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Technical Digital Camera TDC 1b

The TDC 1b mounted on a Nikon Alphaphot, an Olympus GB40, and a Wild M20. An adaptor made to fit the microscope is used in each case, with at least two internal baffles. All photos are taken by the first prototype (TDC 1a) fitted with a Som Berthiot f1.9 25mm cine-camera lens, about 40 years old, plus a hot-mirror filter, working the lens at f8.

As we have explained, a normal digital camera is designed to frustrate any attempt to use it for technical photography. Inside any digital camera, cheap or dear, is a precision made circuit board, carrying on one side the image sensor, and on the other the colour LCD display for showing what the lens is currently focusing on the sensor. Around this circuit board is anything from a few grams of plastic and a fixed lens, to a die-cast piece of costume jewellery with motors, mechanisms and optics in profusion.

The technical camera is a time-honoured model which allows the film carrier, and sometimes the lens, to be bolted to a great variety of instruments and applications. It is big enough to not need micro-controls to operate it, and what really matters is the solidity of the engineering. What is specific to photomicrography is a 1.3 Megapixel light sensor. We removed the entire circuit board from the first cheap plastic digital camera to incorporate an excellent 1.3 Megapixel sensor, and mounted it in an extremely rigid built-up aluminium body. The front of the body bolts to anything and everything, and the circuit board mountings are set with a collimator so the sensor chip surface is accurately parallel to the front panel.

A front panel close-up shows three black-headed recessed screws that mount the circuit board. Don't touch these without a collimator!. The three studs mount lens and adaptor panels, and the image chip is visible. The top panel, inverted here to read, holds all switch and connector details.

The colour LCD, normally used for quick looks and photo checks, is now in the darkness inside the camera, where its internal lighting shows to best effect. On the back of the camera is an eyepiece, adjustable for a wide range of sight from short to long, which the user sets to give a clear magnified display of the LCD. Normal focusing on this augmented display is positive, but not as easy as a classic Pentax SLR, assuming perfect eyesight. We cannot claim critical photomicrography focus is easy, but with the aid of the 2X digital zoom it does become reflexive when you get the hang of it. All the mini-controls on the former plastic case are replaced with full size, best brand (C and K) switches and push-buttons. As a result the TDC 1b drives very much faster than the donor of the circuit board.

This is the electronic cable release. Shutter is the ring-guarded pushbutton on the front. A centre-biased two way toggle controls the digital zoom. The Author's hand is developing wrinkles.

Photomicrography action can be very fast indeed, chasing highly mobile critters round a slide. A plug-in electronic 'cable release' is supplied which puts the shutter button and the digital zoom on/off right in the palm of one hand, while the other hand drives the X and Y shift controls on the microscope slide stage, along with the microscope fine focus. You can run a whole session of 140 Fine quality JPEGS of about 400 Kbytes each without touching any of the other controls. In the body also are two quickly-removable C cells, rather than the AA cells originally fitted in the plastic case. Two manganese/alkaline cells will run a whole afternoon, and we use and recommend for heavy work two nickel/metal hydride rechargeables, but you will have to buy them, and become familiar with how to charge them. If you will not be running the camera hard, stay with the manganese/alkaline cells.

The sewn fabric side wall of the camera has been unfastened from the velcro strip, and peeled back (in seconds) to show the removable batteries, and the internal construction of the box, which uses two end plates, and four pillars. Under the batteries can be seen the edge of the camera circuit board, and the white Molex socket that holds a 64 Mbyte MMC. Intentionally, the MMC cannot be removed without taking a corner pillar off the box, to discourage theft.

If you are using a ledlyt for illumination, all you need for a photo session is the microscope and the camera, with no Mains power needed. What will kill any sharpness in your photos is vibration, either from a poorly made microscope with no rigidity, or running your session on a table standing on a wooden floor!. Even if it is covered with carpet and underlay, a concrete floor is obligatory. We use a kitchen bench on a concrete kitchen floor, and with normal precautions like not contacting the bench while the cable release is pressed, we have no vibration troubles. This even applies to an old Zeiss Winkel metallurgical model, which wobbles like a jelly if you touch it.

This is the Wobbling Winkel, with camera attached. Our joint is solid enough, but the main support fork (just under the objective turret) is manifestly too skinny, even for the normal binocular head. Photos are fine, with care. When the session is over, the slid-in eyepiece is capped to keep dust out. In case the cap is lost, any Kodak 35mm cassette-tin cap will fit.

Once the session is over, the camera is switched from photo mode to file mode, and the USB line from the computer is plugged in. Assuming the camera software has been installed, the JPEG files are then copied across to the computer. If you have a 64 Mbyte MMC card installed in the camera, the camera appears to the computer as an external hard drive of about 70 Mbytes. We have confirmed adequate file-recovery using Win 98SE, and a really excellent interface using Red Hat Linux 8. If you are not photographing, the camera doubles as a 70 Mbyte external drive, with a 64 Mbyte MMC inserted. If you have not used USB before, be warned that not many of the USB ports supplied with motherboards earlier than Pentium 2 models actually worked properly. In our case we disabled the on-board port, and plugged in a D-Link PCI twin USB card with real working ports.

Fitting

The inverted-cone connector used on our camera adaptor to make a rigid joint, by replacing the binocular head, works very solidly indeed. Why does are not all cameras mounted like this on microscopes?.

The plain answer is that it is a very tricky job indeed. The manufacturer has a 'test socket' of exactly the same configuration as the top of the microscope, makes an inverted cone that will fit centrally in the test socket, and then uses a digital or copying lathe to turn out say a thousand pieces, or even, as in the Nikon Alphaphot, die casts them. Making a one-off, or even a few off adaptor, a profile of the cone is turned a little on the 'large side' of the cone on the binocular head. This is tried in the microscope cone socket, and is found to fit, but to one side of centre. The cone is then progressively turned down until it fits right in the centre of the socket when the holding screw is tightened. If I make the adaptor for you, I have to repeatedly check it on your microscope, beside the lathe, until it fits.

Alternatively any skilled toolmaker in your part of the globe can make a brass cone to fit your microcope correctly, and they can make the rest of the adaptor if you prefer, or send the cone to me, and I will fit the rest of the adaptor onto it. Someone has to measure from your microscope objective flange to the top face of the inverted cone socket, in millimetres, and quote that figure to me, so I can work out the correct adaptor length, so the image sensor ends up 160mm above the objective flange.

Price

The TDC 1b, including electronic 'cable release' but not including rechargeable batteries, or 64 Mbyte MMC, costs about $1000 Australian. Extra, and varying with the amount of custom engineering required, is the fabricated adaptor(s) to fit your microscope(s). Allow at least $200 for an adaptor. These prices will not have GST added.