Thursday, October 21, 2010

Grayscale conversion of color images by Paul Baldassini

Please contact me via email:
paul@baldassinifineart.com

Conversion to grayscale

In keeping with recent Studio Notes, I am republishing this post with some minor edits and as a stand-alone Photoshop Studio Note.  This Studio Note and all previous ones will soon be available as downloadable .pdfs on my next website update which include a new page RESOURCES.

After over 30 years as professional graphic artist, I have grown quite used to using image editing software -- mainly Adobe Photoshop -- to develop my compositions.  I am very comfortable with this way of working even though I sketch and draw often, usually at cafe’s. My compositions are initially developed using the viewscreen on the back of my digital camera (I use a Canon G10, an incredible little machine for under $400) and then the images are assessed for usability in Photoshop.  I use both Auto and Program mode, Auto for a moving subject like a farmer on a tractor for example and Program mode for stationery objects, like hayrolls or a tractor idle in a field. This requires a VERY steady hand but produces fantastic source material for paintings.  I will elaborate on this technique in a future Blog posting.

Nothing beats a grayscale image for checking values so I always create a grayscale version of my completed composition as visual reference to check values while painting both the underpainting and overpainting. There are many ways to do things in Photoshop, but the easy way is often not the best way.  Going to MODE >Grayscale and converting from RGB to Grayscale almost always produces a muddy, flat and dead looking image.  And this may be fine for most people, but I use my grayscale conversions for a lot more than just checking values.

First, I can use the data stored in each of the 3 channels (assuming RGB color mode) to significantly improve the tonality and contrast of my original image by creating new alpha channels that have been blended from the Red, Green and Blue channels. If you click on each of the 3 channels separately you will notice that each channel is, firstly and most importantly, a grayscale image already.  From the top (Red channel) down each channel gets progressively DARKER. The Blue channel contains all of the bad stuff -- in a portrait for example, the Blue channel contains the pimples, wrinkles, 2-day beard growth, etc. along with all of the noise (grain) present from the original camera settings.  The GREEN channel, however, contains all of the good stuff this channel BY ITSELF, again in the case of a portrait, will produce a MUCH better grayscale image than simply converting the whole image to Grayscale Mode.

There are several ways to do this.  One is to simply click and drag the the Green channel into the little dog-ear icon at bottom left of the Channel palette right next to the little trash can.  This will DUPLICATE the Green channel into a NEW alpha channel named “Green copy”.  You can easily duplicate Layers the same way.  Then go Image >Mode and select >Grayscale.  You will get a dialog “Discard other channels?”  Click OK or hit the ENTER key and you now have a single channel Grayscale image. Go to >File >Save As and name and save your new image.

A better, and more advanced, way if to use one of the two most powerful and overlooked functions in Photoshop -- Calculations and Apply Image.  They live in the >Image drop down as shown in the screen grab here.  Calculations is used for generating new grayscale Alpha channels only and Apply Image is used for effecting real-time changes to the original color image only.  This post will only deal with the Calculations functions.

For this demonstration I will use a portrait as they best illustrate the technique of grayscale channel blending.  The image is of my daughter. The original image is an RGB file as seen here and next to that is a standard grayscale conversion.  Very dull and flat.  After examining the channels it can be clearly seen that although the Red channel image is too light in the facial tones, the Blue sweater has much more detail than in the Green channel.  The facial tones look much better in the Green channel but the sweater is very dark.  I could use the Green only -- I think its better than the converted Grayscale image -- but it can easily be improved by blending, or combining, the best data of both the Red and Green channels.

Left: original RG image; right: standard grayscale conversion


Below is screen grab of the pane and here’s how it works: go to >Image >Calculations and you’ll get a new pane with options to set and change things.  The first one is Source 1 which is the name of your open file. Unless you have another image open the same physical size, this will be you only option here.  Source 1 has two sub-menus: Layer and Channel.  Unless your file has more than one layer, Background will be your only Layer option here.  If you have more than one layer, be sure to set to the layer you want to blend channels from. The second sub-menu is Channel and here is where you choose the first channel you want use to blend.  Choose Red.  Everything repeats again for the next set of options, Source 2 and your only choice here is your open file so leave it alone.  Set Layer to Background or leave it alone also, and then for Channel choose Green.

Calculations drop-down menu and work pane


Next is where you can really make some radical changes to your grayscale image depending on which Blending mode you choose.  Blending modes are the real core of Photoshop’s ability to manipulate images and If you have never worked with Blending Modes before they may seem daunting.  But please try some out here to see what happens and then you can try them out later on your layered files in color, in real time.

