Old Filter Habits Die Hard
Even in the era of digital photography, the use of filters affixed directly to the front of camera lenses continues to be a popular option in some circumstances. But the results don't always come out as well as they would have had other alternatives been employed.
In days of film, the image you shot in-camera was the image you ended up with. Yes, some tonal and color corrections could be achieved during printing, but for the most part, you had one and only opportunity to influence the appearance of an image. If the exposure needed help to avoid having to choose between blowing out the sky or consigning the foreground into darkest obscurity, you had to modify things at the time you clicked the shutter release. If you felt the lackluster colors needed some help to make the image really pop, same thing. And the tool of choice to address these sorts of issues was the use of filters. I'm talking about the glass or in some cased plastic ones you screwed onto the front of your lens.
Today, the term "filters" can also refer to software tools and plug-ins in programs such as Photoshop, but while their availability has made a dent in the use of lens filters, it has not supplanted them completely. In part this is due to old-time film photographers sticking with what they are familiar with. In part this results from manufacturers of lens filters continuing the drumbeat of advertising in an effort to prop up otherwise sagging sales. Then there's the learning curve associated with editing in the digital darkroom in general influencing the choices made by photographers new to the craft. Sometimes, camera lens filters are still your best option. There's really no way to duplicate the effects of a polarizer for instance, but even when better options exist digitally, the use of lens filters continues, seemingly through sheer inertia.
Take the common warming filter for example. It used to be common practice for photographers specializing in wildlife and landscape photography to fasten a mild warming filter such as a Tiffen 812 or Nikon A2 to the front of every lens they owned in order to improve the look of their images. Even portrait photographers used this trick to warm up skin tones to make their subjects look more flattering. Today, such color temperature adjustments can easily be made directly in-camera with no filter, or even after the fact in the digital darkroom, especially when shooting raw format. That means one less thing to carry around in your camera bag, one less layer of glass to shoot though and worry about getting finger prints on both sides of, and yes, one less thing you need to spend your precious camera buying dollars on. The same is true for all other color compensating and color correction filters.
Then there's the "sunset" filter. You can find these either in evenly colored orange or with a gradient from pale orange on one side, transitioning to more deeply colored orange on the other. The idea was that if nature didn't give you the sunset you hoped for, you could attach one of these to the front of your lens and take matters into your own hands. Presto, instant sunset, even on an overcast day at high noon. Camera store salespeople used to love these things because it was easy to convince customers first starting out in photography that this was how those really gorgeous sunset photos were made. Anyone who had ever tried and failed to get a good sunset image was an easy mark. I admit to having bought one back in the day, even if only to try it out. After a couple attempts though, it became apparent that such filters could never replace the real thing. The color of anything lit by the sun late in the day does appear warmer than normal, but objects in the shade tend to be less effected if at all. If the object casting the shadow is large enough, the area in the shadow should actually be tinted slightly blue from the cooler temperature of open shade. But a sunset filter turns everything equally orange with no regard to the actual lighting conditions throughout the frame. It's puzzling to me that these things are still sold in this era of digital imaging. With only modest effort, you can augment sunset colors in an image with Lightroom or Photoshop, and with much greater faithfulness to what reality would have provided were it in a mood to cooperate.
Graduated Neutral Density (GND) filters are another type of filter that used to be a mainstay for outdoor photographers that have less relevance in the digital era. The range of brightness in the real world can far exceed the latitude of what can be captured on either film or digital. The only way to achieve a proper exposure in both sky and foreground in a single image used to involve the use of Graduated Neutral Density filters. I used to carry around a thick stack of these amazing filters that are clear on one end and graduated to medium or dark gray at the opposite end. By positioning the transition zone over the horizon, with the dark area cutting the sky exposure and the clear area over the foreground landscape, it was possible to balance the exposure and capture an otherwise impossible image. In extreme cases, I used to use two or even three of these in a single image, carefully aligning the graduation with some feature in the landscape to hide the transition. But this wasn't always fully possible. Trees and other vertical elements in the frame had an annoying way of crossing transition zones and revealing the secret to how an image was shot. GND filters do still have their uses of course, but software has become the tool of choice these days for blending extreme exposure situations. I almost never use Graduated Neutral Density filters anymore. Yet its still easy to find lists of recommended filters for landscape photographers, prominently including GND filters.
It's said that old habits die hard, but I think there's more than just this going on. The reason why these types of filters continue to find new adherents is that photographers and those who write about photography continue to recommend them even though such advise is of questionable value these days, and because filter makers and camera retailers continue their efforts to maximize sales, even when doing so is contrary to the true needs of their customers today.