Primary Issues in Image Sharpness

March 21, 2013  •  Leave a Comment

Darkness and LIght

(EOS 7D, 17-40 @ 24mm, f8, 1/600, ISO 400, 5:36 pm)

There is an old saying …. You cannot make a silk purse out of a sow’s ear. That truism holds for photography as well. In order to make a good finished product, you have to start with a quality image. When we are talking about image sharpness, photographers are specifically talking about the definition of edges. Critical parts of the image will be razor sharp … that is, you can easily tell the difference between this and that.

Image sharpness starts even before you press the button on your camera. As Ansel Adams was fond of saying, “There is nothing worse than a sharp image of a fuzzy concept.” The essence of photography is being able to communicate a specific moment to those who are not present, or to interpret it for those who are there.  Entire lifetimes can be spent in pursuit of the one perfect image, and many of us have a difficult time translating our vision into a photographic print.  But this article is not about photographic vision, it is about making certain that what we do capture is decent enough to display.

Once you have the concept, exposure, and the composition of your image figured out, there still remain the technical aspects of making a sharp image. These begin even before the shutter is released. Here are some things that can help improve image sharpness:

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  • Use a sturdy tripod. The sharpest images are captured when the camera is not moving.  Even the slightest movements of your body are exaggerated by the camera, therefore, we use a tripod to be a steady platform for the camera. If you cannot use a tripod, get as much support as possible to steady the camera. If it is windy outside, use your camera bag as a weight to keep the tripod from moving.
  • You might try using the “mirror lock-up” function on your camera so that the shutter does not introduce movement to the camera.
  • Using a cable release gets your hands off of the camera and reduces the amount of camera shake introduced by pressing the shutter release button. If you do not have a remote control or cable release, try the self-timer.
  • Use as low an ISO as possible.  While higher ISO's are much improved in today's cameras, they still do not resolve as much detail as the base ISO of your camera.
  • Having the proper shutter speed and aperture are part of the formula.
    • The aperture will give you sufficient depth of field so that everything that is supposed to be so will appear in focus.  Or, an out of focus background will help the primary element in your photo stand out.
    • Shutter speed should be at least 1 / focal length, especially if you are not using a tripod, to eliminate blur that can be introduced by lens movement. For macro and super-telephoto lenses, double that speed until you have mastered your technique.

Once you have done everything right and captured a “tack-sharp” image on film (or your memory card these days!), you are well on your way to getting a sharp print. If you have not succeeded in doing that, the rest of this discussion will not really help you a whole lot. There is only so much that can be done to salvage an image that was not properly made.  In other words, the best thing that you can do to ensure a sharp image is to brush up on your field techniques!

West Virginia

 

 

The remainder of this discussion is about what to do in the digital darkroom (your computer) once you have properly captured an image. There are equivalent techniques used for film, and that is where these tools and techniques were originally developed, but most people are shooting digital these days.  Most who are shooting Fine Art images shoot in the RAW format so that they can tweak every last bit of information out of the data their camera has captured, and by its very nature, a RAW image needs to have sharpening applied.  It can be argued that it is not needed if you shoot jpg, because the camera has already applied sharpening to your image, but even there, some tweaking is often needed.

What is sharpening and what does it do?  In a nutshell, sharpening enhances the edge contrast to make these edges better define the subject of a photograph.  It makes the differences between tones slightly more distinct so that the line is better defined and appears more dimensional.  Sharpening cannot fix poor focus or camera shake problems, it is limited by the data you present.  Good sharpening, properly done, is said to be invisible.  It simply counteracts the effects of processing pixels to make the edges as distinct as they are supposed to be.  Sound vague?  It probably should.  Until you have seen properly sharpened images, you are likely to think the soft ones you have printed are just fine.  Once you make the adjustment yourself, you very quickly begin to notice the difference.

There are several methods to choose from when sharpening your images, and like most things in photography, the choice is yours. A simple Google search for “image sharpening” returns over 11 million hits.  You can choose to use only the most basic sharpening that is applied automatically, or you can tweak every last detail. It is a very simple fact that the larger you print, the greater the need becomes for custom sharpening to be applied.  Sharpening is not VooDoo Magic, but it does require some study and practice to perfect.

Bruce Frasier and Jeff Schewe (pixelgenius.com) are the acknowledged experts when it comes to image sharpening, and Frazier’s book, “Real World Image Sharpening” is still the textbook of choice for digital image sharpening. Without going into detail, (you can read Frazier's book) the principles that he uses are the basis for the sharpening algorithms that are found in several software packages, most notably Pixel Genius’ PhotoKit Sharpener, NIK software’s Sharpener Pro, and all of Adobe’s products (Lightroom, Photoshop, and Elements). No matter which package you ultimately decide to use, it will take practice to perfect your post-processing technique. This includes noise reduction and image sharpening.  A good website tutorial on sharpening can be found at http://www.cambridgeincolour.com/tutorials/image-sharpening.htm.  (check out their full range of tutorials!)

