Scanned images usually require a few adjustments before you can begin the editing process.
Sometimes corrections can be very simple – here we explain two of the most basic and effective processes you’ll likely need before you start editing an image.
Although you can often copy prints at their original size and appropriate resolution, virtually all of your scanned slides or negatives will need to be resized.
It’s usually wise to match the resolution to your intended end use, because if you enlarge the image after editing, you risk making your adjustments obvious. Different uses have different resolution requirements, which we described in the previous chapter.
As explained, when the originals are small (eg: 35mm film frames) and you want to make prints from them, you need to scan at much higher resolutions. If you scanned a 36 x 24 mm film image at 2400 dpi to make A4 size prints, it needs to be resized to fit on the paper.
While most printer drivers can scale an image file to fit on a specific sheet of paper, it’s best to resize before printing using your favorite image editor’s settings. This gives you much more control over the process and allows you to produce multiple versions of the image, each with its size and resolution suited for a different destination; one for emails, another for printing and another for inclusion in a slideshow that will be viewed on a TV screen, for example.
Resizing is provided even in the most basic editors and it is very easy to do. As an example, we have chosen a 35mm slide taken in Athens in the 1960s and scanned at 2400 dpi. Resizing will make this image usable for printing or sharing online.
The first step in resizing is to select the Image > Size functions in the editor and change the Resolution from 2400 pixels/inch to 300 pixels/inch, which is the ideal resolution for printing. Leave the Resample box unchecked to keep the image at its original size.
If you want to print the image, the one we have selected will fit perfectly on an A4 sheet of photo paper, although it is too large for a snapshot size print. To reduce it to about 15 x 10 cm, it is better to use the publisher’s settings, which will reduce the risk of moire, fringing and other artifacts, rather than leaving it to the printer.
The same dialog is used to resample images when you want to downsample (reduce) or upsample (enlarge) the image. Either way, make sure the width and height settings are linked before checking the Resample box to change the image settings. Pay attention to halos around sharp edges, which indicate excessive sharpness, especially in oversampled images.
Undersampling (top) and oversampling (bottom) settings. Choose the Bicubic Sharper method for downsampling and the Smoother or Preserve Details resampling method for upsampling.
When resampling images for printing, the resolution may be gradually reduced for prints larger than A3, as we see them from greater distances. Don’t be tempted to go below about 200 ppi as this will risk pixelating the image.
When resizing images for emailing, posting to social media, and/or viewing on a computer or TV screen, create copies of your original files with separate filenames. Consider the native resolution of the display itself; if you want the image to fill the screen when opened, try to match the screen resolution.
Many scanned images will require at least some cropping, and you’ll save time if this is done before you jump into further adjustments. A common reason for cropping scanned images is to straighten slanted horizons, a common occurrence when photos were taken with cameras that lack composition aids. Most software provides special smoothing settings to make this process quick and easy.
Most editors offer straightening tools (circled in red in this screenshot of the Affinity Photo workspace). To straighten the photo, simply draw a line along a path in the image that you want to be horizontal or vertical; the software will rotate the image and crop it as shown in the bottom image.
Another popular reason to crop is to remove areas that are irrelevant to the image or too damaged to justify spending time trying to fix them. You can also crop to improve the composition of images, get a different aspect ratio to fit an image in a frame or on a page or sheet of print paper, or change a horizontal image to a vertical one, or vice versa.
Another example of a straighten tool, this time from ACDSee Photo Studio. The same software is shown in the lower screenshot, with the crop tool used to remove a large area of detailless sky containing many imperfections.
While rectangular images tend to look better when posted on websites that have set boundaries, another reason for cropping is to change the rectangular shape of the original to a circle or an oval. It’s surprisingly easy, as shown below.
These illustrations show how to crop a messy hand-cut vignetted original. Step 1: Use the round selection tool to select the area you want to keep. Step 2: Click Select > Invert to change the selection of the area you want to crop. Step 3: Trim unwanted area. Step 4: The final thumbnail image.
Precautions when cropping
1. Culture does not have to be permanent. Always work on a copy of the image you plan to crop and use a non-destructive editor.
2. Since pixels are ignored, cropping will always reduce the overall resolution. You need to be sure beforehand how much you can afford to lose.
3. Any problems inherent in the image, such as noise or lack of sharpness, will be magnified by enlarging the image after cropping.
4. When cropping to a specific aspect ratio, your crop should conform to standard print sizes, especially if someone else will be doing the print.
Resizing and cropping
A healthy harvest
This article by Margaret Brown is an excerpt from the Photo Restoration Pocket Guide
Partner Pocket Guide: Camera House