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attaching cameras to microscopes

Two considerations
optical
mechanical

optical
afocal vs relay (reprojection) vs direct (sensor @ intermediate plane)
  • afocal:  smartphone camera over an eyepiece is one example;
    Canon's 40mm STM pancake lens on APS-C camera also works well. 
    "If you have a 10X microscope eyepiece,
 the lens on an APS-C camera should have a focal length of about 40mm,
 and the lens entrance pupil needs to be positioned
 at the same location as the eyepieces "Ramsden disk".
    - Charles Krebs 1 Aug 2006 
    "The advantage to pancake designs is that
 their apertures are closer to the front of the lens,
 so they are less likely to vignette."
    - rjlittlefield 15 Oct 2016

  • relay (reprojection) adds optics between finite objectives and sensors
  • direct projection was popularized for movie/video cameras;
    works for interchangeable lens digital camera bodies with live view;
    infinity objectives via tube lens are also considered direct projection.

Finite objective common camera optical adaptations from Ichthyophthirius
  18-26mm field diameters are typical at microscope Intermediate Image plane (F3):


Those field diameters work for direct projection with e.g.
Other sensor dimensions want some relay lens with magnification.
Other photo relay lens purposes:
  • reproject intermediate image plane
    ...typically inapplicable for C-mount and mirrorless camera bodies
  • correct / compensate objectives
    ...not required for Nikon CF and other modern objectives
  • correct intermediate image non-planarity

Many USB camera sensors are quite small;
while a reduction lens avoids excessive intermediate image cropping,
IMO undoing microscope objective magnification is "not ideal".

mechanical
Many microscope images are captured by holding a smartphone over an eyepiece.

motion blur
Smartphones and many mirrorless camera bodies have image stabilization;
image capture with other devices wants
  • remote shutter release
  • rigid attachment
rigid attachment

Camera + Microscope Combinations
Attaching microscope objectives directly to cameras is generally considered macro photography,
mostly addressed elsewhere. Attaching a camera body to a microscope with only air between objective and sensor
is generally considered photomicroscopy, and works with finite objectives.

Infinity objectives want a tube lens to make rays finite,
either for oculars or directly focusing on a sensor,
in which case that tube lens may be a telescopic camera lens focused at infinity.
Since some infinity microscopes depend on their tube lens to correct objective aberrations,
projection from infinity microsope's tube lens to camera's sensor may be considered
equivalent to direct projection from fully corrected finite objectives.
AO pioneered infinity microscope production in the U.S..   (read here for more history)
Practically, optical magnifications much over 1x
wants technique and patience (or great image stabilization) for hand-held macrophotography.
For inanimate opaque subjects, hand-holding has few advantages.

Opaque object microscopy requires reflective, rather than transmissive, illumination.
This is called episcopic (contrasted to diascopic) with illumination accomplished either by
external illumination sources or using so-called vertical illumination built into microscopes,
where light may be directed down thru objectives, e.g. using prisms or other partial mirrors
and called brightfield, or coaxially around objectives, called darkfield illumination.
Most conventional (diascopic biological) microscopes can be used with external illumination
for some opaque microscopy, but their objectives are optimized for viewing thru glass slide covers,
which becomes increasingly important for higher N.A. objectives, e.g. more than 10-20x.

Live View, focus bracketing, Abbe

Using a digital camera with zoomed Live View eases focusing.
Beyond convenience, best viewfinder focus with DSLR mirror down may differ that on sensor.
Silent shutter (Canon's mode 2) and remote shutter release minimize vibration during exposures.
Replacing halogen illumination with blue LEDs should improve image resolution;
Raleigh's criterion has Abbe diffraction limit
depend on illumination wavelength and Numerical Aperture (N.A.).
Practically, blue LEDs not only have shorter wavelengths than do red and green;
excluding longer wavelengths also usefully reduces chromatic aberration effects.
However, blue sensors are relatively sparse in digital cameras;  higher sensor resolution compensates.
Used Canon APS-C bodies with Live View and silent shutter (e.g. 50D) can be less than $100.
Free Magic Lantern firmware adds focus stacking to many such cameras.

other considerations
For popular Olympus finite microscopes (e.g. BH2), matching relay lens is wanted
for objective aberration corrections, then DSLR is satisfactory.

If direct projection (without relay lens) is wanted for most infinity (excepting e.g. Leica)
and e.g. Nikon CF finite objectives, DSLR (e.g. T3i) greater flange-to-sensor distance
cannot be parfocal on many trinocular heads.

Used Canon EOS-M series camera bodies with > 20mp sensors can < US$200.
Canon's tether utility is IMO more useful than those of other manufacturers.

Few Canon EF-M models offer focus stacking, applicable for afocal configurations
with a supported autofocus lens.

Some (more modern) EOS RF bodies are now available used for < US$400,
but I lack experience with them.

Sony mirrorless bodies can more often be powered by USB than can Canon;
Sony full-frame bodies typically have built-in APS-C crop mode, unlike Canon,
but Sony's slightly larger than Canon APS-C sensor size is more liable to corner vignetting.

Eye tube SLR camera adapter clamps

 Traditional eyepiece tubes have about 25mm o.d.,

... for which T-mount adapters were made.
Common brands were Kalt, Aetna and Telestar,
but many identical or similar clamps were branded for cameras.

Ocular Swap

 Swapping between regular eyepiece and camera is fairly quick and easy:
1/4 turn releases camera tube
 remove relay lens
 insert eyepiece, find stylus
Reverse steps to resume image capture.

For larger o.d. eyepiece tubes, up to 1.25" (less than 32mm),
  a 1.25-inch telescope clamp can work, e.g. here on a Cycloptic:

AO eyepiece with afocal Canon 40mm pancake f/2.8 STM


instead of eyepiece, photo relay, extension tubes and helicoid to focus projection on camera sensor

... perhaps with shims to fill gap between eye tube o.d. and clamp i.d.:

Eye tube adapters with typical T2 or M42 threads require camera-specific adapters.
A projection ocular and extension tubes should cost less than $100;
monocular microscope heads typically cost much less than trinoculars,
while having less light loss than binocular heads,
and used eye tube camera adapter clamps go for around $15.

Good complete used microscope with epi illumination and bright/darkfield objectives can be spendy.
Starting from scratch, consider Nikon 210mm B/D objectives in an Optiphot 66;
  many were used for semiconductor electronics wafer inspection...

M42 to 30mm to 23.2mm eyepiece adapter


  • CF PL2.5X suspended with Novoflex bellows
    and Canon 6D over tube to AO trinocular head: 

    Much more about trinocular heads here
    • maintained by blekenbleu