Photoshop Tutorial, Save for Web, Sizing, Sharpening, Saving, f8 Pro Photo Photography

This lovely lady was shot on a 10.2 mega pixel camera, full-frame, in RAW format. The image file was converted at 8 bits per channel and saved in a master file as a TIFF image without compression. The resulting file size became 28.3 mega bytes and there is no way that image could be published on a website without having to wait forever for it to download or, as an attachment to an e mail, forget it.
The internet is undeniably the best thing since sliced bread but from a Photographers point of view it has two major drawbacks. Reproduced image quality is abysmal and download time, the time it takes for the complete image to appear on the website screen, is too long. Both of these factors are inextricably linked and improving the one is detrimental to the other.
We must find a compromise between these two traits by producing an image that is adequate - a great word describing something that is not particularly good at anything.
And we do this by image compression.

The first thing to establish is the physical size, width and height, of the resulting published image. If it's for a web page then it must fit into an allocated space so must be resized accordingly. If it's to attach to an email then it must fit on the page neither too large or small. Get your image displayed in the workspace then from the top menu bar > Image > Image Size and the dialogue box opens as this screen grab.

From the master image I have produced a JPEG, converted the background to this neutral greyish colour and as you can see from the 'Pixel Dimensions' still have a huge file of 13.4 MB. If I wanted to Print this the Print Size or Document Size would be 63.82 x 91.19 cm. (Clicking on the down arrow against cm. will allow you to change this to inches or various other equivalents).

Now, before you alter anything else, your dialogue box may not be highlighted as this mine is. What we are actually doing is sizing down the image to the adequate level and this involves 'Resampling'. So engage the Resample box then all options should be highlighted. The dropdown box to the right gives us options as to which Interpolation method we can use for Resampling. * See notes below on these options. For now select Bicubic. Also, engaging the 'Constrain Proportions' box will interlock the Width and Height measurements so that altering one dimension automatically alters the other then the image doesn't become distorted. 'Scale Styles' only come into use when multiple 'Layers' of images are being resized and will be dealt with in 'Layers'. For now ignore it.
Clicking on the box marked 'Auto' opens another dialogue box in which one can establish 'pre-sets' in 'Lines per Inch' (or mm)in 3 output quality levels and is of more use for sizing directly for 4 colour offset-litho printing.

* Nearest Neighbour. A fast but less precise method that replicates the pixels in an image. This method is for use with illustrations containing edges that are not anti-aliased, to preserve hard edges and produce a smaller file. However, this method can produce jagged effects, which become apparent when you distort or scale an image or perform multiple manipulations on a selection. Not the best choice for photographs.
Bilinear A method that adds pixels by averaging the colour values of surrounding pixels. It produces medium-quality results. An equally poor choice
Bicubic A slower but more precise method based on an examination of the values of surrounding pixels. Using more complex calculations, Bicubic produces smoother tonal gradations than Nearest Neighbour or Bilinear. The best option
Bicubic Smoother A good method for enlarging images based on Bicubic interpolation but designed to produce smoother results. Doesn't work so well on image reduction.
Bicubic Sharper A good method for reducing the size of an image based on Bicubic interpolation with enhanced sharpening. This method maintains the detail in a resampled image. If Bicubic Sharper oversharpens some areas of an image, try using Bicubic.
Sharpening by default is never as good as utilizing full control via the 'Unsharp Mask'

Let us say that we want to attach this picture to an e mail and we anticipate the respondent may print the image directly. A decent Print Out resolution would be 200 ppi (dpi being the same thing) so alter the Resolution to 200. Notice how all the other figures have changed accordingly. Forget the Pixel sizes for the moment, just alter the Document Size to 10 cm. wide. You'll see the height has automatically changed to 14.29 cm.
You could make it any size you wish but if it must fit on A4 paper then it must be less than 21x 29.7 cm. Notice now how the Pixel Dimensions (the actual file size) have changed from 13.4 to 2.53 MB. At this point we have not lost any image quality we have merely reduced the image dimensions. Dialogue box should be like this.

Alternatively you may want to resize for internet use in which case forget Document size and work with Pixels As this is a web page and the image of the Lady at the top is a web image we'll go through the process of sizing it for this page. To fit the space the width and height of the image needs to be 249 x 356 pixels.
First, set the Resolution to something appropriate for an LCD Monitor. If your screen dimension is 800 x 600 pixels then 72 ppi should be adequate (that word again). If your screen is the more common 1024 x 768 pixels (as this web page is designed for) then, perhaps, 96 ppi would be better. Then alter the Pixel Dimension Width to 249 and see the Height automatically read 356 because we've got Constrained Proportions.

Notice now, in the screen grab, it shows a Pixel Dimension of 259.7 kilobytes as opposed to 13.4 megabytes. This file size is only about 18% of what it was because of a smaller image size and lower resolution.
In either case, for web or e mail attachment, that's the image resized so click OK and watch the image resize. There is one more crucial step to take before we 'Save for Web' and that is 'Sharpening'. Coming Next.