Automatic zero correction. Conversion of bipolar input signals. Automatic image correction

Many functions in professional raster editors correct defects in images, but color correction has never been considered easy. Automatic correction tools eliminate routine work, leaving only the final operations to the person.

I’ve been working with Photoshop for a long time, so I was skeptical about the news that some developer had released the next version of a filter that automates the process of correcting colors in an image. But curiosity won out and I decided to try it. I downloaded the demo version and tried to understand how such software could be useful for beginners and how it would benefit professionals. Thus was born a review of automatic image correction programs.

I foresee the objection of skeptics - no program can completely replace human labor. But even professionals can get rid of routine: it’s convenient to see the result of several adjustments at once (in the best packages there are up to 7-8 parameters, some can be turned off and you can evaluate the difference). Other programs allow you to selectively influence selected areas of the image (usually limited to three standard ranges: Shadows, Midtones, Highlights and their combinations). In Photoshop, unfortunately, simultaneous viewing of options is only possible in the Variations operation, but the limited settings reduce practical benefit to zero.

But for less experienced users, when working with household digital photos, such software allows two or three mouse clicks to get a completely acceptable result. In fact, in Photoshop there are about a dozen functions for controlling image parameters (Image/Adjustments), many of them have an abyss of adjustments. If you consider that one operation is often not enough (usually the process takes 2-3 stages - correcting tonality, color balance, increasing clarity, and each can take several steps), then the means of automatically correcting the basic image parameters will become a real lifeline.

Human Software Autocorrect

Human Software does not shine with developments that are popular with designers - all products are aimed at beginners who from time to time need to “build” something at an amateur level. As a result, Autocorrect is a simple utility for quickly correcting colors in images (the first one is available and, apparently, latest version). Features include increasing the clarity of photographs, removing moire and color correction (the original mechanism gives good results). In the filter window, you can control the redistribution of tones (similar to Curves in Photoshop) in the composite image and separately in each channel. The speed of action is highly commendable.

Auto F/X AutoEye 2.0

It's just a pleasure to work with such a program

Since 1994, Auto F/X has been developing various modules for raster editors (two DreamSuite sets, DreamSuite Gel and Photo/Graphic Edges). AutoEye Available as a plug-in and standalone application. The main emphasis in the current second version was on the appearance - now it is in a fashionable aquatic interface style.

All controls are divided into three groups: Enhance Controls (removing artifacts), Color Controls (color correction itself) and Creative Controls (special effects). The first contains tools for equalizing color balance in the image (Remove Color Cast), restoring details (Rebuild Detail), noise suppression (Smooth Noise) and moire (Anti-Moire). Settings from the second affect the redistribution of colors in the image (Saturation, Hue, Contrast, Brightness). An interesting setting is Tonal Range, which increases the depth of tone without increasing contrast or changing the overall color balance. You can add additional effects such as blur (types known from Photoshop: Motion, Radial, Zoom). The module gives very decent results, but how relevant its special capabilities are is a moot point. The quality of AutoEye, assessed by removing excess colors (color cast) in automatic mode, turned out to be the highest compared to other filters in the review.

A special feature of the filter is Memory Dots, which remembers the current results for the duration of the workflow. The necessary parameters are recorded in the form of Presets.

iCorrect EditLab 3.0

The developments of the Pictographics company are little known, which, however, does not in any way detract from their significance. EditLab Possessing the most ascetic interface and the minimum number of settings among similar developments, it brings quite tangible practical benefits.

Correction is possible in fully automatic and manual modes. In the latter case, you need to manually determine the gray level in the image using a standard eyedropper, and then the white and black levels (this operation is optional). Based on this data, the utility creates a corrected image. In automatic mode, no additional settings are provided - the Auto button will do everything itself. The same window displays the brightness, contrast and saturation parameters used during auto-correction (you can edit them manually if desired). iCorrect coped well with the task of restoring the color balance, and no other product showed such radicalism (the filter almost completely suppressed the “redness” in the image). But the developers, apparently, decided to leave more advanced operations (moire suppression, clarity enhancement) for us to decide on our own.

