Scanning

I find it most convenient to scan my images from within Photoshop so that the image automatically appears in the Photoshop window.

In Photoshop select File>Import and then select your Twain source.

The intent when scanning is to obtain as much information in the scan as is possible. Your image editing software can't work on information that your scan doesn't collect so get to know your scanner's software and use it to collect the maximum amount of detail in both shadows and highlights. It will have controls with which to optimise the quality of the scan, experiment with settings to find those that suit you best.

I suggest that scanning be done at the highest optical resolution your scanner will allow. My flatbed scanner has a main scan (across the moving bar) of 1200dpi. It has a sub scan of 2400 dpi (it takes 2400 samples per inch as it moves down the document being scanned). According to it's menu it can scan up to 9600dpi which means it scans at 1200 dpi and interpolates (invents) the rest. I find that if I need to increase the file size in this way 'Photoshop' does it better than the scanner software.

When scanning prints, negatives or slides use RGB mode. Monochrome, or grayscale images, typically turn out better if you gather the colour information in the scan and then change from RGB to Grayscale in Photoshop.

An A4 colour print at 300 pixels per inch needs a file size of about 22/3 megabytes which should give a reasonable guide to scanning resolution. If your scanner won't give you this size at it's optical best then let it do the best it can and increase the file size in Photoshop.

If scanning in all your latest batch of slides don't forget to save the imported images at regular intervals. There iis little more annoying than to spend an hour scanning only for the computer to crash leaving one to do it all again.

Having scanned your image and saved it I suggest that the first thing to do when you start work on the image is to create a duplicate layer. Layer>Duplicate layer. This means that if whatever you do doesn't appeal you can always drag the duplicate to the trash can and be left with the original. (Don't forget to create another duplicate.)

I thought it might be useful to illustrate the process I go through when scanning an image with my film scanner. First a word about dpi and ppi. Inkjet printers print at dpi i.e. dots of ink per inch. Scanners scan at pixels per inch (ppi). The two are not related. Unfortunately in scanner software ppi is often referred to as dpi which can cause some confusion. So scanner dpi (as below) is nothing to do with printing dpi.

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When the Twain source opens this dialogue box appears. Here the input is set to the maximum this scanner will produce, rather low by current standards. The output dpi is the resolution I want if I am going to print the resulting file. If the image were intended to be displayed on a web site then the output would be set lower, 96dpi for example. The Input dpi would be lower too depending on the pixel size the resulting picture would appear on screen. Clicking the prescan button causee the scanner to produce a preview of the image. The area to be scanned is now selected by clicking in a corner of the preview image and dragging the selection box to the correct size. This is now displayed as the Input Size along with the magnification and output size for the chosen input and output dpi. So for this image the maximum size I can print at 240 dpi is that shown. If I wanted a 6" x 4" print at 240 dpi these sizes would be entered in the appropriate box and the Input size would automatically change to match. Having obtained thr preview image it can now be adjusted to optimise the scan. This software provides three adjustments 1. Variations, 2. Tone Curve and 3. Levels Histogram.. Adjusting one of these effects the others.
I prefer to adjust the Histogram first. Clicking the histogram button produces this dialogue box.
The Input level sliders in all three channels are adjusted so that they enclose the histogram. The preview image to the right changes to show the effect of the adjustment. I find that when this adjustment has been carried out very often I do not need to use the other two adjustment tools.
Click the Variations button (1) and this dialogue box appears. I use this to make small adjustments to the brightness and/or contrast of the image by moving the appropriate slider, and then clicking the best of the resulting nine images. Colour balance can be adjusted by clicking the dot in the centre of the spectrum circle and moving it appropriately..
The third of the adjustments is by the tone curve. I find that having carried out the previous adjustments I rarely need to alter the curve. Clicking the curve and dragging either up or down lightens or darkens the selected tone.
Here can be seen the effect of altering the tone curve.

When the final adjustments have been made the scan button is pressed, the image scanned and automatically transferred to the image editing programme, Photoshop in my case.