Beginner’s Guide to Sharpening your Photos using Unsharp Mask
Introduction
This guide is a basic introduction to sharpening your photographs in Photoshop using Unsharp Mask, which despite its unlikely sounding name, is the tool of choice for most photographers.
When to Sharpen your Photos
Deciding to sharpen your photographs, and by how much depends on whether your shoot your photographs as JPEGs or in RAW format.
JPEGs
JPEGs have already been sharpened, colour saturated and had contrast adjustments made by your camera, based on the camera’s internal settings. In producing a JPEG, your camera does much of the photo editing work and throws away what it regards as unnecessary data in order to compress the file size and present you with your ready-sharpened photograph.
Sharpening JPEGs further in Photoshop is mostly unnecessary and can result in over-sharpened images (see below). In some cases, additional sharpening in Photoshop might be possible providing it is done on a very limited basis and with care.
RAW
When your camera is set to capture images in RAW format, your camera produces files (photos) that are not manipulated by your camera. It captures all the data from the scene and then hands the image over to you to make adjustments to sharpness, colour saturation, contrast and a range of other variables. Because data is captured in its RAW state and is uncompressed, file sizes are much larger than JPEG files.
With RAW files YOU are in charge of producing the final image, not your camera’s internal settings. As a consequence, you have much more scope to sharpen your RAW images, and make other adjustments using Photoshop. It does mean that you have to spend more time in front of your computer but RAW allows you to be much more creative and produce compelling images.
When Sharpening Can’t Help
Sharpening will not, magically, put out-of-focus photos back in focus, and it won’t make blurred images sharp. It may help give the illusion of improved focus by adding contrast, but that’s all.
It’s essential to capture as good an image as possible ‘in camera’. This means taking care to focus correctly and avoiding camera shake. Use a suitably high shutter speed when hand-holding your camera and a tripod/cable release with slow shutter speeds. After taking your photo, zoom in using your camera’s preview screen to check that your image is sharp.
Effects of Over-sharpening
Over-sharpening makes your photos look ugly. Unsightly haloes appear along edges and dark edges become hard and jagged, pixels become blocked together, losing detail, and other pixels may change colour completely. Over-sharpening also makes any digital noise more prominent.
(Digital noise are random coloured pixels, sometimes seen in shadow and sky areas – more prevalent when shooting at high ISOs.)
How Unsharp Mask works
Unsharp Mask works by enhancing the appearance of detail in an image. It does this by adding tiny increases in contrast at object boundaries. These are known as sharpening haloes. This added contrast results in sharp transitions and detail with clearly defined borders, making the image look sharper overall.
Why is it called Unsharp Mask?
The term Unsharp Mask is a throw back to the days of print processing, when edges of images where masked during processing, to make them look more defined, resulting in photographs which looked sharper.
Where to find Unsharp Mask in Photoshop
In Photoshop or Photoshop Elements, depending on which version you are using, you’ll find Unsharp Mask under the Filter, Sharpen or Enhance drop down boxes, at the top of your Photoshop screen.
Important: Do sharpening Last
It is important to do any sharpening as a last step in editing/enhancing your images. This is because any subsequent adjustments can undo or damage your sharpening.
How to use Unsharp Mask
You will need to have a photo displayed in Photoshop before using the command (sorry if this sounds obvious). Clicking on Unsharp Mask brings up a smaller dialogue box and a mini preview area (check the preview button to display the area at the default 100% view).
The dialogue box has three sliders for Amount, Radius and Threshold. You can adjust these by using the sliders or entering a value directly into the boxes above them. (This is discussed below.)
Test the effect of the changes you make by placing your cursor over the mini preview pane and left clicking with your mouse. This shows a zoomed in portion of the image at 100%, which displays before and after views of the sharpening effect.
To view another portion of your photograph in the mini preview pane, move your cursor back over your main image and left click with your mouse.
About the Unsharp Mask controls
Amount
The Amount setting allows you to adjust the intensity of the sharpening i.e. higher values result in higher contrast along edges. (Settings range from 1 to 500%.)
A good starting point when sharpening RAW images is 100%.
Radius
Radius controls the width (from 0.1 to 250 pixels) of the sharpening haloes. Low radius settings produce narrow sharpening haloes, higher settings produce wider ones.
The value you use depends on the type of image that you are editing and its resolution. Images with lots of narrow edges and fine detail require slightly lower radius settings than images with wide edges and less detail.
Additionally, low resolution images require smaller radius values than high resolution images.
A setting of 1 is a good place to start.
