Ed Schlotzhauer

An artists journey

Category: Craft

  • Black & White – in Color

    Black & White – in Color

    What? Isn’t that contradictory? Isn’t black & white is about the absence of color? I wanted to follow up on a previous article on how we get color information in our digital cameras with a nod to the purity of black and white and emphasize how it is still dependent on color.

    Remove the color filter?

    I indicated before that our sensors are panchromatic – they respond to the full range of visible light. If we want black & white images, shouldn’t we just take the color filter array off and let each photo site respond to just the grey values?

    We could, but most black & white photographers would not be happy with the results. It would be like shooting black & white film. A problem with black and white film is that it eliminates all the information that comes from color. Through interpolation of the Bayer data, we get full data for red, green and blue at each pixel position. If we removed the filter array, we would have only luminosity data. So before even starting, we would be throwing away 2/3 of the data available in our image.

    At that point we would have to resort to placing colored filters over the lens, like black & white shooters of old had to do. They did this to “push” the tonal separation in certain directions for the results they wanted. But this filter is global. It affects the whole image rather than being able to do it selectively as we can with digital processing. And it is an irreversible decision we would have to make while we were shooting. Why go backward?

    What makes a good b&w image?

    Black & white images are a very large and important sub-genre of photography. The styles and results cover a huge range. But I will generalize and say that typically the artists want to achieve a full range of black to white tones in each image with good separation. Think Ansel Adams prints.

    Tones refer to the shades of grey in the resulting print. We do a lot of work to selectively control how these tones relate to each other. Typically we want rich black with a little detail preserved in them, bright whites, also containing a little detail, and a full range of distinct tones in between. These mid-range tones give us all the detail and shading.

    Tone separation

    If one of the goals of black & white photographers is to have high control of the tones, how do we do that? Typically by using the color information. I mentioned putting colored filters over the lens. This was the “way back” solution.

    Landscape photographers like Ansel Adams often used a dark red filter to help get the deep toned skies they were known for. Red blocks blue light, forcing all the blue tones toward black.

    Digital processing gives us far more control and selectivity than the film photographers had. We don’t have to put the filter over the whole lens and try to envision what the result will be. We can wait and do it on our computer where we have more control, immediate previews, and undo. But all this control would be impossible without having a full color image to work with. As a matter of fact, modern b&w processing starts by working on the color image. Initial tone and range corrections are done in color. Good color makes good b&w.

    B&W conversion

    Obviously, at some point the color image has to be “mapped” to b&w. This is called b&w conversion. It can be a complicated process. There are many ways to go about the conversion, and each artist has their own favorites. There is no one size fits all.

    It is possible to just desaturate the image. This uses a fairly dumb algorithm to just remove the color. It is fast and easy, but it is usually about the worst way to make a good b&w image.

    You could use the channels as a source of the conversion. The RGB colors are composed of red, green and blue channels. These can be viewed and manipulated directly in Photoshop. They can often be useful for isolating certain colors to work on. Isolating the red channel would be like putting a strong red filter over the lens.

    Lightroom and Photoshop have built in b&w conversion tools. In LIghtroom, choose the Black & White treatment in the Basic panel of the Develop module. This has an interesting optional set of “treatments” to choose from in the grid control right under it. In Photoshop use the B&W adjustment layer.

    Both of these have the power of allowing color-selective adjustments. This is huge. Tonal relationships can be controlled to a much greater degree than was possible with film. If we want to just make what were the yellow colors brighter, we can do that. Of course, Photoshop allows using multiple layers with masking to exert even more control.

    There are many other techniques, such as channel mixing or gradient maps or plug-ins like Silver Effects to give different and added control. It is actually an embarrassment of riches. This is a great time to be a b&w photographer.

    It starts with color

    What is common to all of this, though, is that it starts from the color information. Color is key to making most great black & white images.

    I sometimes hear a photographer say “that image doesn’t work well in color, convert it to b&w”. Sometimes that works, but I believe it is a bad attitude. B&w is not a means of salvaging mediocre color images. We should select images with a rich spread of tones, great graphic forms, and good color information allowing pleasing tonal separation. Black & white is its own special medium. Remember, though, usually it requires color to work.

  • What the Camera Sees

    What the Camera Sees

    One of the important things every photographer has to learn is to see what the camera sees. It is a different process from painting or other visual art. It is a technical process, not only of how the sensor works but the transform of a 3 dimensional world to a 2 dimensional representation. This is part of our art. We have to understand it and be able to predict the results.

    Static image

    Unless you are shooting video, the end result of the camera’s capture is a static image. That seems like a “duh” to most of us, but it is significant. The entire image is recorded “in one instant”. Yes, I’m ignoring moving shutter slit, HDR, panoramas, time exposures, and other exceptions that can bend the rules.