For this demonstration I want to combine or ADD some of the Green channel to the Red channel, so from the drop-down Blending menu I cho-se Add, >Opacity 100%, >Offset -20, >Scale 2.

Finally at the bottom, you have another drop-down menu where you can choose what to do with the new channel you just created.  The default is New Channel and most often this is what you should do. The default option adds a new alpha channel to your file and you can do with it what you will.  So just click OK, or hit the Enter Key and you will be now see a NEW 4th channel in the Channel palette named Alpha 1.  Double-click on the type only and name the new channel.  I chose “Red.Green.add.-20%” so I could remember what I did.

To make a NEW standalone file click on the new channel highlighting (a blue tint), then go Image >Mode and select >Grayscale.  You will get a dialog “Discard other channels?”  Click OK or hit the ENTER key and you now have a single channel Grayscale image. Go to >File >Save As and name and save your new image.

The other option is to select >New Document. Click OK, or hit the Enter Key and you will now have a new file automatically in Grayscale mode.  Just save and name the new file.  If you compare the standard Grayscale conversion to the Calculations generated function version you can see the difference, even though that differernce may not be that apparent on your monitor and/or at this resolution.

Left: Red channel; center: Green channel; right: blended Red & Green channel





Below is the same treatment applied to a source image for one next paintings. At top left is the standard Grayscale conversion. The others were generated the same way as in the preceding demonstration.  The main way that I utilize my Grayscale images is to produce a large paper proof same size as my prepared panel.  I use this paper to produce an outline drawing of my composition onto my panel by sandwiching a piece of Sally transfer paper between the proof and the panel. The standard Grayscale conversion would have produced too dark an image for me to see the traceable detail, but the Red channel combined with the Green channel kept all important detail light enough to see and easily trace onto my panel.

Top left: Standard Grayscale conversion; top right Red channel; bottom left:  Green channel; bottom right: blended Red & Green channel

Sounds like a lot of work but its actually quite fast, the variations are unlimited and I find it well worth the effort.  It also opens you up to new creative levels of understanding in Photoshop which can only improve your design and composition choices. I urge you to try many of the Blending Modes, especially on layered images, and change the opacity on some to produce a very different range of possibilities from the original image.

That’s it until my next post.  Thanks for visiting.

P.

Tuesday, October 19, 2010

Receding Hayrolls field study — Paul Baldassini

Please contact me via email:
paul@baldassinifineart.com


Receding Hayrolls
Oil on linen, 14 x 16 inches
$375 unframed, plus shipping

This study was started in the field two years ago. I finally got around to completing it in the studio recently after rearranging the hayrolls to make for a more pleasing composition. Although nature always provides the most spectacular sources for painting inspiration she doesn’t necessarily always cooperate in the design department. So I took liberties and license and after a bit of reworking the layout settled on this composition. A few color adjustments and a glaze to darken the lower foreground made it a keeper.

Monday, October 18, 2010

Image Adjustment Part 2: Shadow/Highlights

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“Creativity is allowing yourself to make mistakes. Art is knowing which ones to keep.”   — Scott Adams

Before the introduction of the  Shadow/Highlight Adjustment  in Photoshop CS in 2003, it took a lot of moves to make an underexposed image usable.  False Profiles  (see Studio Note Assign/Convert Profile) were usually the starting point followed by channel blending and then a healthy dose of Curves. If you worked at it long and hard enough you could salvage almost any image and make the client — and yourself — very happy. No need to reshoot or start from scratch or wonder when you’ll ever catch that great sunset again.

Those days, for the most part, are long gone although I still regularly use channel blending, occasionally  False Profiles  and always use  Curves  to adjust images. Thanks to the  Shadow/Highlight Adjustment (SHH)  command complex image manipulations are performed in the background using a simple front end dialog for getting the job done quickly. The Shadow/Highlight command quickly became a favorite with photographers, photo retouchers (like me) and pre-press professional for its amazing ability to bring out details in the shadow and highlight areas of an image that were too dark or too light to see. In fact, the Shadow/Highlight command is so good at bringing out image detail that I apply it to just about all of my images, even those that at first glance don’t seem to need it.

Shadow/Highlight  is only available as a standard image adjustment, not an  Adjustment Layer.  Standard image adjustments are permanent so its a good idea to to protect the original image. So before doing anything (and you should ALWAYS do this first before working on ANY image) duplicate the original image by click-dragging the  Background Layer  onto the little dog-eared icon at the bottom right of the  Layers Palette. You now have new layer named by default  Background Copy.  Double-click the name Background Copy. It will turn a light blue color and you can type a new name right over it. I usually name the layer add  SHH at the end.

