Introduction to Digital Imaging
Lesson 2 | Tonal Correction, Sharpening & Making Selections
This lesson introduces you to sharpening images, making selections and colour correction.
The aim of tonal correction is to make the pixels within an image span a greater range of values from dark to light, this is also known as increasing the dynamic range. Doing this enhances the shadows, mid-tones & highlights, to make your image look more detailed and interesting without compromising any detail elsewhere in the tonal range.
Getting more detail from your image adds more interest to your artwork.
You can enhance an image quite dramatically by adjusting the span or dynamic range of dark-to-light pixels.
Caveat: as a designer, you need to decide how much an image needs adjusting; a picture of a boat at twilight on Great Lake in a Tasmanian winter would be fairly "low-key" ie: predominantly dark or shadow tones.
In this scenario, maximum benefit would be gained by adjusting the shadows & quarter-tones (the middle to darker parts of an image).
Always keep in mind the purpose of the image before you start to change it. For example, will there be a trophy phrase / catch phrase that needs to be in there with the image? If there does, the image may need to be dark to make the type stand-out.
In the example opposite the designer has made it too bright, compromising the "nature" of the image. There is more detail in the mid-tones/ shadows but it has lost that "dark and treacherous" feel and the clouds have been "blown out" and they look "over-exposed". The solution here is to restrict adjustments to everything but the sky. This is where adjustment layers prove useful.
Photoshop expert Martin Perhiniak has developed a series of very useful videos ( PSDTuts+ Photoshop Basix ) that cover all sorts of Photoshop related skills. The core information offered is timeless and well worth the effort.
Watch his Histogram video (see opposite) for an explanation of what "shadows, midtones & highlights" mean in the context of digital images.Watch Episode 8, Adjustment Layers ( you can even download the images used ) then do Learning Task 5 : Adjustment Levels (see below).
Other video tutorials worth looking at:
Adobe TV ( then click on "Photoshop" ) and watch the "Learn Photoshop Getting Started 02 Brightness and Contrast" video tutorial for Photoshop CS3/4.
Youtube hosts a variety of support material from Adobe that covers tonal adjustment.
High Dynamic Range (HDR)
HDR is a trend that's popular because it exaggerates the tonal spread of image data. The tonal correction in HDR makes images look surreal with an explosion of detail across the spectrum.
Check these examples out at Six Revisions. HDR is something an entry-level mobile phone can do.
Photoshop Cafe explains how to make your own HDR image using Photoshop. For this technique you'll need a camera with variable exposure (aka F-stop aka Aperture).
Learning Task: Correcting using Adjustment Layers | Approx. 2 hrs.
Take a photo using your camera's highest pixel count setting at dusk or low light and another during high-noon in full light; avoid direct sunlight however, a bright but overcast sky is good.
If you have full manual control, use Av (aperture priority) and adjust the aperture to get even tones. An F-stop of 3.5 widens the aperture for low-light, conversely F-stop 10-20 reduces the aperture when shooting in bright conditions.
If you don't have a camera with manual control it's likely you'll instead have "presets" for shooting in low or bright light scenarios. Use a preset instead.
For more details on how camera controls work, Digital Photography School is a great place for beginners.
Use a tripod or if you don't have one, rest your camera against something solid. Avoid just holding your camera unsupported when you take a shot. A remote trigger or the auto shutter trigger works well if you don't want to handle your camera at all. Use a timer if you have one.
Save the originals somewhere safe and work on copies in Photoshop.
Use your preferred adjustment layers technique ( curves, levels, vibrancy ) to enhance the images so there is a natural spread of tone with detail in the shadows and detail in the highlights and natural colour.
Critical to this activity is to have your camera either on a tripod or held steady against something stable. If there's even the slghtest movement during the shot you'll lose clarity.
Publish all four images as 1024 px wide, RGB (it should already be RGB, by default), 50 quality jpg to your blog and submit your blog's URL for feedback.
Caption your final images by describing what you thought about the process; did your adjustments make the image better ? Which method gave you the best results? Did you lose any detail ?
Chris Adams 2017
In addition to tonal correction a designer is expected to be able to fix the colour in an image; Photoshop to the rescue! Photoshop offers lots of ways to colour correct your images.
A quick and sometimes effective colour correction tool is Photoshop's Auto-Colour. Try it out; open an image and hit Shift-Ctrl-b or on a mac, Shift-CMD-b . It's easy, but for more control over colour correction you need to put some effort in, so read on.
Check out Photoshop expert Deke McClelland's video tutorial on using adjustment layers which cover a lot of the tools that you will find useful when adjusting colour. There's more to colour correction than what Deke offers but for our purposes it's enough.
If you come across any problems regarding colour correction then you are encouraged to discuss them in our Digital Imaging Forum.
Sharpening an image
Sharpening is an essential step if you want to enhance hidden detail in an image. Just like tonal correction, it can add value to the image. Sharpening can bring an image "to life".
The Photoshop "Unsharp mask" tool offers the best quality for this purpose; it offers greater control over the process, this is a favourite of designers who need to send high quality pictures to print.
"Smart Sharpen" (FILTERS/SHARPEN/Smart Sharpen) is a more popular option for web designers, it offers enough control for the lower-res images that the web uses and it's a lot less fuss.
However, for a detailed explanation of several sharpening tools in Photoshop, watch the tutorial ( 7 mins) from Martin Perhiniak on PSDTuts+
Note: The source image of the cat isn't supplied in this instance).
Note: It's worth watching Martin's video tutorial on Photoshop "Smart Objects" before you watch this.
