# How do I read a scanning electron microscopy (SEM) image?

I'm trying to figure out the magnification of this image. Can anyone explain how to read the numbers at the bottom? What do they mean and how can I determine the magnification from them?

• You'll need to look at the instrument's manual. Guess: S3400 is the instrument model, 15.0kV the electron acceleration voltage. The key info you're after is the 30.0um at the bottom, but you need to find out whether 30um refers to the ten graduated intervals together or whether it refers to each interval (which I think is the more likely case - most natural fibers - I'm guessing this is wool or cotton - would be thicker than 6um that would be implied by a 3um interval). – WetSavannaAnimal Nov 21 '16 at 23:16
• Note that some SEM manufacturers may include rich information in the image metadata. For instance, TIFF images from Philips/FEI XL30 contain roughly 100 entries in their header. Unfortunately, it is not usually preserved when the image got edited. – dominecf Dec 8 '19 at 18:04

The magnification is 1,500 which is displayed at bottom of the image. If you want to know the object size from the image, there are 2 methods.

1. How to know directly the size using SEM. In this SEM image, type of SEM is displayed. That is S3400. S3400 is made by HITACHI. For this SEM system, a data analysis software is installed. So you can know the size using the software.

2. How to know the size from SEM image. In generally, when SEM is installed to lab and room, the scale bar is calibrated for each magnification by administrator or stuff of the maker. The calibration is usually regularly carried out. So the scale bar of the bottom of image can be believed. If the calibration of scale bar is not carried out, it is necessary to do for knowing the size of objects in the SEM images. The scale bar is the right bottom of image. There are constructed with 10 short lines. All lines means 30 um. So you can know the object size using this scale of 30 um.

9.9 mm is working distance. The working distance is the distance between the objective lens and a sample. I comment here, because I couldn't add a comment.

• The magnification is stated as x1.50k. What you are looking at was magnified 1500 times.

• The white strips on the right look like a used-to-be length scale. Maybe it was cut in half by mistake - I've never seen a scale this unclear. There are 11 small equaly spaced lines, which fits to a length scale subdivided in 10 parts.
The value 30 um is then the full length of the scale at $30\;\mathrm{\mu m}$. This fits when comparing magnitude to length scale with similar SEM images, for example this from Wikipedia: