Micro-Tech-Lab Newsletter from 20.11.2008
The december issue of our newsletter is dedicated to the
topic of photography through a microscope. After receiving an
increasing number of enquiries from our customers, we decided that it
would be useful to shed some light on choosing a suitable camera for
taking images using a microscope.
Using full-frame digital SLR cameras in microscopy
The
use of large sensors in microscopy does not have as many advantages as
it does in conventional photography. Having a high number of pixels is
also not hugely significant,
as the image resolution is exclusively determined by the numeric
aperture of the lens. Other camera features, on the other hand, such as
colour depth, signal to noise ratio and light sensitivity, are far more
important.
A
whole range of camera components are responsible for creating
high-quality microscope photos. Therefore it is important that each of
these components is of high quality, as the entire chain can only be as
strong as its weakest link. This signal chain consists of a sensor, an
amplifier, an analogue-to-digital converter (ADC) and a digital signal
processor (DSP).
Picture 1: Signal chain
View Image
When
the photon strikes the sensor chip, it is stored as an electrical
charge. This electrical charge is proportional to the number of photons
present. The analogue voltage is increased by the amplifier before it
reaches the analogue-to-digital converter (ADC). Only now does the
information exist in digital form. Next, the digital signal processor
(DSP) optimises the colour reproduction, and finally the data stream is
processed for storage on the flash memory card (CF/MMD card).
As a rule, full-frame digital SLR cameras
contain only top-quality components, and for this reason they tend to
fall into the higher price bracket. Professional features such as
remote control, mirror lock-up, LiveView and HDMI output generally come
as standard on these models.
In
addition, the colour depth of each colour channel is also important.
Each basic colour (red/green/blue ==> RGB) has a resolution of
between 12 and 16 bits. The higher this value, the more precise the
reproduction of nuances in colour. If this number is multiplied by
three (for each of the three basic colours) the result is the total
memory depth of the colours that will be reproduced. At a resolution of
14 bits per channel, the result is a colour depth of 42 bits. In
comparison, cheap compact cameras have only a 24 bit colour depth. The
uncompressed data is stored in RAW format. Since this format has a
larger storage requirement, users usually select the JPG format
instead, which means that a lot of information is lost. Depending on
the JPG image’s level of compression, a choice has to be made between
storage space reduction and quality.
Overview of some current cameras
|
|
Format (mm)
|
Colour depth (bits)
|
ADC
|
HDMI
|
LiveView
|
Number of pixels (megapixels)
|
|
Nikon D3
|
24 x 36
|
42
|
14 bits
|
Yes
|
Yes
|
12
|
|
Nikon D300
|
23.6 x 15.8
|
42
|
14 bits
|
Yes
|
Yes
|
13
|
|
Canon EOS 5D Mark II
|
24 x 36
|
42
|
14 bits
|
Yes
|
Yes
|
21
|
|
Canon EOS 1000D
|
22.2 x 14.8
|
42
|
n/a*
|
No
|
Yes
|
10
|
|
Olympus E3
|
17.3 x 13
|
36
|
n/a*
|
No
|
Yes
|
10
|
|
Olympus E-520
|
17.3 x 13
|
36
|
n/a*
|
No
|
Yes
|
1
|
* no information available from the manufacturer
For professional use in microscopy, we recommend high-quality full-frame digital SLR cameras,
particularly in the case of special processes (e.g. fluorescence
microscopy). In addition, we offer special LM digital adapters for
full-frame sensors, which guarantee optimum illumination. To help make
your choice easier, we have created a special page on our website:
http://www.lmscope.com/produkt22/Camera_Ranking_en.shtml
Conclusion: If microscope photos of extraordinary high quality are important to you, then you should always choose a digital SLR
camera with a full-frame sensor. It should be mentioned, however, that
cameras with a half-frame sensor or a four-thirds chip can also provide
very good results. Here, it is particularly important that the camera
used is equipped with a LiveView function and mirror lock-up, as only
this will enable you to achieve the optimum level of focus that you
require.
A preview of issue 3 of our newsletter:
- Improving optical resolution through microscopic mounting media.
Related Links
New LM Digital Adapter for:Canon EOS 5D Mark II / Nikon D3x / Canon EOS 7D / Canon EOS 550D / (Rebel T2i / Kiss X4 Digital) / Canon EOS 1D Mark IV / Canon EOS 500D / Digital Rebel T1i / Nikon D3S / Canon EOS 1Ds Mark III / Panasonic Lumix DMC-GH1 / Pentax K-7 / Nikon D300S / Nikon D700 / Nikon D3 / Panasonic Lumix DMC-G2 / Canon EOS 50D / Olympus E-30 / Nikon D300 / Olympus E-620 / Olympus E-3 / Olympus Pen E-P1 / Panasonic Lumix DMC-GF1 / Panasonic Lumix DMC-G10 / Olympus Pen E-P2 / Olympus Pen E-PL1 / Canon EOS 1D Mark III / Sony Alpha 450 / Olympus E-600 / Canon EOS 450D / Digital Rebel XSi / Olympus E-330 / Panasonic Lumix DMC-G1 / Nikon D5000 / Olympus E-520 / Olympus E-420 / Olympus E-450 / Canon EOS 1000D / Olympus E-510 / Olympus E-410 / Panasonic Lumix DMC-L10 / Pentax K20D / Sony Alpha 380 / Sony Alpha 550 /
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