Re: Canon 350D for photomicrography?

I've been using an EOS 10D for a couple of months now. It's very
similar to the 350D and uses the same CMOS sensor. So although I am
unfamiliar with the nuances of the 350D, maybe these notes will help
(I'm sure errors will be quickly corrected :-)

Canon supplies "remote capture" software with the camera which is
connected via USB (cable supplied). It will connect to USB 2.0 ports,
but only gives 1.0 speed. The software is basic (for camera control)
and not scriptable. Most camera settings must be accessed via the
camera menu and internal settings (so make sure it's mounted so you
can see LCD readouts and use the controls without inadvertently
shifting the camera or it's mount in the process). Realistically, you
only control image quality and size (and shutter release) from the
Canon s/w.

There are some commercial (studio-oriented) packages which allow
control of nearly all camera functions but they are pretty expensive.
Remaining observations are based on the use of the standard Canon s/w.
I think the difficulties and annoyances do add up to a case for buying
something more sophisticated; but I've managed OK to date.

The mirror lock function is vital, particularly if you've got your
camera waggling around on a tall photo-mount. There is a clear
softening of images when mirror-lock is not used. With mirror lock
enabled from the main camera menu, there is a 1 second delay between
the mirror swinging up and the shutter being released. This could be an
issue if you want a series of rapid-fire exposures. There doesn't
seem to be a way of making the mirror stay "locked up" between
exposures when using (Canon) remote capture.

Download is zippy for images taken at a small/fine setting, but the
only way to get 12-bit, data is to use the RAW mode. This is full
resolution and takes forever to download which places even more limits
on rapid-fire exposure than mirror lockup does. Possible answer is to
capture to the onboard memory card, allowing many images/second, but
the (Canon) remote capture software insists on downloading each image
straight away :-(

The size of the sensor, at 15.1mm x 22.7mm falls somewhere between
consumer digital camera sensors and the traditional 35mm formats so
it's tough to find a relay lens giving optimum FOV and image scale. I
prefer direct projection so tried adapters for 35mm kit. The compromise
is achieving only a little over half the FOV a 35mm sensor would give.
It also means that for 12 bit data, you have to shoot at full
resolution which, given 7.4um pixels, is way over-sampled for all but
very high NA objectives. It's a shame there's no binned RAW mode as
3x3 binning (equivalent to a small image setting) would yield the ideal
pixel size for my system (my photo-port has intrinsic 3.5x
magnification). Note: I tried mounting the 10D to a trinocular port to
overcome this FOV problem, but it didn't work, so I have gone back to
mounting on the photo-port as it is much more stable. I will attach a
video to the trinocular at some point (funds and missus allowing :-)

The sensor is low noise at most ISO settings, but for longer exposures
(>1 sec) or where heavy post-processing is used (particularly contrast
stretch) I'd recommend you average several dark frames and subtract
them from each image captured. If you don't, there is a likelihood
that fixed-pattern noise will appear in the dark areas of a processed
image.

You'll use aperture or shutter priority modes when using direct
projection. The accepted wisdom is that aperture priority is best, let
the camera judge exposure time, but I prefer to use shutter priority
and select the speed myself (aperture is irrelevant).

I too use an external shutter but only because I don't have any
choice! It's inside my ICM 405 and has to be released in order to get
light to the front photo-port. However, I set the internal shutter to
bulb mode and then use the EOS shutter instead. Mirror lockup ability
removes any shake that might be associated with this method (I've
been unable to detect any quality differences between images taken with
either shutter).

Finally, I haven't bothered with a mains adapter (enough wires
floating around as it is). I turned off the option to display each
picture on the LCD after it is captured and get well over 1000
exposures off each charge. You get half as many with the display turned
on.

Hope this helps

Cheers
Beats

.

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