In the facility, images can be acquired either digitally on the microscope, or can be digitized from a negative or a print. Both methods have their advantages.
Images which are acquired digitally are typically available immediately for analysis or printing. There is no need for development and drying of negatives or for making prints. Typically the images are viewed as they are acquired, so there is a WYSIWYG component (i.e. you know the picture is good as you acquire it). Acquisition is fast, and most students today are very familiar with computers, but not so with photography, so user training tends to be easy.
Silver-based images, however, still retain a far higher information density than do digital images. Photographic negatives have a resolution of at least 100 pixels/mm (although one must also consider other contributions to noise in the image). Hence an 8cm x 10cm negative contains as a minimum 80 megapixels. Since the dynamic range of film is much higher than the 256 grey levels represented by a single byte, the information content of the negative corresponds to more than 160 Mbytes.
Since the negative carries so much information, it is possible (and usual) to digitise
only portions of it for analysis. It is also possible to digitise parts of a negative or
print at different magnifications in order to analyze features at different scales.
It is possible to digitise directly on all the microscopes in the facility. In some
cases the resolution of the image is 1024x1024 pixels, while in others it is significantly
more. In all cases the pixel depth can be one or two bytes.
Digitisation from photographs.
An Epson Expression 1640XL scanner is available. This scans prints or negatives into Adobe Photoshop in a wide variety of formats and at hardware resolutions up to 1600x3200dpi and up to 14 bit pixel depth. This scanner will digitize to a Dmax of 3.6.
MIT-CMSE Electron Microscopy/tonygr@MIT.EDU
Document last reviewed September 27th. 2007.