How To Add a Camera to an Olympus BH2 Microscope
In order to attach a digital camera to the BH2, you will need a BH2-TR30 or BH2-SWTR30 trinocular head (or one of the alternatives listed below) and a phototube adapter which meets the following criteria: 1) The lower mount is compatible with 38mm NFK port on the trinocular head. 2) The upper mount is compatible with the camera body you wish to attach. 3) The adapter is the proper length for parfocality between the camera and the eyepieces. 4) Allows for the required NFK photo eyepiece to be installed in the NFK port on the trinocular head. Listed below are several methods by which you can correctly couple a camera to the BH2.
A Few Words About Parfocality
Regardless of the method by which you mount a camera onto your BH2 scope, it is imperative that the camera be parfocal with the eyepieces (i.e., the eyepieces and the camera must both be in sharp focus at the same focus setting). If you find yourself having to significantly re-adjust focus when switching between using the eyepieces and the camera, this indicates improper geometry of the camera mount, and this is adversely affecting the quality of your camera’s imaging.
So, what’s actually happening when you refocus a microscope to correct a non-parfocal camera image? Let’s start with the obvious. When you change the focus setting from the position where the eyepieces are sharply focused to favor the camera, you’re moving the stage (either up or down) away from its proper position. In other words, you’re changing the working distance of the objective from where the optics were designed to operate to some other position.
This change in working distance affects the position within the optical tube where the objective projects its intermediate image. By mucking around with the plane of focus of the intermediate image, you are in-turn changing the plane of focus of the final image presented to the camera by the NFK photo eyepiece. When you get the plane of focus of the final image to land on the image sensor within the camera, the image is “in focus”.
You are in effect focusing the camera by forcing the optics to operate at a different optical tube length than that which they were designed to operate, and this introduces spherical aberration to the camera image. The BH2 is a very nice scope with very high-grade optics. Do not mess this up by using an improper camera mount!
If you wish to tweak the length of a DIY camera mount to the proper optical length to achieve parfocality with the eyepieces (and you absolutely should do this), be sure to always use the lowest objective magnification available for this. Although higher NA objectives have narrow depth of field than lower NA objectives, these same objectives will have a wider depth of focus. What’s the difference between depth of field and depth of focus? Depth of field describes the depth around the specimen plane which will appear adequately focused t the eyes (which increases with decreasing NA), while depth of focus looks at the other end, and describes the depth around the image sensor which will be acceptably focused (which decreases with decreasing NA). This means that low power objectives will better show errors in projection distance that impede parfocality, as well as errors in the tilt of the image sensor that keep opposite sides from achieving simultaneous focus.
Which Photo Eyepiece Do I Need?
In order to obtain the widest field coverage, it is critical to properly match the magnification of the NFK photo eyepiece to the type of image sensor in the attached camera. The image below shows the relationship of the image sensor to the projected field of view, with two types of image sensors (Full Frame and Canon ASP-C), for all available types of NFK photo eyepieces (1.67x, 2.5x, 3.3x, 5.0x, 6.7x).
The top row of this image shows a comparison of the portion of the visible field seen through the eyepieces that will be captured by an attached camera which utilizes a full-frame (24mm x 36mm) image sensor, for the various magnifications of NFK photo eyepieces in the LB family of optics. The widest captured field, without vignetting, is achieved when the NFK 2.5x is used. The NFK 1.67x will produce corner vignetting, while the 3.3x, 5.0x, and 6.7x will capture proportionally narrower fields of view. If possible, always use an NFK 2.5x with a full-frame sensor.
The second row of this image is the same comparison when using an attached camera with a Canon ASP-C (22.3mm x 14.9mm) image sensor. In this case, the best field of view will be obtained when the Canon ASP-C is coupled with an NFK 1.67X. Any greater magnification than this will capture a proportionally narrower field of view. If possible, always use an NFK 1.67x with a full-frame sensor.
This image shows the field coverages of the NFK 1.67x and NFK 2.5x photo eyepieces, when used with Full Frame, ASP-C, and Four Thirds image sensors, as compared to the visual field of the standard 10x eyepieces. Note that these apply with no intermediate reduction factors (i.e., does not apply to MTV-3 or U-PMTV applications).
