Telephoto Lens Cap for Canon & Nikon Camera Lenses

Archive for January, 2016

TECHNIQUE – Top 5 Tips for Quality Image Files (part 4)

USE ABODE RGB COLOR SPACE

In a digital photography workflow, a principal axiom is that you can start with more and get less but you can never start with less and get more. (It’s not really a famous axiom; I just made it up.) A prime example is taking a tiny 72 dpi JPEG and trying to blow it up to print a poster. It’s not going to work.

Another area where this rule applies is with color spaces. A color space refers for our purposes to a system for representing colors in a numerical form. Adobe RGB and sRGB are the most common color spaces used by today’s DSLR cameras.

adobe RGBThe figure above, which is borrowed from the Eizo website (Eizo makes what are probably the best monitors out there but you’ll pay for it), shows how these two color spaces relate to the broader color space that encompasses all of the colors and tones that the human eye can discern. You’ll notice immediately that Adobe RGB is a wider color space or gamut than sRGB, particularly for greens and some shades of blue. By setting your camera to capture your RAW files in Adobe RGB space, you’ll be taking advantage of more color information than if you shot in sRGB. As with the next two parameters I discuss in

the following sections, choosing the best setting in-camera will allow you to accurately judge your histogram.

Note that the choice of in-camera color space (again, as with the following two sections below) when shooting RAW does not affect the actual RAW data. If you use Adobe Camera RAW, either in Lightroom or Photoshop, a color space is not truly applied to a file until you convert it to say a TIFF, a PSD, or a JPEG. If you use your camera’s own software (e.g., Capture NX for Nikon, or DPP for Canon), the choice of in- camera color space will be read directly and used as the basis for your photo processing.

Just remember, Adobe RGB is the best choice for in-camera setting when shooting RAW for two reasons. You’ll have a more accurate histogram and you avoid any potential for being fooled into working with less information in post-processing.

So, does this mean that sRGB is always to be avoided?. On the contrary, whenever you convert an image to a JPEG for use on the web or for a presentation, you’ll be outputting the file as sRGB because this is the color space that best corresponds to the screens on most modern electronic devices. Files sent to the web with an Adobe RGB color profile embedded won’t look as good. I save files destined for print (magazines, large prints, etc.) in Pro Photo RGB (an even wider gamut than Adobe RGB) and files destined for electronic distribution in sRGB color space.

 

 


lens cap


About the author Gregory Basco
Like many nature photographers, I started my career doing something else. A political scientist by training, my research focused on the politics of the environment in Latin America. I researched environmental politics and ecotourism in Costa Rica and worked here for a number of years as a conservation professional, having first come to the country in 1992 as a Peace Corps volunteer. I now dedicate myself full-time to my own photography and my Costa Rica photo tour company. I work out of my home office in Costa Rica’s central highlands, where I live with my wife, twin boys, our dogs and cats, and various hummingbirds and songbirds that visit our backyard feeders. Visit Greg’s galleries, store, and workshops at Deep Green Photography.

Posted in: General, Photography Gear

Leave a Comment (0) →

TECHNIQUE – Top 5 Tips for Quality Image Files (part 3)

EXPOSE TO THE RIGHT

Exposing to the right is a practice that many people don’t follow precisely because RAW files do stand up so well to post-processing. But shooting RAW doesn’t give us an excuse to be sloppy, and exposing to the right is important for two reasons. The first is simple. If you underexpose an image and then have to pull out shadow detail from the darker areas of an image, you’re going to be introducing noise. But darkening slightly overexposed areas will not give you a loss in quality. This is true because of the second reason.