Threshold
Threshold specifies how much difference in brightness must be present in adjacent pixels before any sharpening is applied. (Settings range from 0 to 255) Low values apply the sharpening to edges with very little contrast. Higher values sharpen only when pixel contrast is higher.
The Threshold setting lets you protect skin tones and slightly noisy skies from being sharpened. Beware: Increasing the value too high can cause unnatural transitions between sharpened and unsharpened areas.
A good starting value is 1.
Suggested Unsharp Mask Settings*
For people:
Amount 150%, Radius 1, Threshold 10
For cityscapes, urban photography, or travel:
Amount 65%, Radius 3, Threshold 2
For general everyday use:
Amount 85%, Radius 1, Threshold 4
*Courtesy of Scott Kelby’s book: The Digital Photography Book Vol. 1. How to make your photos look like the pros’
1Take photographs on bright but slightly overcast days – avoid harsh sunlight.
2Take photos early in the morning – the light is softer and warmer.
3On bright, sunny days diffuse the sunlight or shoot in open shade.
4 On bright, sunny days try backlit photos (protect your eyes).
5 Try shooting silhouetted flowers, plants or trees against sunsets.
6 Use your camera's ‘macro’ setting or highest ‘F-number’, in Aperture Mode.
7 Use a tripod or bean bag to keep your camera steady.
8 Use a tripod which allows you to splay its legs and get down low.
9 Foam mats and knee protectors make shooting flowers more comfortable.
10Fill the frame with the flower – get close. Make the flower the focal point.
11Don’t place the flower in the centre of the frame – offset the image (Rule of thirds).
12 Offset and insects in your frame (Rule of thirds).
13 Make sure your subject is in good condition, use perfect flowers.
14 Try different angles – e.g. the side of the flower, rather than above.
15 Photograph odd numbers of flowers if you want to include several flowers in the frame i.e. 1, 3, 5. Your picture will look better.
16 Avoid distracting backgrounds – look for muted colours, or backgrounds which compliment the colour of the flower(s).
17 Avoid white backgrounds; these draw your viewer’s eye away from the subject.
18 Take your own background e.g. black or dark green card, or better still – velvet.
19 Don’t use ordinary on-camera flash, switch it off.
20 Use a reflector such as a mirror, tin foil or white card to fill in shadows and add interesting light to your subject.
21 Avoid very breezy days – your photos won’t be sharp.
22 Use a support to stabilise your subject if there is a breeze.
23 Shoot early in the morning, when there is usually less breeze.
24 If the breeze is a problem, try shooting in ‘Sports mode’ or in ‘Shutter Priority’ mode at 1/250th second or more, and use continuous shooting.
25 Alternatively, use the moving flowers to create and an abstract image e.g. use blur creatively.
26 Take photos indoors by placing the flowers on your window ledge (use a reflector to fill any shadows, or use the backlighting technique).
27 Use your cameras ‘Cloudy White Balance’ setting – this adds warmth to your photos.
28 Use a small water sprayer to add ‘dew’ to your flowers.
29 Use a watering can to add ‘rain’ to your photos. Shoot in ‘Shutter Priority’ mode at around 1/125th or 1/60th second for good results. Use a timer or an assistant to sprinkle water onto the flowers. Backlight the rain for the most effective images.
30 Try black and white or sepia shots for something different. Use editing software or your camera settings.
31 Print out your work: make cards, framed pictures, canvas prints.
32 Learn more about photography and flowers. Get inspired and have fun.
In this section I explain how to resize your images using the Image Size box. I will use the following examples:
1)Increasing resolution for high quality prints.
2)Reducing resolution for the web or email.
1) Increasing resolution for high quality prints
When you open an image in Photoshop and then display the Image Size box the resolution of the image as captured by your camera is shown in the Resolution window. (You can use the drop down boxes to the right of this window to change the unit of measurement to Pixels per Centimetre if you wish, but I like to stick to inches as ppi is the unit that most people use.)
You can enter different values into the Resolution window, which alters the resolution of the image. For example, you can increase the resolution to 300 ppi, in order to produce a high quality print form the image.
How to increase resolution
Leave the Resample Image box – unchecked. This increases the density of the pixels in the image by reducing the physical size of the photo. In other words, the total number of pixels in the image remains the same, before and after altering the resolution.
In this example the physical size of the photograph went from 16.667 inches wide and 22.222 inches at a resolution of 180 ppi, to 10.0 inches wide and 13.333 inches highat 300 ppi. Total pixels remained the same at 12,000,000, and File Size at 34.3M.
Saving High Resolution images
To avoid confusion, I save my print ready images by adding the physical dimensions and resolution to the file name. For example ‘Dog 10ins x 13.3 ins @ 300 ppi’.
