bar. Art requires from the artist a degree of emotional investment and an elevated subjective experience, as well as the skill to express visual concepts beyond “here’s something pretty,” “look where I’ve been,” or”see how lucky I was”.
I resonate with this concept of plasticity. It gives structure to my desire to create images that are not simply representations of what is there. I want to use the camera and other parts of the technology of photography simply as tools to help me capture what I visualize and feel.
©Ed Schlotzhauer
Make art
You might get the impression that I am not a fan of AI. Well, I definitely am not a true believer. It could be a useful tool for some things. One of the big problems is that most people do not understand its limitations, so they believe it is something it is not.
By it’s nature, AI cannot be creative. It is a compendium of what it has been trained on. The output of AI is a statistical prediction of a response given an input. So, at best, it is an average of what it has been given. It cannot think or feel or have inspiration.
I am a human. I do think, get depressed, find inspiration, feel love, and see things in my own quirky way. If those are faults compared to AI, then I readily admit to being deeply flawed. But from those flaws, and all the other strange bits of my makeup, I can create art. Because my art comes from my unique human understanding and viewpoint.
I like my camera. It is a great tool. I have actually read most of the user manual in order to know what features it has and to pick which I choose to use. The reality is that I probably only use, I would guess, less than 20% of its capabilities. That’s OK. It’s a tool, not the center of my attention.
I know that designs have gotten so good that camera manufacturers are up against boundaries of physics. It is easier to add value through new “intelligent” tricks than to expand resolution or dynamic range or reduce noise. AI is a hype magnet and a path of least resistance. I get it.
Who/What is in charge?
But if the next camera I select is bloated with AI features and the price is double because of that, I will pass. I can even envision them wanting me to pay a monthly subscription to use the features in my new camera. If these things happen, my next camera is likely to be an older, used camera with less features but better raw performance and easier manual operation. Yeah, I’m an old curmudgeon. I get to be. I’m the artist in charge.
The camera does not make images. The artist does. It will continue that way for me as long as I have something to say about it. And I do. 🙂
So modern cameras are wonderful tools. I would love to have a new one. But are you an artist or just someone who takes pictures? If you are an artist, do not forget that the camera is basically just a dark box that holds the lens and sensor in the right positions. It is an instrument allowing us to create art. The artistic intelligence is in you. Do not surrender your artistic vision to a machine.
Photography is based on technology more than most other arts. That does not mean the technology makes the art.
“The equipment of Alfred Stieglitz or Edward Weston represents less in cost and variety than many an amateur ‘can barely get along with.’ Their magnificent photographs were made with intelligence and sympathy – not with merely the machines.”
Ansel Adams
February 12, 2025
Why Do We See 255 Everywhere?
Do you ever wonder about the magic number 255 you see all over Photoshop and even in Lightroom Classic if you look? It seems like 255 pops up everywhere. Why is that? It is a strange number to choose.
It’s just a number
First let me say that at this point in time, 255 is just a number without meaning. It is the number chosen to represent the maximum value of a channel or color. Something has to be used to represent the maximum value. Looking back, 100 (as in 100%) would have probably made more sense. But we have 255.
Think of it like Fahrenheit and Centigrade scales. The boiling point of water is 212 in Fahrenheit and 100 in Centigrade. Either way, it represents the same thing, the boiling point of water. That does not change no matter how the number is represented.
So when you see 255 just read it as the maximum value of that thing. If that is the level you wish to understand, this would be a good point to stop reading this article. 🙂
Personally I hope you continue. Understanding some of the history and details of our tools can only help improve our craft.
Roots in binary
Before we go deeper I need to justify where the number 255 comes from. It is rooted in binary coding. You are probably familiar with digital notations. We have lived with it for so long it seems to permeate everything around us.
Please pardon me for going full on Geek here. I so seldom get to use my training that it is fun. A very, very brief background: when digital computers were being developed, it was found to be simpler and more reliable to create circuits that were either on or off, no in between states. This was called a bit. A piece of data that was either off or on, noted as 0 or 1. The advantage of this seemingly silly decision is that the bits could be made very small and can be operated on very fast.
©Ed Schlotzhauer
A single bit by itself isn’t very valuable. To represent realistic information and do calculations bits were combined together in larger units. The next widely used unit was 8 bits. This came to be called a “byte”. Eight bits is a byte – Geek humor.
