Thursday, May 21, 2009

Editing Photos for Print: When to Convert to CMYK?


Thank you for the great comments and suggestions on my posts about printing your own Artist Business Cards on my painting blog. I hope that some of you will be inspired to have cards printed (and I would love to see your results!).

Loredana asked a really great question this week: "When you work on your photos to correct levels or balancing or anything else, do you work on RGB and after you modify it, you switch to CMYK to print?; or you switch to CMYK directly and you modify it later? I noticed a big difference from one to another when I watch the folder's preview and find the CMYK quite uncomfortable to watch!"

The simple answer (with a few extra details):

For Print:

  • Start with RGB, and do all or most of your editing in RGB.
    RGB is the native format for most digital files.
    Some editing procedures are not available in CMYK.

  • Convert to CMYK as the last step only if the file is being sent to a print house.

  • If you are printing from your home or office printer, you can use RGB or CMYK. Try both and see which you prefer.

For Internet images (blogs and websites):

  • Images to be used only for onscreen viewing (websites, blogs) should NEVER be converted to CMYK.

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For a more thorough explanation of CMYK vs. RGB try this link:
http://www.printernational.org/rgb-versus-cmyk.php

(You may want to review the earlier post on File Types, too.)
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Monday, May 18, 2009

Color Balance: Removing unwanted color cast in your images

What follows is a repost of one of the most popular tips in this series thus far.
(final edited photo below: 3 Tangerines, oil, 9" x 12")


So, you've tried the Levels and maybe the Hue/Saturation tricks, but your image is still not quite there: maybe you've got a decidely 'cool' or 'warm' cast that is not present in the actual artwork. This is where Color Balance can be of use. I tend to use this one near the end of the editing process, as it seems more subtle to me. This is the tool for when your values are right, your contrast is correct, but the color is just a little off.

The image below has been edited for contrast and levels already; it does have a bit of a 'milky' look in real life, but the red of that tablecloth is off.

To open the color Balance dialog box, click Cntrl+B (Cmnd+B for Mac users, or Image/Adjustments/Color Balance in the top toolbar). As in previous tips, I've used a 'control' image duplicate on the left so you can see the change.


Starting with the Midtones, move the sliders to add more color as needed
; like many of the Photoshop tools, you will need to trust your eyes and experiment. It's also very handy to have the artwork right where you can see it as you make these adjustments.


In this case I could see that the tablecloth photo had too much purple (blue) in it, and needed to be more red. (I had painted it with a warm red earth, Blockx Capucine Yellow Deep.) The sliders were moved toward red and yellow, respectively.


In a separate step, I adjusted the 'highlight' colors
, again choosing to move toward red and yellow, but also a bit toward green. (Another mini tip: For each adjustment you make, copy the previous layer and adjust on the new layer. Then if you really get lost, you can back up).


As a final step, I adjusted the Shadows
, this time moving toward Magenta and Blue. This step was more logical than intuitive; shadows are often cooler shades. This is so close to original painting, I've amazed even myself.

Thursday, May 14, 2009

Hue: How to Correct Color with the Hue/Saturation Command


Just to show that the pros don't always get it right, either! I took this painting to a professional photo lab and paid to have a good image of it put on CD. I have to admit I was dismayed when I got it back-- my lovely chartreuse dahlia (seen at left in the final edited image: Sunny Mandahlia, 30"x30") was now leaning seriously into orange-- (see below)!
(I have the feeling that digital cameras are programmed to shoot a full spectrum of color; when given a monochromatic image, it 'confuses' the interface and it tries to make up the difference, with sometimes odd results.)



Using Hue to edit and refine your artwork photos.
In the sample below, I've opened the original file and made a duplicate layer to edit on, as before. For the purpose of the tutorial, I've made a second 'control' image to help show the changes in progress.


To begin, click Ctrl + U (Cmnd+U for Mac users, or Image/Adjustments/Hue-Saturation on the top toolbar. This will bring up the Hue Saturation dialog box.


For this image, which I want to be less red and more green, I've moved the Hue slider to the right. Notice it doesn't take much; I've only gone from 0 to 10.

Note that the Hue adjustment method tends to work better on predominantly monochromatic images like this one; if your artwork encompasses more than a short range of color you may get some surprisingly interesting (if not useful) results.



Originally when I set this tutorial up, it was to show how to correct the color shift using the Green and Red Channels in Levels. While this can be done, I found that in this instance, using Hue was much more expedient. I'll revisit the issue of color adjustment with Levels at a later date, with a different image.

