Ed Schlotzhauer

An artists journey

Category: Mastery

It’s A Green World
That’s not an environmental statement. As far as our cameras are concerned, green is the “most important” color. I’ll explain why green is foundational to our photography.
Bayer filter
In my previous article I discussed the Bayer Filter and how it allows our digital cameras to reconstruct color. I made a cryptic comment that it was important that there were twice as many green cells as red and blue, but I did not explain. I’ll try to correct that. It is fascinating and highlights some of the brilliance of the Bayer filter design.
“Bryce Bayer’s patent (U.S. Patent No. 3,971,065^[6]) in 1976 called the green photosensors luminance-sensitive elements and the red and blue ones chrominance-sensitive elements. He used twice as many green elements as red or blue to mimic the physiology of the human eye. The luminance perception of the human retina uses M and L cone cells combined, during daylight vision, which are most sensitive to green light. ” This is quoted from Wikipedia. Let me try to unpack it a little.
Color description
There are several ways to describe color. Some, like the HSV or HSB or Lab models, separate the concepts of luminance and chrominance. Luminance is the tonal variation of a scene, the brightness range from black to white. Hue and saturation define the color value and purity.
It is all very complicated and, in reality, only interesting to color scientists. I strongly recommend you view this great video that explains how the CIE-1931 diagram was created and what it means. It answered a lot of my questions. As photographers and artists we have to be familiar with some of it. For instance, we have all seen a color wheel like this:
This is a simplified slice through the HSV space at a constant, maximum lightness. Such a model is useful to us because it shows all colors with their most saturated form at the outer edge and least saturated (white, colorless) in the center.
Our eyes
This is nice, but it is all possible colors, not what we really see. As the quote above about Bayer said, the eye is most sensitive to green. Green is right in the middle of the range of light we are sensitive to, the visible spectrum. Here is a plot of our sensitivity to visible color:
From: https://lightcolourvision.org/wp-content/uploads/09550-0-A-BL-EN-Sensitivity-of-Human-Eye-to-Visible-Light-80.jpg
It is clear to see, just as Mr. Bayer said, we are most sensitive to green. This is why there are twice as many green cells in the Bayer filter as red and blue. The green is used to measure the luminance, the tone range of the image. This information is critical to deriving the image detail plus the color information through a complex set of transformations.
Why is is so important to get a good measure of luminance? Because of another interesting property of the eye. We are more sensitive to luminance than color. Luminance gives detail. Think of a black and white picture you like. That image is pure luminance information, no color information at all. Yet we see all the fantastic detail and subtle tones perfectly.
Color adds a lot of interest to some images, but we can recognize most subjects perfectly well without it. The opposite is not true in general. If you took all the luminance information out of one of your images it is basically unrecognizable.
Example
Here is a quick example of a typical outdoor scene here in the Colorado mountains. This is the original image:
If I convert it to Lab mode and take just the luminance channel (L) we get a black & white version containing all the detail and tone variation that makes it recognizable:
But now if I copy just the color information (the a and b channels) it is … surreal?:
Why green?
I hope I have demonstrated some of the reasoning behind the Bayer filter. It is a key to our ability to capture color information with our cameras.
The human eye really is most sensitive to green. Having half the color filters in the Bayer filter array as green allows maximum ability to construct the luminance data we are so sensitive to. The magic of the sophisticated built in data processing algorithms let the Raw file converters take all this information and derive the luninance and color information we rely on for our images.
Does this mean we should shoot more green subjects? No. I don’t. Many on my images have little discernible green in them. Take the image at the top of this article. I love the colors in this mountain stream. I don’t look at it and think “green”. The color range is very full, though.
As I write this it is the depth of winter here. Much of the shooting I do right now is very monochrome, almost black and white. The Bayer filter is not there to make our images more green. But if you look at your histogram or channels you may be surprised at how much green data is there. Think about it, a black and white image is 33% green.
Thank you Mr. Bayer and all the scientists and engineers who have done such a great job of perfecting our digital sensing over the decades. You are doing an excellent job!
March 9, 2022
How We Get Color Images
Have you ever considered that that great sensor in your camera only sees in black & white? How, then, do we get color images? It turns out that there is some very interesting and complicated Engineering involved behind the scenes. I will try to give an idea of it without getting too technical.
Sensor
I have discussed digital camera sensors before. They are marvelous, unbelievably complicated and sophisticated chips. But they are, still, a passive collector of photons (light) that falls on them.
