The background is that I've been trying out a Canon Powershot digital
camera on a tripod with the Canon Zoombrowser software that lets the
camera be controlled from a computer via the USB.

This works well but illuminating the subject (a ragbag of documents and
old pictures) with desk lights using ordinary GLS lights gives a
visible pulsing of light which can be seen in the monitor due to the
50Hz mains frequency. [which means 2 flashes per sec or 100Hz] This
isn't ideal as it clashes with typical camera exposure speeds.

SFAIUI professional copystand lighting is expensive, so looking for a
method of obtaining a smoothed light.

One possibility would be DC lighting, but it needs to be quiite bright.

Another possibility might be flourescent lighting - but does phosphor
coating on the tube provides some lighting persistance?

Any views on feasibility of either (& how to achieve it) or any other
suggestions would be most appreciated.

TIA

jim wrote:

The background is that I've been trying out a Canon Powershot digital
camera on a tripod with the Canon Zoombrowser software that lets the
camera be controlled from a computer via the USB.

This works well but illuminating the subject (a ragbag of documents and
old pictures) with desk lights using ordinary GLS lights gives a
visible pulsing of light which can be seen in the monitor due to the
50Hz mains frequency. [which means 2 flashes per sec or 100Hz] This
isn't ideal as it clashes with typical camera exposure speeds.

SFAIUI professional copystand lighting is expensive, so looking for a
method of obtaining a smoothed light.

One possibility would be DC lighting, but it needs to be quiite bright.

Another possibility might be flourescent lighting - but does phosphor
coating on the tube provides some lighting persistance?

Any views on feasibility of either (& how to achieve it) or any other
suggestions would be most appreciated.

TIA

Fluorescent is much worse in this respect. I used to use a twin 8'
fitting for photos, just picked suitable slowish exposure speeds. If
you want to get rid of 100Hz for quicker shutter speeds, the simplest
solution is high current filament lamps. High current means thick
filament means lots of thermal inertia. So we're talking 500w halogen,
or 12v 50w halogens.


NT

"jim" wrote in message
ups.com...
The background is that I've been trying out a Canon Powershot digital
camera on a tripod with the Canon Zoombrowser software that lets the
camera be controlled from a computer via the USB.

This works well but illuminating the subject (a ragbag of documents and
old pictures) with desk lights using ordinary GLS lights gives a
visible pulsing of light which can be seen in the monitor due to the
50Hz mains frequency. [which means 2 flashes per sec or 100Hz] This
isn't ideal as it clashes with typical camera exposure speeds.

SFAIUI professional copystand lighting is expensive, so looking for a
method of obtaining a smoothed light.

One possibility would be DC lighting, but it needs to be quiite bright.

Another possibility might be flourescent lighting - but does phosphor
coating on the tube provides some lighting persistance?

Any views on feasibility of either (& how to achieve it) or any other
suggestions would be most appreciated.

TIA
Ordinary fluorescents are worse than incandescents.
Have you tried low power fluorescents? They are switched electronically at
high frequency and should avoid the problem.
John

jim wrote:

Another possibility might be flourescent lighting - but does phosphor
coating on the tube provides some lighting persistance?

If you go for lights with electronic ballasts then the fliker rate will
be in the kHz rather than the 10s of Hz

These are quite cheap, work nicely, and have a good colour temp:

http://www.tlc-direct.co.uk/Main_Ind...ing/index.html


--
Cheers,

John.

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In article . com,
jim wrote:
The background is that I've been trying out a Canon Powershot digital
camera on a tripod with the Canon Zoombrowser software that lets the
camera be controlled from a computer via the USB.

This works well but illuminating the subject (a ragbag of documents and
old pictures) with desk lights using ordinary GLS lights gives a
visible pulsing of light which can be seen in the monitor due to the
50Hz mains frequency. [which means 2 flashes per sec or 100Hz] This
isn't ideal as it clashes with typical camera exposure speeds.

I'd be surprised if what you're seeing is indeed the lights varying in
intensity. It's more likely to be something to do with the monitor.

--
*Never put off until tomorrow what you can avoid altogether *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article . com,
jim wrote:
The background is that I've been trying out a Canon Powershot digital
camera on a tripod with the Canon Zoombrowser software that lets the
camera be controlled from a computer via the USB.

This works well but illuminating the subject (a ragbag of documents and
old pictures) with desk lights using ordinary GLS lights gives a
visible pulsing of light which can be seen in the monitor due to the
50Hz mains frequency. [which means 2 flashes per sec or 100Hz] This
isn't ideal as it clashes with typical camera exposure speeds.

I'd be surprised if what you're seeing is indeed the lights varying in
intensity. It's more likely to be something to do with the monitor.

I wouldn't. I have a tacho that works on ac components of light. Its
unusable in artificial light. Even incandescent. Only way to use it is
with a torch...

I'd advise LV halogens fed of a regulated DC power supply.