    This “in one instant” is significant because our eyes work in a totally different way. We can only see a small spot at a time. We continually “scan” around a scene to “see” it all. Our brain stitches all these scans together marvelously to give us the impression of a complete scene. We are not aware of it happening.

    What difference does it make? Well, there are subtleties. If something moves in real life, our eyes jump to the movement and study it. Movement has a higher priority in our brains than static things.

    Our photograph no longer has that movement or flashing lights. It is a flat and static collection of pixels. We have to learn techniques to stimulate the viewer’s eye in other ways. We learn that the eye is drawn to the brightest or highest contrast areas. That informs how to capture the scene and process it to end up with results that help direct our viewer to the parts of the image we want to emphasize. It helps a lot to anticipate what we are going to want to do. This is part of learning how the camera sees.

    Depth of field

    The static image we create may or may not seem in sharp focus throughout. This is known as depth of field. It is referring to which parts of the scene are in “acceptable” focus. The aperture setting controls the range of this good focus area.

    Remember that the 3 main things controlling the exposure of an image are the aperture, the shutter speed, and the ISO setting. The aperture controls the amount of light coming through the lens at any instant. How long the sensor is exposed to the light is the shutter speed. And the ISO setting is the sensitivity of the sensor to the light. A side effect of the aperture setting is the control of effective depth of field.

    In real life we do not see limited depth of field. Our eyes focus on one small area at a time. Each spot we focus on is in sharp focus. The resulting image our brain paints is that everything is in focus. Try it. Look around where you are now. Then close your eyes and try to remember which parts were out of focus. Spoiler – there aren’t any. We remember it all in focus.

    So this is a big disconnect between what we perceive of a live scene and what we record in a photograph. Some photographers see this as a problem if they cannot keep the entire scene in sharp focus. But intentionally making non-subject areas blurry can also be used for artistic effect. Since this is different from how our eyes see, this creates something that stands out. It can change our perception.

    But like it or not, it is something that the camera sees differently and we need to learn how to handle it.

    Shutter speed

    To our eyes, things seem to be either frozen sharply or “just a blur” moving by. Things are usually only perceived as a blur if we are not paying attention to them.

    But for the camera, the shutter is open for a certain amount of time and things are either sharp if they are still or blurred if they are moving. The camera does not understand the scene and it is not smart enough to know what should be sharp.

    Let me give an example. Say you are standing beside a road watching a car go by. If we care about the car (wow, a new ______; that would be fun to drive) we are paying attention to it and we perceive it as sharp. To the camera, it is just something moving through the frame while the shutter is open. It has no name or value. The photographer has to determine how to treat this motion. What it should “mean”.

    So the photographer may pan with the car to make it appear sharp while the rest of the image is blurred. Or the intent might be for the car to be a blurred streak in the frame. Either way, it is a design decision to be made because the camera records movement differently from us.

    The lens

    Unlike us, our cameras let us swap out a variety of “eyeballs” – the lens. We have a certain fixed field of view. That is why camera formats have a particular focal length designated as the “normal” lens. For a full frame 35mm camera like I use, the “normal” lens is in the range of 45-50mm, because for this size sensor this corresponds to the field of view we typically see.

    But most of our cameras are not limited to that. We can use very wide angle lenses to take in a larger sweep of scene. Or we can use a telephoto lens to bring distant subjects close or to restrict our view to a narrow slice. Or we can use macro lenses to magnify small objects. All these things give us a new perspective on the world that would not be possible with our regular eyes. This is another way the camera sees that we need to learn to use.

    Mapping to 2D

    The world is 3D. Pictures are 2D. It seems obvious. Yet we must be aware of the transformation that is happening.

    In the 3D space we move in, we are acutely aware of depth and movement in many axes – length, width, height, pitch, roll, yaw, and others. We use this information automatically to interpret the world. But it is lost when the scene is captured on our 2D sensor.

    We sense depth. “In front of” or “behind” come automatically to us. Our camera is not as smart. The camera sensor records everything in front of it as a flat, static image. The scene is mapped through the particular perspective of the lens being used and onto the flat sensor.

    An example to illustrate. This is a classic. You take a picture of your family downtown. The scene looks perfectly fine and normal to you, because you intuitively realize the depth and separation of things. It gives you selective attention. But when you look at the picture there is a very objectionable telephone pole poking out of Uncle Bob’s head. You did not pay attention to that at the time because you “knew” the pole was far behind him and you dismissed it. The camera doesn’t know to ignore it. All pixels are equal.

    Light

    This is fundamental to our cameras. There has to be a light source. The camera sees only light from a source or light that is reflected or transmitted by objects. But being humans, we interpret the real world as objects. They are “there”. They have mass and form and value and color. Not so to the camera. It doesn’t ascribe meaning to a scene. All a camera can record is light. Our fancy sensor doesn’t see a red ball. It detects, but doesn’t care, that there is a preponderance of light in the red band being recorded.