This image shows the relative field coverages of the various NFK photo eyepieces, when used with a Full Frame camera and no intermediate reduction factors (i.e., does not apply to MTV-3 or U-PMTV applications).
Compatible Cameras
At a minimum, a suitable camera for the BH2 must have a lens mount that can be adapted to the BH2, with a resulting image sensor placement that is the proper position from the NFK photo eyepiece, and must have an image sensor whose size is compatible with one of the Olympus NFK photo eyepieces, for proper field coverage.
Vibration caused by the shutter and mirror in older DSLRs can be problematic for image sharpness in photomicrography. Traditional solutions for mitigating vibration include electronic flash, long exposure times, mirror lock-up, and isolation stands that support the camera above the microscope, without direct physical coupling.
Newer DSLR cameras have the ability to take exposures electronically, after the mirror has been raised and the shutter has been opened, to allow for vibration-free exposures. Mirrorless cameras of course do not have the mirror to cause vibration at all. These camera types are preferable to the older DSLR cameras without electronic exposure capability.
CANON CAMERAS: Canon EOS DSLRs and mirrorless cameras are probably the most common camera type used on Olympus BH2 scopes. There are a few reasons for this popularity.
First, the Olympus Photomicro L Adapter, which was originally made to attach a 35mm Olympus OM SLR to the BH2, can be easily adapted to the Canon EF or RF mounts, by using an inexpensive OM-EF or OM-RF adapter sourced through eBay or Amazon. A properly made adapter will allow any Canon digital camera body with EF or RF lens mount (with no attached lens) to mount onto the Photomicro L Adapter and provide imaging that is perfectly parfocal with the microscope eyepieces.
Next, the common-as-dirt NFK 2.5x photo eyepiece, which was originally made for 35mm film imaging, is a perfect match to a full-frame Canon, since full-frame sensors are the same physical dimensions as 35mm film.
Alternatively, the NFK 1.67x photo eyepiece (which is much more expensive than the NFK 2.5x, on the used market) is a good match to Canon cameras with the ASP-C sensor.
EOS cameras come with EOS Utility software that allows the camera to be controlled in Live View mode, via a USB connection from a computer. Live View allows the computer monitor to be used for verification of focus and composition and allows images to be saved directly to the host computer.
Newer Canon EOS cameras (starting with the 5D Mark II, 7D, 40D, 450D and 1000D onwards) have a silent EFSC (Electronic First Shutter Curtain) mode that makes them well suited for photomicrography. This mode virtually eliminates mechanical vibration by starting the exposure electronically after the mirror has been raised and after the shutter has been opened.
FULL-FRAME CANON: Suitable Canon models with full-frame image sensors include the 5D Mark II, 5D Mark III, 5D Mark IV, 6D, 6D Mark II, R8 and RP. These cameras work well with an NFK 2.5x photo eyepiece and are a perfect match to the 35 WHK 10x/20 L finder eyepiece.
ASP-C CANON: Suitable Canon EOS models with ASP-C image sensors include the 7D, 40D, 50D, R7, R10, R50, R100, 600D (Rebel T3i), and 1100D (Rebel T3). These cameras work well with the NFK 1.67x photo eyepiece, but the field of view does not quite match the 35 WHK 10x/20 L eyepieces.
OM-EF and OM-RF ADAPTERS: The OM-EF or OM-RF adapter allows Canon DSLR or mirrorless bodies to be attached to the OM mount of the Photomicro L Adapter, positioning the image sensor at the same place in the optical path that the film plane in an Olympus OM camera would be located. This ensures perfect parfocality with the microscope’s viewing eyepieces. These adapters are readily available on eBay or Amazon, at a very low price.
A properly designed OM-EF adapter makes up for the 2mm registration difference between the OM and EOS DSLR bodies, while a properly designed OM-RF adapter makes up for the 26mm registration difference between OM and EOS R mirrorless cameras.
