Ed Schlotzhauer

An artists journey

Category: Technology

Ideas about the mechanics, techniques, and technology behind image making.

  • Night Photography

    Night Photography

    Most people put away their cameras when the sun goes down. But night photography can be a wonderland of visual interest. It does require some new disciplines and knowledge, though. It’s a different world at night.

    What’s to know? My camera has excellent exposure metering. I just point it at the subject and take a picture. Right?

    Well, your mileage may vary. If you are taking pictures with your phone or taking jpg images, you will get pretty good results sometimes. That is because the jpg processor is making many creative decisions for you to try to render an image it thinks you wanted. If it guessed right it might do an OK job.

    With night photography, more than many other types of image making, you really need to be the decision maker in charge of your images. Your intent determines how you approach each scene. The type of subject, the type of light available, whether or not movement is desired, the mood desired, weather conditions, etc. all factor in to the strategy. And most of these factors are interrelated.

    Type of image

    A portrait at night will (probably) require a well lit subject. This may involve external lights and/or reflectors. A star field scene, on the other hand, may have just a vague or silhouetted foreground. No lights, but you need to know good techniques for capturing the stars as crisp points. A cityscape at night may require very long exposures to streak car lights.

    Movement

    A big decision is if movement is desired or not. Some possibilities: a street scene with everything crisp and frozen, a street scene with car lights and people streaked, a star field with crisp points of light, a long exposure star field with obvious streaks from rotation of the sky, a portrait with a crisp subject but blurred background motion. Each of these requires a different exposure approach and different planning and preparation.

    Motion is often one of the signature characteristics that distinguish night images. It is something you completely control by your exposure settings.

    Mood of image

    The time of day, the subject matter, and your desired treatment establish the mood of an image. Time of day? We’re talking about night. Well, “night” starts at different times. There is sunset, twilight, dusk, blue hour, and full darkness. I don’t have space here to discuss each one, but I love all of them and enjoy making images in each. Probably blue hour and full dark are my favorites, except I can seldom resist a beautiful sunset.

    Blue hour probably deserves some discussion. This is the time after the sun is completely gone and the orange glow is gone from the sky. The sky is a rich, dark blue and still light enough to set off a foreground like city lights. It is a beautiful time of day. Blue hour is perfect for some city skylines and for some landscapes.

    Full dark is required if you want to see the stars. It is probably necessary if you want long exposures like smoothly streaked car lights.

    But all of this is modulated by the desired result. Do you want dark and gritty or more cheerful and upbeat? Is it a realistic image of architecture or an abstract?

    Full manual control

    You will usually need to override the auto exposure of your camera. The poor exposure system with fail miserably trying to determine what you want if you point it at an almost totally black sky. So a camera with full manual control is required. You will need to determine and set the ISO, aperture, and shutter speed yourself.

    This is not as bad as it seems. You will learn some guidelines for initial settings for the scenes you most commonly shoot. And with digital, it doesn’t cost much to shoot some test shots. Since you can get immediate feedback you will quickly zero in on the correct settings.

    Technology and technique

    Night photography is an extension of normal daylight photography. Some new techniques must be learned. They are specialized, but most are pretty straightforward.

    Night photography generally implies longer exposures. This implies keeping the camera rigidly positioned. Therefore a good tripod is almost a necessity. And a shutter release to minimize camera shake when you press the release button. And if your camera is an SLR with a mirror, you need to know how to lock the mirror up to eliminate shutter slap motion.

    Let me emphasize again, a good tripod is necessary. Don’t scrimp on this. Get the best you can afford and use it all the time. I generally use Really Right Stuff tripods and heads (I get no compensation for this), but I know that Gitso is also very good. There are many good tripod manufacturers, I just don’t have first hand experience to allow me to recommend others.

    Unless you are going for really long exposures, you will often need to use a high ISO at night. Many modern digital cameras have excellent high ISO performance. If you go back to film days or early digital cameras, you probably think of ISO 800 as a really fast and grainy setting. Not anymore. On the Nikon Z7 I use now, noise is hardly detectable at 3200!

    Another example of a specialized night photography technique is the “rule of 500”. Like all photography “rules” it is a guideline. It can be a helpful starting point for setting up a night sky shot. For a full frame camera, set the ISO to 3200 and the shutter speed to 500 / [focal length] seconds. So using a 24mm lens, that is 500/24 or approximately 20 seconds. This is a great guideline to memorize for when you are out in a really dark place at night trying to get the night sky exposure tweaked in.

    Noise

    Noise during the image capture is a potential problem unique to digital sensors. At least we do not have to try to estimate reciprocity failure as we did with film. Noise in electronics is a function of temperature. Long exposures power the sensor much longer than usual, which can heat it up and increase noise (it looks kind of like grain).

    Most camera manufacturers provide a setting to have the camera take a dark frame immediately following an exposure. This gives a noise sample which is automatically subtracted form the image you just took. This does a pretty good job of compensating for the sensor noise. Sometimes you will want to use it and sometime not. I usually do not, because it is often cold when I am out, which minimizes noise. The main cost of the noise cancelling is doubling the exposure time. If you set a 20 seconds exposure it will immediately follow it with a 20 second noise sample.

    Post processing

    Post processing is almost always required, in night images or any others. It is common to want to reduce luminance and/or color noise, to make the blacks deep and full, to sharpen, and, for some scenes, increase saturation or contrast.

    I mention it here, not because night photography necessarily needs it more, but to emphasize that you need to shoot RAW and always post process.

    After the sun goes down

    A whole new world opens up when the sun goes down. Don’t put your camera away as soon as sunset fades! Get out and experiment. Try some different things. You don’t have to go to Moab and shoot grand night sky shots of the Milky Way with arches in the foreground. Experiment in your city. Learn to be confident manually setting exposures. Practice until you regularly get the results you want.

    Try it! Don’t worry about failing. It can be fun and instructive! I ended up loving some of my failures.

  • Is Black & White a “Thing”?

    Is Black & White a “Thing”?

    Is Black & White photography an art form in its own or is it a way to salvage images that just didn’t work in color? Hear me out before you flame me. I love B&W and believe it is a special medium.

    History

    Black & White is where we started. It is our history and beginning. Looking only at commercial films, the early world was totally black & white. There were a variety of film designs, with tradeoffs of speed, contrast, fog level, etc. Because processing was done chemically, the entire roll had to be exposed at the same speed. Generally, a photographer became familiar with a handful of films. Lots of work was required to become familiar with the film’s exposure characteristics. Different films were selected for different uses and effects.

    In the black & white days lots of work was done in camera to adjust the tone values. Filters, usually red or orange, were used while shooting. Their selection was based on the artist’s subjective judgement of predicting the outcome.

    The system worked pretty well for decades.

    Color

    Then along came color. It really took off in the 1950’s with the introduction of Kodachrome.

    Finally ordinary consumers had what they thought they were missing – a color image. Color film sales dominated black & white.

    Digital

    In the early 2000’s digital cameras became practical and affordable. Now color film was eclipsed and it virtually disappeared from the market. Digital had better resolution, better dynamic range, it was cheaper, and we could print our own pictures on cheap inkjet printers.

    So why, with all these advances, does anyone care about black & white anymore?

    Digital saved black & white

    The technological benefits that made digital imaging take over mainstream photography also brought huge advances to black & white images. A modern sensor is amazing. It captures more information than black & white film and it captures and retains the color information. This can be used later to tailor the tonality of the b&w image. And it allows far more control than color filters and a chemical darkroom.

    The tools we have, like Lightroom and Photoshop, are very advanced and are able to exert a degree of control that would have been unthinkable in the film days. At the same time we have highly mature multichannel inkjet printers with sophisticated inks giving us archival prints. Added to that the development of many types of papers for printing and the options available to a black & white artist today makes this a golden age.

    Why black & white?

    But color is readily available and everyone can print it cheaply. Why would anyone still want black & white?

    This gets to the heart of the issue. A black & white print is perceived as an entirely different experience. Black & white sheds the distraction of color. What is left is tones, shades of gray. These emphasize the shapes and forms of things. Composition and graphic design comes more to the fore. It is an alternate view of reality. That causes us to look at the image differently.

    This difference is the beauty of it. It is a different interpretation of the world. The viewer immediately sees it is different and the artist can lead them through his composition more easily to see what he wants to emphasize.

    I have heard photographers say “this didn’t work in color, lets try black & white”. That is a very limited perspective. I would turn it around and say “this image really needed the color information to make it work, so we can’t do it in black & white”.

    Ansel Adams once said “the negative is the score, and the print is the performance”. This is still true, except the negative is a raw file and the print and processing are all done digitally. No dark room. No chemical mess.

    So is black & white a thing in its own right? Definitely! It is a great art form with a long and glorious history. Today is the best time ever to be doing or viewing black & white images!

  • The Sensor

    The Sensor

    Putting up a nice safe technical post this week. What is the sensor and why do I care? If we just click the shutter button and expect to see magic happen on our screen, isn’t that enough? No, I obviously do not think it is enough or I wouldn’t be writing about it. The sensor is the heart of the technology of image capture. Without a great sensor none of this would be possible.