An individual imaging site is a small area that collects light and turns it into an electrical signal that can be read and stored. The sensor packs an unimaginable number of these sites into a chip. A “full frame” sensor has an imaging area of 24mm x 36mm, approximately 1 inch by 1.5 inch. My sensor divides that area into 47 million image sites, or pixels. It is called “full frame” because that was the historical size of a 35mm film frame.
But, and this is what most of us miss, the sensor is color blind. It receives and records all frequencies in the visible range. In the film days it would be called panchromatic. That is just a fancy word to say it records in black & white all the tones we typically see across all the colors.
This would be awesome if we only shot black & white. Most of us would reject that.
Need to introduce selective color
So to be able to give us color, the sensor needs to be able to selectively respond to the color ranges we perceive. This is typically Red, Green, and Blue, since these are “primary” colors that can be mixed to create the whole range.
Several techniques have been proposed and tried. A commercially successful implementation is Sigma’s Foveon design. It basically stacks three sensor chips on top of each other. The layers are designed so that shorter wavelengths (blue) are absorbed by the top layer, medium wavelengths (green) are absorbed by the middle layer, and long wavelengths (red) are absorbed by the bottom layer. A very cleaver idea, but it is expensive to manufacture and has problems with noise.
Perfect color separation could be achieved using three sensors with a large color filter over each. Unfortunately this requires a very complex and precise arrangement of mirrors or prisms to split the incoming light to the three sensors. In the process, it reduces the amount of light hitting each sensor, causing problems with image capture range and noise. It is also very difficult and expensive to manufacture and requires 3 full size sensors. Since the sensor is usually the most expensive component of a camera, this prices it out of competition.
Other things have been tried, such as a spinning color wheel over the sensor. If the exposure is captured in sync with the wheel rotation then 3 images could be exposed in rapid sequence giving the 3 colors. Obviously this imposes a lot of limitations on photographers, since the rotation speed has to match the shutter speed. A real problem for very long or very short exposures or moving subjects.
Bayer filter
Thankfully, a practical solution was developed by Bryce Bayer of Kodak. It was patented in 1976, but the patent has expired and the design is freely used by almost all camera manufacturers.
The brilliance of this was to enable color sensing with a single sensor by placing a color filter array (CFA) over the sensor to make each pixel site respond to only one color. You may have seen pictures of it. Here is a representation of the design:
Bayer Filter Array, from Richard Butler, DPReview Mar 29, 2017
The gray grid at the bottom represents the sensor. Each cell is a photo site. Directly over the sensor has been placed an array of colored filters. One filter above each photo site. Each filter is either red or green or blue. Note that there are twice as many green filters as either red or blue. This is important.
But wait, we expect that each pixel in our image contains full RGB color information. With this filter array each pixel only sees one color. How does this work?
It works through some brilliant Engineering with a bit of magic sprinkled in. Full color information for each pixel is constructed by interpolating based on the colors of surrounding pixels.
Restore resolution
Some sophisticated calculations have to be done to calculate the color information for each pixel. This makes each pixel end up with full RGB color values. The process is termed “demosaicking” in tech speak.
I promised to keep it simple. Here is a very simple illustration. In the figure below, if we wanted to derive a value of green for the cell in the center, labeled 5, we could average the green values of the surrounding cells. So an estimate of the green value for cell red5 is (green2+green6+green8+green4)/4
From Demosaicking: Color Filter Array Interpolation, IEEE Signal Processing Magazine, January 2005
This is a very oversimplified description. If you want to get in a little deeper here is an article that talks about some of the considerations without getting too mathematical. Or this one is much deeper but has some good information.
The real world is much more messy. Many special cases have to be accounted for. For instance, sharp edges have to be dealt with specially to avoid color fringing problems. Many other considerations such as balancing the colors complicate the algorithms. It is very sophisticated. The algorithms have been tweaked for over 40 years since Mr. Bayer invented the technique. They are generally very good now.
Thank you, Mr. Bayer. It has proven to be a very useful solution to a difficult problem.
All images interpolated
I want to emphasize a point that basically ALL images are interpolated to reconstruct what we see as the simple RGB data for each pixel. And this interpolation is only one step in the very complicated data transformation pipeline that gets applied to our images “behind the scenes”. This should take away the argument of some of the extreme purists who say they will do nothing in post processing to “damage” the original pixels or to “create” new ones. There really are no original pixels.
