How to scan photos – the best settings

This tutorial will show you what settings to look for in your scanning software to produce the best results when you are scanning. As there are many different scanning programs available, each manufacturer having its own or recommended version it will be too difficult to go into detail for any one version of the software. However all scanning programs will come with similar settings available, perhaps with different names, so it will be just a matter for you to investigate all the menus and buttons (or consult the software manual) in order to find these settings.

Scanners will come with a standalone program on an installer CD/DVD or with a website link to download a program that will allow you to scan images and save them to your computer. If you have a copy of Adobe Photoshop or Photoshop Elements, it is possible to scan directly into Photoshop, just go to FILE->IMPORT and then choose your scanner from the list of those available to you.

CanoScan Toolbox software
Fig.1. CanoScan Toolbox software for Canon scanners

This tutorial is a guide to the important settings you will need to set in your scanning software in order to get the best results for the final image.


Fig. 1. on the right shows the startup screen for CanoScan Toolbox the scanning software that comes with Canon scanners. I clicked SAVE from the toolbox at the top of pictures as I want to save my scan directly to the computer. You can either set the following settings in the box you see in fig. 1., or if you follow the steps 1-3 you can open the main scanning window to preview the scan and set the settings.

  1. Click the Display the Scanner Driver checkbox.
  2. Choose the filetype and where you want to save the scan on your computer.
  3. Click the scan button to open the main window, (as fig. 3.)

1. Output Resolution

Setting the output resolution
Setting the output resolution, in this case it is called ‘Destination’.

Firstly think about what you are going to do with the image once it has been scanned. If it is only going to be emailed to a friend or used on a website then the ouput resolution will not need to be very high. However, if you are ever going to print the image, either to your own photo printer, or for use in a commercially printed leaflet or brochure, the output resolution will need to be higher.

The general rule of thumb is:

  • For online screen use only, emailing, websites etc. the scanning resolution should be set to 72dpi.
  • For printing to your own printer on normal plain paper a scanning resolution of 150dpi is better.
  • For high quality commercial printing or printing on glossy photo paper the scanning resolution should be set to 300dpi.

You should have an option in your scanning program to set the resolution, search the menus to find this, make a note of where it is for next time and make sure you check it before each scan as it may revert back to it’s default setting between scans.

2. Mono scanning and colour modes

It used to be best that when you are scanning a photo for a specific purpose, e.g. for printing to a black and white printer or use in a mono leaflet, it was best to scan the image in that colour mode. If you had a colour photo and were only going to use it in black and white, then setting the scanning software to scan black and white produced the best results. These days however with image manipulation packages such as Photoshop, it is easy to convert a colour image to black and white (mono) and doing it this way will produce better results.

Type of picture
Fig. 3. Setting the colour mode of the original picture in the source option. Black and White or Colour.

It is always important to check the colour mode in scanner settings when scanning a photo in order to get the best results. Follow these tips:

  • If you are scanning a black and white photo, set the colour mode to Mono or Black and white to produce the best results. Scanning a black and white photo in colour mode can produce a colour cast making the image look dull with a pinkish or yellowish overall tint. The file size will also be smaller if you scan a mono photo as a mono image. See fig. 3. above which shows how to set the colour mode in the CanoScan Toolbox software, in this case it is called the SOURCE meaning the original photo.
  • If you are going to use the final image in commercial printing, the colour mode should be set to CMYK, rather than RGB. This choice isn’t available in every scanning program, but if it is, it is worth using for high quality print ready images. If you can only scan using RGB then you can change the colour mode in other image manipulation programs such as Photoshop. This is seen as an advanced option in some scanning programs.

3. Enlarging images

Setting the final size for the image
Fig. 4. Setting the final size for the image, this is important for enlargements.

If you need the final image you have scanned to be larger than the original it is best to enlarge it in the scanner settings so that it is scanned larger. This will give much better quality than if you scan at 100% and then enlarge it later on.