    History

    Going back, there was rubbing pigment on the wall of caves – Oops, too far. Photography as we would recognize it started in the early 1800’s. Motivated photographers had to mix their own chemicals and wet coat their own glass plates, in the field, in the dark, right before exposing them, then processing them quickly, in the dark, in the trailer they brought. Not for the short attention span crowd.

    In the late 1800’s Kodak produced commercial coated transparent film, on a nitrate base. Keep it away from your candles – poof. A few years later cellulose based safety film was invented and replaced the dangerous nitrate film.

    Around this same time roll film was also invented, so more than one exposure could be made before changing film. This was a contribution to most photographers. Leica’s adaptation of the 35mm film size and the development of an excellent, small hand held camera system greatly advanced the use of photography. In 1935 Kodak released one of the greatest advances in photography – Kodachrome film. Color photography was finally practical and it became very popular. A very large market for both color and black and white film developed with Kodak, Fuji, Agfa and many other brands vying for position.

    This is not an exact history of the development of photography and all of its branches. The point is that the technology of recording images has always been central to photography and it has been a subject of heated discussion/argument by photographers. I have witnessed people almost coming to blows about Kodachrome vs Fuji Velvia.

    Film Was Our Sensor

    Most “serious” photographers had their 2 or 3 favorite films that they used regularly. They learned the characteristics of each well enough that they could predict the results. This is very important, because photography has always been a mixture of technology and art. How the sensor (film) records light is necessary to know so the artist can determine how to use it to achieve the results they want. Pushing the limits of the sensor technology was a common artistic effect.

    But then photography’s “shot heard around the world” happened in 1975. From Kodak’s web site: “Kodak invented the world’s first digital camera. The prototype was the size of a toaster and captured black-and-white images at a resolution of 10,000 pixels (.01 megapixels).” From that trivial sounding start, Kodak killed it’s own business and the multi-billion film business around the world. Digital sensors forever changed the course of photography. And this was a good thing for photographers.

    Digital Image Capture

    Image capture in a digital sensor is completely different from film. Instead of photons of light causing a chemical reaction in the film, the photons caused the emission of electrons in the sensor chip. These electrons are accumulated over the duration of the exposure, then transferred out serially and sampled to “count” the electrons. From this, complex and high speed processing reconstructs an array of “pixels” (picture elements) which is so dense it fools our eye into seeing a smooth image. This constructed data set is recorded onto a memory chip in the camera. Then usually transferred to a computer.

    Over the years, good engineering has improved the process so much that few people still argue that images from film are superior to digital captures. My personal transition happened in about 2004. I finally concluded that the Nikon D70 was at least at parity with 35mm film. That was a 6 Mega Pixel sensor. The image accompanying this post was shot with that camera. Now, when I look at a good quality scan of a 35mm slide compared to a capture off my 47 Mega Pixel Nikon Z-7 sensor I have to shake my head and marvel at the improvement of our photographic technology. Yes, some of this comes from greatly improved lens design, but the sensor is one of the biggest effects.

    So with digital sensors I am free to push the limits more, to experiment more, to have more fun with photography, to post process to a much larger degree. Sensor development has removed many of the barriers of resolution, dynamic range, reliability, noise, etc. Photography now can be driven more by artistic vision than by a struggle to produce a usable image.

    Do We Need To Understand the Technology Anymore?

    Do we as artists need to know about the technology of our sensors? I believe YES. Photography is unique in being a strong mix of technology and art. A good craftsman cannot ignore either of them. These marvelous devices must be understood to be used to their full potential. Digital sensors have limitations and their own quirky characteristics. Dig in; understand the transfer curves; understand the dynamic range; understand the behavior at maximum brightness or darkness; understand noise; understand moire patterns. Understand other related things like the focus system in your camera. Nothing is trivial. But have a very high regard for the sensor.

    Much more can be written about the sensor. I may in the future if requested. As an engineer I enjoy digging into the technology.

    To the sensor developers at Kodak and Nikon and Canon and Sony and Fuji and all the others – Thank you!

  • Does DPI Matter?

    Does DPI Matter?

    People sometimes get hung up on DPI like it really matters. It doesn’t, at least not in the way you may think. The number of pixels matters. The scaled resolution of an image to print matters. DPI is just a setting and an indication of when scaling is required. Where I’m really going is to say an artist must be a craftsman with his tools and technology.

    I get information from people all the time requiring image previews at a certain DPI. One client even required images at 72 DPI stating that it was for my protection – implying that a lower DPI image wouldn’t be copied or stolen.

    The number of pixels is what is important. DPI is just a setting. You get it by taking the dimension of the image in an axis and dividing it by the desired print length of the axis. So if I had an image that was 3000×3000 pixels and I wanted to make a 10×10 inch print, 3000 / 10 gives 300 DPI. This is a good resolution for printing. I know from looking at the DPI that no additional scaling or interpolation needs to be done.

