Table of Contents
- 1 What is a flatbed scanner, and how does it work?
- 2 Other Types of Scanners
- 3 Scanning Negatives
- 4 Things to Consider When Looking for a Flatbed Scanner
A scanner analyzes an image or document, processes it, and saves the information to your computer, mobile device, or SD card. These digital versions of the scanned documents or images can then be edited, shared, and archived.
While the purpose of scanners is the same – to scan documents and images- different kinds of scanners are better suited to perform specific scanning tasks. They also differ in terms of the quality of images they capture. Keep in mind that these scanners are intended for producing 2D documents and images. Scanning and producing 3D objects is another bowl of soup entirely.
What is a flatbed scanner, and how does it work?
A flatbed scanner is a standalone unit that has a flat scanning area and a lid. The glass scanning area looks like the surface of a photocopier. Like a photocopier, the documents or images you want to scan need to be placed on the scanning glass area. They are then scanned one by one – requiring you to place and remove each document in between each scan manually.
Because each document or image needs to be manually placed on the scanning area, scanned, and removed, using a flatbed scanner can be a time-consuming task. Some models allow for scanning multi-page files. You will still need to scan each page individually but can save them all in one file on your computer or device. Overall, flatbed scanners tend to produce high-quality scans.
Flatbed scanners work very well to scan fragile documents like newspapers or older, historical documents. You can also use them to scan non-traditional objects like coins, textiles, or flowers. They are also ideal for scanning thicker items like health-insurance ID cards.
Types of flatbed scanners.
There are two main types of flatbed scanners: charge-coupled device (CCD) and contact image sensor (CIS). Charge-coupled device scanners have a collection (also called an array) of sensors that generate an electrical charge when they are exposed to light. This electrical charge is then turned into an image. Most flatbed scanners use this technology. It provides the scanning of images with a wide range of colors at high scan speeds. The drawbacks of CCD technology are that they need to be calibrated regularly, and they cannot scan very wide images.
Contact image sensor scanners make use of newer technology. These flatbed scanners are more portable and require less power than CCD scanners. In a CIS scanner, the image sensors are much closer to the scan bed. That also means that they are much closer to the object that is being scanned. Other positives are that contact image sensor scanners take less time to warm up and need to be calibrated less frequently than charge-coupled device scanners. The drawbacks of CIS scanners are that they produce lower resolution images that often have more inferior color quality than CCD scanners.
Most flatbed scanners follow these steps when scanning an image:
- The document is placed on the scan area or glass plate, and the lid is closed. The lid is usually either white or black. This gives the scanner a point of reference to identify where the edges of the document lie.
- A lamp lights up the document.
- A scan head (made up of mirrors, a lens, filter, and usually a CCD array) is slowly moved across the document. The scan head is attached to a motorized belt that moves it along. It is also attached to a stabilizer bar that holds it steady while it moves across the document. This avoids producing blurry images.
- The image of the document then gets reflected in a number of mirrors (between two and three). Each mirror is curved slightly – this focuses the image onto a smaller surface.
- The image gets reflected onto a lens from the last mirror. This lens concentrates the image through a filter onto the CCD array. The CCD array then generates an electric impulse that gets converted into digital information. This information then shows up on your computer as an image.
Other Types of Scanners
Besides flatbed scanners, there are various scanners – all servicing different needs and requirements – you even get scanners that can scan images directly from your mobile device. The type of scanner that you use greatly depends on the job that you need to get done.
In contrast to the flatbed scanner, a document scanner, or sheet fed scanner, has a dedicated tray where you can place multiple documents that need to be scanned. An automatic document feeder feeds the documents through the scanner. The documents then move over the immobile scan head, which auto scans one document at a time. A sheet-fed scanner resembles a small, portable printer.
This type of scanner is best for batch scanning jobs where you need to scan multiple unbound pages. A document scanner with a sheet feeder tray saves you from having to manually open the lid, placing the document on the scanning area, and removing it once the scan has been completed.
Some sheet fed scanners (or automatic document feeder) scanners allow for ‘duplex scanning.’ That means the scanner can scan documents that are printed on both sides. For faster duplex scanning, you could consider investing in a scanner that has two scan heads. These then scan the two sides of the document simultaneously. They also tend to be more expensive.
Another option is to go for a model that first scans one side, mechanically turns the page over, and then scans the other side. Lastly, you could use a scanner with a driver that incorporates a manual-duplex feature. That means you will have to manually turn over pages that are printed on both sides. The manual-duplex feature would work well if you only have to scan double-sided documents now and then. On the other hand, if you have many documents that are printed on both sides, it might be worth spending a bit more on a scanner that does this automatically.
A handheld scanner works similarly to a flatbed scanner. With a handheld scanner, instead of the scan head being attached to a motorized belt, the entire scanner moves over the document by the person holding it. Handheld scanners are the ultimate portable scanners and especially handy for tasks that require fast scanning and quickly capturing text or images, but they don’t always generate high-quality images.
A slight variation to a handheld scanner is a pen scanner. A pen scanner can trace over text. The scanner then scans, processes, and transfers the text to a computer or mobile device.
A drum scanner is used to capture and reproduce images with a lot of details. They essentially work as a high-quality digital camera – making them perfect to use as a photo scanner. These scanners make use of a technology called a photomultiplier tube (PMT). In a drum scanner, the document or image that needs to be scanned is attached to a glass cylinder – hence the name drum scanner. Light bounces from the image to a sensor in the middle of the cylinder. This sensor splits the light that comes from the image into three beams. Each beam is then sent through a color filter into a photomultiplier tube. Here the light is converted into electrical signals and eventually into digital information.
