Microscopes - Digital Camera & Video Basics
Part 2 - IMAGE OUTPUT
An Image
The microprocessor manipulates and decodes the digital information which has been converted from photons to electrons to digital format and binary code, (e.g. 11001001).
Once this is done, we finally get some type of image on our cameras LCD display screen. It can now be stored on the cameras storage media, whether it be on a hard drive or SD card. This can now be called a digital file.
Are Digital Cameras as Sensitive to Colour as Human Eyes?
Depending on the type of sensor (chip) and filters used, generally they are. Some key points on digital sensors and filters are: -
- Less sensitive to blues(~400-500nm)
- More sensitive to red, NIR (Near Infrared) and IR (Infrared)
- Green is the most important colour for the human eye to perceive correctly to have “correct” colour.
What is blooming?
We talked, in part one about photosites and how they “soak” up the light allowing the chip to be stimulated. When a photosite becomes “overfull” with light information, it can contaminate adjacent photosite.
This causes fringes between light and dark objects in photos (high contrast). This is sometimes mistakenly known as chromatic aberration. It usually is attributed to cameras with small photosites and can be remedied sometimes via post processing but is not always perfect.
Blooming - high fringing in high contrast conditions
What is Grain?
Technically speaking, digital images have no grain.
We see grainy images, which is sometimes called noise, because the noise is coming from our sensors and usually from too long exposure (hot pixels) or sometimes picked up from CMOS transistors surrounding each photosite.
Noise can come from increased gain as well (distortion) which can be adjusted on film and digital cameras.
Noisy Image - shows “hot pixels”
What is Sensitivity?
A sensitive film needs LESS light to record an image (high ISO [International Standards Organisation] number). E.g. ISO of 1600, 3200 and even 6400
Digital camera sensitivity is the same and is also measured in ISO (pronounced “eye-so”) numbers.
As you increase the ISO numbers you increasing the “Gain” or volume control of the sensor which may be required for fast shutter speeds or low light conditions, but if not correctly adjusted can give you very noisy images.
High ISO = High Sensitivity = More Noise
Image File Formats
There are various different file formats that images are saved and/or imported or exported. This is another subject all on its own and they all have advantages and disadvantages. We may visit this at a later stage.
They are, to name a few: -
- BMP Bitmaps
- JPEG Joint Photographics Expert Group
- TIFF Tagged Image File Format
- GIF Graphics Interchange Format
- RAW Raw Image Formats
There is around 20 different digital file formats, but listed above are the more popular formats.
JPEG Digital File Format
The most popular file format for everyday use is JPEG.
It is an image file that can be compressed and made smaller without too much deterioration of image quality.
We call this Lossy compression and once the information is compressed and lost it cannot be regained. It deteriorates even more when the compressed file is compressed over and over again.
JPEG is the compression format used when sending pictures via PDF.
With Lossy compression we remove some detail and colour information, but this can be adjusted on our cameras and computers to low/medium or high compression quality. This also adjusts the image file size.
JPEG sorts the image information into colour and detail. It compressors colour more than detail because our eyes are more sensitive to detail than to colour. It has a unique ability to make the compression less visible to the naked eye.
JPEG also sorts the detail into fine and coarse. JPEG discards the fine detail first when compressing the file size because our eyes are more sensitive to coarse detail than to fine detail.
100% JPEG quality - good quality image
60% JPEG quality - hard to notice difference
10% JPEG quality - clearly lower quality image
There is a lot to think about when choosing cameras and their attributes, but is there really? These days the cameras we see whether it be domestic grade or commercial are fully automatic with optional manual settings that are really never fully utilised, understood and therefore never touched.
I hope this has enlightened you a little and given you a foundation and basic knowledge of imaging in general and the applications which can be applied to your GLOBAL dental microscope and your family holiday shots!
General Key Tips
Fine Focus Lever
Sometimes the least used part of your microscope, but most important.
If you are not using your fine focus lever, we can provide the training to make this element of your microscope more productive. Making major movements of yourself and the microscope to accomplish minor and micro movements is time consuming and unproductive. Remember to par focus the microscope before each case.
Objective Lens
Check your objective lens to make sure it is screwed in all the way. If you see threads on the bottom ring, it needs tightening. If an assistant removes the green protective lens cover by trying to unscrew it rather than pressing it on or off, he or she may inadvertently unscrew the metal lens cover plate resulting in the glass optics falling free.
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For any Global Microscope User Group correspondence, please contact Peter Di Medio on +61 414 856 696 or peter@inline.com.au
For any Sales, Training or Applications issues please contact Mario Falvo on +61 418 228 558 or mario@inline.com.au or myself, Peter Di Medio on +61 414 856 696 or peter@inline.com.au