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Post-production in digital Photography…my lecture to the camera club.

Post-production in digital Photography

Post-production tools include Adobe Photoshop & Lightroom, DXO PhotoLab 7, Topaz Studio, Luminar, ON1, and Capture One Pro. Free (with purchase) post-production software includes Nikon’s NX Studio, Canon’s Digital Photo Professional, and others.

1. Shoot JPEG or Raw or both. Your camera allows you to shoot JPEG (Joint Photographic Experts Group) images, Raw files, or both simultaneously (a menu option).

JPEG shooters often have a host of camera functions and options at hand to alter JPEG image appearance. Nikon has Picture Control, Canon: Picture Style, Olympus: Picture Profiles to choose the look and appearance of JPEG images. These can be very useful in that a particular shooting style, such as Neutral, may be difficult to replicate in post-production.

Below, original JPEG image or original JPEG image created from a Raw file? No one can tell.

JPEG images are as close to a finished product as your camera’s menu selections and firmware (software) can achieve, but post-production software has a lot to offer JPEG shooters in terms of perfecting image exposure, color, sharpness, brightness, and contrast to name a few. Advanced post-production software is technically more sophisticated and easier to use than a camera’s editing tools.

Raw files are not images until undergoing “demosaicing” in a post-production Raw processor. Raw is the preferred format for many professional photographers but many professionals prefer to shoot JPEG. Unlike JPEG, a Raw image receives only minimal in-camera processing. A professional wedding photographer may shoot JPEG and Raw to provide JPEG images quickly but later process Raw files according to experience and needs.

In sum, most all camera menu options applicable to JPEG photography have no effect on Raw files. But Raw file shooters enjoy almost all of a camera’s technical and exposure options.

2. Camera, lens, and post-production software. Lens color aberrations and distortions are issues that both camera and lens engineering or post-production may address. Lens color aberrations result in blue-yellow, magenta-purple, or red-green color fringing along contrasting edges of an image. High quality lenses employ specialized low-dispersion fluorite lens elements to address color fringing. Alternatively, a post-production program can be used to remove color fringing. Some post-production programs correct color aberrations automatically.

Aberrations include Lateral (or transverse) chromatic aberration which occurs toward the outer perimeter of a lens and the common longitudinal (or axial) chromatic aberration (caused when the wavelengths of different colors (RGB) do not converge at the same point but, rather, before or after the surface of a lens’ element. These occur at the center of the lens and diminish toward the edges.

Vignetting, or darkening at the corners of an image, may be addressed in a modern digital camera’s software engineering or in post-production. This may also apply to barrel distortion or pincushioning but generally not to vertical and horizontal alignment. Both Nano Crystal and Super Integrated Coatings are used to suppress flare and ghosting and for greater color fidelity (reliability) and higher contrast.

3. White balance. White balance may be adjusted in camera or in post-production. Improper white balance choices result in 85% of all undesirable color casts in images. Many cameras deliver superior results with white balance set to automatic or automatic that preserves warm colors. I recommend automatic white balance to my beginning photography students who shoot JPEG as they may forget to change this setting in a different lighting environment which can be quite problematic to correct in post-production.

In Raw files, white balance is a “sidecar” file that can be changed without degrading the original Raw file. A user specified Kelvin color temperature can result in a warmer (more amber) or cooler (more blue) psychological “feel” in an image.

With film, we buy a film option that works well in the lighting conditions you anticipate. So, the white balance is fixed. Screw on filters also aid us in dealing with proper white balance when using photographic films. Is white paper always “supposed to be” white in an image? Typically, yes.

“Color temperature” is a concept pioneered by Nobel Prize winning German physicist Max Planck in 1900. Color temperature ranges from amber and red at 2000K, such as a horseshoe on a blacksmith’s anvil, to 3200K in an incandescent bulb, to daylight 5500K to 6500K, then blue 8000K. A giant blue star may have a temperature (and color temperature) of 10000K but things can only get so blue. In passing, absolute zero is 0K, while water freezes at 305K.

Many modern Nikon digital cameras allow white balance to be adjusted in detail. The adjustment scale can be chosen in the camera’s menu and ranges from blue to amber (horizontal) and green to magenta (vertical). “The horizontal axis is ruled in increments equivalent to about 5 mired, the vertical axis in increments of about 0.05 diffuse density units.” Link. Credit: Nikon Corporation. Illustration by Ed Ruth C 2020.

