Q. Is a digital camera as good as film for taking electron microscope images?
Q. What good is having a digital camera on an electron microscope?
Q. How do I import the digital images into Photoshop?
Q. When I look at the image size it says 72 or 173 dpi. Can I get higher resolution images?
Q. Is there an alternative method for getting my EM images into a computer?
Q. Is a digital camera as good as film for taking electron microscope images?
A. No. At a given magnification, the resolution of commercially available digital cameras doesn't even come close to what you can get with film. The best available cameras (2k by 2k) cost more than $150,000 and only provide a resolution of around 2000 pixels per inch. In comparison, film has a resolution of approx. 10,000 pixels per inch, counting each silver grain as a pixel. The grayscale depth of film is also much better than a 12-bit digital camera, which only provides 4096 shades of gray.
Tip: The lower resolution of the digital camera is more severe at lower magnifications than it is at higher magnifications. To take best advantage of a digital camera, try to shoot pictures at the magnification you will use for printing. This is usually between 3 and 10 times the magnification you would use for film recording. You can also make the images appear sharper by using an unsharp masking filter in Photoshop or another image processing package.
Q. What good is having a digital camera on an electron microscope?
A. Although you will probably still want to use film to obtain publication quality prints, the digital cameras can be very useful. They allow you to focus at relatively low illumination intensities, minimizing the damage to your specimen. They allow you to manipulate the contrast, which can be useful for detecting small gold particles in immunogold labeled specimens. They can reduce the time and tediousness of surveying and recording results from large experiments where not every image needs to be publication quality. The images are also of sufficient quality for many morphometric functions such as particle counting and measurement of feature dimensions.
Q. How do I import the digital images into Photoshop?
A. FOR THE SEM: Use the "Open" function of the File menu. Check "Show All Files". Choose the "Raw" format and double click on the image you want to open. When the dialog box pops up enter: 512 for both width and height. Leave "Count" set to "1" and "8-bits" selected. Type 1024 in for "Header Size". Click "OK".
FOR THE TEM: Files are saved as TIFF. Just use the "Open" function of the File menu and double click on the image you want to open. If you have saved your images as 16-bit, you will have to change them to 8-bit to take advantage of all Photoshop features.
Q. When I look at the image size it says 72 or 173 dpi. Can I get higher resolution images?
A. Yes. The dpi specification only pertains to how the data is rastered on the display screen or output by the printer. The actual resolution of the image is determined by the size of the camera array, the magnification of the microscope and the size of the camera pixels. The array dimensions and pixel size of the camera are fixed. The default display of the images from the SEM is a 7 inch by 7 inch, 72 dpi image. The default for images from the TEM is a 6 inch by 7 inch, 173 dpi image. You can display or print an image with higher dpi by reducing its size using Photoshop. In the "Image" menu, choose "Image Size". Uncheck "Resample" and type in the dpi you want. Click OK. For the SEM if you typed in 300 dpi, you will now have a 1.7 inch by 1.7 inch 300 dpi image. For the TEM the new image will be 3 inches by 4 inches. This can be printed as is, or if you want a larger print size, you can choose an enlargement in the Page Set Up dialog box. From Photoshop, you can print a 200% enlargement with no detectable loss in image quality.
Q. Is there an alternative method for getting my EM images into a computer?
A. Yes. We now have a high resolution film and print scanner. You can take your EM negatives and scan them into our computer and then transfer them to your computer by Ethernet or disk. The scanner is a Microtek Scanmaker 5, which has 2000 x 2000 dpi spatial resolution and 12-bit grayscale depth. There is no glass between the film and the scanner bed, so Newton rings are eliminated.