Among the original settings, I would like to note the automatic binding of the specified areas to three specific color ranges (Skin, Foliage, Sky). It looks like this: let’s say you need to correct your complexion. First, using the eyedropper, we “clip off” the places that should have a flesh color (to make it easier to determine which colors fall into the selected range, turn on the Show sampled region parameter in Preferences), and then click Skin. The utility adjusts all colors that fall within the range to the standard skin color values ​​of Europeans. A troublesome task turns into a simple operation. The same applies to adjusting the color of foliage and sky. If the result is not satisfactory, you can reconfigure the default values ​​and save them for recall (Save Color Circuit). Expand the program's capabilities for adjusting image brightness and saturation.

Intellihance Pro 4

The first is a powerful tool for automatic complex image correction. The asset includes 8 adjustments, covering all frequently used functions: Descreen, Dust&Scratches, Contrast, Brightness, Saturation, Cast, Sharpness, Despeckle. Each has several predefined values: for example, Auto, Newspaper, Magazine and Fine Art are available for Despeckle, which guarantees the removal of moire that occurs when scanning any materials, and to align the color balance in the image, the Purify Gray Balance, Remove Cast settings have different effects. and Aggressive Removal. To facilitate the operator’s basic tasks, all settings are organized into 25 predefined sets and placed in Photoshop menu as a separate Extensis item. Of course, you can create your own settings and also have accelerated access to them.

The starting point for using Intellihance is to set the Quick Enhance full automatic correction mode, the settings of which, according to the developers, eliminate most problems. After this, you can compare its quality with the result of other settings aimed at solving specific problems (their names speak for themselves). Accordingly, the quality of the program in such a semi-automatic mode depends on how accurately the best correction option is determined. It seems to me that understanding them is very difficult even if you have experience in color correction, and the procedure for correcting an image can come down to automatically going through all the available settings. I quickly got tired of this and preferred to manually adjust only those parameters that I considered necessary.

For manual correction, the Fine Tune mode is used, in which image parameters are controlled using graphs and sliders (like those found in Photoshop), which gives additional flexibility. The result is in the same window. The disadvantage of this mode is the small size of the graphs, which does not allow you to manage them with the same degree of accuracy as in Photoshop.

Power Variations is a powerful analogue of the Variations function known from Photo-shop. It simultaneously displays up to 25 variants of the original image on the screen, while the basic one can be pre-processed (many ready-made settings are offered for different cases). The step of changing the parameters varies widely (Preferences). To control color, there is a special panel with information in the form of RGB, brightness and contrast.

A recent update (4.1) added support for Photoshop 7 and Mac OS X.

Intelligent Automation

Not a single module in the automatic correction mode showed truly high-quality results with all images (it coped well with some, but with others the processing left much to be desired).

Even on similar tasks (removing a dominant color in different photographs), the same product gave noticeably different results. There are many explanations for this, but I would like to focus on the practical conclusion: not a single program, even the most intelligent, can replace human experience. Consequently, such utilities can be used only under heavy workload, for processing many images of the same type, and only at the first stage of correction, and the final refinement must be done manually. Where would we be without them?

About the author: Mikhail Borisov([email protected]) - writes reviews for Publish software and useful tips on prepress and web design.

Autocorrect

AutoEye 2.0

iCorrect EditLab 3.0

Intellihance Pro 4

Photoshop can do it all

Photoshop provides a rich arsenal of manual color correction tools, allowing you to control the slightest nuances of color in an image. Typically the procedure consists of three stages:

1. tonal correction (setting white and black, determines the range of colors);
2. color balance correction (removing the dominant shade);
3. increased clarity (increased level of detail).

