New NBTV camera project

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Postby gary » Fri Oct 26, 2012 8:28 am

This is a little off topic for this particular build, but the subject of the amount of light available caused me to think about Doug Pitt writing that sun light would be an ideal source but that he was always thwarted by that nice cool cloudy weather the enjoy in England.

Now here in Oz we have a surplus of bright sunny days, especially at this time of year. I have always wanted to try this out but my cameras have never been portable enough to try it out (I have to correct that some day).

So here's a challenge to Aussie builders - build an outdoors NBTV camera!
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Postby aussie_bloke » Fri Oct 26, 2012 11:46 am

I will certainly be adding more transistor amplification stages to the head amp to try and make the phototransistor more sensitive, obviously there will be the noise factor the big curse of any form of amplification hehe so should I encounter that I will look to noise suppression circuitry.

Yeah sunlight would be a good way to test, my camera is in the garage, I tried yesterday to get a picture of the front yard from the sunlight but my camera is still not sensitive enough, so more amplification is needed. Yeah Britain seems to have a lot more cloudy/rainy days than sunny days, I often humorously refer a rainy drizzle day over here in Oz as "British weather", Tasmania is actually a bit like Britain as there's more rain/cloud/snow down that way, I remember because I grew up there as a kid :). Getting back on topic if to test with direct sunlight I could use a mirror and reflect the sun into the garage straight into the lens of the camera and see how it comes up on the monitor ;).

Anyhow a lot of work to do on my camera/monitor so will keep you's updated as I progress with it!
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Postby gary » Fri Oct 26, 2012 11:52 am

aussie_bloke wrote: I tried yesterday to get a picture of the front yard from the sunlight but my camera is still not sensitive enough


I have yet to see an NBTV camera that could capture a landscape (although Baird did it with a mirror drum camera - e.g. horse race) - The real proposal is to have direct sunlight on a (suitable NBTV) subject within the range of the camera (usually less than a few metres).
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Postby Harry Dalek » Fri Oct 26, 2012 1:26 pm

gary wrote:This is a little off topic for this particular build, but the subject of the amount of light available caused me to think about Doug Pitt writing that sun light would be an ideal source but that he was always thwarted by that nice cool cloudy weather the enjoy in England.

Now here in Oz we have a surplus of bright sunny days, especially at this time of year. I have always wanted to try this out but my cameras have never been portable enough to try it out (I have to correct that some day).

So here's a challenge to Aussie builders - build an outdoors NBTV camera!


Can i ask Gary how much light was used on your indoor camera ?
I suppose if you had a light meter and tested the light in the room reflected off what ever your trying to film say like your toby jug and did the same test out side you'd have a idea of the difference at least .

Could then adjust that indoor light to the amount of a sunny day cloudy day ... i was thinking of those old analog light meters used in photography i am not sure newer versions are made these days i have one or 2 old ones in my collection but using something like that to test and adjust your light levels indoors would make sure it would work out side .

The head amp type Troy is making adding on stages might be the thing for this experiment i am not sure of its limits but the key to it working in just out door light must be how good your senor is and or head amp is.

I was converting the one you helped me with but i need to put it in a light proof box to do any thing like that ....i will have to learn to do some multi tasking .

Yes i find better off at least try to limit size of these things for me more to keep it safe .
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Postby gary » Fri Oct 26, 2012 1:36 pm

Which one? The FSS used as projector lamp, and with the other I used a 500w workshop type light.

I think if you tried to implement the brightness of a spring/summer day in Oz:

a) you would melt

b) you would go bankrupt from the effects of the "no carbon tax (sic) under the government I lead" tax...
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Postby Harry Dalek » Fri Oct 26, 2012 2:51 pm

gary wrote:Which one? The FSS used as projector lamp, and with the other I used a 500w workshop type light.

I think if you tried to implement the brightness of a spring/summer day in Oz:

a) you would melt

b) you would go bankrupt from the effects of the "no carbon tax (sic) under the government I lead" tax...



I did mean the the indoor light Gary Ok 500 watts yakes ! .

The reflected light is the thing to measure not the sun or lamp i think..

