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You have THREE classes to work on this project, including the first day spent working with the tutorial.
1) COLOUR CAST CORRECTION TUTORIAL
2) COLOUR CAST CORRECTION PROJECT
3) HOW TO CHECK WHITE BALANCE SETTINGS ON A .JPG IMAGE FILE
1) COLOUR CAST CORRECTION TUTORIAL
Today, your teacher will guide you through the process of colour cast correction. This is a very useful skill when it comes to "rescuing" images that have been taken with improper white balance.
Download the full-size image from Google Classroom or from HERE.
Sample image:
This method is best used when the original image has parts that are true white and true black. It is based on the idea that by telling Photoshop what is supposed to be black, white, and true grey, Photoshop will be able to tell what the undesirable colour cast is and be able to neutralize it.
What's wrong with this image?
Well, it looks too yellow and brown, doesn't it? Sort of like a poorly-chosen Instagram filter. This is precisely what a colour cast is: an unwanted tint of your image. Our job now is to identify the intruding colour and remove it as best as possible.
Step 1: Open the sample image in Photoshop.
Step 2: Add a "Threshold" adjustment layer.
Your image should look black and white. The threshold adjustment will basically round every pixel to either black or white, depending on where you place the slider. Our next goal will be to establish the "black point" and "white point" of our image, which will give Photoshop a reference to work with.
Step 3: Find the black point. Move the Threshold slider all the way to the left (everything will turn white), and then slowly bring it back to the right until you see the first blobs of black.
Step 4: We now want to sample the black blob. Find the Eyedropper tool (keyboard shortcut = "I") and look in the sub-menu and select the Color Sampler tool (can also press Shift-I until it comes up).
Step 5: On the toolbar above the image, change "Point Sample" to "3 by 3 Average". This will help us in case the pixel we end up choosing is a bit off.
Step 6: Now that we've chosen the Color Sampler tool, zoom right in to whichever black blob "came up first" with the threshold slider and left-click once in the middle of some black pixels. A crosshair-style cursor with the number 1 should appear. If you can't see a big enough black area, go back to the threshold slider and adjust it more to the right.
Step 7: Now it's time to find the white point. Re-activate your Threshold Properties window by left-clicking on the threshold adjustment layer (see arrow below).
Step 8: This time, move the Threshold slider all the way to the right. In this particular example, there is actually pure white (255) already in the image so we can leave the slider at the far right. (In your own images, expect to move it a bit to the left). Your Color Sampler tool should still be active (re-activate it with "I" if not), so left-click inside some white area. Notice the number 2 appear. That's our white point.
Step 9: Now we're going to take some steps to find out the gray point. Delete your Threshold layer (don't need it anymore). Duplicate your background layer (select it and press Ctrl-J). Then, on the new copy, select Filter > Blur > Average.
Your image turns to a gross pea-soup-y brown-ish colour. Why did we do this? Well, in a purely balanced image, the "average" colour should be pure grey. Thus, the difference between grey and this colour is what we want to identify and remove from the original image. Theoretically, that should give us a more natural look.
Step 10: Turn off the Background Copy layer. Add a Curves adjustment layer (should appear on top of the other layers. If not, move it up there).
Step 11: In the Curves layer Properties box, notice the three eyedroppers (if you float the cursor over them, Photoshop will tell you what they are). We need to now tell Photoshop that those sample points we took earlier should in fact be pure white and pure black. Select the top eyedropper (black).
Step 12: Left-click right on top of the Sample Point #1 you took earlier. (You might want to zoom in for this so that you can be exact. If you miss and click on non-black pixels, this might wreck the image). You might notice a slight change in colour. Also, if you look at the curves graph, you'll see that the individual RGB curves have moved slightly in response to your action.
Step 13: Click on the bottom of the 3 eyedroppers (white) in the Curves Properties window and then click on Sample Point #2. In this particular example you won't see any difference because it was already pure white, but in your own images you'll likely see movement here.
Step 14: What's really going to make the difference here is the grey point. Select the middle eyedropper (grey), and then turn on the background copy (gross pea-soup-y) layer so that it's visible.
Step 15: Left-click anywhere in the image and the brown colour should turn to grey. This has removed the perceived colour cast from your image. Final step, then, is to turn off the Background Copy layer to reveal the original image. You've just calibrated the Curves adjustment layer to fix the colour cast, so your job is done!
Here's where we started, and here's where we ended up. Not bad!!!
WORTH REPEATING: This method is best used when the original image has parts that are true white and true black. If your image doesn't have anything close to pure black or pure white, this method will not work very well.
Two final tips:
1) If the effect is a little too much, you can always reduce the opacity of the Curves layer to make the effect more subtle.
2) You can also correct the image further by adding a Color Balance adjustment layer and trying to remove the "offending" color.
2) COLOUR CAST CORRECTION PROJECT
Your job is to take three (3) photos each, in the lighting conditions and using the white balances indicated in the rubric. You will then "correct" the colour cast of each one using the method we learned yesterday, and submit three (3) corrected images along with the originals.
If you weren't here last class, consult the comprehensive, step-by-step tutorial found in the previous lesson!
SHOT LIST
1) Location #1 - shoot with WRONG white balance pre-set
2) Location #2 - shoot with WRONG white balance pre-set
3) Location #3 - shoot with WRONG white balance pre-set
CAMERA SETTINGS
Shooting mode: Your choice
Image quality: JPG (NOT RAW!!!!)
White balance: As indicated above
How to change White Balance on the Nikon Z50: Check here
Other settings: Up to you!
WHAT TO SHOOT
Images can have a person in the shot, but don't have to. Subject is your choice, but create purposeful and artistic shots! Composition counts, so please do not take lame, boring snapshots that you could take with your phone.
TIP FOR SUCCESS
Ensure that there is something white (or really close to white) and black (or really close to black) in your images for the colour cast removal steps to work properly. Remember the baseball game image from yesterday? It had black and white (rather, things that were supposed to look black or white).
TO HAND IN:
1) Upload all images to Classroom.
2) Complete the rubric and TURN IN the project.
3) HOW TO CHECK WHITE BALANCE SETTINGS ON A .JPG IMAGE FILE
In-camera, you can check your settings by pressing the View button and then scrolling up or down using the D-pad.
In Windows, checking white balance is somewhat annoying. If you right click and choose PROPERTIES, you'll see this familiar menu:
Unfortunately, Windows will only list white balance as "automatic" or "manual." That's not very helpful.
So, you need to use other software to look up your settings.
Our computers all come installed with Adobe Bridge (the Adobe photo viewer), so let's use that. Go to the Start menu, type "bridge," and open it up!
It should look something like this:
Look at the bottom right, and select the Camera Data drop menu. You can drag the boundaries to make the box bigger and easier to view.
Under White Balance, it'll still only say "Automatic" or "Manual," but if you look at Light Source, it'll give you the specific white balance you're looking for:
*** One more annoying piece of information: Because of proprietary rights, Nikon and Adobe have different names for the same settings. So, be aware of the following:
Fine Weather = Sunny
Tungsten = Incandescent
Cool White Fluorescent = Fluorescent
The others should be obvious.
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