Let's start in order. Stage one - setting the brightness. The simplest operation to redistribute pixel brightness is Levels. The top chart displays the current distribution of brightness in the image, and the bottom chart shows the entire available range - from 100% white to 100% black. Three sliders are responsible for the darkest, neutral and brightest points in each channel or composite image. When you move the first slider towards light tones, the contrast of the image decreases (the darkest areas become lighter), the same happens when you move the slider responsible for the brightness of the image itself. light point, towards dark tones (shift to the gray area). Intermediate brightnesses are determined by linear approximation. By changing the position of the neutral point, you can further influence the redistribution of dark and light areas.

A more powerful operation is Curves. Unlike Levels, it changes the brightness of pixels more flexibly: the uneven law is often used to increase contrast in the image. To do this, the graph is given an S-shape: all pixels with brightness less than 50% are forcibly darkened, and more than 50% are brightened. If you move only the extreme points on the chart, you will get the same effect as when using Levels.

The second stage is adjusting the Color balance. One of the most popular color correction operations is designed to redistribute colors in an image (the main purpose is to remove the dominant hue). It is advisable to enable the Preserve Luminosity option, which preserves the brightness range.

There are other ways to change the basic parameters of an image (hue, saturation, brightness): separately in each of the main color ranges - the Hue/Saturation or Selective Colors operation; directly choosing a color using a pipette - Replace color(Replace color). By specifying the range of capture of adjacent shades, you can change the color parameters within a wide range.

To automatically correct certain image parameters, Photoshop has a built-in set of functions (Image/Adjustments) - Auto Levels, Auto Contrast, Auto Colors.

Auto Contrast increases the brightness range of an image, setting the darkest point to 100% black and the brightest point to 100% white. The intermediate values ​​shift, making dark areas darker and light areas lighter. Since the operation is performed on a composite image, no color shifts (imbalances) occur. Auto Levels does the same thing, but analyzes each channel individually. Accordingly, color shifts are almost always guaranteed. But the Auto Colors operation restores the lost color balance, and, in principle, it alone is often enough for quick color correction of acceptable quality.

Before you decide to purchase additional correction software, try all the capabilities of Photoshop first - it’s not for nothing that it is called the flagship of work with raster images.

Dealing with artifacts after scanning

As a rule, scanned images require, in addition to color correction, removal of dust, scratches, moire, and sharpening. There is a whole arsenal of tools for this in Photoshop (Noise/Dust and Scratches, Despeckle, Unsharp Mask), but for high-quality results you need preliminary preparation images - precise definition areas of influence of the filter.

The Despeckle filter removes moire that occurs during scanning. But sometimes its one-time use is not enough. Then the filter is reused or Noise/Median is applied with a Radius value of 1-2 pixels.

In principle, Photoshop can deal with dust and scratches (Dust and Scratches), but often the quality of its work leaves much to be desired (it noticeably blurs the details in the image). Therefore, it is advisable to protect small parts from the effects of the filter. Considering that they are most perceived by the eye as changes in brightness, and not color, we will work in the LAB (Image/Mode) color model. We go to the brightness channel L, duplicate it and use the Find Edges filter to highlight sharp changes in brightness (to make them appear even sharper, the contrast can be increased). We save the channel as an image mask and calmly apply the Dust and Scratches filter - the mask protects sudden changes in brightness from the influence of the filter, which is what was required.

Image Doctor

Among third-party manufacturers offering solutions to improve the quality of photographs, I would like to note the development of Alien Skin. The company is well known for its generation filters (EyeCandy, Xenofex, EyeCandy 4000, Splat!) for various raster packages. Recently, developers have turned their attention to the problems of image correction and now offer Image Doctor - a collection of four filters: Smart Fill, Scratch Remover, Spot Lifter and JPEG Repair. In principle, they do not fall under the category of tonal correction tools, since their direct work is “worn out” images.

The first of them is used for invisible retouching of large areas of the image, but for an acceptable result on a complex background it will have to be applied several times. Scratch Remover will remove small artifacts found in scanned images: scratches, fold defects. But it works extremely slowly and therefore is unlikely to compete with the usual method of cloning using the Stamp tool in Photoshop. If the image was compressed with a high degree of JPEG compression and the loss in clarity is very noticeable, try using JPEG Repair - it restores the original quality of the image (and although the main effect is achieved by the Blur Edges parameter, the result is still definitely better Smart Blur from Photoshop - the first one preserves more fine details). The filter removes the characteristic blocky structure of “overcompressed” images, only slightly reducing the clarity of small details.