Beware!
You can increase both the resolution and alter the physical size of an image at the same time. For example, increase resolution form 180 ppi to 300 ppi and, at the same time, change the width and height dimensions. However, to do this Photoshop has to ‘invent’ pixels and add them to the image. This increases the total number of pixels in the image. Beware: Increasing the size of the image too much will degrade its quality. If you do have to use this method, use it in moderation; limit any adjustments to no more than 10% of the File size.
In the above example, I increased the width by 0.5 inch, the height increased by 0.667 inch. The effect was to add more pixels to the image. Total pixels increased from 12,000,000 to 13,230,000 (3150 multiplied by 4200). File size grew from 34.3M to 37.9M.
How to increase the resolution and size of your image
Step 1: Follow the procedure used in the How to Increase Resolution section above. The aim of this first step is to increase the resolution of your photograph without adding pixels. This gives you the starting point for the next stage: to increase the physical dimensions of the image.
Step 2: You might need to re-open the Image Size box.
Check the Resample Image box and then choose Bicubic Smoother from the drop down menu. Remember to check the Constrain Proportions box, too. This ensures that any changes you make to the width of the image automatically change the height proportionately, and vice versa.
The new resolution (from Step 1) will be displayed in the Resolution window. Next, adjust the Width or Height of the image in the Document Size section. Don’t overdo it!
2) Reducing resolution for the web or email
There are times when you need to reduce the resolution of your images, for example, to display them on a website or to email them (where the image doesn’t need to be subsequently printed).
As discussed in Part 1 of this tutorial, computer screens have a maximum display quality of 72 ppi. You can upload higher resolution images onto your website, but computer screens cannot display them at anything higher than 72 ppi.
Keep your website images to 72 ppi and their pixel dimensions so that they can be easily viewed in different browsers.
How to reduce the resolution and pixel dimensions of your photos
Open your image and then the Image Size box.
Check the Resample Image box and then choose Bicubic Sharper from the drop down menu. Remember to check the Constrain Proportions box, too.
Enter 72 ppi into the Resolution window, and then enter the dimensions you require into the Width or Height windows of the Pixel Dimension section.
Changing one will automatically adjust the other. The pixel dimensions and the resolution of your image will be reduced.
Saving your low resolution images
Use Save As or Save for Web to save low resolution images to your hard drive. I add the words ‘web res’ or ‘72 res’ to the file name so that I can see that the image is a low resolution version of the original, and avoid possible confusion.
The Image Size box enables you to adjust the dimensions of your photograph, including its physical size, resolution and file size. (I will explain these terms below). Before that, I will explain where to find the Image Resize box and what it looks like.
Opening the Image Size box.
Open an image in Photoshop
Go to Image – then Image Size and the Image Size box will be displayed on your screen.
In other versions of Photoshop you access the Image Size box via Image – Resize – Image Size
Explaining the Image Size box
File size
This is an Image Size box for a photograph I uploaded into Photoshop. 34.3M shows the size of the image in megabytes. This is the amount of space that the image will take up on my hard drive.
The file size of a photograph is determined by how much data is stored in the image. For example, an image with lots of detail contains more data than an image of a clear blue sky. It also depends on the file format in which you capture the image. RAW files capture all an image’s data. If your camera captures images as JPegs (the default setting), file sizes will be smaller because your camera processes each photo and compresses each image file, throwing away what it regards as unnecessary data.
Pixels
A pixel is the basic unit of the composition of an image on a television screen, computer monitor, or similar display. The word pixel is based on a contraction of pix (‘pictures’) and el (‘element’).
The Image Size box shown here is for a photograph which is 3000 pixels wide and 4000 pixels high. Multiplying these two numbers together gives 12 megapixels (12,000,000 pixels) – which is equivalent to the number of image sensor elements of the camera that I used to take the photograph.
Document Size
In this case, the image dimensions are 16.667 inches wide and 22.222 inches high. This can be worked out by dividing the number of pixels along one edge by the resolution, i.e. 3000 pixels divided by 180 ppi (resolution) equals 16.667 inches and 4000 pixels divided by 180 ppi equals 22.222 inches.
Resolution
Pixels per inch (ppi) describes how many pixels an image contains per inch of distance in the horizontal and vertical directions. In the above example the resolution is 180 ppi. The camera captured the image at 180 ppi. This is the default setting on the camera which I used to take the photograph. Other cameras output the images at different resolutions, such as 240 ppi or 72 ppi.
High Resolution and Low Resolution
The more densely packed the pixels, the higher the image resolution. Sparsely packed pixels make low resolution images. For example, high quality prints require high resolution images of around 300 ppi. Low resolution images are used for websites. This is because computer screens can only display images at a maximum resolution of 72 ppi.
