In the first part of this series, I considered general image appearance and color. While I am not assigning any particular order of importance, I did that first because I think it is the most “in-your-face” aspect of photography. Color, brightness, contrast, and appearance in general is what first draws the eye. But after some visual inspection, I think the eye becomes more discerning, and almost immediately sees – and critiques – image sharpness. It also think it is important to understand that the first two topics, color and appearance and sharpness, are very much interrelated. As we noted in Part 1, in all of photography, we are dealing with “appearance,” and with the viewers very individual capacity to interpret what they see. But things like saturation, brightness, contrast and exposure can certainly influence the appearance (and importance) of sharpness, both visually and mechanically (overuse of some of the “appearance” algorithms can deteriorate images and reduce apparent sharpness). I am not saying that every image must be in razor sharp focus. Rather, I am saying that awareness of this aspect of photography is important.
Do we really need to sharpen our images? Years ago, on the old AOL photography board, I got into a “discussion” with another photographer. He didn’t believe any sharpening was necessary because his newest name-brand DSLR produced razor sharp images straight out of the camera (they didn’t). Another photographer commented on an image we were “critiquing,” and said: “looks sharp to me.” While unintentional on his part, he made a point I want to underscore here. Much of photography is appearance. And this is perhaps nowhere more true than in the concept of image sharpness.
Sharpness is a significant consideration that is often very misunderstood. Perhaps the most important concept here is that every technical definition I have ever read or heard speaks of “apparent” sharpness. Apparent sharpness is influenced by viewing distance and the size of the image being viewed. But every lens has a focus point where it is at is at its most sharp, and good focusing technique remains critically important for the photographer. For years there were really only about 3-4 factors that influenced apparent sharpness: the quality of the glass, the characteristics of the film, the size of reproduction (usually print), and the ability of the shooter. Glass continues to have a large influence. Indeed, as the digital sensors get larger (in terms of pixels), the difference in lens quality is exacerbated. There is a very real difference in the sharpness of focus of images rendered by a good quality lens and a poor quality lens. Modern manufacturing technology has perhaps made the divide between traditionally lower quality lenses (think, generally, cheaper third-party manufacturers) and high quality lenses generally made by the major camera companies. And even between them, there were even significant quality differences – usually between their less expensive offerings and their “pro-quality” expensive glass. Today some of the third-party lenses are virtually indistinguishable in glass quality (often the differences come down to build quality and re-sale value).
Technique, of course, will, always be a critical factor in all parts of photography. Understanding depth of field, sharp focus and how (and when and when not) to attain it, and what the limits of sharp focus in your particular image are continue to be important. And yes, even if you use auto-focus (AF), which has gotten very, very good over the years, you still need to understand what it is doing and how to use it. In fact, AF can fool even an experienced shooter who is not paying attention. Some years back, I blogged about some differences between my full-frame and APS framed Nikon DSLRs. An astute pro friend and mentor of mine, pointed out that an image I was using to illustrate flowing water was out of focus. The corresponding one wasn’t. I let the AF fool me and didn’t pay attention to the details.
nearly every image made from a digital camera could benefit from some sharpening
Most of us no longer deal with film characteristics. But digital imagery has added a new factor to replace the film consideration. Sharpness in film was mostly determined by its grain structure. Digital sharpness is mostly a matter of pixel size, number and configuration. A digital photograph is comprized of many (thousands) of tiny pixels, represented by computing’s most basic “1’s” and “0”‘s, stacked around each other. Imagine a Lego creation. Each one of those little lego blocks represents a pixel, for our purposes. If you step away from the object, the further away you get, the less obvious the indvidual legos, and the more the object looks like its intended form. Also, smaller blocks, more densely packed will take on the form sooner than larger ones as you pull away. Our “lego” pixels, however are tiny. You generally cannot distinguish individual “blocks” without substantial magnification. Take any image and increase its on-screen size, and you will eventually begin to see the individual pixels, and how the stack around each other to make the image. Note that they are rectangular. The border between each pixel creates a line, and generally, depending on the width of that line and the difference in contrast or color between the pixels, you can get a kind of “jaggy” look from the square corners (sometimes referred to as “stair-stepping). Known as “aliasing,” this latter effect can look cartoonish, to downright unpleasant, and is the common result from raw “sampled” images from a camera sensor. Most currently sold camera sensors have an anti-aliasing filter in front of the sensor, which has the effect of slightly blurring those “aliased” pixel borders. Of course is a lot more complicated than my elementary explanation, but hopefully it is enough to understand why sharpening is “a thing.”