It turns out that 8 bits is enough to start encoding useful information. For instance, it will hold 1 character. A byte is big enough to code all the upper and lower case letters, punctuation, and some special symbols. At least in English. And we will see that it holds a useful amount of image data.
Let me give a very simple description of digital value coding using 3 bits:
Each combination of the 3 on/off values is assigned a value. The encoded values range from 0 to 7.
Going back to the unit we called a byte, the 8 bits can encode 256 values, 0 to 255. This is the origin of the magic 255.
History of Photoshop
It is hard to think that there was a “before Photoshop”. Thomas Knoll needed to develop ways of doing analysis on images for his PhD thesis. In those days, nothing was available, so he taught himself programming and developed a library of operations. Here is an interesting interview with Thomas.
His brother John worked for Industrial Light and Magic. He saw applications for image processing in some things they were doing, so he encouraged Thomas to enhance his library. Eventually they decided to try to make it a product. Adobe was interested. It is amazing how things come to be.
In the days when the library, later Photoshop, was developed, the state of the art of image representation was to code each pixel as 3 8 bit values. One byte each for red, green, and blue. Each color had the value range 0 to 255. This number scheme became baked in to Photoshop and a standard metaphor of the user interface.
©Ed Schlotzhauer
Today’s data
Early digital cameras shot 8 bit images. Today, though, images and Photoshop has grown well beyond that. As an example, my Nikon Z7 II captures 14 bit data. Each red, green and blue channel is 14 bits. That is 16384 values per channel instead of 256. Some other cameras have even more bit depth.
Photoshop allows us to select if we will treat our files as 8 bit or 16 bit or 32 bit. With all these variables it could impose a huge burden on the user to deal with the actual value range of the data he is editing. Some of these numbers get to be staggering (for 32 bit data each channel has 4,294,967,296 values). Adobe chose to keep the maximum number we see at 255. In effect, it became an arbitrary measuring scale we work with across the apps.
By the way, Lightroom uses 32 bit data internally. You do not get a choice. But even in Lightroom (Classic at least) the 255 illusion peaks through in one place. Look at the Tone Curve tool. The scale is 0 to 255.
Still, it’s just a number
Fahrenheit or Centigrade. It is just an arbitrary number to represent the same thing, the boiling point of water. Adobe has kept that historical number 255 and given it the implied meaning of “maximum”. It no longer has a tie to the actual size of the data you are editing or the maximum value of an 8 bit chunk of data.
©Ed Schlotzhauer
They have done us a service in this. I would hate to think of the mental complexity I would have to go through if this number changed all over the place to be the actual values I am working with. But a simplification comes with some challenges. People tend to forget why the simplification was made. Even that one was made at all.
When you are using the curves tool and other things, freely accept 255 as meaning “maximum”. Do not forget and think that your data only goes to 255. Or that it has somehow discarded all those other wonderful bits our modern cameras give us. When someone tells you that white is 255/255/255 and seem to think that is the actual value of their data, remember that is just a number on a scale. Smile to yourself knowing you probably understand it at a deeper level than they do.
I don’t have many images in my catalog that are actually 8 bit data. I am very glad the technology has moved on in wonderful ways. And I am grateful for the simplified scale that normalizes what I see when I am working with all this data. Thank you Adobe. This is something you did right. It doesn’t matter what the number is, something had to be defined as a convenient value for “maximum”.
Today’s image
The image at the head of this is actually 8 bit. An 8 bit jpg file. All the data is actually 0 to 255. Back in 2006 that was about the best I could do with the camera I had. It’s not terrible. I like the image, but I wish I could shoot it again with a modern camera.
As a matter of fact, all the images in this article are 8 bit. I wanted to emphasize that it was a very workable system.
Side note
In today’s digital systems we seldom worry much about a few bytes. Every time I press the shutter on my camera it writes about 50 million bytes to my memory card.
I mentioned that digital bits could be made very small. As an example, Apple’s M4 processor, which is their main CPU as of this writing, has 28 Billion transistors. On one chip. That is hard to comprehend. It certainly wasn’t anticipated when Thomas Knoll developed Photoshop.