Camera Settings
Note: To capture the maximum number of pixels in an image you should set your camera to its ‘Large’, ‘Superfine’/’Highest quality’ settings (or your camera’s equivalent). If you don’t do this your camera will capture smaller images, for example, your 8 megapixel camera might only produce 5 megapixel images.
Does this matter? Yes, if you want to produce large prints. More megapixels mean larger prints and the ability to crop images, whilst maintaining quality. If you only want to produce small prints or display them on your computer or the internet, you don’t need high megapixel camera.
Photo Print Size Guide
This is a guide to how big you can print your images and maintain quality at different megapixel levels.
Megapixels
Print size
at 300 ppi *
Print size
at 200 ppi *
2
5.8 x 3.8 ins
8.7 x 5.8 ins
3
7.1 x 4.7 ins
10.6 x 7.1 ins
4
8.2 x 5.4 ins
12.2 x 8.2 ins
5
9.1 x 6.1 ins
13.7 x 9.1 ins
6
10.0 x 6.7 ins
15.0 x 10.0 ins
8
11.5 x 7.7 ins
17.3 x 11.5 ins
12
14.1 x 9.4 ins
21.2 x 14.1 ins
16
16.3 x 10.9 ins
24.5 x 16.3 ins
22
19.1 x 12.8 ins
28.7 x 19.1 ins
* Maximum 3:2 print size
See Part 2 of this tutorial – To find out how to use the Image Size box.
Just want to let you know about a photography workshop that I’m running in aid of Hospice at Home, West Cumbria.
It is a flower photography workshop (but I will also be helping you learn how to use your digital cameras). It’s on Tuesday, 18th August at Moota Garden Centre, near Cockermouth, Cumbria, CA13 0QF, starting at 6pm until 9pm.
Loads of opportunity to get some great flower photos. Why not come along, learn something new and help out a worthwhile charity.
There’s even a free glass of wine!
Price is £25 per person. ALL proceeds go to the charity.
We are now running small group courses in the beautiful Borrowdale Valley. We have teamed up with the Mary Mount Hotel, who are are hosts for two days. The hotel is located in extensive grounds, close by the shore of Derwentwater. The scenery is stunning.
Courses include two full day's tuition, all meals and two night's hotel accommodation.
Next dates: Course: 4th and 5th August (Accomodation 3rd and 4th)
Course: 8th and 9th September (Accomodation 7th and 8th)
Book now to avaoid disappointment. Call Mark on tel: 07964 887 338 or email: mark@better-photos.co.uk
Waterside Walks in the Cumbria and the Lake District
The launch of my latest book: Waterside Walks in Cumbria and the Lake District seems to have gone well. It's good to see it appearing in more and more shops throughout the region. Early indications are good.
Apart from the two book signings at Waterstones in Carlisle and Kendal, I've had very little time to market the book. Thankfully, my publishers, Countryside Books, are on the ball. They've been sending out press releases to the media, which have resulted in lots of good reviews in the press.
The book is also available through Amazon and other major on-line book sellers.
It’s good to be spontaneous. Acting on the spur of the moment, without too much preparation or thought. It’s something that I’ve always liked doing.
So, yesterday evening I threw my camping gear into a rucksack and headed to Buttermere. I needed to escape my computer (I spend too much time sat in front of it) and get out and enjoy some sunshine. When I got to the campsite, I quickly pitched my tent, then headed to the Bridge Hotel for a pint of Buttermere Bitter. It was nice to sit and chill out in the beer garden and admire the surrounding mountains. The beer soon disappeared, it must have been evaporation or something. I got myself another beer and watched the eels in the stream next to the pub. They are obviously used to kitchen staff and customers feeding them scraps of food because they were accumulating next to the pub. It was a fascinating sight.
I decided to walk to the Fish Inn and enjoy another beer in different surroundings. I tried a ‘Thirst Quencher’, a pale ale, brewed by Keswick Brewery. A refreshing summer pint, and highly recommended. The bar was very busy, so after my thirst had been suitably quenched I headed back to the Bridge Hotel and ordered a steak and ale pie (and chips)….oh, and another beer.
Afterwards, I strolled down to Buttermere Lake and then back to my tent for the night.
This morning, I got up at 5 am and decided to walk down to Crummock Water. I thought I might see otters, which are active at dawn and are known to be in the area. When I got to the lake, there were no otters in sight but the morning light was amazing. I had my compact camera with me and spent the next hour or so, taking photographs of the backlit Yellow Iris and the lake. It was a really nice experience.
