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20x is my favorite objective power.
Using AO Series 10
for objects without coverslips,
Olympus MSPlan objectives were the hot setup,
but I first acquired a cheap set of MEIJI S.PLAN M objectives.
While mostly using reflected illumination, a transmissive calibration slide eases comparisons,
using coverslips according to objective engravings.
Captures by Sony α7 RII
and Imaging Edge Desktop;
Many APS-C sensors have more pixels in objective image circles, but
35mm sensor enables flexible (e.g. square and precisely centered) crops.
Unlike too many Canons, Sony cameras get power from USB while tethered.
Although Bayer matrix camera sensor
captures red and blue channels every other row and column,
downscaling images 2x impacts sharpness.
Example crops near center from 42 megapixel image of 100x100 1mm grid @50x:
original |
2x downscale, then rescale |
difference |
Infinity objectives by Nikon Eclipse trinocular vs Canon EF 70-200mm vs AO/Reichert microStar trinocular head;
CF finite objectives by direct projection.
First impressions:
- 100W Optiphot 2 eyepiece images are uncomfortably bright for < 20x; view with ND400
- Image circles are constrained by RMS thread for objectives < 10x power.
- Image circles are constrained by tube lens aperture for objectives > 10x power.
- 10x objective images are not circular when objectives are not parcentric with tube lens
- Sony α7-RII sensor is 35.9mm and 7952 pixels wide
- From
ImageJ - Analyze - Plot Profile, Olympus MSPlan 5x edges are > 10 pixels wide:
... while Nikon CF Plan Epi 20x edges are 6 pixels wide:
... the limit for minimal aliasing artifacts.
- Imaging Edge Remote histogram helps condenser diaphragm adjustment
- Microscope image dynamic ranges are well within JPEG limits; no need for camera RAW.
- JPEG quality 85 reduces image sizes about 90% from Sony
Extra fine with imperceptible impacts.
- Fine focus by camera lens is nicer than by microscope stage control.
- EF 70-200 aperture setting strongly influences captured objective image circle.
- Aligning and centering camera lens as tube lens wants fiddling.
- Blackening AO/Reichert trinoc photo tube interior addressed flare artifacts.
- I had forgotton how comfortable are AO 180 eyepieces;
my eyes feel a decade younger viewing thru them instead of most Nikon CFWs,
which are nominally interchangeable in my experience.
AO/Reichert trinocular coverslip 34mm parfocal objective comparisons
Phil Mathewson summarized AO and Reichert objectives compability.
Generally. despite more artifacts, newer coverslip infinity objectives appear sharper than AOs,
perhaps thanks to modern coatings.
parfocality puzzle
With AO objectives nearly parfocal by shims
and tube length tweaked by diopter adjustments between low and high power:
- "final" stage fine focus thru eyepieces
- then camera still wants over 10mm focus adjustment (by focusing helicoid).
Nikon NIKKOR-Q 20cm 1:4 vs Canon EF 70-200 f/2.8L IS
Canon wins for aperture (field)...
| MS Plan 5x |
MS Plan 10x |
CF Plan EPI 20x |
UMPlan Fl 20x |
 Canon EF 70-200 |
 Canon EF 70-200 |
 Canon EF 70-200 |
 Canon EF 70-200 |
 NIKKOR-Q 20cm |
 NIKKOR-Q 20cm |
 NIKKOR-Q 20cm |
 NIKKOR-Q 20cm |
Other tube lens comparisons
Most famously, by Robert OToole,
as discussed on photomacrography.net.
Interestingly, Robert discovered some better results by defocusing an object,
then focussing tube lens beyond infinity,
which also reduced overall magnification to the sensor.
Robert called this "pushed down", reducing tube length between sensor and tube lens.
This worked for him with Raynox DCR-150, with 144mm from sensor to tube lens,
and Sigma Life-Size Attachment Lens (LSA) at 145mm sensor-to-tube lens.
Perhaps this provoked objective aberrations that compensated tube lens aberrations,
and might work for other combinations involving tube lens focused at less than infinity...?
In 2021 testing,
Robert declared Raynox DCR-150 the best tube lens for Sony α7R IV 35mm sensor,
(208mm sensor to lens, minimal objective spacing),
but no camera telephotos were tested.
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