Preparing for a digital slide competition

My local camera club has been asked to put together it's best images to enter in the regions photo competition. It's a chance for each club in the area to showcase their ability and also to see how they stack up against others. For this year we need digital images that will be projected instead of prints or slides. The standards say 1024 x 768 pixels maximum resolution, JPEG images, sRGB colour profile. Trouble is that makes for a small image with few pixels. Scaling images down for projection is something that needs a bit more than just resize in Photoshop.

Resize in Photoshop will get an image the right size, but when you downsize an image a lot then you also lose detail and sharpness. You also hide noise so it's not all bad.

The next tough part is the contrast, most projectors have quite a high contrast ratio and also a tough approach to shadow detail. A lot of grey and black areas in images tend to be rendered dark grey. In terms of highlights there's also a good chance that your images will blow out the highlights when projected too. It's a bit like putting quite a steep S curve on your images in Photoshop. You can see the effect your self on your images by applying an S-curve and moving the ends of the curve up and down the vertical axes. Something like this one below is an idea of a particularly bad condition projector.

Here I made the input level of 0 give me 20 on the output and the input level of 255 give me 240 on the output as the starting points to cover the restricted range of black and white the projector displays.

So create a curve adjustment layer over your image and call it Projector. It's important that this is a layer since you will need it to be the top layer of any work you do to the file, effectively giving you a preview of how the image may project. From there I often duplicate the background and then use the shadow highlight tool to recover an image to look good with the Projector curve over the top. Turn off the Projector curve layer from time to time to see how the image is looking.

The next part is sharpening, it's important to sharpen the image again compared to what sharpening you may have done on a full resolution image. Remember downsizing the resolution will weaken the sharpening you may have applied before. So now look at the image at 100% on your monitor and sharpen with the unsharp mask some more. Typically amount of 70, radius 0.8 and threshold of 2 is a good place to start but you'll need to adapt this for different images. I also like to do this and then use the fade unsharp mask and select luminosity to try and avoid sharpening colours just edges.

Now let's hope that none of my camera club colleagues read this before the submission deadline

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