4. Color adjustments. (see attachments) Some color adjustment functions require much study, but color saturation is the easiest fundamental color tool used in post-production. Individual colors may be saturated or desaturated. Over saturation results in a “color Godzilla.” Vibrance is similar to saturation but affects colors other than primary colors.

Color casts may also be addressed by using a post-production Curves tool’s white point “eyedropper” over a suitable highlight to good effect. The Curves tool is ubiquitous to all quality post-production programs. I experiment with the eyedropper tool in areas of tonal transition to eliminate color casts.

All post-production color editing assumes a color calibrated computer monitor that is not nearly as bright as your television. Photo processing is typically done at 175 nits whereas the average television is 450 nits…much to bright for photo editing. A monitor that is too bright will produce a dark print and vice versa.

5. Histograms, dynamic range, exposure, and brightness. Histograms aid us in determining exposure by illustrating the “dynamic range” of our exposure. They also aid in establishing a white point and black point in an image as needed. I keep an eye on an image’s histogram from viewfinder through post-processing.

The height of any area of a histogram reveals the proportionate number of pixels in that tonal area. A Black and white histogram shows luminosity values or brightness. We perceive different colors to have varying degrees of brightness in uniform lighting. The luminance ratio is: Red 0.3, Green 0.59, Blue 0.11. A color histogram reveals the distribution of RGB values in an image. See also: https://edruthphoto.com/histograms/

The following works best for raw shooters. In the viewfinder we may choose to expose to the right (ETTR). Here we closely monitor the histogram to “push” highlights. Or, as they say, “expose for highlights / develop for shadows.” However, we must be cautious, or we may obtain “blown highlights” where subtle detail becomes unrecoverable.

Skilled observation of an image’s histogram anticipates a proper exposure both in the initial image and in post-production. However, we do not alter exposure settings in a properly exposed image to increase brightness, because we will lose image detail. Instead, we use a post-production “Brightness” adjustment which brightens an image from black point to white point without significantly degrading exposure. See also: https://edruthphoto.com/histograms/

Contrast is adjusted using the classic “S” Curves adjustment or a Levels adjustment. Some programs offer micro and/or fine contrast.

6. High ISO and digital noise.  All post-production software programs offer a function to reduce digital noise in an image. As we increase ISO (See: International Organization for Standardization, Geneva) we experience a loss of “signal to noise ratio” in our image. Noise is digital static at the photosite level. Light is power, less light, less power. Less power, less color accuracy. Decreased color accuracy results in noise. A quality noise reduction function reduces noise without sacrificing fine detail. The best noise reduction tools work using Raw images.

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7. Masking. Masking allows us to select all or part of an image to apply adjustments such as color correction, sharpening, color correction, special effects, or filters. Masks are created by using a selection tool to draw a “marque” around an area of the image, or by using a brush to brush in the mask as you would use a paintbrush, or by creating a variable opacity gradient fill to select a portion of an image. For example, the photographer may use a gradient to isolate an area from horizon to foreground in a landscape photograph. All post-production programs have a unique method for applying masks. Some are too complex for normal humans.

All post-production programs have a tool or tools for removing spots, streaks, blobs, and such, that can detract from our subject of interest. We may choose to adjust a brush or spot removal tool for both size and hardness. We use “feathering” to reduce hardness so that our changes will blend into the image and not be noticeable as human tinkering.

Various filters allow us to distort, stylize, sharpen, or blur an image, or create any number of lighting effects. “Plugins” are filters that may run as an attached program.

8. Sharpening…Unsharp Mask. The history of “unsharp mask” began during the 1930s in a darkroom in Germany. Sharpening increases “apparent sharpness” in an image by placing a thin “halo” between contrasting areas. Sharpening is a “magic trick” that can’t make a lens sharper than it is but can make a lens’ image appear sharper and more appealing to the eye – this is called “acutance.”

Sharpening, it has long been said, must be done in such a subtle way that the effects of sharpening are pleasing, but the technique used is not detectable.

Sharpening may be done more than once in a workflow. A specific “output sharpening” may be applied, especially when an image is intended to be printed. A slightly exaggerated sharpening technique MAY increase the visual appeal of a printed image because most printers are blunt instruments. As a novice sharpener, begin with: Amount 100%, Radius 0.5 – 1, Threshold 0.