Monday, May 11, 2009

Levels Part 2: Correcting a Black and White Image with Set Point in Levels or Curves.


In Photoshop, there are often different ways to accomplish similar goals.

In this tutorial, I've referenced the 'Levels ' function, but you can also try this with 'Curves'. And in addition to working on black and white images, either of these tools may help in editing your color images as well.

When you are in Levels (or in Curves), you can use the eyedroppers in the lower right corner of the box to set your black and your white. Just click on the "white" eyedropper, and then click on a place in your photograph that you know is white... then do the same thing with black... and it virtually color-corrects for you.
Diagram A.

Here's the step by step: I've opened the original dark file (as you can see, the same funky sketch from last time), and made a copy of it for on screen comparision.

To begin, Click on Ctrl + L (Cmnd+L for Mac) or from the top toolbar, Image Adjustments/Levels to bring up the Levels dialog box. (for Curves, substitute + M; the dialog box will look different but the eyedropeers will be in the same position.)

Note the eyedroppers in the lower right hand corner as shown in Diagram A above. Click on the farthest right one, the 'Set white Point' dropper. Choose an area on your image that you know to be (in life) true white (in this case I clicked on the lower lefthand background), and click on that area with the dropper. Voila!

If the image didn't turn out quite how you wanted, click Ctrl + Z for undo, and try the step again with another 'white' area of the image. (Notice the middle graph, called a Histogram, and how it changes in these steps. The histogram measures the relativve amount of light and dark across your image).

As Carrie pointed out, do the step again using the left hand dropper to set your black point; I've done it here, using the shadow under the babushka's lower lip.
Big Thanks to Carrie Jacobson who emailed me her photographer-husband's Photoshop Tip --
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Tuesday, May 5, 2009

How to Correct Contrast with the Levels function, part one.


Levels magic

Levels is one of the most useful Photoshop tools I know of. It can be used to correct both color and contrast. It takes a little practice and some trial and error, but it can work wonders to improve your photos. I'll show several examples over time of how this tool works in various situations.

Right image: Final edit, Datura, 20"x20" R. Garriott

Today’s tutorial starts with an overly dark photo. This can happen a lot when photographing paintings with a lot of white in them. Let's see if we can fix it. (Note that it’s already been cropped and aligned as per tip 2. I've made a duplicate layer to edit on.)



Click Ctrl + L (or Cmnd + L for Mac) to open the levels dialog box
(it can also be accessed from the top toolbar: Image/Adjustments/Levels)
(Note: I've shown a duplicate file to better show how the levels works)



Using the default tab (Channel: RGB), slowly adjust the three arrows until the image is closer to your original art. I suggest starting with the middle arrow first:

  • the basic rule for the middle arrow is left is lighter, right is darker.
  • To darken your darks, move the left point inward;
  • to lighten your lights, move the right pointer back towards the center.
  • Make sure the 'preview' box is checked so you can watch the transformation.
  • If at any point you feel you've lost control, click cancel and start again.
  • Once the image is where you want it, click Enter.

This image will still need a little color correction, but you can see how much improved the photo is with this one simple step.

Saturday, May 2, 2009

How to Calibrate Your Monitor


To calibrate one's monitor means to reset it to an accurate display of light and color.

To make sure your seeing your own images accurately, you may want to calibrate your monitor every couple months. (This link provides a 'test page' of black and whites that may help you decide whether to perform a calibration. Handy instructions are provided: http://www.photofriday.com/calibrate.php

Calibrating your monitor can be a simple and free process. If you have Adobe Photoshop installed, you will already a calibration tool, Adobe Gamma, installed as well. To access it on a PC (scroll down for instructions for Mac):

  • Go to your Start button (lower left corner of your screen), /Control Panel/Adobe Gamma.
  • Move the pop up box to a lower or upper corner (this will make sure it not covered up by the monitor settings overlay in the next step). Then just follow the on screen directions.


  • The pop up box will walk you through adjusting your monitor settings; when ask to make adjustments for contrast and brightness, you will want to use the buttons on the bottom frame of your monitor (example shown below). You may find it helpful to look up your monitor model online for instructions on how to adjust your particular settings.

Mac users, try this link for information on calibration for the mac: http://www.computer-darkroom.com/colorsync-display/colorsync_1.htm

Here's an alternate explanation on monitor calibration, which includes a link to a free calibration tool, Quick Gamma, for those of you without Photoshop:
http://www.wikihow.com/Calibrate-Your-Monitor


If your monitor is very old, with a faded or discolored display, and doesn't seem to respond well to calibration, you may want to consider replacing it.