Learning | Preparing Images for Digital Projection
This note gives guidelines for the preparation of digital images intended for projection on the Optoma EP728i digital projector which is now available for presentations and slideshows. The guidelines may be modified in the light of experience; comments are welcome.

Digital images for projection may come from any suitable source. The main ones are: digital camera, scanned film (slide or negative), and scanned print. Images may or may not have been adjusted in an image editing program such as Photoshop.

Start by making a copy of your image to work on, so that your original is protected. Before altering the image size, make any other adjustments required, (eg cropping, colour balance etc). Flatten the image if it contains more than a single layer. If you plan to carry out sharpening, do not do it yet.

The projector has a native resolution of 1920 x 1200 pixels and this is the "ideal" image size for projection. The laptop computer used to drive the projector has the same resolution. The image does not have to be this size however. SPF/PAGB and Angus Cup ask for images 1600 px by 1200 px. So we'll go with this. If the image is too large or too small, it will be automatically adjusted by the software to fit the projector, but this is a process over which you have no control, and so it is better to re-size the image yourself. It is inadvisable for both the width and height to be less than ideal as this will lead to loss of sharpness. If the image is larger than ideal, the file size will be bigger than it needs to be and it may take longer to load.

If you wish to adjust the image size in Photoshop, first make a duplicate of the image (if you have not already done so,) or save it under a different name to avoid overwriting the original. Next, select Image > Image Size... from the drop down menu.

Initially, the width and height will probably be different from those required. Make sure that "Constrain Proportions" and "Resample Image" are ticked, and that "Bicubic" is selected as the resampling method. Also make sure that the units are pixels in the upper (Pixel Dimensions) part of the dialog box. For a landscape format image, set the width to 1024 pixels. The height changes automatically. If the resulting height is more than 1200, set it to exactly 1200. The width will decrease. For portrait format, set the height to 1200 pixels. Do not try to set both width and height as they are linked. Ignore the "Document Size" section, including "Resolution", as this is irrelevant for projection. Click OK. Save, making sure that you do not overwrite your original.

To summarise: A landscape image should have a width of 1600 pixels with height less than or equal to 1200 pixels. A portrait image should have a height of 1200 pixels. Square images should be 1200 px by 1200 px.

The image viewing software used at present does not use colour management, unlike Photoshop which uses colour profiles to calibrate the colours. Consequently, a projected image may look different from how it appeared in Photoshop on your monitor. If the image has the "sRGB" embedded profile, there should be no problem, as the projector is used in its sRGB mode. Most digital cameras automatically put this profile into JPG format images. For images with a different profile, or no profile, you should convert them to sRGB. There should be no change in the appearance of the colours in Photoshop, and the colours should still be correct when projected. This does not guarantee correctly projected colours as there may be other reasons for colours being wrong. If your projected images do not look as expected, please discuss this with a committee member.

After all adjustments have been made, save the final version and do not make any more changes to it. In principle, any of the usual image file formats can be accepted, (eg, TIF, PSD, PNG, JPG), but to ensure maximum compatibility with a variety of software, it is best to use JPG format, with a high quality setting. Make sure that the sRGB profile is included when saving.

Image files can be accepted on any of the following media: CD, DVD, USB Flashdrive, camera memory cards, and email. Whatever you use, make sure that your submission can be identified. On certain occasions, files containing complete slideshows can also be accepted, although not for competitions. Suitable slideshow files can be created with various programs including Powerpoint, Irfanview, PicturesToExe, ProShow Gold, Photoshop Elements, and Lightroom.

Original notes were prepared by Alistair Ramsay of St Andrews Photographic Society in January 2008 and we are grateful for his permission to use an amended version of them here. Any errors in amending and adding to the original notes are the responsibility of the CCC Webmaster not Alistair!