This second reason is even more compelling but requires a bit more explanation. DSLR cameras in general have about five stops of dynamic range. Recall from above that a 12-bit RAW file has 4,096 possible tonal values in each color channel. If we array the stops of dynamic range along our monochromatic or luminance histogram, we’ll notice that each stop (from left to right) contains two times more information than the previous stop. And notice also that most of the possible color values are in the brightest areas. That is, our camera can capture only a relatively few dark tonal values and lots of bright tonal values.

photo exposureAs the figure above illustrates clearly, fully half of the tonal values are in the brightest fifth of the histogram. So, if you don’t have at least some pixels heading out into that rightmost fifth of the histogram, you’re wasting half of the potential tonal information that your camera can capture!

Exposing to the right does not mean overexposing to the extreme though. It simply means that you should expose your image so that the brightest tones in your scene display out into the right fifth of the histogram. If you want detail in the whitest or brightest parts of the scene, however, you need to take care to take them just to the edge of the histogram but not over.

Take the image of a Montezuma oropendola below. This is one of the tougher birds in Costa Rica to expose properly because of the white skin on the face and the black feathers around the head and neck. Underexpose this one, and you’ll have no feather detail in the blacks. Overexpose too far, and the white skin will be blown out white with no detail at all.

Below is a screen shot of my untouched RAW file and the resulting histogram. Notice that there is some space on the left edge of the histogram. This means that the dark feathers are not pure black. And notice that the brightest pixels go right out to the right edge but not past. This means that I made the image as bright as I could in order to capture feather detail in the blacks but without blowing out the white skin. You’ll note also that there is a large amount of pixels clustered toward the middle right of the histogram. This is the background, which is represented by brighter than average mid-tones. The background in this shot was distant forest but there was some fog moving through, which meant that the background was indeed a bright but fairly dull green.

photo exposureIn terms of exposing to the right, there is a caveat that applies especially to the rainforest, where light is usually scarce. Let’s say that I’m shooting a monkey that’s moving around a bit. I have my lens
aperture set wide open, I’m getting only 1/60 of a second, and I’m already at ISO 3200. That is, I’m doing everything possible to get just barely enough light for a sharp image. I take a shot and check my histogram and find that I really should be pushing my exposure one stop to the right to get good detail in the monkey’s dark fur. I have a bit of a dilemma now — how to get that extra stop of light.

I can’t open up my aperture any further; it’s already wide open. If I adjust my shutter speed to let in one stop more light, I drop to 1/30. I think that’s going to make it hard to get a sharp image in this situation, and it’s also placing me into the territory where mirror vibration becomes a concern. So, I don’t want to take my shutter speed any slower. I could take my ISO from 3200 to 6400 but, even though my Mark IV is quite good at high ISOs, I’m not enamored of 6400. So, this is a case where not exposing to the right and brightening the exposure in post-processing may actually be a better or at least equally valid choice. I want a sharp image so I need that shutter speed. And going to ISO 6400 will introduce noise, perhaps just
about as much as taking the image at ISO 3200 and brightening it by one stop in post-processing.

This, of course, is a fairly extreme situation but it’s worth noting because there are some potential tradeoffs involved when exposing to the right. Still, it’s a good habit to have and will help you to get the cleanest image files possible in the vast majority of shooting situations.


lens cap


About the author Gregory Basco
Like many nature photographers, I started my career doing something else. A political scientist by training, my research focused on the politics of the environment in Latin America. I researched environmental politics and ecotourism in Costa Rica and worked here for a number of years as a conservation professional, having first come to the country in 1992 as a Peace Corps volunteer. I now dedicate myself full-time to my own photography and my Costa Rica photo tour company. I work out of my home office in Costa Rica’s central highlands, where I live with my wife, twin boys, our dogs and cats, and various hummingbirds and songbirds that visit our backyard feeders. Visit Greg’s galleries, store, and workshops at Deep Green Photography.