    But what if I wanted to print that same image at 30×30 inches? In this case the DPI would be 100. I know that is too low. To print it well I should scale and interpolate it to at least 240 DPI. This is simple to do in Photoshop and Lightroom and various other tools are available to do it. So the DPI is really only useful as a metric to the person making a print or for a designer creating a layout. How did I know 100 DPI was too low? I have to know that. That is where I’m going.

    What’s the use of even bringing it up then? Well, I believe it shows a certain lack of rigor or even understanding by the people using the digital products. Too many artists say “I’m not technical. I just do things by feel.” That is too simplistic in the digital world. It is great to say you’re more interested in the artistic outcome than the technology. I agree with that. But pixels and sensors and lenses are the tools and resources we work with to create. An artist has to be a craftsman who knows his tools well. He has to know when and how to scale a collection of pixels to create an excellent print. He has to know when and how to sharpen an image to make it look great without introducing artifacts of over sharpening. He has to know how to do black & white conversions. He has to know how to do color corrections and tone mapping to achieve the look he wants. These things are specific technical skills and require knowledge of what is being done and why.

    I’m not saying an artist or craftsman must use the latest, best, most expensive tools. No, use the tools that you’re comfortable with and that work for you. But master them. Whatever your tools, you should be an excellent craftsman with them.

  • Technology is Important

    Technology is important in photography, maybe more than most other arts. I sometimes hear photographers say “I’m not interested in the technology; I just want to make pictures.” This seems to usually have one of 2 meanings: either they really do know the technical side but they are making an exaggerated statement to say that artistic considerations are more important, or they really don’t consider the technology. This later group is needlessly limiting their potential.

    The term “photography” comes from Greek words meaning “writing with light”. It is a good name. Photography is unique among arts in that (for the most part) we start by capturing something that is there in front of the camera. Most other visual arts start with a blank canvas and the image has to be built from scratch by the artist. I’m not arguing that this makes photography more of less valuable than, say, painting. Just that the process is different.

    Since we are capturing something that exists, we must know how to use the tools we have to maximize our success. Taking digital image capture as the norm, there is the lens, the camera body, the image correction process, and the creative manipulation process. Modern photography absolutely requires a good computer system.

    • Lens : The focal length and maximum f/stop determine the envelope of what can be captured for a certain scene. The focal length sets the magnification or “cropping” or framing of the subject. The f/stop choice determines the depth of field — the relative amount of the field of view that is in acceptable focus. They also interact to control the amount of light entering in to the camera sensor.
    • Camera body: In a typical modern camera this controls the exposure, the focus, the shutter speed, the image capture, and the initial image processing. Exposure is a combination of the ISO speed (the relative sensitivity setting of the sensor), the aperture, and the shutter speed. The image is captured on the sensor, a large silicon chip. The sensor is perhaps the most critical piece of technology in the system. It has a maximum number of pixel it can capture and a dynamic range — the range of brightest to darkest data it can record. The data coming from the sensor is not the image ready for viewing. It must have sophisticated and high speed processing done to it before it can be written to the memory card or even previewed on the back of the camera.
    • Image correction: Even after the processing done in the camera, every image needs some correction. This is not a flaw, it is a required part of the process. Typical processing at this stage include color correction, a little bit of sharpening, some tone correction (e.g. reduce highlights and/or raise shadows), and cropping.
    • Creative manipulation: This is a later stage of processing, maybe using in the same software; maybe not. This may include tone mapping, black & white conversion, removing extraneous objects, compositing images together, blurring, sharpening, and many other operations.
    • I’m not even considering here the final output. This can be prints, web postings, stock images, etc.

    This is neither a tutorial of digital processing or meant to scare you away from photography. It is just stating what is involved to do a better than average job.

    The point is that a good artist will have an excellent working knowledge of every one of these steps. Each one is an important factor in determining the final outcome. You have to become very familiar with your tools. It is necessary to work with them over and over for so many repetitions that they are second nature. An artist must make dozens of conscious decisions, often in a fraction of a second, in the dark, or in bad weather, to get the result they envisioned. This might be heresy to many, but my opinion is that an old camera you are intimately familiar with is better than a sophisticated new camera that you don’t know how to use quickly. (So get the new camera and spend a lot of time learning it 🙂

    Any visual art involves making things. Making things requires tools. A good artist learns their tools well. This is one of the things that separates the good ones from the mediocre. When I hear someone say “I don’t do technology” I interpret it to mean “I’m not serious about my art.” Is that unfair? Not to me, but let me know what you think.