December 25, 2024
The Magic of the Lens
Do you ever stop to think about your lenses, besides wanting a shinny new one? There is a magic of the lens that we seldom consider and perhaps do not even understand.
Many constraints
My perception is colored by my background as an engineer. I see a modern lens as serving so many constraints that it is a wonder they do the job as well as they do. We expect high resolving power and “good” bokah. It needs to have a good zoom range but be small. It must be weather sealed and rugged, but inexpensive. And, of course, issues like low chromatic aberration and great edge to edge sharpness and low distortion and minimal light falloff (vignetting) and minimum flare are all givens. Oh and blazing fast auto focus, too.
The poor lens designers are in a tight place. Luckily for them computer design tools have advanced greatly. Also, new materials are available to help overcome some of the design problems of the past.
Still though, we ask a lot of a professional grade lens. Probably more than we realize.
Simple lens
We have an idea in mind of how a lens works. You probably did an experiment in High School Physics with a simple lens. Then you took it out and fried some ants.
What we normally picture is a biconvex lens. Don’t let a fancy word scare you. That just means both sides are thicker in the middle than on the edge. Like this:
By DrBob at the English-language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2065907
The rays (red lines) illustrate how the lens focuses on a point. That focusing is what images the outside world sharply onto our sensor.
This is true. It works. But nothing in life is simple anymore.
Reality
The reality is that, because of our high expectations and the piles of constraints to satisfy, real lens design has to be much more complex.
I am going to use the Nikon Z 24-120 f/4 zoom as an example. For two reasons: it is a representative high quality modern design, and I like it – a lot. It is my go-to lens for everyday use.
Lens design has gone far beyond the “simple” lens pictured above. Here is a cutaway of the Nikon lens:
Photography Life: https://photographylife.com/reviews/nikon-z-24-120mm-f-4-s
We can see that it has many lens elements (a word for a piece of glass in a lens) – 16 of them to be exact. Few of them are simple biconvex elements. Some of them are exotic glass. Things like high refractive index (they bend light more sharply than regular glass) or other properties. Some are aspherical. This means they are quite complex designs to achieve specific results. These are hard to design and manufacture. Usually they are necessary to correct for effects of other things and make the resulting image better.
Zoom
Let’s look at a few specific features. This lens has a 5x zoom range, from 24mm to 120mm. Now you would think that, for the lens to zoom 5x, it would have to get 5 times longer. This would be true for a straightforward design.
However, us users of the lens would not like that. It would have to be very big and bulky to do that. And it would be awkward when zoomed all the way out. It would be long and off balance the camera.
But complex design magic and some of those special lens elements allow them to shortcut physics. it zooms over the 5x range while only extending to less than twice it’s collapsed length. Amazing and very welcome.
Reflections
The real world is not a well behaved bundle of parallel rays coming into the lens, like in the simple lens picture above. Light is coming from everywhere. Most of it is what we want to end up on the sensor. But a lot isn’t. Light coming in from a sharp angle tends to “bounce around” inside the lens and cause a lowering of contrast. Kind of a fog look.
Modern lenses have special coatings on the glass and use some of the special types of glass i mentioned to fight this. These go a long way to canceling the reflections.
It used to be that shooting in the direction of a very bright source, like the sun would always cause unwanted internal reflections that degrade the image. Now it is amazing how little that happens. I really only worry about that if the sun is directly or nearly directly in view.
©Ed Schlotzhauer
Chromatic aberration
Chromatic aberration is something we seldom consider, except when we are getting down to the last details of a final print. One of the nasty realities of physics is that each “color” of light is a different frequency. The amount of “bend” the lens gives to light is dependent on the color (frequency) of the light. This means not all the colors focus at the same point. That’s bad.
Have you every looked very closely at magnified blowup of a sharp edge in one of your photos? Especially if it is in a high contrast lighting situation. You may see a slight fringe of green or purple around the edge. This is called chromatic aberration. Not all the colors focusing together.
One of the purposes of the exotic glass and all the elements in modern lenses is to minimize this. They do a pretty good job.
But they are not perfect. Luckily it is a simple check box in Lightroom Classic to have the software automatically remove chromatic aberration.