I see a sunny day is 100000 lux but is that pointing at the sun the sky as it would have to change depending on the reflective surface ..depending on your light distance would that 500 watt light be the same as the sun shining off the toby jug illuminating that small area ...the reflective light measured might show its similar...don't know speculating...
But sounds like out door nbtv is easier than indoor ?
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Postby gary » Fri Oct 26, 2012 3:51 pm

harry dalek wrote:I did mean the the indoor light Gary Ok 500 watts yakes ! .


And I could have done with a lot more - however I was using a very insensitive set up.

harry dalek wrote:The reflected light is the thing to measure not the sun or lamp i think..


Well the brighter the source the more light is reflected - but no need to measure as there is never going to be anything brighter than the sun (at least not in my life).

harry dalek wrote:I see a sunny day is 100000 lux but is that pointing at the sun the sky


Well that is what you then have falling on your subject if you position the camera and the subject correctly, the amount of reflected light is irrelevant as the attenuation percentage is the same for whatever your source is - in other words the more light falling on the subject the more makes it to the sensor.

harry dalek wrote:- the amount
as it would have to change depending on the reflective surface ..depending on your light distance would that 500 watt light be the same as the sun shining off the toby jug illuminating that small area ...the reflective light measured might show its similar...don't know speculating...


Well I suppose if you had a focussed beam of light that was arranged to hit the subject and bounce straight off into the camera lens that may be true - but that is not what you would normally have.

I think the sun being effectively a point source makes things easier - you might be able to get a 500 watt lamp in a position that is as effective but it would probably be in front of the camera lens!

harry dalek wrote:But sounds like out door nbtv is easier than indoor ?


Oh I wouldn't necessarily say that - after all it is more difficult to build a portable unit than one that is just lashed up on the bench (as mine normally is). But you should, I am told, get more light to the sensor outdoors (on a sunny day) - there is NEVER enough light no matter how sensitive your set up is - with the possible exception of using a photo multiplier - so more light good less light bad.

I should point out that one of the disadvantages of bright indoor lights, as Bairds subjects found, is the heat they generate. This is one of the major reasons I feel an FSS is an easier approach for a first time attempt.

Having said that it gets pretty hot under an Australian summer sun - and there is more UV!

Anyway I am just repeating an idea I attribute to Doug Pitt - I have never tried it myself.
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Postby Klaas Robers » Sat Oct 27, 2012 1:58 am

Troy,

just for fun: place a sheet of white paper on the Nipkow disc as a kind of projection screen. Then you will see the image of your subject. That will be dimmed in respect to the lamp and the three holed stone. This image should be focussed sharp on the surface of the Nipkow disc.

Then I see that you have lots of stray light on your Nipkow disc. Try to find a kind of black tube and slide that over the projector lens. In this way you may darken the path between the lens and the Nipkow disc. That will improve your contrast, at least make the black parts darker.

Then also screen the part behind the disc, the condensors and the photo diode or -transistor. The Nipkow has only one hole "open" at the time, so the amount of light passing the disc is very little. Then all stray light spoils the functioning of your photo sensor. So a closed box or a back cloth (Baird used that very frequently).
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Postby aussie_bloke » Sat Oct 27, 2012 2:12 pm

Klaas Robers wrote:Troy,

just for fun: place a sheet of white paper on the Nipkow disc as a kind of projection screen. Then you will see the image of your subject. That will be dimmed in respect to the lamp and the three holed stone. This image should be focussed sharp on the surface of the Nipkow disc.

Then I see that you have lots of stray light on your Nipkow disc. Try to find a kind of black tube and slide that over the projector lens. In this way you may darken the path between the lens and the Nipkow disc. That will improve your contrast, at least make the black parts darker.

Then also screen the part behind the disc, the condensors and the photo diode or -transistor. The Nipkow has only one hole "open" at the time, so the amount of light passing the disc is very little. Then all stray light spoils the functioning of your photo sensor. So a closed box or a back cloth (Baird used that very frequently).


Thanks for the suggestions.

I have recently placed a sheet in front of the scanning area of the Nipkow disc to get an accurate idea whether the subject is focused and in correct position or not.