    By its very definition – photo-graphy means writing with light – photography is dependent on light. Our modern sensors are marvelous products. We can shoot at very high ISO and make exposures in almost total darkness. But if any image was recorded, there was some actual light available.

    Everything in every image we make is a record of light. More than almost any other art form, photography is dependent on light. Photographers must be intensely sensitive to the direction and quality and color of the light sources that are illuminating our scene. Likewise we must be very aware of the objects the light is falling on, their shape and texture and reflectivity and color.

    Learning to see, again

    Art in general, and photography in particular, is a lifelong learning. We learn to see creatively. We learn to see compositions and design. And we have to learn to see the way the camera sees. This is the way we capture the image we want.

    Note, after writing this I found this good article by David duChemin. He is a great writer.

  • How We Get Color Images

    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.

    Black & White

    Our digital cameras all have a color filter array over the sensor to enable color image information. But if you create black & white images, you then have to convert the pixels back to monochrome. That seems useless extra work.

    But think about it. We have much better control converting a color image to black & white, because more tonal information is available. We can create better separation of tones by using the available color data.

    Some die hard black & white photographers have the color filter array removed from their sensor. This converts the camera into a true high resolution black & white device, but the photographer now must use color filters at exposure time to help with the tone separation, just like in the old film days.

    It seems better to me to take all the color data into our image processing software and do the conversion there. We are not having to guess what filtration to use in the field. But that’s just my opinion, and what the vast majority of digital photographers do.

    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.

  • Craft Completes Magic

    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.

  • It’s Not Necessarily About the Outcome

    It’s Not Necessarily About the Outcome

    Sometimes the muse abandons us or conditions conspire against us or we get interrupted by something urgent. This can make us create pictures that do not live up to our expectations. But unless we are shooting for a client, we probably should not worry so much about the results we get, the outcome. We should remember to enjoy the creative exercise and have fun.

    We all want great images

    I assume that creating exceptional images is a goal for most of us. I know my expectations are high. We study technique and browse images by great artists we appreciate. We spend a lot of time getting to a location, exploring, setting up, composing. But it doesn’t always work.

    Despite our best efforts, we are often disappointed. What we get may not be great. It may not even be very good. This can be very disappointing if we only judge our self by the outcome.

    They won’t all be great

    It is not uncommon for me to go out for a day of shooting and end up throwing most of them away, with none to add to my portfolio. Does this make me a failure? I try to see it differently.

    I hope we can be philosophical about it. Sometimes all we seem to get from our effort is experience. Hopefully we learn from our experiences and improve our craft. That’s a bittersweet benefit. But the reality is we will learn more from a failed shoot than a successful one.

    I’m coming to see that I am evaluating it wrong. My attitude was that I failed unless I got a number of great images. I concentrated on the outcome. There are greater goals.

    The process may be as important

    Sure, it is disappointing to not have captured those scenes that called to us at the time. But it is an opportunity for self-examination. What caused them to be unspectacular? Was there something we could have done different?

    The editing process is a mirror where we can see how our mind worked and even see our soul to some degree. The images are captured. For better or worse, the bits are there on the computer. Now we have to deal with them. We can process them, but we cannot change them substantively – well, usually not.

    I actually see something cathartic in deleting bad images. I have evaluated them and analyzed the problems and learned what I can. Now I have no more need of them. Remove them from my world. It’s a purging. In most cases I actually have an informal goal of throwing a certain percentage of my images away in the early stages of editing. The thought process is that I should be experimenting and working at the edge of my comfort zone. This causes a lot of failures. Failure is just part of learning.

    Enjoy your art

    Maybe I’m weird, but I see art as a work of joy. We should love what we do. Loving what we do is not the same as creating great work. They may be related, but they are not the same.

    There are times when I go out and don’t end up with anything to keep except the memory of the great scene and the feelings I had. That is enough. Good art should be based on the feelings we are trying to convey. If I had the feelings but couldn’t realize them in the image, that means I am on the right track but I have to learn more. That is a challenge for artistic growth. I have seen too much art that is technically perfect but seems to me devoid of feeling.

    There is a lot of talk about “flow” in the artistic process. Have you really experienced it? Not the fake stuff that is hyped by a lot of self-help gurus. There is no “hack” or shortcut to get there.

    I developed the ability in my previous professional career, before I ever heard the term defined. There was a “place” I could easily drop into, a creative mode where I did great work and would be completely unaware of time for hours.

    I can occasionally find the same place in my art, both when shooting and when processing. This is a reveling in the work regardless of the outcome. Yes, true flow is independent of what we might or might not produce. It is the joy of creation.

    Let’s learn to revel in the process, the flow. We will create great things, but that is not the goal in itself. The joy of creation will carry us to become greater. Look at what you are becoming, not just what you are producing.