Adding proverbial “insult to injury,” when converting an image to digital “1’s” and “0’s,” an image processor engages in interpolation, from the fixed grid of pixels on the sensor, in order to complete the entirety of the image. Interpolation turns nature’s continous tones into discrete pixels, and the process itself often results in some softeness, regardless of the quality of the sensor and lens. And finally, the process of re-converting the pixels to media (especially print media) can result in significant softening of an image. This is why sharpening – at differing stages of the processing, and for different end purposes, is so important.
Given all this, it stands to reason that nearly every image made from a digital camera could benefit from some sharpening. I am hedging here on purpose. Recall my earlier reference to “apparent” sharpness. The anti-aliasing process will vary, based on color, lighting conditions, the presence (or not) of contrast in the image, etc. I almost always run some sharpening on an image at some point during my post-processing. If you “capture” your images only as JPEG (or in a few cameras that have the capability: TIFF), the software in the camera will sharpen the image and in more sophisticated DSLR cameras, you have some ability to “adjust” the sharpening. In most cases, I recommend you capture raw images. They will not be sharpened until post-processing, because it takes raw conversion software to do that. There are a couple “high-end” cameras out there (Nikon, Sony and Canon have them for sure – I would guess so do other major manufacturers) that do not have the anti-aliasing filter. That seems to be an important item especially for landscape shooters. It has its own set of problems. But the beauty is that in post-processing, you can generally fix all these issues.
All this stuff seems like a lot of work … but the good news is that all this complicated stuff has already been done for you!
Every photo software program has some manner of sharpening capability. Some are better than others. Many (Photoshop’s sharpening tools come to mind) are complex and difficult to learn and require a lot trial and error. Most authors and power users recommend sharpening in steps. Generally, they suggest a “pre-sharpen” designed to counteract the effect of the sensor anti-aliasing filter; case-by-case “targeted sharpening” on specific parts of an image (euphemistically called “creative” sharpening), and finally, a sharpening step designed for the type of output (generally print or monitor) and size of image being rendered. The Orange lily below is an example of an unsharpened raw conversion on top, a “pre-sharpened” image in the middle, and a fully sharpened for monitor image on the bottom. All 3 were rendered from raw using Photoshop’s Adobe Camera Raw (ACR) engine. I set the sharpening settings to no sharpening in the ACR conversion (more on that later). Both stages of sharpeing were pushed to their “100%” adjustment. It may be difficult to see the difference between the first two images. Part of this will be variances between monitors and part of it that “perception” thing I mentioned at the beginning. I am basically trying to illustrate the process here. The final image, for example, might be considered by some to be oversharpened. Oversharpening can yield a “crunchy” artificial look. Sharpening (like most aspects of photography) will often be a matter of taste. Of course, it is important that you get the desired sharpness when making the image with the camera. No software (yet) can “fix” or sharpen an image that is blurry because the shooter didn’t get it right in the camera. Here we are mainly talking about working with the limitations of digital presentation.
If this stuff really excites you (you may want to seek counseling 🙂 ). There are some good explanations out there on the internet, and some really good print references. I recommend “The Digital Negative,” by Jeff Schewe. If you are a real masochist, you might want to pick up and read “Real World Image Sharpening,” by the late Bruce Fraser and Jeff Schewe. In Photoshop, there was a “sharpen” algorithm that was, frankly, a pretty blunt instrument, and there was “Unsharp Mask” (a term that actually comes from the old “wet” darkroom). Years back USM was the best tool and it was – for me at least – a mind-boggling math problem, involving 3 settings known as radius, threshold and amount. I know, right? 🙂 . This all seems like a lot of work. But it is worth the effort in many cases.