Yep I am aware of the stray light issue, at the moment my camera/monitor is set up to a makeshift operational status for testing which is why everything is exposed at the moment but I definitely intend to place enclosures over the whole apparatus to keep the stray light out, plus I will have to place a keyhole like mask cover over the Nipkow disc scan area to mask off stray light coming in from the right side as the first hole in the disc starts at the edge.

Now in update with my camera/monitor, I have now added 2 more transistor amplification stages to the phototransistor circuitry and I guess it has improved the sensitivity of the image pickup a bit but still need to use a 150W lamp to shine on the subjects to get something on display and the subjects have to be shiny as well like a screwdriver, I haven't yet been able to display anything a bit more complex yet, I have wave a screwdriver up and down the lens and could see the shaft of it move up and down. Anyhow lots of work to be done on this camera, I now must refine it all and secure everything to it as a lot of the parts are just held with tape and blu-tack so they could be easily maneuvered, also need better supports for the disc as the holes are wide enough to cause the spindle to wobble at higher rotation speed. Anyways stay tuned for the next update.
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Postby gary » Sat Oct 27, 2012 4:41 pm

Troy, it is very well known amongst NBTV experimenters that a moving picture gives the impression of greater detail.

I very strongly recommend that you have some kind of arrangement during testing that gives you a moving subject.

I attach a short video of my own arrangement comprising a microwave oven motorised turntable in a biscuit tin with a pudding container lid as the turntable. My subject is often the Toby jug shown.
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toby on turntable.avi
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Postby Viewmaster » Sat Oct 27, 2012 5:25 pm

As I am building a NBTV televisor without any moving parts how about a NBTV camera without any moving parts too?

First thoughts are a 48x32matrix of light sensitive cells addresed in a similar way to my Niptrix.
BUT the cost would be enormous as 1532 cells would be required.
Anyway to reduce the number?

Or, if one had an old 405 line TV camera maybe defocus the scanning beam to cover only 32 lines per frame.........

....just the meanderings of a nut! :lol:
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Postby AncientBrit » Mon Oct 29, 2012 6:28 pm

Gary mentioned that one of the problems with a mechanical camera is the lack of sensitivity and wondered whether in the UK there was enough light to produce a reasonable picture.

Attached is a series of stills from a movie clip I recorded back in March 1999 using the disc camera I described in Newsletter 25/4.

Each frame is a 32x64 pixel image and I used only 5bit recording.
No gamma was applied, hence the poor grey scale.

The camera was located in my garage looking out onto a minor road at the bottom of the driveway.

You can see the outline of a car passing in the 3 frames.

Regards,

Graham
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Disk cam Car 2 Still frames.bmp
Disc camera "OB"
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Postby gary » Mon Oct 29, 2012 6:37 pm

That's marvellous Graham! No doubt it would look even better in motion (do you still have the full files?).

And that is using the club's dome sensor is it not?

Did you ever post any physical photos/drawings anywhere?
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Postby AncientBrit » Mon Oct 29, 2012 6:53 pm

Hi Gary,

Yes I have all the recordings but as I explained they are a succession of bit maps and need some of my software to view.

The samples are NBTV line synchronous so there are always 64 samples per line

They are not WAV files.

Yes, the photo sensor was/is the club Dome sensor.

Only publication was in the Newsletter, but not here on the forum.

Cheers,

Graham
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Postby gary » Mon Oct 29, 2012 7:05 pm

AncientBrit wrote:Hi Gary,

Yes I have all the recordings but as I explained they are a succession of bit maps and need some of my software to view.


That's not a problem as I have your software (unless this is different from some previous material you gave me - actually, come to think of it, I think that was for your colour system).

EDIT - aaah I have the .ps7 file version too

AncientBrit wrote:The samples are NBTV line synchronous so there are always 64 samples per line

They are not WAV files.


Are they packed 5 bit or converted to 8 bit on record - they sound like they would be easy enough to decode.

AncientBrit wrote:Only publication was in the Newsletter, but not here on the forum.


But you only submitted the circuit and text did you not? Or have I missed something? No problem, it's just I and others (I am sure) are always interested in other people's builds.
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