There are three types of adapters available for Canon EOS bodies: These include adapters which are available with no internal chip, those with an auto-focus confirmation chip, and those with an EMF chip. The EMF chip tricks the Canon EOS camera into thinking an actual EF lens is attached. This chip enables focus confirmation (via viewfinder beep/light) and EXIF data modification, which allows manual lenses to be used in Manual or Aperture Priority modes. The features of these adapter types are detailed below.
FOUR THIRDS / MICRO FOUR THIRDS: It is possible to use digital cameras with Four Thirds and Micro Four Thirds image sensors on the BH2, but the best you can do with these cameras is to couple them with the very expensive NFK 1.67× photo eyepiece, and even then, the field of view captured by the camera will be substantially smaller than the viewing eyepieces. Adapters are available through eBay or Amazon to attach Four Thirds or Micro Four Thirds cameras to the Photomicro L Adapter.
SONY NEX: Adapters are available through eBay or Amazon to attach Sony NEX cameras to the Photomicro L Adapter. These cameras contain an ASP-C sensor and should be used with an NFK 1.67x photo eyepiece.
Minolta AF: There are adapters on eBay and Amazon that may allow Minolta AF bodies to be used with the Photomicro Adapter L. These adapters seem to include an optical lens which might make them suitable for the BH2 (but this has not been confirmed).
Sony α: There are adapters on eBay and Amazon that may allow Sony α bodies to be used with the Photomicro Adapter L. These adapters seem to include an optical lens which might make them suitable for the BH2 (but this has not been conformed).
NIKON F: It is not possible to adapt a Nikon F camera body to the OM mount on the Photomicro L Adapter, since the flange distances of the two mount types are incompatible. It is theoretically possible to remove the OM mount from the Photomicro Adapter L and attach a Nikon F mount in its place, but such a conversion would require careful centering and shimming to maintain parfocality with the viewing eyepieces.
T-MOUNT CAMERAS: T-2 adapters are available for many camera types, including Olympus E, Canon EOS, Nikon, Minolta, Pentax, Panasonic, Sony α, Sigma, and Sony NEX (and possibly others) to allow these camera body types to be used with third-party T-mount adapters, such as the Diagnostic Instruments PA1-10A, or with the DIY MTV-3 T-Mount described below.
Olympus Camera Mounts
Photomicro L Adapter
Photomicro L Adapter
The Photomicro L Adapter (Olympus 7-C545) was the official Olympus solution for attaching an Olympus OM SLR camera body to the BH2 microscope. These were available in a metallic silver cover, to match IMT, BH, and CH scopes, as later in a cream colored version, to match IMT2, BH2, and CH2 scopes. The lower end of the Photomicro L attaches to the 38mm dovetail (with NFK port) on the trinocular head, while the upper end accepts the Olympus OM-mount camera body, placing the film or image sensor of the camera the proper distance from the NFK photo eyepiece for parfocal imaging.
The design of the system is such that when one of the Olympus NFK photo eyepieces is placed into the top bore of the trinocular head (before the Photomicro L is attached), the resulting optical configuration projects a fully corrected image of the specimen under observation directly onto the film plane or image sensor of the attached camera.
The total magnification of the resulting image, as projected onto the film plane or image sensor, is the mathematical product of the magnifications of the objective lens and the NFK photo eyepiece. For example, a 10X objective lens and an NFK 2.5X photo eyepiece will produce a total magnification of 25X at the film or sensor plane (i.e., the image projected onto the film or digital image sensor will be 25X life size).
An NFK photo eyepiece must always be used in this application since it provides the necessary optical corrections for the Olympus LB objectives used in the BH2, and since it projects a focused image directly onto the film plane of the attached camera. NFK lenses of the following magnifications were available: 1.67X, 2.5X, 3.3X, 5.0X, and 6.7X.
When using a standard DSLR with an APS-C or ASP-H image sensor, the NFK 1.67x is the correct photo eyepiece to use. Unfortunately, the NFK 1.67x is very rare and is therefore quite expensive (often in the range of $600 to $1000 on eBay). If instead of an APS-C or APS-H camera, you use a full-frame DSLR (which has an image sensor the size of a 35mm film frame) then the much cheaper NFK 2.5x is the correct photo eyepiece to use. The problem with this approach is that full-frame DSLR bodies, even in used condition, are about as expensive as the NFK 1.67x. If you’d like to add a camera to your BH2 without breaking the bank, you can simply do what many people do and just use an NFK 2.5x with your APS-C or APS-H camera and live with the resulting reduction in the field of view.