9. Cropping and aspect ratio. We crop with an eye to enhancing visual communication or, as we say, composition. The traditional 35mm format (actually 36mm x 24mm) has an aspect ratio of 2:3. This is very close to the “Golden ratio” (Parthenon, Athens), Other aspect ratios are 4:5 (micro four-thirds also 8” x 10”), 4:3 older movies, 1:1 B&W?, 16:9 gamers or “widescreen” as in larger monitors. Typically, we may rotate an image as desired during cropping. Fill the frame?

10. Color models, color spaces, and bit depth. The three most notable color models are RGB, Lab, and CMYK. RGB (red, green, blue) are additive colors such as are used in a computer monitor. CMYK (cyan, magenta, yellow, and black) are subtractive colors used in printers and printing presses. K – the black plate is keyed to align a printing press. Your color printer very likely uses a proprietary color space within the CMYK color model. Converting RGB to CMYK is called… conversion. Within the RGB and CMYK color models there are numerous color spaces.

Your camera allows you to choose the Adobe RGB color space or sRGB color space. Adobe RGB is a larger color space. Stock photo agencies may require that images be in the Adobe RGB or sRGB color space. Many inexpensive color monitors display somewhat less than the sRGB color space. The sRGB color space is very frequently used in web pages and inexpensive color printers. In post-production, we may convert color spaces as desired, but we cannot add colors by moving to a larger color space. In-camera color space selection has no effect on raw images. Here we select a color space during output.

More sophisticated post-production programs such as Photoshop will allow you to view a proof of your image before printing. Out of gamut colors will be noticeable in the proof. Ink is money.

The trend in post-production is toward using a very large RGB color “gamut” (gamut etymology: a range of notes used in medieval music) color spaces, such as ProPhoto RGB (Adobe) in post-production. A larger color space prevents saturated colors from falling “out of gamut” during post-production manipulation. Out of gamut colors stand out objectionably in a print.

Bit depth: Color bit depth (or simply bit depth) gives us photo editing power without fear of losing image quality! Greater color depth prevents posterization (solid colors overtaking color transitions) or banding especially in JPEG images.

The Microsoft Windows 3.1 (1992) operating system used 256 colors or 8-bit (RRR,GGG,BB). (2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256). That is 2 to the 8th power. In post-production 0 is a number, so white is 0 and black is (saturated) at 255. The 0-255 scale is still used in Photoshop where midtones are in the area of 128.

Today, we have billions of colors available because we use 16-bit “color depth” during post-production. Many post-production programs automatically use 16-bit depth (16-bits for each RGB color channel). That is 2 to the 48th power (2 16th x 2 16th x 2 16th).

However, all JPEG images use 8-bit per RGB color channel but may be processed in post-production using 16-bit color depth. See: www.color.org

11. Output size adjustments, printing, and file formats. All post-production programs allow image size adjustment and compression options. All JPEG images are compressed. During output, the user selects image size and level of compression.

When we resize an image, we must supply the desired length and width, in pixels or inches, as well as the desired resolution in PPI (pixels per inch). PPI represents the image’s on-screen or in-print resolution. I resize images using 300 PPI not 72 PPI, 72 PPI is an often referenced but quite obsolete resolution.

My internet images are 1800 to 2200 pixels on the long side. My web hosting company further reduces this size to WebP (.webp) or Web Picture Format. Graphic professionals also use TIFF (Tagged Image File Format – Adobe 1986) a “cross-platform” lossless (optional compression) file format.

High-end printers use 300-360 PPI to print in so many DPI (dots per inch). Quality newspapers print at 150 LPI (lines per inch). Photographers think in pixels, picture frames are in inches. A camera sensor of 6000 x 4000 pixels, such as the Nikon D7200, will make an excellent 20 x 13-inch print (6000/300=20” , 4000/300=13”) we can push this to a standard picture frame size of 16” x 20” without noticeable loss of resolution.

12. Ethics. Original Jurassic Park: “Your scientists were so preoccupied with whether or not they could, they didn’t stop to think if they should.” Post-production that misrepresents reality can be immoral and dangerous. A false impression may encourage risk-taking. Intentional misrepresentation may be defamatory.

A four-shot panorama can be stitched together effortlessly in Adobe Photoshop.

Addendum

I have added this section concerning digital image post-production as this is so very important for maximizing the utility of every camera and lens. We often read reviews of lenses or cameras where a criticism is of a nature that can easily be addressed in post. For example, vignetting in some lenses. Such is quite easily removed (or added if you wish!) in post. So I will build upon this incrementally over time but beginning with DxO PhotoLab 7 Elite, which I believe is an exceptional Raw file processor. Ed Ruth also teaches post-production in Bakersfield, California. Link to classes here. Link to my book page here.