Film photography is making a comeback. There is just something about shooting on film that adds something special to the experience. Nowadays, you can get everything from 355mm to medium format roll film, or even large format sheet film. Using film to shoot is an experience in itself – as is the development of the images. But what if you don’t have access to a darkroom or want to create and store digital versions of your images? Well, for that, you could use a specialized film negative scanner.
A film scanner is a way to scan your film negatives to generate digital files that you can then save, edit, share, and print. Scanning negatives give you better digital results than scanning printed copies – especially those old, faded photos that you have lying around. You can use a flatbed scanner to scan negatives – some even come with specialized holders for various film formats. However, using a dedicated film scanner will give you better results.
Basic negative scanners can produce reasonably good quality images that you can use to view digitally or share on the internet. More expensive models will allow you to create digital images that produce high-quality prints. They produce higher resolution images with a longer dynamic range, higher Dmax, and more accurate color balance. They also create images that are clearer and sharper.
All negative scanners work roughly the same: a light source lights up the film, and an image sensor records the details. The information then gets converted into digital data. The difference between entry-level and more expensive models lies in the complexity of this process and the technologies that they use. These two factors mean that higher-end negative scanners generally produce better quality images.
While a higher-end scanner might produce better images, it might not be the best scanner for your needs. The same goes for entry-level models. When looking for a negative film scanner, the most critical point to keep in mind is what you will be scanning. Some scanners exclusively scan 35mm film strips. In contrast, others could scan only mounted slides, and others still could scan a variety of film formats.
Entry-level film scanners are easy to use and produce scans quickly. They usually include automated film handling and frame-recognition features. These scanners also often automatically correct exposure and color. Entry-level scanners are easy to use and usually compact. The trade-off is that they tend to produce lower resolution images. If, however, you are looking for a scanner that will produce images that have a higher resolution and produce high-quality or large prints, you might need to consider a higher-end scanner. High-end scanners often resolve any film grain that you might have on your original image. This contributes to the clarity and sharpness that you will get when using a high-end film scanner.
Some flatbed scanners have a transparency unit specifically for scanning film images into digital formats. These flatbed scanners offer you more versatility over which film formats you can scan. All flatbed scanners can scan 35mm film, and most can scan 120 films. There are also a few options on the market that allow you to scan large format sheet film and even 8mm cine film.
Things to Consider When Looking for a Flatbed Scanner
What will you be scanning?
People mostly scan photos and documents (unbound pages) with a flatbed scanner. Other objects you could scan include magazines and films like slides and negatives. Some models have removable lids to scan thick objects. This makes a flatbed scanner a good option when you are looking for a book scanner. People also often make use of flatbed scanning to create scans of original documents or objects that could be easily damaged, like old letters or postage stamps.
On the other hand, if you need to scan large amounts of documents, a sheet fed scanner might be a better option.
If you are using your scanner primarily to digitize images captured on film, you could consider buying a scanner dedicated solely to that. On the other hand, a flatbed scanner will scan most film formats and is versatile enough to be used to scan a variety of other objects.
The resolution of a scan is measured by how many pixels are displayed in each inch of an image. It is usually expressed as ppi (pixel-per-inch) or dpi (dots-per-inch). Each pixel or dot is a specific color, and the colors next to each other combine to create a color image – much like the pointillism art technique.
When there are more pixels per inch, the pixels are smaller, and the image shows up crisper and clearer. If you have fewer pixels per inch, they will be more prominent, and images will appear pixelated. When this happens, you see each enlarged block of color instead of a cohesive image.
Most scanners create scans with a resolution of between 200 and 300dpi. Pictures or images where you need to zoom in and crop small areas of the image or that need to be enlarged significantly might need to be scanned at higher dpi. That goes for other kinds of originals that require higher resolution scanning. For example, the images you will produce from a 35mm slide or negative scan will likely need to be printed much larger than the original. For this, you will need to scan them at a higher resolution. In these cases, a scanner with an optical resolution of between 3,200ppi to 4,800ppi might be required.
When looking for a flatbed scanner, you need to consider the size of the documents that you will be scanning. Most flatbed scanners have a letter-sized platen (scan area). While this is sufficient in most cases, it could be a problem if you need to scan larger images like legal-size pages.
Some scanners come with the required scanning software. In other cases, you might need to download or purchase scanning software. While most scanners are compatible with the majority of scanning software, the program you choose will depend on your specific scanning needs. You might consider some features: the ability to edit your photos or images, optical character recognition (OCR), a business-card archiving or management feature, text indexing, and the capacity to generate searchable PDF documents.
Considerations specific to a negative film scanner.
Besides the above considerations, you might want to look out for some of these features when purchasing a scanner specifically for scanning negatives:
- Dust reduction technologies. A dust reduction feature embedded in your scanner means you will spend less time cleaning your images after they have been scanned. Keep in mind that you should still clean the dust off your negatives with some compressed air or a soft cloth before you scan them.
- Dmax. This is a measurement of optical density. It affects the amount of detail that the scanner can record of thinner areas of film. These areas include shadows in negatives and highlights in positives. The higher the Dmax number, the more detail it can produce of deeply shadowed areas on the films.
Flatbed scanners are incredibly versatile. The most obvious use for them is to scan documents and images to store them in a digital form. On top of that, you could use a flatbed scanner to scan unique or fragile objects like historical documents and other non-traditional objects like fabrics, coins, and flowers. You could also use most flatbed scanners to scan and convert your film negatives into photos.