Dear All,
The following is meant to be constructive, not a criticism.
Taking photos of an oscilloscope dispay is a bit of a 'black art', especially when one is dealing with low-repetition waveforms as encountered in NBTV.
First the hardware. It's neccesary to have a moderately good 'scope that reliably triggers on the appropiate point in the waveform to obtain a stable trace. The trace should be not too bright and sharply focused, the graticule illumination should be visible but not dominant.
The photos attached are of my old Goldstar OS8100 'scope I've had since 1993, it has now been retired.
The camera. Assuming that you're using a digital still camera, don't get fixated on Megapixels. Photo 1 (colour) is a reduction of what came out of the camera, it's 1803 x 1455 pixels, i.e. 2.6 Megapixels. Less by far than most cameras nowadays. But it conveys the data well enough.
Photo 2 is a further reduction and conversion to monochome for publication. It's less than 1 Megapixel and yet still conveys all the information needed. The jpg file size is only 115kB.
These photos show about one and a third frames of NBTV, this results in a 6.25Hz repitition rate on the screen. To get at least a single sweep requires an exposure time of at least one 5th of a second. That's assuming you can release the shutter just at the right moment.
A better ploy is to use a much longer exposure, in this case it was about 4 seconds. You'll need a tripod or some other method of keeping the camera firmly stable. This action intergrates the multiple traces to produce the what appears to be a solid stable trace.
The next consideration is the cameras focusing distance, these pictures were taken with a camera to screen distance of about 200mm, this requires the use of a 'Macro' function, allowing you to get closer than needed for the family snapshot.
Keep the extranious light to a minimum so there is no reflection from the screen which reduces the contast, black-out the room or do it at night with the lights off.
Finally, some software to crop/resize/convert the raw picture. The simplist one I know is Irfanview, but Picture Publisher or Photoshop are equally effective (and more flexible).
I hope this helps, happy snapping!
Steve A.
P.S. For those interested the waveforms are of the action (or more correctly the inaction) of many of the DC-restoring circuits published.