One of PhotoLab’s features that I find most compelling is the Light > Contrast option which includes options for Contrast, Microcontrast, and Fine contrast. An “Advanced settings” option allows the contrast to be applied to Highlights, Midtones, or Shadows as desired. In the above photo (Z50 & Z 14-30mm S, 1/4000s, f/7.1, ISO 200, EV1) texture is emphasized using PhotoLab’s contrast options. In the photograph below, shadows were deepened resulting in, perhaps, too much contrast.

Knowing when to “quit” is an important aspect of post-production.

Although post-production software can be used to process any digital image file, photographers who shoot Raw have a distinct advantage.

What is Raw shooting?
Using your camera’s menu you may choose any number of image outputs. These often include JPEG Large, JPEG Medium, JPEG Small, Raw & JPEG, and Raw (sometimes compressed Raw). I choose Raw for every shooting situation, except perhaps, interval shooting where a large number of images in Raw format would be timely to process.

The advantages of Raw shooting are many. First, Raw is an image file not a finished image. To process a Raw file, we must use software such as DxO PhotoLab to “demosaic” or interpret the Raw data. In the final stages of using such software, we choose the file format and make changes to image size as appropriate for our needs, photo print or online media. Typically, we choose a JPEG or TIFF file format. A TIFF file retains far more data than a JPEG file and is useful if further software rendering is anticipated such as in Photoshop.

Second, a Raw file includes exactly what your camera’s sensor captures. A modest amount of in-camera alteration is needed for us to use the Raw file. Much of what a camera’s “CPU” does to process the light that strikes a sensor involves math most of us would run from screaming.

Third, a Raw file has a wider “dynamic range” than a JPEG file. While all digital images range from black point, shadows, three-quarter tones, midtones, quarter tones, highlights, to white point, a Raw file delivered to us at 16-bit depth whereas a JPEG file is an 8-bit file. Eight-bit (2 x 2 x 2 x 2 x 2 x 2 x 2 x 2) gives us 256 tones from black point to white point whereas 16-bit gives us 65,536 tones from black point to white point. In digital post-processing, 16-bit is like having $65,536 for vacation vs $256. Both are in the same black point to white point wallet, but the greater sum offers you many, many more options.

If we alter shadows or white point in a JPEG image, we risk banding or loss of color detail. With a 16-bit Raw file we would really have to go nuts to risk losing a detectable amount of tonal information. Suppose we took an image 5-stops underexposed. Using Raw processing, we can bring such an image back to the point where we can recognize it. Not so much with a JPEG file.

Fourth, Raw gives us everything our sensor can deliver without compression, All JPEG images are compressed to some extent, thus JPEG Fine, Normal, or Basic compression ratios. Consequently, a JPEG Small with Basic compression is a small image indeed. A Raw file can be output to any JPEG size or compression ratio. Raw’s power is in post-production options. These are many.

Fifth, white balance adjustments are a “side-car file” to a Raw file. Not so with JPEG where white balance is backed into the finished JPRG product. This is not to say we cannot add a touch of cool blue (higher Kelvin color temperature) or a dash of amber (lower Kelvin color temperature) to a JPEG file but with a Raw file no tonal information is lost in the transition.

Sixth, although shooting Raw requires Raw processing software, DxO PhotoLab performs this task effortlessly for almost every imaginable camera. In fact, DxO has researched almost every combination of camera and lens to produce a workflow that maximizes the potential of the camera and lens you are using. So, when I shoot My Nikon Z50 with my Sigma 50mm f/1.4 Art lens, no worries. DxO has tested this combination and PhotoLab responds accordingly.

Seventh. When you shoot Raw, we do not have to worry about Picture Control, high ISO noise reduction, “Scene” modes as PhotoLab can deal with all such stuff. Lens distortion or chromatic aberrations are also managed very well by PhotoLab.

Eighth, to enlarge an image for print, nothing beats what can be done with a Raw image. There are a number of programs available that can double the effective resolution of your modern digital camera without noticeable (mentionable anyway) loss of detail.

I hope that I have talked you into switching from JPEG to Raw. But if you have been a JPEG shooter for some time, you can transition from JPEG to Raw gradually by shooting both (Raw + JPEG in the menu).