Posted in: General, Photography Gear

Leave a Comment (0) →

TECHNIQUE – Top 5 Tips for Quality Image Files (part 2)

 

histogram

Cloud forest vegetation, Costa Rica

KNOW YOUR HISTOGRAM

If you don’t use your histogram, you’re putting yourself at risk of underutilizing the information that your fancy DSLR camera (which truly is an amazing machine!) can capture. The histogram allows you to ensure that you’re getting as much tonal information as possible in your images, and it also allows you to focus on capturing the detail you want for certain important parts of any scene. As discussed above, the amount of information in RAW files does allow for a fair amount of post-processing without degrading the image too much. Nonetheless, getting the best exposure possible in-camera is going to mean a better final image, and you’ll also be more satisfied with your effort when you get it right.

The histogram is a big help in this regard but many people seem mystified by it. It’s actually quite simple. The histogram is basically a bar graph in which the x-axis represents the total range of tonal values in a given image from 0 to 255. That is, even in color images, there are 256 possible shades of monochromatic tonalities or luminance values, from pure black (0) to pure white (255). The y-axis indicates the number of pixels having a specific luminance value.

You’ll also see color histograms but most professional nature photographers will tell you that they don’t use these very much if at all. The only time I use them is to check the red channel in a scarlet macaw or maybe the blue in a specific flower or a hummingbird like the violet sabrewing. The consensus among the other pro nature photographers that I know, however, seems to be to master the use of the monochromatic/luminance histogram. Indeed, I have my camera set to display only this histogram by default.

histogramOne often hears that a classic bell-curve is a “good” histogram. Nothing could be further from the truth, and as an aside I think the obsession with having no bright highlights and no dark shadows has led in part to the current HDR craze (that’s a story for another post though!). That said, there are many images for which a bell-curve will indeed be a great histogram.

In the nesting toucan image above, for instance, you can see that the majority of the luminance values are clustered in the center of the x-axis. This makes sense because there are a lot of middle-toned greens
and earth tones in the image. At the tails of the graph (the left and right edges), there are many fewer pixels with extreme dark or light luminance values. And indeed, the values stop just before the left and right edges of the histogram, meaning that I have detail in the darkest and brightest parts of the image.

histogramAs this glass frog image shows, however, there is no one “good” histogram. The correct or optimum histogram will vary depending on the image. Glass frogs are nocturnal so the black background, in addition to being graphically pleasing for this image, is perfectly natural. It gives a very different histogram than the more classic toucan image above but one that is equally correct.

Note that there is a big spike of values pushed up against the left side of the histogram. This means that there are quite a lot of woefully underexposed, pure black areas. I wanted the background to be black, and so it is. You’ll also notice that there are varying luminance values represented by the dark greens and lighter greens in the image but that, importantly, there are no pixels at the right edge of the histogram. Again, this is fine for this image as there are no values that are white or even close to it. Had I put a flash on the leaves in the background in order to make the background green, the histogram would indeed have been closer to a bell-curve. That’s not what I wanted for this image though

histogramAbove is another example of a non-traditional histogram but one that is entirely correct for this image. Note here that there is a big spike that bumps up against the right edge of the histogram. This means
that there are lots of overexposed highlights; in fact, a spike this big and this close to the edge means that these values are pure white and that they contain no recoverable detail. If I had wanted this image to be a silhouette of bird and tree against a cloudy sky, I would be in big trouble because the whites are blown. Of course, that wasn’t the intention here so the overexposed whites are just fine.

 


lens cap


About the author Gregory Basco
Like many nature photographers, I started my career doing something else. A political scientist by training, my research focused on the politics of the environment in Latin America. I researched environmental politics and ecotourism in Costa Rica and worked here for a number of years as a conservation professional, having first come to the country in 1992 as a Peace Corps volunteer. I now dedicate myself full-time to my own photography and my Costa Rica photo tour company. I work out of my home office in Costa Rica’s central highlands, where I live with my wife, twin boys, our dogs and cats, and various hummingbirds and songbirds that visit our backyard feeders. Visit Greg’s galleries, store, and workshops at Deep Green Photography.

Posted in: General, Photography Gear

Leave a Comment (0) →