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Preparing files for Image Evaluation and Digital Competitions

This tutorial was prepared in 2008 but the principles still apply. NOTE HOWEVER that the current (2019) maximum file size is 1920 pixels width and 1200 pixels height with a maximum file size of 2MB.

Step-by-step instructions for Photoshop users

These instructions assume that you are familiar with Photoshop to the extent that you know how to open a photograph with the application, make adjustments and print it on your own printer or save it as a high-resolution image for printing by a photo lab. The essence of this technique is to make a low-resolution version of the image that is suitable for projection using the camera club's data projector.

Adobe Photoshop CS3 was used to create these instructional images. If you are using a different version of Photoshop there may be minor differences in the wording of menu options but the procedure is the same.

There are more sophisticated ways of preparing low resolution images for web display (which is essentially what we are doing with this process) but the method described below is simplest and more than adequate for the purposes of Digital Review.

Step 1: Open and edit the image

Get the image to the stage where you have finished your editing and you want to create the low resolution JPG file for Image Evaluation and Digital Competition.

Step 2: Convert to sRGB colour profile

Note: This step is not required if you will save the image to a JPG format using the File/Save for web method described in Step 3 (Save for Web presentation) below. If you use that method, Photoshop will automatically convert the colour profile to sRGB for you.

The sRGB colour profile is one that is universally acceptable for the display of images in a web environment. If your image is not saved with the sRGB profile applied, the colours will not display as you expect. Your image may already be using the sRGB colour profile if that is the default profile you use for editing in Photoshop. If you know that to be the case, you can skip the instructions below and go straight to Step 3. Save for Web presentation.

The author of these instructions uses the Prophoto RGB colour profile for editing. So every image needs to be converted to the sRGB profile before it is saved.

  1. Using the Photoshop menus at the top of the screen, choose Edit/Convert to profile...
  2. You will see the dialogue box shown below.
  3. Select sRGB IEC61966-2.1 (or something that looks similar) from the Destination Space Profile dropdown list, and click OK
  4. Your image is now ready to be saved for Web presentation

Step 3: Save for Web presentation

  1. From the menu, choose File/Save for web... or use the keyboard shortcut alt+shift+ctrl+s
  2. You will see the screen shown below. The blue dots and numbers have been added to illustrate the steps listed below the screen shot.
    1. Click the Optimised tab if it isn't already visible
    2. Select High (for starters) from the JPEG quality dropdown list
    3. Click the Image Size tab, where you will see the original size of your image (in this example 1920x1920 pixels)
    4. In the New Size properties group, you can enter the new pixel dimensions desired for your Digital Review photo. Remember that the maximum width is 1920 pixels and the maximum height is 1200, as per our DR guidelines. Ensure that the Constrain Proportions box is ticked.
      Note: The image in the example is square, so 1080 has been entered for both the height and width values.
    5. In the resampling Quality property, select Bicubic Sharper from the dropdown list. This is a good setting for images that are being downsized (downsampled) and will deliver adequate sharpness.
    6. Click Apply and the image in the preview window will be downsampled.
    7. Now look at the size (in kilobytes) of the previewed image. This is the size that it will be saved on your disk drive. If the size is under 2M, you can proceed to Step 8 of this sequence.

      If the size is more than 2M, you need to make further adjustments to get it below 2M. Here are some ways you can do that...
      • Reduce the pixel dimensions in the New Size properties group (see Step 4 above). Don't forget to click Apply to see the effect of these changes on file size.
      • Select a lower quality setting in the JPEG quality dropdown list (See Step 2 above)
      • Enter a lower value in the Quality value box below the Optimised checkbox in the Preset properties group. In the example above, the value in that box is 60.
      • Reveal the JPEG quality slider and adjust the value

      Check the size of the image again as you did at the start of Step 7. Keep making adjustments - as per the bulleted list above - until the size falls below the 2M limit.

      Preview image at 100% Set the size of the preview image to 100% so that you can see an accurate representation of how the final, resized image will appear. When you alter the JPG quality controls in this screen, the changes are reflected in the preview image. You'll be able to see how far you can reduce the quality settings before the appearance of the image becomes unacceptable.

    8. Click Save and follow the prompts to save the low-resolution DR image somewhere on your hard drive using the Digital Review file naming convention (Why not create a special folder for these images and call it My Evluation Images). When you are ready to upload your images to the Coppermine gallery, they'll be easy to find in that folder.
      Note: Click here to read the Digital Review file naming convention
    9. That's it. You're done!

About JPEG file sizes and etiquette

JPEG is a lossy compression format. The resulting file size of a JPEG image depends on the following factors:

Saved at 800x600m pixels with a JPEG quality of 60, the file size for this image is 29.4k Saved at 800x600m pixels with a JPEG quality of 60, the file size for this image is 184.5k

Whilst the file size limit for Image Evaluation is 2MB, you will find that it's easy to keep file sizes below that limit. For DR purposes, there is no benefit in creating files with excessive JPEG quality.

In most cases, you will find that a JPEG quality of 'high' or a range 0f 60-70 is perfectly adequate. If you create an image with a quality in that range and it turns out to be 50k (for example), please don't be tempted to increase the JPEG quality values, and make the file closer to the 2M limit, reasoning that it will look better. The improvement in quality will be barely noticeable, if at all, for our purposes. You probably have a small file because the subject matter of the photograph is lending itself to the strengths of the JPEG compression algorithm.

It's good etiquette to keep your files as small as possible while preserving reasonable image quality.