Other considerations
If you ever carry a camera around all day you learn to appreciate light weight. Lens designers would like to design their lenses with a very sturdy metal shell and structure. But we would not like to carry that. Modern plastics and design techniques have allowed the designers to create our lenses at a more user friendly weight while still being sturdy enough to hold up to hard use. Thank you.
Did you know that some lenses make the light come into the sensor is a certain direction to make the sensor receive the photons better? Did you know that most of our zoom lenses, especially, have quite a bit of distortion and vignetting and resolution falloff at the edges? Those are some of the things that are part of the tradeoffs. But one reason they are traded off is there’s a bit of perceptual and software slight of hand.
First, we don’t notice it much. Really. We are not as sensitive to it as you would think. Unless you spend your time photographing test charts. Second, many of us set Lightroom Classic to look at the model of the lens and automatically apply a “correction” to the image we see. Adobe has a database of lenses with mathematical models to correct their distortions. This is a good thing.
As a matter of fact, Nikon has a special deal with Adobe such that the great Z 24-70 f/2.8 lens is automatically corrected in Lightroom Classic, whether or not the user selects that. It is impossible to defeat it. Hardware and software are joining in a symbiotic relationship. Making an image is a blend of both and it will only increase with time.
Almost everything done to solve one problem creates another. This is why designs are so complex and expensive. Everything is a tradeoff. It is all a question of how good can we make this property while not letting that other one get worse than a certain level.
©Ed Schlotzhauer
Magic
I am in awe of these brilliant designers. They achieve beautiful balance. Like I said, I regularly use this example lens I have talked about and I am generally very happy with it. But let me emphasize that pure, unexcelled technical perfection is not usually my goal. A lens like this is “good enough” for 99.9% of my needs.
For me, as a user, I take the camera out and start using it. What I see and feel is more important than technology. Sometimes, though, my engineer nature kicks in and makes me marvel at the complexity. But really, I shoot and expect my great gear to capture what I want. And it usually does. Marvelous.
The magic of the. lens. Like most good magic, how it works is invisible to us. But occasionally stop to consider how lucky we are and what an incredible piece of technology we have attached to our camera body.
Feature image
The image at the top was shot with this Nikon Z 24-120mm f/4 zoom lens I have been using as an example. This is the Hotel de Ville in Paris – their Town Hall. You can’t really tell in this small jpg, but I am completely happy with the capabilities of this lens. If the opportunity arose I am sure I could make a very good 60″ print of this. Here is a section of it zoomed to 100%.
100% section, ©Ed Schlotzhauer
Let me assure you that I am not affiliated with or sponsored by Nikon. I am just using this nice lens that I use frequently as a representative example of what a modern zoom lens is and is capable of doing.
December 4, 2024
Out of Focus
A few months ago I wrote about being in focus, both technically and mentally. I want to go a little deeper into how technical focus happens in modern cameras and an an experience I had recently where what I did was out of focus.
What is focus
Technically, focus is simple when the lens is adjusted so that the part of the subject you are most interested in is sharply defined. Your lens has a focus ring to use to manually focus. Most of us probably use the camera’s built in auto focus capability. This is much more precise than my old eyes. And a lot faster than most of us can do manually.
Focusing physically moves one or more of the lens elements inside the lens barrel. This is required to adjust the focus point.
I will let you argue whether focus is an absolute, precise point or just an acceptable range. I will just say that I am swinging away from being adamant about absolute technical perfection and leaning more toward artistic judgement and intent. Set your own values you will live by.
Whether we manual focus or use auto focus, we observe in the viewfinder the image moving from a fuzzy blob a crisp, detailed representation of the scene before us. Unless we have a very old piece of technology in our camera with something called a split image viewfinder. I had this in my first SLR. It was magic and awesome for most of the subjects I shot.
The split image viewfinder showed the image sharp regardless of focus. The image was divided into 2 pieces in the central circle. The pieces were offset from each other when out of focus. Use the focus ring to bring the 2 halves into alignment and the image was sharply focused. Magic. Enough trivia, though.
Little did I know this was a type of and precursor to what we now call phase detection auto focus. Let’s get a little deeper into the technology.
How does it work?
Auto focus in a DSLR or mirrorless camera is complex and requires many precise components. But it works so well now that we tend to take it for granted.
There are 2 basic technologies in modern cameras. The older one is called contrast detection and the newer and better one is called phase detection.
