Above: Lanscape Orientation 3:2 Ratio

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1 Aspect Ratios in Photography Although we now live in a digital age where most images are viewed on a computer screen rather than in print, we must always acknowledge that for a single photograph, it can only become a physical artefact when printed. Although there is nothing to say that a photograph cannot be printed at any arbitrary or non-standard size, the reality is that to get high quality photos printed at reasonable cost they have to conform to standard sizes, which effectively means fixed aspect ratios. It is also worth noting that many internet web sites (and social media sites) which accept users image content are controlled by CMS (Content Management System) which are most often optimised for images with a 4:3 aspect ratio; the most common aspect ratio for photos created by compact cameras and camera phones. Aspect Ratio: Definition The aspect ratio of any photo is simply the ratio of its longest side to its shortest side: so if you have a camera which produces images 2700 x 1800 pixels, then the the aspect ratio is 2700:1800 = 3:2. If your camera produces images which are 2400 x 1800 pixels, then the aspect ratio is 2400:1800 = 4:3. The modern norm is to always describe aspect ratios with the larger number first, e.g. 3:2 and 4:3 with the larger number indicating the longest side - regardless of the orientation of the photograph. However there are many who prefer the aspect ratio to indicate the orientation of the photograph with the length (or width) always put before the height. So for example someone may describe an aspect ratio of 3:2 as 2:3 - all this really indicates is the photograph content is in portrait orientation rather than landscape - but the ratio of the longest side to the shortest side is still 3:2. Most photographers would still describe a portrait oriented photo as 3:2 or 4:3 rather than 2:3 or 3:4. So for the purposes of these notes, ratios will always be given with the larger number first and the larger number will always represent the longest side, regardless of the orientation of the subject matter in the photograph. See examples below:- Above: Lanscape Orientation 3:2 Ratio Right: Portrait Orientation 3:2 Ratio, but might sometimes be given as 2:3 following the geometry convention of x and y axis Aspect Ratios in Cameras and Photo Printing Almost all modern digital cameras will be either 3:2 or 4:3 aspect ratio, however there are many more standard sizes and aspect ratios when it comes to printing. For example a 10in x 8in photo is a very commonly requested print size with a multitude of photo frames available to buy, but it has an aspect ratio of 5:4 and so therefore if you have taken a photo which is 2700 x 1800 pixels (3:2) then much of the area of the original photo has to be lost because the size required is only 2250 x 1800 pixels. Note that photo sizes such as 10x8 or 9x6 are always given in inches which can obviously be converted to metric sizes. The dominance of American and Japanese photo printing equipment and the combined consumer markets of North America and Asia requires that Europeans get used to working in inches.

2 Module Requirements For this module it is a requirement that all photographs submitted as part of a portfolio must be printable at a standard size and aspect ratio. The aspect ratios of all submitted photographs must be one of the following: 2:1, 3:2, 4:3, 5:4 or 1:1. 1:1 is obviously a square photograph. 2:1 is where the length is twice the size of the height; commonly known as wide format. Choosing / Changing Aspect Ratio Students should also be aware that choosing the correct aspect ratio for any particular photograph is part of the task in editing a photograph. It is the case that many photographs can be greatly improved simply by changing the aspect ratio and that editing a photograph to suit the original aspect ratio, rather than considering a different one, is limiting the scope of the editing. In the two examples shown, both photographs are improved by changing the aspect ratio, even although this involves removing some areas of the photograph:- Example 1 The photo on the left (example 1, below) is the original 3:2 aspect ratio where the width is set by the need to keep the subjects more or less in the centre of the frame. Scaling the photo up (within the original 3:2 area) to remove the unwanted top and bottom areas might be considered, but this would mean that the left hand side of the man on the left would be cut off, if we are to keep the subjects in the centre, or alternatively we could simple scale it up and move the subjects off to the right. However none of these is as good a solution as changing the aspect ratio from 3:2 to 4:3. Example 1: Left 3:2 Aspect Ratio, Right 4:3 Aspect Ratio Example 2 The photo at the top (example 2 next page) is the original 3:2 aspect ratio where the width is set by the width of the building captured within the scene. However the original includes some sky area and a great deal of foreground area which is less interesting than the subject. The sky area may be tolerable but foreground definitely detracts from the photograph, making it seem like a study of autumn leaves rather than a quaint rural hotel. By changing the aspect ratio from 3:2 to 2:1 the photograph loses the less interesting areas at the top and bottom and seems to concentrate the view on the most interesting area.