Although the Photomicro L adapter was designed for use with Olympus OM-mount cameras only, it can also be used with Canon EOS (EF mount) DSLRs or older Canon FD mount SLR equipment by adding a very inexpensive OM-EF or OM-FD adapter (available from Amazon or eBay) to provide a fully parfocal solution. Other camera types may or may not be adaptable to the Photomicro L, so be careful. Some (such as Nikon) will not provide proper positioning of the image sensor relative to the NFK photo eyepiece to achieve parfocality with the eyepieces.
In general, the following DSLR camera types can be mounted onto the Photomicro L, using the appropriate lens mount adapters, to provide parfocal imaging for the BH2: Canon EOS cameras, Sony NEX cameras, and the various 4/3 or Micro 4/3 cameras. When using a Canon EOS, use the NFK 2.5x photo eyepiece for camera models utilizing full-frame sensors, and use the NFK 1.67x for camera models utilizing APS-C sensors. When using a Sony NEX, use the NFK 1.67x projection lens. For 4/3 or Micro 4/3 cameras, the best results will be obtained using the NFK 1.67x projection lens, but even then, the field of view of the resulting images will be noticeably restricted (as compared to the view through the eyepieces). For cameras using 4/3 sensors, better results would be obtained with an MTV-3 or U-PMTVC adapter, rather than the Photomicro L, since the MTV-3 / U-PMTVC contains an integral 0.3X reduction optic to increase the field of view.
MTV-3 and U-PMTVC
MTV -3 / U-PMTVC Adapter
The cream colored MTV-3 adapter (Olympus 7-C555) was the official Olympus solution for attaching C-mount video cameras to the BH2 microscope. Like the Photomicro L adapter, the MTV-3 adapter connects to the 38mm dovetail of the trinocular head, along with a suitable NFK photo eyepiece, and allows the resulting optical configuration to project a finished real image of the specimen under observation directly onto the image sensor of the attached C-mount camera.
The MTV-3 differs from the Photomicro L Adapter in that the MTV-3 accepts a C-mount camera body, and contains an integral 0.3X reduction lens, whereas the Photomicro L Adapter accepts an Olympus OM-mount camera body and contains no reduction optics.
When used with an NFK 2.5X photo eyepiece, the MTV-3 with its integral 0.3X reduction lens projects a real image of approximately 16mm diameter onto the image sensor in the attached camera. This sizing is a perfect match to the 1″ sensor used in many C-mount video cameras.
Although the MTV-3 was designed for use with cameras containing a 1″ sensor, a 2/3″ sensor (which has a diameter of 11mm) is also usable with the MTV-3, but will provide a somewhat reduced field of view, compared to the 1″ sensor.
The requirement for a large sensor size unfortunately excludes many of the modern C-mount cameras out there today. The Nikon J1 and V1 cameras have a CX sensor of the proper size, and with a suitable C-mount adapter should work well with the MTV-3.
The C-mount threads and the 0.3x reduction lens within the MTV-3 adapter are integral to a top piece, which is held in place by a single thumbscrew and is therefore easily removable. The fact that the top piece with the C-mount and reduction lens can be easily removed is a mixed blessing.
On the one hand, this removable top piece makes it quick and easy to remove or attach a C-mount camera, without having to screw or unscrew the camera onto or off of a fixed C-mount. However, because this top piece was removable, many of the MTV-3 adapters available on eBay these days (perhaps even most) are missing this critical piece.
Many potential buyers of the MTV-3 (and likely many sellers, as well) do not know that these adapters are incomplete. Be sure to look for this critical piece if you intend to buy an MTV-3, since you cannot attach a C-mount camera without it.