I understand your point of view. I used to embrace it, to an extent. But get over it. There is no such thing as “pure” data from your sensor, unless maybe you are using a Foveon-based camera. All images are already interpolated to “create” pixel data before you ever get a chance to even view them in your editor. In addition profiles and lens corrections and other transformations are applied,
Digital imaging is an approximation, an interpretation of the scene the camera was pointed at. The technology has improved to the point that this approximation is quite good. Based on what we have learned, though, we should have a more lenient attitude about post processing the data as much as we feel we need to. It is just data. It is not an image until we say it is, and whatever the data is at that point defines the image.
The image
I chose the image at the head of this article to illustrate that the Bayer filter demosaicking and other image processing steps gives us very good results. The image is detailed and with smooth, well defined color variation and good saturation. And this is a 10 year old sensor and technology. Things are even better now. I am happy with our technology and see no reason to not use it to its fullest.
Feedback?
I felt a need to balance the more philosophical, artsy topics I have been publishing with something more grounded in technology. Especially as I have advocated that the craft is as important as the creativity. I am very curious to know if this is useful to you and interesting. Is my description too simplified? Please let me know. If it is useful, please refer your friends to it. I would love to feel that I am doing useful things for people. If you have trouble with the comment section you can email me at ed@schlotzcreate.com.
March 2, 2022
Craft Completes Magic
Craft completes magic. I read this in a book on writing poetry by Robert Wallace. This was a new thought to me. It is unusual in my world for a random phrase to seem to crystalize immediately as truth. This did. I have often written about the 2 sides of art as being the creative, the magic, and the technical, the craft. I love the way this brings them together and completes the whole.
The magic
Oftentimes we artists focus almost exclusively on the creative aspects of what we do. After all, we think this is what separated us from other artists. And to a large degree, it is true.
So we look at the work of others we admire. We plan or write or set projects to focus our thoughts. We look for the new and different. The driving challenge is how can we bring a unique perspective to the things we see in the world.
Sometimes the muse visits us and we feel we have truly made magic. It is a great feeling. Creativity breeds creativity. We try to go on to leverage this new stage into even more.
But, have you ever had a guilty feeling, looking at your new creative work, that it could have been executed better? Not necessarily more creatively, but with better craftsmanship? Sometimes we don’t know how to make our great idea into a finished work of art. Concentrating too much on just one aspect can throw us off balance.
The craft
I believe our craftsmanship is as important as our creativity. Not a replacement, but to balance and complete our work. It’s this completion I want to emphasize.
There are 2 tendencies I see in a lot of photographers that disturb me. Some seem to feel that a technically perfect image is a good image. Some others take the attitude that “I’m a creative, I don’t know the ‘techie’ stuff”. I believe that either of these, if they drive your behavior too much, lead to bad ends.
Ansel Adams famously said “There’s nothing worse than a sharp image of a fuzzy concept.” This, to me, is the danger of overemphasizing technical perfection. I see this a lot in online critiques where the objections are things like not enough depth of field or that the color correction may not be completely true to the original scene. The reality in many cases is that no amount of technical improvement is going to give this image life.
If you don’t have an emotional connection with the scene and a definite point of view to share, then it isn’t going to get great by technical skill.
On the other hand, it frustrates me to hear even professional photographers dismissively say they don’t do “tech”. Sorry, but photography is a uniquely technical art form. If you don’t understand and appreciate and know how to control the technical aspects you are at a severe disadvantage. You can end up with images that show a great idea but you were unable to produce a gallery-worthy image.
The whole
There is a symbiotic relationship between the creative and the craft. Mr. Wallace, who I quoted at the start, related it to the two legs of a runner. The creative leg propels you forward. Then the craft leg helps you bring it into being, which also thrusts you forward to another level. These work together, alternating, each with strengths to add. Neither is complete without the other.
A comedian doesn’t just walk out on stage and think up funny things. He spends many hours on each skit, refining and rehearsing and tuning it before you ever hear it. Likewise, a magician spends countless hours working on an illusion to make it smooth and believable, to make the magic happen. A musician practices day in and day out for years to get and stay good. Yes, famous musicians still practice scales. It trains their technique.
Art is hard work. It is hard to do creative things and it requires great skill to make it real. No one can tell you what you can or can’t do, or how you should do your art. But I believe that if we don’t put in as much work on the craft side of our art as on the creative we will never achieve what we could.
A boring image will never be great because it was technically perfect. On the other hand, you don’t get a free pass to ignore the craft because you are a “creative”. As the initial quote says, craft completes the magic.