Of all the filters in the collection, Spot Lifter is the most interesting. Its task is to nullify contaminated areas, smoothly transferring them into the background image. The principle of operation is based on shading the problem part (feather) with partial duplication of the border area inward. The quality of the filter is average. You can get no worse results by skillfully using the standard Photoshop set (in particular, the Healing Brush).

The cost of the filter is $130. The capabilities of Image Doctor do not justify the price, which seriously reduces its practical value.

Still Photoshop?

As can be seen from the example of Image Doctor, most of the defect-reduction tools, for which you will have to pay extra money (as well as tools for automatically correcting colors in images), are quite implementable using standard Photoshop tools. Powerful Tools appeared in the seventh version of the editor - these are Healing Brush and Patch.

Basically, Healing Brush is a more developed analogue of the well-known Clone Stamp. The tool, as it were, “dissolves” the cloned area in the edited place, exactly repeating all the features of the latter (texture, hue, brightness). This is convenient even for retouching fairly large areas of the image. Available adjustments include brush size and blending mode ( blending mode).

Patch works only on the selected area, using it as a cloned sample or retouched area. Both tools cope well with various artifacts (creases in folded areas, stains and unwanted writing on photographs).

There are several ways to remove the unwanted effect that occurs with a bright flash and insufficient lighting. Regardless of the choice, it is useful to first create a copy of the document (Image/Duplicate) and increase the size of the adjusted area in it to 100 or even 200%. In order to check how they look in the general context when making changes, place the window with the duplicate so that it does not overlap the original document.

The easiest way to suppress is the Sponge tool. By selecting right size brushes and hardness, just brush over areas with a red tint. Their saturation will decrease, and the pupil will become a more natural color. The procedure is repeated several times.

The second way is to manipulate the layer blending modes. First, “pipette” the color of the pupil with an eyedropper and on a new created layer (Layer/New) use a brush to outline the areas with a red tint. Set the active layer's blending mode to Saturation and experiment with its transparency. If the pupil looks unnatural, duplicate the active layer and set its blending mode to Hue. By adjusting the transparency of the layer, you can achieve a completely believable result.

Image brightening

Duplicate the layer and set its blending mode to Screen. If the result remains too dark, repeat the operation; if too light, try making the layer partially transparent. To darken overexposed areas, the easiest way is to create a transparency mask for the layer and use a brush of the appropriate size to darken the problem areas. Both operations with layers when adjusting images are standard, and therefore in other cases they can be used without restrictions.

Dimming the image

Duplicate the image onto a new layer and set its blending mode to Multiply. If the result is unsatisfactory, use the already known operation with repeated duplication, changing the transparency and creating a mask.

If the image is faded, you can duplicate the layer and set its blending mode to Soft Light. Next steps standard.

Increase contrast

In early versions of Photoshop, contrast was increased only by giving the curve an S-shape in Curves (or using Auto Curves), in “seven” appeared new mode Vivid light, which brightens pixels with a brightness of less than 50% and darkens the rest, generally gives a similar effect.

Magazines are freely available.

On the same topic:

Color correction integral component process of processing digitized images. The need for it especially often arises during the pre-press preparation of photographs: film negatives tend to fade over time, shifting the overall gamut of the image towards blue or red. Digital cameras also do not guarantee perfect quality due to uncontrollable errors manual settings balance. Of course, modern graphic editors have the necessary tools to correct color errors manually, but this is not very effective when processing documents in streams. Fortunately, there are a number of inexpensive third-party solutions that can automate the process of color correction of images as much as possible.