If, on the other hand, you would like to buy an MTV-3 for the sole purpose of installing a T-mount camera to the BH2 (as described in this video), you will only need the outer tube. The MTV-3 outer tube was used for this particular project because the MTV-3 contains an elegant and well engineered mounting mechanism which will not mar the 38mm dovetail on the trinocular head. Whatever you do, please do not pay full price for a bare MTV-3 tube. Point out to the seller that what they have is only half of an MTV-3 and pay accordingly.
As an alternative to the MTV-3, the very similar Olympus U-PMTVC adapter (Olympus U-V210), which was made for later BX microscopes, can be used to attach a C-mount camera to the BH2. The black U-PMTVC has one advantage over the cream-colored MTV-3, in that the design allows for a slight adjustment of the optical length to tweak the parfocality of the attached camera. This is accomplished by loosening two set screws and rotating the bottom piece, relative to the top piece, until the camera is parfocal to the eyepieces, then snugging the set screws to hold this focus setting.
Olympus specified the reduction factor of the MTV-3 in a non-standard way. A C-mount reduction factor is normally stated to be relative to a 1″ sensor, such that a C-mount adapter with a 1.0x reduction factor would require a 1″ sensor, whereas an adapter with a 0.3x reduction factor would require a 1/3″ sensor. In contrast to this, Olympus specified their reduction factor using the standard NFK 2.5 photo eyepiece for 35mm cameras. The NFK 2.5 produces a real image of 48mm diameter, so the 0.3x reduction factor within the Olympus MTV-3 reduces this down to 16mm, for compatibility with a standard 1″ image sensor used in many video cameras. So, this means that an industry standard C-mount adapter with a 0.3x reduction requires a 1/3″ sensor, the Olympus adapter, with a 0.3x reduction, requires an NFK 2.5x and a 1″ sensor.
The table below lists various sensor sizes that were commonly used in C-mount cameras, along with the most appropriate NFK photo eyepiece for each of these sensor sizes. In addition to the standard CCD sizes, this table also includes the 4/3, Micro 4/3, and Nikon CX sensor sizes, which are used in many modern mirrorless cameras and can be converted to C-mount using inexpensive and readily available adapters. DSLRs are generally not suitable for use with the MTV-3 / U-PMTVC since the mirror-swing of a DSLR prevents the C mount threads from being close enough to the image sensor plane to achieve parfocality with the microscope eyepieces. DSLRs can be used with the BH2 when connected with the Photomicro L Adapter.
TVZ-M Zoom Video Lens
TVZ-M Zoom Video Lens
Olympus made the TVZ-M Zoom Video Lens (Olympus # 7-C567), which was a device of 2-piece construction with a parfocalizing collar and a C-mount adapter that was removable from the main body. The TVZ-M was mounted onto the 38mm dovetail of the trinocular head or PM-ADF adapter and had a variable magnification range of 0.55x to 1.1x. The TVZ-M performed the compensation for the lateral chromatic aberration in the intermediate image that was normally provided by the NFK photo eyepiece, and was therefore used without an NFK photo eyepiece in the setup. There seem to be very few of these in existence, and they are true BH2 Unicorns.
MTV-3 T-Mount
T-Mount Using MTV-3
Olympus made no provision for attaching a T-mount camera to the BH2. The Empire of Dirt Workshop has developed a simple 3D-printable adapter which allows a bare MTV-3 tube to be used to attach to the NFK port on the trinocular head, along with a helicoid focus and a few adapters, to provide a parfocal T-mount for the BH2. Once you have a T-mount, you can then adapt to a great many camera types using the appropriate T2 T-rings. See this video for details of building and using this adapter on your BH2. If you wish to use this method, be sure to adjust the helicoid for proper parfocalization with the eyepieces using a low-power objective.
IMT2-PT
IMT2-PT
In addition to the BH2-PT described above, Olympus also made IMT2-PT phototube, which was intended for the IMT2 inverted scope. The IMT2-PT also works well on the BH2. Like the BH2-PT, the IMT2-PT can replace the traditional binocular or trinocular viewing head and provide a camera port (without requiring the PM-ADF adapter). The Photomicro L adapter or the MTV-3/ U PMTVC adapter (or suitable third party alternative) attaches to the 38mm dovetail of the IMT2-PT, along dropping an NFK photo eyepiece into the NFK port on the IMT2-PT. Like the BH2-PT, you lose the ability to directly view the image through the ocular lenses, but when using a suitable camera with live-view functionality, this can also be a workable option for some people.
