Re: Cheap&cheerful setup for an occasional optical microscope photograph?

In article <8rqdg1doq5aoq90e7028s9gj40bg4rv7ar@xxxxxxx>, Charlie+ <charlie@xxxxxxx> writes 
On 18 Aug 2005 10:01:06 -0700, "rchiovetti@xxxxxxx"
<rchiovetti@xxxxxxx> wrote as underneath my scribble :


Hi Robert - its just an ordinary compact Pentax S5i (5MP) - it has I
think x4 optical and x3 digital on top.  Not possible to actually
select aperture priority but it chooses to shoot at f2.8 -3.5 which is
wide anyway!
I have fully settable intensity on the microscope in any case.
Eyepiece focus from a subject at infinity is 21mm but it is a 160mm
tubelength microscope, so probably focus from the microscope would be
about 18mm?  My problem was not being able to photograph the full eye
view available in the microscope from Mk1 eyeball!  Filling the camera
frame (with reduced view angle) is no problem!
I suppose I could get out my OM stuff + bellows etc. etc.,  which is
gathering dust in a cupboard - but developing/printing is just far too
much trouble these days for a very occasional picture!
Ill do a bit more playing and see if I can get in focus subject with a
closer camera.. if  I can, that should do the trick.
Charlie+

Charlie,

If the "fully settable intensity" on your microscope is a voltage control to dim the lamp, it is not the best way to control exposure.

It will probably work, after a fashion. The reason it is not really a good method is that the changing voltage causes the bulb to run at different temperatures, which means the light will change colour. It is possible that the AWB control on your camera will reduce the effect, maybe not - it would certainly be a major problem on film.

The best method of controlling illumination on microscopes is by ND filters inserted into the light path. For continuous control you can use two crossed polarisers, though these do reduce the light by at least 50% even at maximum brightness. They also need to be good ones, to avoid giving a colour bias.

BTW, in answer to your original question, the simplest way I have found for quick photomicrographs is using an eyepiece with a screw thread cut on the top rim which fits the front thread of a Coolpix 9xx/4500 camera. There are some Leitz eyepieces which already have this thread, and some Zeiss eyepieces which have a raised rim just right for threading on a lathe (a competent machinist should be able to do this for you with no trouble).

The eyepiece screws into the Coolpix and the whole lot simply replaces the eyepiece you were using.

Sorry if this duplicates something others have said, I have been away.

David
--
David Littlewood
.

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