AutoEye 2.0 (AutoFX Software)

AutoEye 2.0 is a new version of the popular software product designed to improve the quality of digital images by restoring color detail and enhancing clarity. As before, AutoEye 2.0 is released as either independent program for Windows and Macintosh platforms, or as a plugin for the most common graphic editors: Adobe Photoshop CS, Jasc Paint Shop Pro, as well as Corel Photo Paint and CorelDRAW 9.0. Although all of these programs have built-in image correction tools, AutoEye 2.0 differs favorably from them due to the use of unique proprietary technologies Intelligent Visual Imaging Technologies (for example, the plug-in does not rely on traditional curves and histograms in its work), allowing it to solve the same problems more simply way, as well as automate as much as possible and, therefore, speed up their implementation.

Thanks to the use of “intelligent” tools, the developers managed to extremely simplify user interface programs. All controls are grouped into three sets: Enhancement (image error correction), Color (color adjustment) and Creative (art processing), and to control all changes made to the image, a single panel is enough, which is undoubtedly much more effective than traveling through numerous dialog boxes and extensive menus.

Color Mode Controls, in turn, is responsible for adjusting the color of the image. Through the use of advanced blending algorithms and correction tables, the program is not only able to restore colors that have faded when shooting or scanning the original, but also allows its user to change their original gamma - again, with literally two or three clicks of the mouse.

To save preliminary work results without making changes to the source file, AutoEye 2.0 allows you to save current settings in separately stored profiles. The program accepts files in .psd, .tiff, .bmp, .jpg, .gif, and .png formats as source documents. If the Adobe Photoshop .psd format is selected for processing, information about the layers is saved.

AutoEye 2.0 price $129. The demo version can be downloaded from the developer's website http://www.autofx.com/demo_center.asp.

AliveColors 1.1 (AliveColors)

AliveColors 1.1 convenient and easy-to-use utility entry level, which has extensive capabilities for color correction and retouching of digitized images with one button. Efficiency is achieved through the cumulative use of a number of procedures hidden from the user by a simple visual interface.

AliveColors 1.1 includes eight built-in color correction functions, as well as a set of traditional tools for “mechanical” image editing, including tools for selecting, cropping, rotating and inverting the active layer. Although for fine-tuning the user has access to almost all procedural parameters, in most cases the program copes with restoring image quality automatically (Automatic correction by Channels and Automatic correction by Brightness functions).

Along with automatic color correction throughout the document, AliveColors 1.1 allows for more subtle editing, such as sharpening, creating a blur effect, or selectively replacing colors in a selected area of ​​the image. It is noteworthy that the results of all operations performed are displayed in real time in the preview window, and the history saving function allows you to go back several steps.

AliveColors 1.1 supports the TWAIN protocol, so images can be loaded into the program directly from a scanner or from a digital video camera connected to a computer. The only drawback would be the overly limited set of raster file formats known to the program (there are only four .bmp. .tiff, .jpg and .png), however, this limitation applies only to the stand-alone version of the utility, while AliveColors 1.1 is also available as a plugin for Adobe Photoshop, Corel Photo Paint and Jasc Paint Shop Pro. Along with the full version, the developers offer it free option with reduced functionality (automatic color correction mode is turned off).

Price AliveColors 1.1 27 euros. A demo version can be found on the developer's website at http://www.alivecolors.com.

Color Mechanic Pro (Digital Light & Color)

Color Mechanic Pro is a plugin developed by Digital Light & Color for Adobe Photoshop and Photoshop Elements, which includes a fairly powerful and convenient mechanism for correcting and editing image color. Unlike most programs in its class, Color Mechanic Pro operates in the HSL color space, and its work is based on algorithms for separately editing channels and then combining them. Selective analysis and approximation calculations are performed in a fully automatic mode. In fact, the user's role is reduced to selecting an object for correction (color control is carried out using HSL hexagons and fine-tuning sliders); At the same time, the plugin supports selection areas created with standard Photoshop tools.

In addition to the “full-fledged” version of the plugin, the user is offered its lightweight version Color Mechanic Standard. The main difference between them is that in full version Editing of both RGB and CMYK images is available in 16-bit per channel mode, while in the simplified version it is only available for CMYK. In addition, the full version interface has several auxiliary tools, as well as an unlimited command stack for returning to a previous state.