I have written on histograms, a subject I consider vitally important to photography. Histograms and their interpretation are the basis of contrast detection auto focus. It is brilliantly simple in concept and in process as what we do when we are manually focusing.
If an image in the viewfinder is out of focus, the pixels are blurred together. Kind of like looking through a fog. A result is that in the histogram, the values are clustered in the center. This is an indication of low contrast. But when an image is sharp, there is a wider range of brighter and darker pixels. This illustrates it:
From https://digital-photography.com/camera/autofocus-how-it-works.php
Focus process
So conceptually, the system moves the focus a little and measures again to see if the histogram got more narrow (more out of focus) or wider (sharper) . If it got more in focus, continue moving that direction and measuring until the peak contrast if found, But if it got more out of focus, move the focus the other direction and continue the process. It is a hunting process to find the optimum focus point. Just like we do to manually focus.
Unfortunately, this process is slow. It can take seconds to arrive at the focus. This is why phase detection auto focus came to prominence.
In phase detection auto focus, some of the light coming through the lens is split off to a separate sensor. Like the split image viewfinder I mentioned above, it is further split into two paths. Through some brilliant engineering, they can determine in one measurement how far off focus is and in what direction. The focus moves there quickly. Note that in mirrorless cameras all the light goes directly to the sensor, so these auto focus sensors are built directly into the sensor.
I said that phase detection is “better” than contrast detection. That is true as far as being very fast. Actually, contrast detection can achieve more precise focus. There is a kind of system called hybrid the combines the strengths of both. I will not discuss that or go into the bewildering variety of focus areas or focus modes.
Out of focus
This is all great as far as technology goes. It works quite well in the cases it is designed for. We are lucky to have it.
But all of these systems rely on the sensor having enough light to see some contrast. It doesn’t work in the dark. Yes, there is another variation on auto focus that is called active auto focus. It shoots a red beam from the camera to illuminate the focus area. This has a very short range and does not help the scenario I’m about to describe.
Recently I was in Rocky Mountain National Park, over on the west slope where there is little light. It was full dark on a moonless night. The mountains all around provided lovely silhouettes. The stars were astonishing. Beautiful. I had to stop and get some star images.
A trailhead parking lot provided a great and convenient place to set up – wondering if those occasional sounds I heard in the dark were bears. I guess not. It was perfect. Except. There was not enough contrast to focus, even at 6400 ISO. And the viewfinder image was too noisy to be useful for manual focus. I did not have a powerful enough flashlight to cast enough light on the nearest object, over 100 yards away, to allow the focus system to work.
Adding to the problem, the lens I brought on this outing did not have a focus scale (a curse of modern zoom lens design). Normally, in low light, I switch to manual focus and set the lens to infinity for a scene like this. I guessed, but missed badly for a big section of the images. They were uselessly out of focus. I am ashamed to show an example, but like this:
©Ed Schlotzhauer
Experience is a great teacher
I write frequently advocating that we study our technology to become expert with it. And to practice, practice, practice to know how to use our gear, even in the dark. I failed. I encountered too much dark and a lens I had never tried to use in low light. The combination tripped me up. I am ashamed to admit I did not follow my own advice well enough.
But every failure is a learning opportunity, right? It can be a great motivator and reinforcer. I did some research and discovered a “hidden feature” I never knew my camera had. It should save me the next time I do this.
My Nikon camera has a setting I had never paid any attention to called “Save focus position”. When On (the default) it remembers the focus position of the current lens when the camera is turned off and restores it on wake up. But when Off – this is the brilliant part – it sets the lens to infinity on wake up. Now I will have a known infinity focus setting, even in total darkness! This setting is now in my menu shortcuts so I can access it quickly.
I would never have learned about this feature if I had not failed so spectacularly. Experience really is a great teacher.
So dig into those obscure settings you never bother with. There sometimes is gold there.
Keep learning and failing!
The featured image
That night’s shooting was not all bad. I nailed the focus on this star shot. It was purely of the stars and had no foreground. This foreground has been substituted from another blurry image that night (actually, redrawn by hand).
This is artistic expression rather than literal reality. I do that a lot. As photography progresses and matures, I believe that is more and more the norm.
October 30, 2024