BH2-PT
BH2-PT
The Photomicro L Adapter and the MTV-3 / U-PMTVC setups described above can be rather expensive, especially when you factor in the cost of the required NFK photo eyepiece and the potential upgrade from a binocular to a trinocular head. One way to lower the total cost of these solutions is to eliminate the viewing head from the setup entirely.
Olympus offered a BH2-PT vertical phototube, which is essentially a vertical monocular tube for the BH2. When used with the PM-ADF adapter to provide the required 38mm NFK photo eyepiece port, this phototube can replace the traditional binocular or trinocular viewing head and will allow a camera to be attached to the BH2.
The Photomicro L adapter or the MTV-3/ U PMTVC adapter (or suitable third party alternative) attaches to the 38mm dovetail of the PM-ADF adapter (after dropping a suitable NFK photo eyepiece into the NFK port of the PM-ADF). You of course lose the ability to directly view the image through the ocular lenses, but when using a suitable camera with live-view functionality, this can be a workable option for some people.
The BH2-PT can occasionally be found on eBay, but be careful. There was a very similar version, but with a shorter top tube, that will not provide parfocal imaging and is therefore not suitable for the BH2.
PM-ADF
PM-ADF
The PM-ADF adapter mounts onto the 23mm ocular tube of the BH2-PT, and provides a 38mm NFK photo eyepiece port.
Camedia Adapters
Olympus made a series of adapters to allow their Camedia 2000, 3000, 4000, and E-series cameras to be attached to the BH2 using the MTV-3 C-mount adapter. These include the following.
- C3040-ADL
Third-Party Camera Mounts
PA1-10A
Diagnostic Instruments PA1-10
The Diagnostic Instruments (more recently, Spot Imaging) PA1-10A camera adapter was a third-party alternative to the Olympus Photomicro L adapter. Although the PA1-1-A is no longer manufactured, it can often be found on the used market at a lower cost than the Photomicro L adapter. As with the Olympus solution, the PA1-10A provides a camera mount that’s parfocal with the viewing oculars to produce fully corrected images.
Like the Photomicro L adapter, the PA1-10A attaches to the 38mm dovetail on the BH2 trinocular head and must be used with a suitable NFK photo eyepiece. The PA1-10A differs from the Photomicro L adapter in that instead of an Olympus OM mount on the top, it features T2 threads (42mm x 0.75mm), to allow various camera body types to be attached using the appropriate T2 T-ring adapters.
Diagnostic Instruments sold the EOSC-T2 T-ring adapter to allow Canon EF-mount camera bodies (e.g., EOS) to attach to the PA1 10A, and the CANC-T2 T-ring adapter to allow standard Canon FD-mount bodies to be attached, but these also are no longer manufactured and can be quite hard to find these days. Fortunately, generic T2 to EF and T2 to FD T-ring adapters are readily available at low cost on eBay or Amazon which can be used to attach Canon cameras to the PA1-10A.
It should be noted that there are two distinct variations of this Diagnostic Instruments adapter that can be found in the wild, both of which are marked as “PA1-10A”. One variation has a circular dovetail on top with female T2 threads internal to the dovetail, while the other variation has male T2 threads.
What About the Other Diagnostic Instruments Adapters?
Diagnostic Instruments made multiple C-mount adapters that were sold as compatible with the BH2. These adapters, which did not provide for the inclusion of an NFK photo eyepiece in the optical path, were available in models made for 1/2″, 2/3″, and 1″ image sensors, as listed below.
- DD50BHC (black, 0.5x, for 1/2″ sensors)
- DD63BHC (black, 0.63x, for 2/3″ sensors)
- DD10BHC (black, 1.0x, for 1″ sensors)
Note that in the paragraph above, I stated that these adapters were “sold as compatible” and did not say that they “were compatible”. Why did I use that wording? The answer is simple. These DI adapters do not provide the necessary compensation for the lateral chromatic aberration present, by design, in the real intermediate image created by LB objectives. Because of this, the images they produce will contain significant lateral chromatic aberration.