Price Color Mechanic Pro $50. The demo version (it does not allow you to save correction results) can be downloaded from the developer’s website at http://www.colormechanic.com.

Digital ROC Professional (Eastman Kodak Company)

The DIGITAL ROC Professional plug-in is sold under the Kodak brand, one of the veterans of digital photography, but the range of potential users of this program is by no means limited to owners of digital cameras. On the contrary, this tool will be useful to any person who, on duty or in free time you have to face the need to quickly and effectively color correct a problematic image. The plugin provides the ability to both automatically restore a document and subsequently manually adjust the color balance to achieve an optimal result.

DIGITAL ROC Professional's algorithms analyze the color gradients of the loaded image to identify introduced color or overall tonal imbalance caused by poor original quality or hardware calibration errors. Based on the results of this analysis, the program generates compensating hue curves in each of the color channels (16-bit processing mode is supported). More fine tuning brightness, contrast and color range can subsequently be carried out manually for this purpose, a preview window is provided in the plug-in dialog panel, updated in real time.

DIGITAL ROC Professional works with files from a variety of sources, including digital cameras, flatbed scanners and slide scanners. In the latter case, the plugin has additional built-in tools to improve image quality by suppressing traces of film grain.

The plugin is compatible with all Adobe versions Photoshop from 5.0, Jasc Paint Shop Pro 7.0 and later, and other applications that support the Adobe plugin model. DIGITAL ROC Professional costs $50, and a demo version of the program can be found on the developer's website at http://www.asf.com.

iCorrect EditLab (Pictographics International Corporation)

iCorrect EditLab a powerful professional tool for automatic color correction of images, released as a plug-in for Adobe Photoshop and a number of other most popular graphic editors. The program mechanism is focused on complete color correction on the scale of the entire document, based on automatic analysis of the color information contained in the file, recognition of pre-defined sets of shades (for example, the color of the sky, foliage, human skin, etc.), as well as user-specified parameters and current Photoshop (or other “mother application”) color management settings.

iCorrect EditLab provides a fully automatic mode of operation, however, at each of the color correction steps, the user has the opportunity to agree with the option proposed by the computer or make his own edits to it. The entire editing operation consists of four successive stages. At the first, the program performs balancing according to a neutral shade, determining those areas of the image that should be painted in a gray color of medium intensity, thereby eliminating the effect of the so-called color cast. The second step is to find the limiting points for white and black. Next, iCorrect EditLab adjusts the color saturation, as well as the contrast and lightness of the image. The fourth and final stage is the most difficult - in it the program restores the natural coloring of individual shades.

The cost of iCorrect EditLab is $100. You can find a demo version of the plugin on the developer’s website at

Table 1 - Instructions for automatic correction of tool parameters

During machining, the cutting edge of the tool must follow exactly along the programmed path. Due to the differences in the instruments used, their dimensions must be taken into account and entered into the control system before starting to play the program. Only in this case can the trajectory be calculated regardless of the parameters of the tools used. Once the tool is installed in the spindle and the corresponding compensation is activated (compensation for its dimensions), the CNC automatically takes this correction into account.

Figure 1 – Instrumental complex

Address H performs length compensation, and address D performs radius compensation.

Length compensation is possible in two ways: in relation to the front plane of the spindle and in relation to the “zero tool”.

Figure 2 – Tool length compensation in relation to the spindle rake plane and to the zero tool

In the first case, the compensation value can only be positive (for the figure Figure 2 Н1=70.832, Н2=81.712, Н3=100.003), in the second case, choose a “zero tool”, which has a zero compensation value, and the remaining compensation values ​​can be both positive and negative (for the figure Figure 2 Н1=-20.813, Н2=0, Н3=25.821). In both cases, the compensation values ​​are stored in the corresponding table.