A sharpening workflow includes:

  1. RAW Pre-sharpening and Noise Reduction
  2. Content specific or creative sharpening
  3. Print Sharpening

 

SOFTWARE TOOLS

There are dozens of software packages available to accomplish these tasks, and even the free ones available online offer at least basic functionality. I am not going to argue about which is best, or even appropriate for you. Use the tools you find most comfortable. I am most familiar with Lightroom, which uses Adobe’s Camera RAW engine. In Lightroom, there are several places you can adjust sharpening that correspond to Frazier’s 3 step sharpening theory (I believe Aperture and most others do similar things):

  • Clarity Slider & Details tab. These are global adjustments to the whole image that control local contrast, sharpness, and noise reduction. The Lens Corrections tab also has bearing, as Chromatic Aberrations can also affect image quality.
  • The touch up tools such as the adjustment brush and the graduated filter are for “Content Sharpening.”
  • Print dialogue automatically calculates final sharpening for output type and size

Although Lightroom and Aperture produce “good” results, finicky users are always going to end up wanting more from their images.  Photoshop allows you to use your personally preferred method for both noise reduction and sharpening. You can use one of Photoshop’s built in sharpening methods, write your own action, or buy a plug-in. The built-in methods are adequate, but not excellent. Actions are much faster in the long run, but most still need customized. Plug-ins are specialty tools that have been developed for this function and usually work exceptionally well. I use all of the above, but for everyday use, I find the level of control in Lightroom to be adequate. Only as I print larger Fine Art prints do I need to use the custom tools, layers, and masks that Photoshop provides. Your mileage may vary.

  • Photoshop & Elements.  Filter>Tools>Sharpen (or Noise for Noise reduction).  The tools here have improved dramatically with each new version of Photoshop, and there are many ways to achieve proper sharpening using them.  If you do not have a third party plug-in, you can still get excellent results by learning to properly use what is here.  The Unsharp Mask tool is the preferred choice for sharpening, and you must be very careful with the noise reduction tools, as they will all soften your image.  Even Gimp has a version of this built in, so you really do not need to spend a lot of money to get what you need!
  • Photoshop Actions.  Actions are the way to go for repeated tasks and can make image sharpening much simpler.  There are sharpening actions you can buy, or you can write your own.  I have actions for Capture Sharpening, High Pass, High, Medium, and Low frequency detail sharpening, and Mid-Tone contrast enhancement.  One size does not fit all, and even when using actions, I have to tweak the results.
  • Plug-ins and Stand-Alone software.  These guys specialize in image sharpening and noise reduction, which by now you have figured out is not an easy thing.  There are several excellent titles available for controlling noise and sharpening your image, and most are available for a trial download, so try out a few before you buy so that you get something that is both comfortable to use in your workflow and produces results that you like.

If you are going to spend the money on tools like Photoshop, NIK Software’s Sharpener Pro, PhotoKit SharpenerPhoto Ninja (formerly Noise Ninja), Neat Image, Topaz, etc, know that you are going to have a learning curve and make sure that you are going to get your money’s worth. Work with your tools and try various methods to find out what works best. There is no single tool or method that is exclusively able to produce excellent output, it is the operator who does that! All of the above (and more!) are tools to help you achieve the best possible print from your image. 

CAVEATS:

  1. Knowing what a properly sharpened image looks like takes a lot of looking. Study the photographs of photographers you respect. Sorry, but online viewing is not particularly helpful in this regard, you need the real deal. Pay particular attention to the details, and what the in-focus part of the picture looks like. Do yourself a favor and also look at poorly sharpened images so that you know what they look like too. 
  2. Apply the correct amount of noise reduction and sharpening. Too much noise reduction, and your crisp image goes soft, too much sharpening and it has ugly halos or gets crunchy.
  3. Use the tools you’ve got. Before investing in expensive software or falling for every advertisement that crosses your screen, learn to use the tools you already have. Most of the time, with a little research you can learn the tricks to do the same things. One of the fundamental rules of photography is to learn to use the tools in front of you before moving on.
  4. Read and study. These are not easy topics, and most of us would rather be shooting, but some homework is necessary. For example, different sharpening is needed for different sized prints, different papers, and different printing processes. This can be a VERY in-depth study.  You might also find that different sharpening approaches work better for specific applications. 
  5. Looking at your images on your monitor is not the same as looking at prints. You will learn to judge what level of on-screen sharpening works best in print by trial and error, comparing your print to the on-screen version. 

Happy Shooting!

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