And there is good news. All this complicated stuff has already been done for you. Starting a number of versions back, a group comprised of pro-users and some of the actual Photoshop Team set up a collaboration known as Pixel Genius (Martin Evening, Seth Resnick, Andrew Rodney, Mike Skurski, Jeff Schewe, and Bruce Fraser). They created a Photoshop “plug-in” known as Photokit Sharpener. I used Photokit for a few years as it incorporated the 3-step sharpening mentioned above, and was much easier to use (if less versatile) than Photoshop’s native “unsharp mask” algorithm. They might have been the first ones to do it on a commercial scale, I don’t know. But over the years, a goodly number of competitors have emerged, and now there are a plethora of programs which are either Photoshop “Plug-ins,” stand-alone, incorporated into their own suite (OnOne, DxO and Topaz are examples). Recently, Pixel Genius announced that it would close, and their final gift to us was a freeware, freely downloadable, most current version of their product (I haven’t tried it yet, but just downloaded it and will for sure play with it).
By “consistent,” I do not mean use the same settings every time, by the way
It really doesn’t matter which on you use, in my opinion. Many, if not most, of them are good. They all work differently. The point is, you should probably obtain one of them and use it – preferably one you are comfortable with and incorporates reasonable ease of use. Just search for “image-sharpening software” and you will find lots of information. When I made the move to NIK software (formerly NIK, then Google, and now owned by DxO), I eventually started to used its Raw Presharpener and Sharpener Pro modules. I did so mostly because I was using the other NIK modules and I liked the ease and familiarity I gained from its interface. The 3 examples above were made using NIK.
Another thing that is worth noting is that most raw conversion software today (at least the integrated programs like Photoshop, OnOne, etc.) generally have sharpness settings in the conversion process, which may very adequately handle the first stage of sharpening. Because I routinely use NIK pre-sharpener, I have my raw converter sliders set to zero for sharpening. I think it is important, once again, to have a good idea what is going on underneath the hood. I think having sharpening set up in the raw converter and then doing an additional “pre-sharpening” would not only be redundant, but would result in unintended results, defeating the purpose of sharpening the image. I am not certain which of these are better (though my intuition tells me it may be the plugin programs), but I think the important thing is to think about it, have it as part of your routine and be consistent about it. By “consistent,” I do not mean use the same settings every time, by the way. To me, this is one of the risks of the raw conversion settings. They are often hidden in the interface from your view. I just downloaded the free version of Photokit and will try to do some comparisons for my own interest soon. One of those things to play around with during the winter ( oh yeah. I forgot. I live in Florida now. We dont’ have “winter” 🙂 ).
Overuse of any of these global adjustments will often defeat the purpose of all of this
There are other post-processing issues that will have an affect on apparent sharpness. One of the most important is the contrast adjustments most software offers. For years, “contrast” was basically the only adjustment available. It operates globally on the image and basically works with the blacks and whites. In order to use it effectively one often had to do some complex masking of an image in order to achieve the intended result only on the parts of the image that needed it. Currently, there is another pretty sophisticated global adjustment. It has different names in different softwares, but Photoshop calls it “clarity.” This adjustment attempts (rather successfully, I think) to adjust contrast just in the mid-tones which are generally not visually effected by the more global “contrast” adjustment (or at least you cannot see them because the highs and lows are so dramatic). Even more recently Photoshop and other have added another adjustment (called “dehaze” in Photoshop), which has the same effect of targeting just certain tones in an image. While not truly “sharpening,” these adjustments often make the image “appear” sharper to the eye.
A final word of caution. Overuse of any of these global adjustments will often defeat the purpose of all of this. As we mentioned above, it is possible to “oversharpen” an image for its purpose, and it can result in an ugly or unrealistic look. Creatively you might want to play with this. Note that I said “for its purpose.” When making inkjet prints on my Epson home printer, I often had to sharpen an image to the point that on-screen it looked overdone, but turned out a very sharp and pleasing print. Conversely, there are adjustments that do not really have anything to do with sharpening – directly (recall the comment that everything is interrelated). One of the best examples is the much overused “saturation” slider tool. I recently ranted about what is see as abusive overuse of “saturation “(especially – for some reason – with fall foliage images – sometimes by shooters who really should “know better”). To see the effect of this tool, open an image in your favorite image processing software and magnify it enough so you can at least begin to see the pixels. Then move the slider to its upper limit and back down again slowly. Observe what happens to the definition around the saturated colors. These days I only very rarely use the “saturation” tool on an image – partly for this very reason.
Next up: In the final instalment, I will cover compositional considerations of post-processing . . .