The center of the cutter moves along an equidistant path parallel to the contour of the part, spaced from it by an amount equal to the radius of the cutter. The equidistant path is also called the path of the cutter center. The compensation values ​​for various instruments are entered into the table; for example: D1=14 (with a cutter diameter of 28 mm); D2=22 (with a cutter diameter of 44 mm). The direction of displacement is determined by looking at the trajectory from top to bottom, that is, from the “+Z” side towards the “-Z” direction.

Figure 3 – Principle of equidistant correction

Along the contour and those frame mates for which the angle of inclination of the tangent remains unchanged, the equidistance is uniquely determined by the parameters of the contour. In other irregular cases of external frame mates, the CNC system calculates the mates of equidistant segments in accordance with instructions G68 or G69.

Figure 4 – Unambiguous definition of an equidistant contour and calculation of external connections of equidistant segments

In the case of irregular mates of internal contours, the CNC system calculates the intersections of equidistant lines to determine the desired trajectory. In some cases, this can lead to complete distortion of the contour. To avoid this, some CNC systems have a “collision control” function.

Figure 5 – Calculation of internal connections of equidistant segments

In order for the CNC system to have time to perform an offset relative to the programmed contour, it is necessary to add an approach section to the original trajectory. In this section, automatic tool radius correction is activated. Most systems require a distance of at least the tool radius to travel to activate correction. Required condition to activate the correction is the presence of precisely linear movement at the working feed.

Left tool radius compensation – G41. The G41 instruction initiates a positive equidistant offset to the left of the workpiece as viewed in the feed direction. To implement the correction, the cutter radius is programmed in the D-word, and the tool number in the T-word. Together with the G41 instruction, linear movements can be programmed; then activation of equidistant correction will occur “along the path” of movement to the end point of the frame.

N60 G41 X... Y... Z... D...

N65 G41 X... Y... Z...

Tool radius compensation right - G42. The G42 instruction initiates an equidistant offset to the right of the workpiece as viewed in the feed direction. Everything else is identical to instructions G41.

Tool length compensation - G43. Tool length compensation is accomplished by programming the G43 command and the H data word. Typically, length compensation is activated in conjunction with idle movement in the Z axis.

Cancels tool radius and length compensations – G40, G49. Tool length compensation is canceled by programming the G49 or H00 command. Tool radius compensation is canceled by programming G40 or D00 commands. Cancellation of the G40 compensation may be accompanied by straight-line movement in the active plane. In this case, the exit from the equidistant trajectory is carried out “along the path” to the end point of the frame. If circular interpolation functions are active, the action of the G40 instruction must not be accompanied by movement.

Pairing equidistant lines at the junction of frames (along an arc) – G68; along the trajectory of intersection of equidistant lines – G69. The instructions are modal and work with active equidistant correction. Their action comes down to the automatic generation of an arc (G68) or a trajectory of intersection of equidistant lines at the junction of “not smoothly” mating frames. The G68 instruction initiates automatic connection of an equidistant gap using an arc of radius r.

Figure 6 – Automatic connection of equidistant gap along an arc

Instruction G69 initiates automatic connection of the equidistant gap along the intersection path of the equidistant lines.

Figure 7 – Automatic connection of equidistant discontinuity along the trajectory of intersection of equidistant lines

As I already said, you do not need to know how these tools work, but you need to know something else - in which cases you should give preference to one or another tool to get better results.

To make it a little easier for us to understand this issue, let's slightly repeat the theory. As you know, the entire variety of colors displayed on a computer monitor is generated by shifting the three primary colors - red, green and blue.

White color is obtained by mixing red, green and blue in equal proportions and full intensity. Black is the complete absence of all three primary colors. Yellow, for example, is made by mixing red and green. Mix red and blue to make magenta, while green and blue together make turquoise. Apply shifts of red, green and blue in varying proportions and their shades in all possible shades, and you will end up with millions and even billions of colors.

Photoshop mixes these three primary colors using color channels. One channel is for red, another is for green, and the third is for blue. We can find these color channels in the Channels panel, which, by default, is nested in the same stack as the Layers panel. Click on its tab at the top of the panel group to open it:

Open the channel panel by clicking on the corresponding tab.

