Dropouts
 

I know we've recently had a thread about dropouts on DVCAM but there's something I've noticed that I wonder if anyone else has experienced. The other day I filmed a play with my DSR-390, the stage was completely black apart from the actor and about 4 times through the 1 hour show I saw a little spec of white in the black area. It wasn't a square like dropouts normally are but just a tiny dot of white that appears for a frame then goes, it appears at different parts of the screen. Anyone ever seen this, or is it just a dropout as normal but not quite as big and ugly.

I've only had the camera a couple of months should I run a head cleaner through it?

Any advice would be great.

John.

That may be a CCD pixel acting up, known as a hot pixel. (I guess you still have a warranty.)

Hi Frank,

I just edited my post to mention that it's not in the same place each time, it appears completely random.

John.

Just read in my camera manual at the back there are notes on the characteristics of CCD sensors and one of the notes is on White Flecks. It says white flecks may appear on the screen during use under high temerature conditions. This can also happen during normal conditions if the sensitivity is increased.

Could this be it? It was very warm where I was filming.

John.

I would think it would have to be pretty darn warm. It sounds like it might be related to the low-light conditions. Were you using your camera in a mode which increased low-light response? Either way, it still means you've got a border-line hot pixel situation. Personally, I wouldn't accept a randomly-firing pixel under those circumstances, and none of the camcorders I've owned, either consumer or prosumer, ever did it. Are you sure this is a camera you want to keep? ;)

It could very well be heat related. Bigger cameras, like the DSR-390, produce substantially more heat than your average mini DV camera. Some pro cameras even have a peltier element to aid in cooling. Cooling the chip improves the S/N ratio and helps prevent anomalies like you're seeing.

Also, it could be just a little ghosting. Just a thought.

Hi Paul,

The camera was at F8 with no gain so there was nothing going on that would increase the sensitivity. I've mailed Sony so I'll see what they say. I'm not convinced on the hot pixel thing due to it's randomness.

John.

Sent my Email to Sony prime support at around midnight last night and had a reply by midmorning today, excellent service from prime support just for future reference they said:-

"Hi John,

Thanks for the mail. The phenomenon you describe could well be related to the temperature issue described in the operation manual page 140 (Characteristics of CCD sensors).

Each pixel in the CCD block can spontaneously discharge if the temperature increases beyond a certain level. This causes the white flecks described. This is common to all CCD blocks, and does not affect subsequent operation of the pixel.

Your DSR390P has an automatic pixel noise adjustment to correct bad pixels. If you wish to ensure the levels of charge in the pixels are uniform, perform a Black Balance (page 129) This takes an average reading of the pixels surrounding any suspect pixel, and adjusts it accordingly. The best way to see if any pixels are over-charged, is to cover the lens of the camera, switch on maximum gain and look at the output on a monitor screen. You may see one or two dull white spots, the black balance should compensate.

Normally, a few dead pixels will be inevitable (out of millions) but should there be many spots of bright light, and in the centre of the screen, you may wish to contact us again for advice.

In conclusion, you probably do not have anything to worry about regarding the white flecks, but it is worth checking the pixels using the method described on a regular basis to keep ahead of any individual pixel failures that may occur.


If you have any further questions, please contact us again by mail or you can call the telephone helpdesk on 01256 68 38 50 where we will be happy to help.

Best regards

PrimeSupport"


So I'll keep an eye on it for the moment.

John.

I was pretty sure it was related to heat. I don't think you have anything to worry about. Using the gain control may increase the anomaly, because gain up increases the heat produced.