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Signal to switch on and off external illumination

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Re: Signal to switch on and off external illumination

Postby WalterMo » Mon Feb 11, 2013 8:41 am

Hello David,
I don't think that for my illuminator above an additional diffuser is necessary. The illuminated area is really homogenous, nearly perfect.
During my last test with a large white cupboard in front of the object (for white balancing) I again saw that the illumination is fine.
In my opinion a diffuser is only necessary if a low number of high power LEDs (á 3W or >) is used.

To increase the light intensity some more RGB LED stripes should be used.

Walter
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Re: Signal to switch on and off external illumination

Postby illustrami.com » Mon Feb 11, 2013 12:06 pm

Hi Walter

I agree that the illumination is homogeneous, virtually perfect, but still the direct incident light is not the best for photography.

Basically, you see the burns on the right corner front side of the can for example, that is one of the things one want to avoid.

There to obtain a perfect photo the solution is a diffuser or a post elaboration, the latter being a painy extra operation that can be done only when minor burns are present, imagine a shot with plenty of burnt spots, It would be a real time consuming unnecesary task.

Normally a diffuser is always used, it is kind of necessary

In general a diffuser enhance the photo quality to a better level ranging from little differences to a total difference depending on the material being photographed.

With non reflective mat objects burn spots will not be present, but that is the only case when diffuser will not be really necessary even tough the photo could overall be better using it.

I would give it a try.

I always use some diffuser device, either professional or DIY, the only drawback is that the total light output to achieve best results is to be elevated to a certain degree (some light is lost with a diffuser), working in the phptograpic/video studio ti is almost unthinkable to not have anything ready at hand to help

But also some tricks can be used under certain circumstances, for example to remove only that burnt stripe, it's not sure as achievable but in theory, it would be possible to use a single narrow stripe of diffuser matter in front of some LED just to stop the direct beam to that corner.

Once the "perfect" texture is taken, without burns and glossy spots, nor fades or shady parts, rendering the object one can decide wether wants more or less light, highly reflective surface, mildly reflective, mat, whatever will be liked or anyway good for the case can be achieved, this will be a task of the renderer tough, should not be already included in the texture as far as possible.

So paradoxally if I anyway want a burn in that corner, I prefer to get it in the rendering stage process instead of having it directly in the texture.

By the way the illumination is very good, I was guessing that the colours are more natural already from the very little previous sample where it was not optimal as in the latter, the fact that the panels are sort of beige as in nature and the tippex spots are perfect white as it should be is the best proof that is very good.

Bye
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Re: Signal to switch on and off external illumination

Postby WalterMo » Tue Feb 12, 2013 10:02 am

David,
I am not a photographer so I don't know all the facilities of the photography. But do you think that a very diffuse light source can avoid all the reflexions which are visible on the cocoa can? You had surrounded them in green.
I have just checked the reflexions of this can by my eyes turning it in my hands. The light source was the gray in gray diffuse sky over Braunschweig. But if I adjust the „right“ angle then I will see reflexions from the shiny surface and the surrounding aluminum frames at bottom and top. Only if I hold the can against the sky and look in the same direction then there are no reflexions. But this case cannot be used for photography. Or if I tilt the box by a big angle.

That there were minimal reflexions on the posted screen shot some days ago when the projector was active is due to the fact that the incidence angle was also rather big.

Walter
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Re: Signal to switch on and off external illumination

Postby VDX » Tue Feb 12, 2013 10:59 am

... photographers avoid specular reflections with 'diffuse' light-sources - either the flash illuminates not the object but the (mostly whire) ceiling or a white blanchet is placed between the lamp and the object.

For microscopy I've built 'shadowless' (and specular-less) illumination with light-rings made with 24 superbright LED's beaming not on the target but in a hollow half-sphere painted with white-translucent colour and embedded glass-microspheres for better diffusing/reflection :wink:

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Re: Signal to switch on and off external illumination

Postby illustrami.com » Wed Feb 13, 2013 2:18 pm

Hi Walter and Viktor

Yes Walter, it is that tricky, nothing strange

It is somewhat an intriguing matter, as Viktor wrote also passive illumination is much used

In general the goal is to have enough light but never producing specular reflections, it is possible to use a wide amount of devices and methods to achieve this, among which diffusers, reflection panels, filters, curtains, different kind of illumination lights and so on, but in general for the creative whatever do the job is good, even a finger out field that stop one extra unwanted beam is ok as long as you can take the shot, in fact it is a matter of manipulating light rays going into the camera.

For example in a studio every window is obscured, virtually the work is done in complete obscure room except than the illumination needed to to have a good set.

When outdoors of course there is no way to coop with natural light, but still many methods are used to enhance it, by means of reflectors which augment it or curtains that dim it to a desired level, even certain locations are much better than others because of the latitude etc. and or because of the surroundings colours etc... (and of course the weather and the time is extremely influential)

Whatever mix of light might be good, artificial light mixed with natural one, diffused, reflected, filtered... whatever, what really counts is what you get on screen (for photography that must be appreciated to human eyes)

When there is no way in any fashion to get rid of the burns then a special matting invisible spray is used, for example if this box could not be illuminated in any way without specular reflections the spray would be the last resource to do a good job anyway (to be used with caution as can introduce other flaws is over used)

Now to do the texture in the case of David with an external panel will suffice to have enough powerful panels with a diffuser, so best approach is given for everybody, then a PRO photographer will know how to fine tune the set up for his own needs.

Let say that a standard diffuser on the panel (can be economic and quite good, no need for very complicated things) is the good choice for a basic setup good for everyone in all cases

Especially well done illumination sets will be autonomously done by those who know what to do and need higher level photography, and they will appreciate that a basic diffuser is already included if they start with a "ready to go" basic modular panel system.

Bye
Davide
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