Ed Schlotzhauer

An artists journey

Category: Technology

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

  • 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.

  • Yes, You Need to Backup

    Sorry. I know no one wants to think about this dirty subject, much less talk about it. But is is a necessary part of a digital artist’s process.

    Back in the “good old days” images were created on film. You kept the film in holders or sleeves in a file of some sort. Barring major fire or flood, you were pretty well backed up. The negatives or slides were fairly insensitive to water, tolerated a wide storage temperature range, and would last for decades or longer.

    Forward to today. It has been many years since I exposed a piece of film. ALL my work is digital. And all the derivative works I create are digital. There are significant advantaged to digital images, but there is one glaring, horrible downside: when the disk they are on dies, they are gone. They are not a physical object.

    Oh, but disks are very reliable. You can’t remember the last time one of yours crashed. (Cue whistling in the graveyard music). Here’s the reality: your disk is about to fail and there is little ability to predict when. After it fails is not the time to be doing a backup.

    In a past life I was an engineer, so I know something about this technology. I’ll try to keep it pretty basic. Most of us use rotating magnetic storage (e.g., the hard disk). This is an amazing technology. Bits are stored as microscopically small magnetic blobs on platters of metal spinning at, typically, 5400 or 7200 RPM. The data is read and written by “flying heads” that fly above the surface of the platter a few micro inches away. This is like a fighter jet flying at supersonic speed 10 feet off the ground. It’s a wonder it works, but it has been engineered with enough layers of protection to make it very reliable. The other fast growing technology is Solid State Disk (SSD). It is completely different and usually much faster. Just because it is smaller and faster does not make it more reliable. There are many more failure modes associated with SSD than rotating disks.

    What does this matter to me? My disk drive is rated at 1,000,000 hours MTBF (mean time before failure). It should be good practically forever. There is a reason disk makers throw out numbers like that. They are very impressive without really meaning much. It is a statistical measure of a large population of devices. It does not mean yours or mine won’t fail tomorrow.

    What to do? The ugly “backup” word. I won’t recommend specific software or hardware, except to say if you are using Macs, please turn on Time Machine immediately. Instead I will give you an idea of the paranoid extremes I go to.

    Yes, I use Time Machine for one level. It is a marvelous invention. It backs up my images and the computer every hour. My images are actually stored on a RAID drive. This means the information is redundant and one drive can fail with no loss of data. My drive is also very fast. The data on this RAID disk is also backed up daily to 2 other RAID drives. All of this is completely automated and requires no attention from me. About once a week I rotate a copy of my image data to off site storage, so it is backed up in another physical location.

    I’ll confess it again: I am paranoid about this. But the last 2 times my computers crashed I didn’t lose anything. I use (and love) SSD as my main computer storage. I have stacks of rotating disks with many terabytes of data on them. With a good backup plan I don’t worry at all about losing data.