3 Example 2: Top 3:2 Aspect Ratio, Bottom 2:1 Aspect Ratio Photo-printing Sizes Anyone who has received printed photos through the the post should realise that the prints always have a bend in the direction of the longest edge: This is nothing to do with packaging or any poor handling in the post; it occurs naturally because the photos are printed from a roll of photo printing paper. The width of the roll is always equal to the shortest side of the photo, for example 6 inches. So the different standard sizes are made by cutting from the roll at set lengths. For a roll which is 6 inches wide, cuts are made at lengths of 7.5 inches, giving a photo sized 7.5 x 6 (5:4 aspect); or cut at 8 inches giving a photo sized 8 x 6 (4:3 aspect); or cut at 9 inches giving a photo sized 9 x 6 (3:2 aspect). These photo print rolls obviously come in various widths: 4in, 6in, 8in, 10, 12, etc. So therefore the 8 inch wide roll gives standard sizes 8x8, 8x10, 8x10.67, 8x12 and 8x16 with respect to the standard ratios 1:1, 5:4, 4:3, 3:2, 2:1. Standard Sizes in Pixels No matter what camera you use, you should know its default aspect ratio and the size of your photos in pixels. This is the basic information which allows you to calculate the various frame sizes for different aspect ratio photographs. Some cameras allow you to choose different frame size settings, some of which effectively alter the aspect ratio. However most cameras allow different size settings purely for quality versus file size reasons, but all options are likely to be the same aspect ratio. Every photographer should create and refer to a chart which shows exact pixel dimensions at all the standard aspect ratios. The simplest way to calculate the image size is to start with the default image size and multiply one of the sides by the aspect ratio required. Where the new aspect ratio is to be narrower than the camera default, then multiplying the shortest side by the desired aspect ratio gives the size of the longest side. When the new aspect ratio required is to be wider than the camera default, then multiplying the longest side by the inverse of the desired aspect ratio gives the required size of the shortest side.

4 Example A: Camera with default aspect ratio of 3:2 (e.g x 2400 pixels) 1:1 Aspect Ratio: Longest Side = Shortest Side (2400) x 1/1 = 2400 pixels Photo size = 2400 x :4 Aspect Ratio: Longest Side = Shortest Side (2400) x 5/4 = 3000 pixels Photo Size = 3000 x :3 Aspect Ratio: Longest Side = Shortest Side (2400) x 4/3 = 3200 pixels Photo Size = 3200 x :2 Aspect Ratio: No change required. However the calculation still conforms to the formula if tested. Photo Size = 3600 x :1 Aspect Ratio: Shortest Side = Longest Side (3600) x 1/2 = 1800 pixels Photo Size = 3600 x 1800 Example B: Camera with default aspect ratio of 4:3 (e.g x 2400 pixels) 1:1 Aspect Ratio: Longest Side = Shortest Side (2400) x 1/1 = 2400 pixels Photo size = 2400 x :4 Aspect Ratio: Longest Side = Shortest Side (2400) x 5/4 = 3000 pixels Photo Size = 3000 x :3 Aspect Ratio: No change required. However the calculation still conforms to the formula if tested. Photo Size = 3200 x :2 Aspect Ratio: Shortest Side = Longest Side (3200) x 2/3 = 2133 pixels Photo Size = 3200 x :1 Aspect Ratio: Shortest Side = Longest Side (3200) x 1/2 = 1600 pixels Photo Size = 3200 x 1600 Using the Canvas Size Function in Adobe Photoshop The Canvas Size function within Adobe Photoshop allows you to change the aspect ratios of your photographs very easily, provided that you have calculated the pixel numbers in advance (or better still, put them into a chart). The screen shot below shows the specific changes that were made to change the image in the previous example (Example 2) to change its aspect ratio from 3:2 to 2:1. The original 3:2 size was 5184 x 3456 and all that was required was to change the height within the Canvas Size dialogue box from 3456 to 2592.