In the panel we see red, green and blue channels, plus a fourth RGB channel located at the top of the panel. Don't let the RGB channel fool you, it's not really a channel at all. RGB stands for "red, green and blue" and is simply a combination of the red, green and blue channels working together to give us a complete color image.

If you look at the red, green and blue channel preview thumbnails, you'll notice something that might seem a little surprising - these color channels aren't actually in color at all! Instead, each one is a halftone image. In fact, if we look at them more closely, we can see that the black and white image of each channel is different from the other. To preview how each channel looks in the document, simply click on it. For example, I'll click on the Red channel to select it:

Selecting the red channel.

With the red channel selected, the full color version of my image in the document is temporarily replaced with a grayscale version. So what does a black and white image mean when the red channel is active? This is how Photoshop shows the intensity of red in a picture - the brighter the area, the more red is added to the full color version, while darker areas have less saturated red. Areas of pure white in a black and white image have red at its full intensity, while areas of black have no red at all:

Preview of the red channel. Bright areas contain more red than dark areas.

To see what the green channel looks like in the document, I'll click on it in the Channels panel.

This action will temporarily disable the display of the red and blue channels, showing me only the green channel in the document. Here we see another grayscale image, but it's slightly different from what we saw with the red channel. This happens because the intensity of green in different areas of the photo is naturally different from the intensity of red. Again, the brighter the area, the more intense the green color it is, while the darker areas have a less saturated green. Any areas of pure white have full green intensity, while areas of pure black have no green at all:

Green channel preview. Lighter areas = more intense green, darker areas = less green.

If we now look at a black and white image of the blue channel, it will be just as different from the others and work exactly the same. My photo contains a lot of blue (or any other color that uses blue as its main ingredient), so the blue channel looks overall darker than the red and green channels:

Blue channel preview. The lighter the area, the more blue is involved in mixing the color in the full color version.

So far we've learned that Photoshop mixes the red, green, and blue color channels to produce all the colors we see in an image. Now, based on this, let’s try to figure out which of the three tools under consideration is best for us to use when. Each of the three automatic commands manipulates color channels differently, producing different results. Next, I'll briefly describe how each of them works before we look at them in action.

The Auto Contrast tool is the most basic and straightforward of the three discussed in this tutorial. When we select it, Photoshop analyzes a composite of all three color channels (in other words, it treats all three as if they were one black and white image) and simply converts dark pixels to pure black, brightens light pixels to pure white, and redistributes all other tonal values ​​between them. The result is an image with improved overall contrast. It's important to note that because it treats all three color channels as one composite image, Auto Contrast does not change the colors in the image. It simply enhances overall contrast, making it a good choice for images that don't suffer from any color issues.

Auto Tone is similar to Auto Contrast in that it also darkens dark pixels to pure black, brightens light pixels to pure white, and redistributes all other tonal values ​​between them, but it has one major difference. He doesn't do this based on three channels, mixed into one, and based on each channel separately, which means that the red, green and blue channels will also be adjusted individually. We know that Photoshop uses the brightness values ​​in each individual color channel to determine how much of each color to mix in the full color version, so by changing the color channels independently of each other, we will change the colors in the full color photo because... The brightness values ​​in the channels have been changed. This means that, unlike Auto Contrast, which does nothing more than increase overall contrast, Auto Tone changes the colors in the image at the same time it increases contrast. If an image has an unwanted color cast, Auto Tone may be able to correct it.

Auto Color is similar to Auto Tone. It also darkens dark pixels to black and brightens light pixels to white on a channel-by-channel basis, so that the red, green, and blue channels will be adjusted separately and independently of each other. But Auto Color goes one step further. Instead of simply redistributing all the tonal values ​​between them, it attempts to correct any unwanted color cast by neutralizing the midtones in the image. This is usually (but not always) done by Auto Color best choice to automatically correct contrast and solve color problems at the same time.

IN next material I will tell you how to use the tools correctly and effectively automatic settings images.