Photoshop Layers Palette. The New/Duplicate Layer icon is circled in red.

Now open the  Shadow/Highlight Adjustment  window by going to >Image, >Adjustments, >Shadow/Highlight and you’ll see a window that looks like this:

Photoshop Shadow/Highlight Adjustment default window settings.  They will produce an unsatisfactory adjustment and need to be changed.  Start by checking the Show More Options box.

Shadows  value of 50% is usually way too much to start with and will result an unnaceptable image adjustment. A simple change to the default settings is all that’s necessary to quickly produce a significantly improved image. Start by checking the  Show More Options  dialog and you’ll get an expanded window that looks like this but with default Photoshop default settings instead of my settings that you see here.

Photoshop Shadow/Highlight Adjustment with new values replacing the default settings. These settings will give you a much better starting point for producing a great looking image and you can adjust them as necessary for each image. Click Save As Defaults after resetting the numbers and these settings will be permanent whenever you call up the Shadow/Highlight Adjustment .

The expanded version of the Shadow/Highlight dialog box appears a bit intimidating at first, especially since the simplified version contained only two sliders, but not to worry. The expanded window is divided into three sections — two of the three sections,  Shadow  and  Highlight,  are exactly the same with each group containing three sliders to help bring out shadow or highlight detail in the image. Below the Highlights section is the Adjustments section which offers a few more options for adjusting the image.

The first slider,  Amount,  is straightforward enough. It controls how much you want to open up the shadows, making them appear brighter. After you become more familar with what the various setting do to alter the image you can just punch in the numbers. But for now draging the sliders is the way to go and you’ll see the results on your image in real time as you make your adjustments. Drag the slider towards the right and you’ll recover more shadow detail. Rarely, if ever, will you need to set the amount past 50 as your image will start to look weird and unnatural. start  If you drag it too far, you'll brighten the shadows too much. That’s why I start with a value of 25 — to see how it looks then go up or down as necessary from there. Every photo is different so just keep an eye on your image as you drag the Amount slider and set it to whatever looks good for now.

The next setting is the  Tonal Width  slider. This determines the range of tonal values that will be affected by the adjustment. Lower numbers affect only the darkest areas (values) of the image. Moving the slider to the right will expand the range to include more of the midtone values. There’s no right setting so just experiement to see what looks good for your particular image. A good starting point for  the Tonal Width  setting of 50%.

The last slider in the group is the  Radius  setting which determines how the other two adjustments you just made will blend in with the rest of the photo. A low Radius value will make your image your appear noticeably flat with harsh transition areas between the adjusted and unadjusted areas of the image. I think a higher Radius value works best so start with a value of 90 pixels and adjust up or down from there. After setting the Radius value you may want to go back and re-adjust the first two settings — I often go back and forth several times before I see something I like.

The  Highlights  group works the same way as the  Shadow  group. I tend to go easy on the highlight settings as overall image contrast can easily be compromised so minor changes often help. My new settings are: Amount 6%; Tonal Width value of 50% and a Radius value of 90px. The settings that work best on your image will most likely be different but these settings deliver a good starting point.

The last group,  Adjustments,  help to restore color saturation and midtone contrast that might have been lost after making the new Shadow and Hightlight adjustments. The first slider,  Color Correction,  is not really a color correction at all, but a saturation adjustment.  Move it to the right and the color saturation increases; to the left the color is neutralized. The  Midtone Contrast  slider is used to increase midtone brightness values giving the image a bit more “punch” if desired. Leave the default  Color Correction  alone and setting  Midtone Contrast  value of +6 is a safe start.  Black Clip  and  White Clip  specifies how much of the shadows and highlights will be clipped (reset) to the new Shadow (0) and Highlight (255) colors in the image. Larger values means greater image contrast so don’t set them too high or you’ll be right back where you started, more or less.

Lastly, after resetting the numbers, click  Save As Defaults,  and the new settings become the default settings. Below is an image before and after these new default settings have been applied. Simple, painless and no need to adjust further. At least as far as image  Shadow  and  Highlight  are concerned. Of course, there will always be the need tweak an image further and it will usually be necessary to make a REAL color correction, most likely by applying  Curves,  and then the image will require  sharpening.

Left: Original image from digital camera sRGB default color space.  Right: Same image with Bruce RGB Assign Profile and new Shadow/Highlight Adjustment applied.

That’s for Image Adjustments Studio Notes parts 3 and 4.

See you soon!

P.