5 Note that the dialog box has some positioning options which allow you to define the area of the new canvas from within the previous area. A marix of buttons allow you define from the top, bottom, left, right, top-left, top-right, bottom-left, bottom-right or centre. Although this can sometimes be helpful, there is no scope for minor adjustment. However this is only important if you have a single layer background JPEG file. If you have a normal Photoshop layer (perhaps a duplicate of a background layer), then the original image size can still be moved around freely within the new (narrower or shorter) canvas size; so you are able to choose the exact section of the original that you want to be in the new canvas. For this reason it is very important that you Select All, Copy and Paste the background layer (or Duplicate the background layer) before altering the Canvas Size. You can easily Flatten Image back to a single background layer when satisfied with your changes. Using the Crop Tool within Adobe Photoshop It is very easy to use the Crop tool to change the aspect ratio of photographs within Adobe Photoshop. It is quicker and more immediately visible when compared to using the Canvas Size function. The Crop tool also allows you to move your locked background layer within the area to be retained after cropping. The screen shot below shows how to change aspect ratio using the Crop function. The main difficulty in using Crop rather than Canvas Size is that the cropping is essentially a free-hand control function with no definite stop at the correct aspect ratio. The only guidance is given by the small W/H indicator which appears informing you of the extent of the cropping. In order to get the new aspect ratio correct, you need to have quite a steady hand and keep an eye on the H (Height) value. And of course you need to know the correct value in advance. Although using the Crop tool seems more convenient than changing the Canvas Size, there are some distinct disadvantages to using it. The first of these is perhaps obvious from what has already been stated; i.e. that it is very easy to create a non-standard aspect ratio (and photo size) simply by a slip of the hand or by not paying attention to the H/W indicator. The second is that cropping either the width only or the height only allows you to calculate the numbers prior to cropping, or look up a chart, however if you decide to crop both the width and the height during the same crop operation, you would require to have someone sitting beside you working a calculator to be sure of ending up with a standard aspect ratio. Just as with Scaling, it is possible to hold the Shift Key whilst cropping to crop proportionately. So provided that you do the initial crop correctly to a standard aspect ratio, you could then hold down the Shift Key and crop proportionately (from a corner) to preseve your new aspect ratio.

6 Perhaps the most problematic consequence of cropping rather than using Canvas Size and/or Scaling is that if you are editing a batch of photographs for printing, then you will end up with a set of photographs which are all different sizes in terms of pixels, depending on how much you required to crop them. This effectively means that some might make better quality prints than others, and because you are viewing them on a computer monitor with a resolution of 72dpi, it is very difficult to judge how the quality will turn out when they are printed at a resolution of up to 600dpi. You would need to know how much you can crop an image before its smaller size interferes with print quality. As a rough guide 2400 x 1800 pixels (4.3M Pixels) is the absolute minimum for a 8in x 6in photo to print at acceptable quality. To print the same image as a 12in x 8in photo 3600 x 2700 pixels (9.7M Pixels) is required. These calculations are based on 300dpi being the minimum acceptable print quality for photographs. Using the Scale Function and Canvas Size Function When we use Scale or any other Tranform function within Adobe Photoshop, we force the software to resample the image in order to keep the same number of pixels within the frame. Because all of the Tranform functions force a resampling of the image there is some loss of quality compared to the original, and for this reason there is an argument in favour of simply cropping the image to a smaller pixel size rather than scaling up within the frame to preserve the original pixel size. Despite all of the disadvantageous previously highlighted in relation to cropping, cropping rather than scaling might be worth considering. However this only holds true in the case where no other Tranformations are required. In other words the image would have to be near perfect apart from the cropping required. If you crop an image and then later decide that you need to use Rotate, Skew, Distort, Perspective or Warp - then you will end up with a lesser quality image because you will force a resample a smaller image rather than a larger one. Because of this and the likelyhood that most photographs, no matter how carefully taken, will normally benefit from using at least one Transformation process, it is recommended that students use Scale to remove unwanted areas within photographs, and use Canvas Size to change aspect ratios where required. Note that scaling proportionately can be schieved by hold the Shift Key whilst scaling from a corner. (See previous notes). Note also that Adobe Photoshop groups all of its Transform functions (Scale, Rotate, Skew, Distort, Perspective and Warp) within the Transorm sub-menu and allows you to carry out as many of these functions and change from one to another as often as is required, before it resamples the image. This helps greatly to preserve as much image quality as possible, because all of the software calculations apply within the same single resample. However it is still recommended that one instance of Sharpen is applied before saving the image. This effectively puts back some of the sharpness which may be lost due to resampling, especially if the scaling was substantial. Changing Aspect Ratio in Other Software Programs Whether using Canvas Size or Crop to change the aspect ratio of your photographs within Photoshop, both require a bit of effort, skill and knowledge. It is worth noting that new software programs specifically designed for photographers and photo editing, such as Apple Aperture and Adobe Lightroom actually have an Aspect Ratio or Photo Size function which has options for 10x8, 8x6, 9x6, 7x5 etc. and changes the frame size automatically whilst still allowing you to move the original image within the new sized frame. Unfortunately, since this is one of the most popular features of Lightroom it is unlikely that Adobe will add it to Photoshop in the future.