In your scanning settings you should find a setting for image OUTPUT SIZE, it may ask you set an actual size, A4, A5 for example, or specific dimensions in centimeters or millimeters. Some may even allow you set a percentage increase. Find where this setting is, and then set it to the final size you want the image to be. The scanner will then enlarge it as it scans still keeping the scanning resolution that you set before.

It is always better for quality to have a larger image that you can reduce down, rather than a smaller image that you need to enlarge. For now all you need to remember is that enlarging images loses quality, whereas decreasing the size of images keeps the quality. You will be able to find more information on image resolution and resizing in a later article on Enlightenment.

Fig. 5. below shows how to set a reuseable custom final image size in the CanoScan Toolbox software. This is useful if you have a number of pictures to scan that you want to be the same size at the end. Follow the steps:

  1. Give the size a name and set the dimensions in centimetres or inches. Then click the ADD button. This will save the setting and you will see it in the list on the right.
  2. Click the SAVE button at the bottom of the window. Now the next time you want to choose that size, it will appear in the drop down list seen in fig. 4.
Setting a reusable final image size
Fig. 5. How to set a reusable final image size in the CanoScan Toolbox software.

4. Descreening

Descreening is a technical term and is used to explain the technique used to get better quality when scanning an already printed image, i.e an image from a book, magazine, or something you’ve printed to your own printer.

If you look at an image printed in a book or magazine very closely or under a magnifying glass you will see that it is made up of tiny dots. The process of scanning an image is turning it into dots or pixels to display on your screen or print later. So when you scan a printed image that is already made up dots, they clash with the dots that the scanner is creating and produce a horrid square pattern in the resulting image, also known as a Moiré pattern. In printing, these dot sets are known as line screens, and so the process of softening the Moiré effect when scanning printed material is known as descreening.

Scanned postcard moire
Fig. 6a. Scanned postcard showing the Moiré pattern. (Click on the image to enlarge it.)
Scanned image with descreen
Fig. 6b. The same postcard scanned with the descreening set. (Click on the image to enlarge it.)

You may find that the scanning software you are using doesn’t have the descreening option as it sometimes deemed to be an advanced feature. The descreening process is in fact a slight blurring effect, so you could set a slight blurring feature to the scanning setting if you have this option available instead. Otherwise you will have to use a photo editor such as Photoshop to blur the image and reduce the Moiré effect. The common line screens are 150lpi, or 175lpi if your settings have these options, otherwise set the descreen to 5 and use trial and error to produce a good quality image. It may mean rescanning the image with a different descreen setting to get the best result.

Advanced settings CanonScan Toolbox
Fig. 7a. The advanced settings of the CanonScan Toolbox software.
Advanced settings descreen
Fig. 7b. Setting the descreening option in the advanced panel of CanoScan Toolbox.

Fig. 7a. Show the advanced settings available in the CanoScan Toolbox software. This offers the user more freedom in setting sizing, resolution and other effects.

  • The red arrow in fig. 7a. shows where to set the colour mode or the ‘type’ of the original you are scanning.
  • The circled area shows the options for setting the output size of the final image. There is a drop down menu to choose a preset size, or boxes for inputting specific dimensions.
  • Fig. 7b. shows where the descreening option can be turned on.

5. Saving the image

Again the file format you save the scanned photo in will depend on it’s final use. The most common image formats are .tif, .jpg, .eps, .png.

  • For most uses the .jpg or .jpeg file format set with ‘high quality’ compression is perfectly adequate. It will keep the file size fairly small, but still have good enough quality to print on your own printer. These images are perfect for online use, and email. Please note that in some cases the compression applied to jpg images can cause the image to lose quality, so if you need a better quality image for printing, save the file in the format suggested below.
  • For high quality printing it is best to save the image as .tif or .tiff. This file format is commonly used by commercial printers for good quality results. You can apply compression to this file format at the point of saving, but it will not produce any loss in quality. The file size can be considerably larger than the jpg format, and is therefore no good for online use or emailing.

That’s all for this tutorial on the basic settings for scanning images. Future articles will explain how to touch up your images, resize and print them.

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