A selection in Photoshop is the region that the user "marks-off" or isolates ready for some sort of adjustment or alteration. It's very similar to the masking function in Adjustment Layers.
Why make a selection?
Watch this 12 min. tutorial video from Lynda.com. It's for Photoshop CC but applicable to all versions. It demonstrates why selections are useful.
Photoshop has lots of ways to make a selection. This is one of its strengths. No other image editing application has the same flexibility in this regard. Here's a list of ways to make selections :
- magic wand/ quick selection tool
- rectangular, elliptical, single row/single column selection tools
- quick mask mode (very flexible method using standard brushes to make selections)
- make selection from alpha channel (sophisticated approach when working with fine hairs)
- pen tool then convert the subsequent path to a selection
- colour range select (making selections based on colours)
- type tool without filling to make type-shaped selections
- lasso tool, polygon lasso tool & magnetic lasso tool
- quick selection tool
- ctrl-a (Apple-A) = select all the image
- ctr-l (Apple-D) = de-select current selection
- ctrl-; (Apple-;) = hide selection outline
- inverting selections
- transforming selections (Howard Pinsky | YouTube Instructor)
You'll be practising a few of these methods in Learning Task 6 | Kathy Car.
Watch this 10 minute tutorial video from "Infinite Skills" (see right), it's for CS5 but also applies to CS6. The instructor Andy Anderson demonstrates a range of selection techniques that we'll be using a lot for our Photoshop work.
The latest selection Tools in Photoshop CC2015.5
This 14 min tutorial video demonstrates new "Select & Mask" Tool. It's a tool that can deliver results very quickly and easily. It doesn't work on all images however, only ones with a distinct high-contrast edge for the item you want to select.
Making Selections & Combining Images
Making selections and combining images goes hand-in-hand. A designer is often asked to combine images together to add greater interest to the message/ product.
The Kathy Car task (below) combines images using a simple drag and drop from one Photoshop document to another.
Things to consider when combining images :
- images might be different sizes
- images might be different resoultions
- images might be different modes
- images might be different colour/saturations
- images might have mis-matched lighting settings and the sun angle / shadow angles are different
Combining images with different sizes
A great work-around for combining images with different sizes is the "transform tool".
If you drag n' drop or copy n' paste an image into your Photoshop document and it's the wrong size, then simply EDIT/TRANSFORM the image and drag the handles to re-size it.
Mis-matched colour modes
If the image you want to combine is a different mode (RGB or CMYK for example) to the one you're already working on then change either one so they both use the same colour mode. If the images are different colours or saturations use the adjustment layers techniques to remedy.
Using a mask to combine images. This links to a great short text tutorial on PlanetPhotoshop.com that might help you in the LT6: Kathy Car Task.
The Patch Tool & Clone Stamp Tool
There's another thing you need to know how to do before you jump into Learning Task 6 and that's how to remove artefacts such as spots, wires, scratches and street clutter.
There's several ways to do this and the Patch Tool is a great way to remove spots, dots, telegraph poles and wires and for finer control the Clone Stamp Tool is a great option.
Learning Task: Kathy's Car | Removing artefacts, making selections & combining images | Approx. 6-8 hrs.
Selecting artwork and changing its background is a popular task in print/web publishing and Photoshop offers tools such as Patch, Clone and Quick Mask to make the process relatively easy.
For demonstrations of the Patch Tool, Clone Tool and Quick Mask Tool, download and view the supporting demo. videos from our shared Google Drive Folder. Contact your teacher to get access.
Download this image of Kathy's car Open it in Photoshop, remove the street furniture (chain and bollard), select the car using either Quick Mask or Pen Tool method and with your Move Tool, drag it into a destination image. Not sure how to do this? Watch the supporting videos or jump into our Digital Imaging Forum and ask for help there.
Note: Any images you find need to comply with copyright license. If you grab an image off the Internet ensure it's ok to use. Creative Commons (CC) offers very flexible usage rights, another simlar source is UnSplash and for even more free options.
Match your background
Key to the success of this task is to get the sunlight and shadows on the car to match your background, so study the kathycarcrop image and then take a photo that has similar light/ shadow direction and saturation / brigthness.
Submit it as a 60 quality .jpeg via email and publish to your blog with a caption describing what you thought of the activity, what did you find easy / hard and where can you see yourself using this skill.
Chris Adams 2017
Layer Masks | Merging images together
Understanding how Layer Masks work in Photoshop is vital if you're interested in making high quality compositions.
"Technoscott" on YouTube does a fine job of explaining how Photoshop Layer Masks work (7:41 mins)
Here's another YouTube video from bluehourphoto.com on essentially the same thing (shown opposite).
Sitepoint offers a similar resource worth a look:
This demonstrates how you combine two images together with a linear fade.
For a detailed explanation of some of the amazing power of Photoshop in combining / merging images including Layer Masks check out this demonstration by Martin Perhiniak at PSDTuts+ Basix
Watch the videos then try Learning Task 7.
Learning Task: Combining Images using Layer Masks | 4 hrs
This task requires you to use a layer mask to merge two photos. Here's another reference for learning more about layer masks and combining images.
The Brief :
You need to produce artwork that demonstrates your mastery of merging images using a Photoshop layer mask.
The only guidelines are it needs to be 1000 px wide, RGB and saved as a .jpg 60 quality. The theme is up to you.
Publish to your blog and submit your blog URL using the Assignment Tool | Notes option. Caption your photo with comments on what you thought of the process.
Chris Adams 2017
Lesson 2: Summary
Mastering the selection tools, layers masks, tonal correction / sharpening tools and blemish removal tools are an important part of image editing. Being able to use these gives you a lot of creative options.