I once asked Spot Imaging (formerly Diagnostic Instruments) about the older adapters (excluding the PA1-10A discussed above) that they used to sell for the BH2. An excerpt of their response is included below. Based on this response, I would not use any Diagnostic Instruments adapters other than the PA1-10A on a BH2 scope, as they are not technically suitable for the BH2.
Kinch Adapter
Kinch Adapter
Since neither the Olympus Photomicro L nor the Diagnostic Instruments PA1-10A adapter are currently manufactured, a better option might be the Olympus 38mm to T-Mount adapter manufactured by Richard Kinch, at http://www.truetex.com/olympus-38mm.htm. Like the Olympus Photomicro L adapter and the Diagnostic Instruments PA1-10A adapter, the Kinch adapter secures to the 38mm dovetail on the trinocular head, along with an NFK photo eyepiece, and through the use of a suitable T-mount adapter, accepts a compatible DSLR (e.g., Canon EOS) to provide a parfocal solution to produce fully corrected images.
Eyepiece Camera
USB Eyepiece Cameras
“So, what about those little drop-in USB cameras sold by companies like Swift and Amscope, that replace one of the eyepieces. Surely those will work?” No, unfortunately they will not work properly on the BH2. Since the optical design of the BH2 relies on the eyepieces or the NFK photo eyepieces to provide some of the required correction for chromatic aberration, replacing an eyepiece with one of these little cameras will produce images with significant uncorrected lateral chromatic aberration. This will be visible in the resulting images as color fringing which gets progressively worse the further you get away from the optical axis (i.e., the center of the image).
Now, if you were to replace the Olympus LB objectives on your BH2 with Nikon CF (Chromatic-aberration Free) objectives from the same era (or some other fully compensated objectives), the little eyepiece camera would drop in and work just fine, since all the compensation for chromatic aberration would be provided within the objectives themselves. But Nikon optics on a BH2 feels like giving up.
DIY Camera Mounts
Cell Phone
Afocal Imaging
A time-honored approach to photomicrography is to simply position the lens of a camera very close to one of the eyepieces and shoot photos afocally through the eyepiece. When done correctly, the resulting images can be of very high quality.
A problem with this method is that it is rather awkward to position a camera to shoot down one of the eyepieces on the BH2, since the BH2 eyepieces are inclined (i.e., not vertically oriented). Additionally, the presence of the camera on one eyepiece makes it difficult to look through the remaining eyepiece.
Because of this, it is tempting to instead just drop an eyepiece into the NFK port of the trinocular head and proceed that way. The problem with this approach is that it doesn’t generally work, since the diameter of the NFK bore is too small to accept the normal WK10X or WHK10X eyepieces. They will go in part way, but they will not seat to the proper position to make the camera images parfocal with the eyepieces. If you’re using a BH2-PT phototube, the solution is simple. Just remove the PM-ADF adapter and drop your 10X eyepiece directly into the ocular tube of the BH2-PT. A WHK is better here than WK, since it has a higher eyepoint, but either of these can be made to work.
Another lesser-known option is to use a WHK15-L eyepiece in the NFK port. So long as you use the regular “-L” version and not the “-H” helicoid version, it will drop right into the NFK port just fine. The 15x eyepiece will provide a reduced field of view as compared to a normal 10X eyepiece (it will be similar to that obtained using an NFK 2.5X with an APS-C or APS-H camera) but that may still be an option for you.
Another way to take the occasional image without spending a lot of money is to just take images afocally using your smartphone. Simply hold the phone up to one of the eyepieces and snap the picture. It sounds a bit easier than it actually is, because you have to be very careful to make sure that the camera is properly aligned with the optical axis of the eyepiece before taking the shot. But with a little care in alignment, the results can be excellent.
There are inexpensive adapters available to allow a smartphone to mount onto a microscope eyepiece and be adjusted for proper alignment with the eyepiece. Once you get that part working, you can experiment with the digital zoom function of the camera to prevent vignetting of the images.