February 23, 2022
Cooking
No, you’re not in the wrong place. I have not suddenly changed from writing about art and photography to giving cooking lessons. I am exploring an idea that occurred to me recently. I think our cooking style reflects our photographic style, and maybe vise versa.
Weird, but stay with me for a minute.
Cooking styles
Do you cook? I hope so. It is rewarding and satisfying. A kind of art in itself.
What kind of cook are you? Do you follow the “rules” (e.g. follow the recipes) or do you “wing it”? Is your pantry and refrigerator well stocked so you can always come up with something? Or do you take your recipe to the store and buy what you need for it? Is your goal to exactly recreate the dish as specified in the recipe or do you apply creative license? Do you plan our the week or months meal list ahead of time or do you come home and try to decide what is for dinner that night?
We are all in different situations and make different tradeoffs. For instance, if you are cooking for a large family you tend to do things different than if you are cooking for one or two. If you are cooking for someone with food restrictions you may have to plan more carefully.
I’m intrigued by the idea that how we cook gives some insight on us as an artist. I think you will see where I lean in my thinking.
Recipe follower
Some people follow recipes exactly. They will not even try it unless they have all the ingredients and equipment necessary before starting.
If you exactly follow the recipe I think that says something about your style. Could it mean you are likely to follow influential artists and try to create in their style? Do you enjoy going to workshops where a leader will guide you to locations and help you compose shots to get similar results as theirs?
Maybe this means you also browse social media and photo sites looking for images you like to give yourself ideas for your work. Is your reaction “I wish I had shot that; I’ll try to do it”? Then research the location so you can plan to go there and capture something similar.
Recipe is a suggestion
Another approach I observe is the cook who looks at recipes, but mostly for motivation and ideas. They will freely substitute ingredients and end up with something substantially different from the recipe. Good, but not the same.
This cook, I believe, has greater confidence and experience. They know they can cook. That is not the issue. What I want to make tonight and how do I like it seems to be the basis of their decisions. A recipe, to them, is a kind of general guide. Descriptive, not prescriptive, to get sociological.
The recipe calls for an ingredient they don’t care for, so they substitute something else. It calls for something they don’t have, so they use something they have on hand. Not random substitutions, but based on knowledge of the ingredients and their effect on the dish. All the while, they know they will create something good, regardless of how close to the recipe it is.
Artistically, it seems this person is more likely to say yes, thanks, but I see it a little different. I’m going to shoot this other view. They have the confidence to follow their own vision, even if an instructor is trying to lead them in a different way.
What recipe?
Another cooking style I see is someone who seldom if ever consults a recipe. After all, most cuisine styles are fairly simple. There are general principle about how to combine things and what things go together to create certain flavors. Italian food has certain patterns based on certain ingredients, as does Mexican or Chinese or most any other recognizable type. When you learn the patterns almost any dish can be created. Most dishes are variations on the pattern. No recipe needed.
This person is experienced and confident. They can go into their pantry and quickly envision a dish based on what is there. If they served it to you, you would probably say “that is very good. What is it?”. And they would just say it is an Italian inspired dish they made up.
As an artist, they probably would not be in the instructor led workshop. They would just be out on their own, following their own muse, confident in their own decisions and style. Their attitude would be that they may not be as good as that instructor, but they would rather make their own decisions and go their own way.
The best style
Which of these styles is best? I think it is impossible to say. What you are is what is best for you.
But I wonder if there is a progression? When we start don’t we strictly follow recipes? As we get more confidence and experience perhaps we learn to be more free with the recipe. Eventually we learn the principles well enough that we give ourselves wide latitude in creating according to our own tastes.
I will admit that, in cooking, I am somewhere between the “recipe is a suggestion” and “what recipe?”. I have extensive files of recipes and cook books that I used to follow. If I have something in mind to fix I may still consult a recipe, but more for inspiration and to get an idea of what ingredients the recipe designer used. When the cooking starts I am likely to set the recipe aside and “wing it”. What I serve may only slightly resemble the original, but it will be good. 🙂
No one told me how
This comes around to a fundamental truth of being an artist: you are on your own. You are solely responsible for your art. No one can make the artistic decisions for you. It is a lonely but empowering place.
You can either spend your time copying your favorite teacher or develop the skill and confidence to go your own way. Until you find your own way it is not really your art yet.
Even when you are determined to be your own person, it doesn’t come with instructions. It can be very difficult and unsettling: this or that subject, what treatment or color palette, reject what I used to do and go a different direction? No one is there to guide you. It really is a “the buck stops here” situation.
Hence, the idea that the person who can endure, even thrive, in this situation probably also expresses himself in his cooking. I believe the artist is often comfortable also making creative decisions in the kitchen. Recipes become unnecessarily restrictive – just another set of rules.
Unscientific
If you haven’t thought it already, let me be the first to say this is totally unscientific. It is my hypothesis. My own idea. I do not intend to do a scientific study to prove or disprove it. I just put this out here to help us understand ourselves better as artists. Let’s just think about it and kick it around.
I don’t want you to perceive this as a black & white, all or nothing proposition. It is more a metaphor of art. For instance, if I am trying a new recipe for a dish I am unfamiliar with, I usually follow a recipe. Once. 🙂
What do you think? Is there any correlation between artists and their cooking style? Let’s discuss it! I want to hear from you!
Excuse me for now, though. I have to go home and figure out what is for dinner.
February 9, 2022
Beautiful Chaos
I am thinking about some words by William Neill in his book Light on the Landscape, combined with an old country song by Diamond Rio named Beautiful Mess. I’m referring to the visual chaos of the normal world around us. Managing this chaos is one of the great challenges and rewards of outdoor photography.
Visual chaos
Alas, the world outside is a chaotic place visually. Things just aren’t naturally arranged to make it convenient for us poor outdoor photographers. Plants are in the way. Trees aren’t in the right place for the best design. Rivers bend the wrong way. Clouds are too much or not enough or arranged wrong. Weather doesn’t cooperate. Sigh.
I say that facetiously, of course. That chaos and the difficulty of making something pleasing out of a cluttered scene is one of the unique and challenging parts of photography. If it was too easy it would be difficult to create outstanding images.
Bringing order
I love this challenge. The inner designer in me rises to it. It is a very satisfying mental exercise to try to mold a chaotic scene into a clean and appealing image. This is one of the defining characteristics of photography. Painters start with a blank canvas and selectively add only the elements they want for their scene. But photographers must start with an existing, disordered scene and simplify it.
We have many techniques to apply to do this. Lens selection will widen or narrow our field of view. We can change our point of view to include significant parts or exclude distracting elements. Selective focus can emphasize the areas of attention. Exposure can be used to darken or blow out parts of the frame where you don’t want any detail. Long exposure can change moving elements into a different graphical design. These and other techniques give us great control over the arrangements of the parts.
But above all, it is a design challenge. We have to decide what is key to the scene and how to emphasize that and minimize distractions. Is it the S curve of a river or the graphical arrangement of branches? Is it the forms or the leading lines that draw the eye a certain way? Most scenes can be arranged to bring an interesting view. Some more than others, but most can be improved.
Refine
Following on from a previous post, we need to very consciously work to refine our design after we set it up. This is a weakness of mine that I plan to improve. I have long training in composition. When I walk up to a scene I tend to do a tremendous amount of subconscious evaluation to select a composition. My natural tendency is to set up and shoot what I visualized as I came on the scene and stop without taking it further.
But I know that many designs can be enhanced by exploring variations. I will try to discipline myself to do this more diligently. Move – left, right, up, down – look for improvements in the composition with slight shifts. Look closely at the entire frame to make sure there are no distracting elements that could be eliminated by in-camera techniques. Walk more to see if a more dramatic change of viewpoint could help.
Most of all, I need to make sure I look and think. What I have is good, but can I make it better?
Don’t over analyze
A caution, though. Don’t over analyze the situation. Design and creation should be an act of joy. When you are learning new techniques it is normal to have to concentrate a lot on what you are doing. But try to get to the point where it flows naturally. To where you move with it and follow your instincts. Trust your instincts.
Shooting in the outdoors should be energizing. We should feel excited about what we are seeing and capturing. Don’t let the joy get sucked out for you. Creativity is exciting and invigorating. Most of us aren’t going to get rich at this. We should at least have fun and feel satisfied.
This is a journey of discovery. Enjoy the journey and have fun!
Note on the image
The image in this article is personally satisfying to me. It is a location that brings me joy and that i return to as often as possible. Despite wading through mud, swatting mosquitoes and trying not to slip in and get swept downstream, I loved the scene. I did follow my advice in 2 significant ways: I worked it until I got to a composition I loved, and I had a great time.
I hope you will find scenes that bring you such joy.
February 2, 2022