Dead pixels
 

One of the first times I used the slow shutter function (frame accumulation), I noticed several pixels were out. There was even on area that seemed to be a grouping of dead pixels.

After going through several black balances (as recommended by Val at Sony) they were no longer apparent, but how can there be dead pixels in a brand new camera and how long can you mask them until there are too many to "fix"?

I had the same thing happen with my 330. The area got too big to mask and Sony had to replace the block. The first time the new block had a very strange bug and the camera began drawing so much power that my ac power suppy couldn't generate enough voltage to run the camera(although two stacked v-mount batteries would). They ended up replacing that block with a new one and the power supplies worked again.

I'm posting this for the benefit of you and anyone else who might run into similar issues so it might help you cut to the chase in getting repairs done quickly and without fuss.

The pixels are not normally "dead". What you are seeing is pixels that have a higher output for a given amount of light than perhaps they should. They show up more in frame accumulation mode because the the error is accentuated by time. In normal use you wouldn't see the difference. Almost all CCD blocks will have hot pixels. Leave a camera on for a few hours and turn up the gain and your almost sure to see some. Most manufacturers only regard a pixel to be a problem when it shows up at 0db gain at a standard frame rate/shutter speed.

It is thought that taking CCD's on aircraft flying on polar routes (transatlantic for examle) can lead to increased pixel failures due to the way the earths magnetic field concentrates solar radiation and other solar matter near the poles.

Most broadcast cameras have very good pixel masking circuits that can correct for hot pixels. This isn't a Sony specific problem and affects both video and stills cameras.

Alister, you always provide very accurate info. Thanks

Just to clarify, on my 330 the same problems as in shutter accumulate began showing up in normal images. Sony did have me try the black balance a number of times, and it wan't until they actually had the camera in their shop that they fully agreed there was a serious problem. I'm extremely happy it was under warrenty.

Being still on the learning curve with the F350, I'd be interested in knowing What exactly are the visual symptoms of dead pixels?

Thanks.

Michael Knight.

There are actually two kinds of defective pixels. One is a stuck, or HOT pixel where the pixel will not go dark. It would manifest itself as a colored single dot on the image somewhere. It will be one of the primary colors because it's a single pixel on one of the three ccds.

The other is a dead, or DARK pixel. This would be a spot on the image that would have one of the three primary colors missing and would show up as the wrong color.

All of this is due to the nature of CCDs which are charge coupled devices. If the charge won't drain between refreshes, you get a hot pixel. If it won't accumulate a charge between refreshes, it's a dark pixel.

-gb-

dead pixels..?
 

Just finished a shoot, 24p 1/48th shutter, my camera literally has 6 hrs on it.. practically brand new.

My client called, said it looks fantastic, however he thinks the camera has 4 "dead pixels" , seen of course in black/darks of the frame.

Can this be possible? He told me he tested 2 monitors and both of his monitors did the same.. and of course, I am away until late monday, so I unable to check the camera until then.

just thought I would throw up a post to get any ideas/opinions,

Thanks,

Ryan

You can always mask them in FCP with a colored overlay. I'll ask Paolo to respond to this.

To mask dead pixels in your camera, do three times black balance, the software of your camera will mask the affected pixels.

To save footage with black or white pixels use a FCP plug-in called DH_Reincarnation from www.digital-heaven.co.uk. It's a 40 dollar plug-in that replaces up to two dead pixel areas intelligently with new pixels at a time. It saved a lot footage for me. This option works only for FCP. Maybe there are simular options for other programs.

An other -not so nice but will do- option is to make an overlay in Photoshop with black dots on spot of your dead pixels. This works well on white pixels in dark areas. Yes, they show up as black dots in white areas, but are nearly noticed there.

I had a similar problem. The black balance is supposed to mask the pixels. For some reason, I guess I got the bad block in the batch - the number of dead pixels kept increasing on my 330, especially in the frame accumulate mode. Sony finally replaced the block under warrenty.

When the camera came back it would no longer run on any of my ac power supplies. It would run on two stacked v-mount batteries. It seemed the new block had a weird flaw that caused it to draw too much power. Sony didn't believe me at first but eventually I sent the camera back in, they found the same power issue, and replaced the block with another new one.

That was about six months ago. The camera has been perfectly reliable and stable since then, with no dead pixels or odd power issues or anything else.

I'm delighted with the camera and would (and may) buy another one (after I see what's coming out in the spring) and it was good that Sony (albeit with a little prompting) took care of this expensive problem.

Thanks for the reply.

Did you notice the dead pixels on a field monitor, or thru your view finder? in my situation.. I can't even recal any in my field monitor, nor in the viewfinder,, which is why it seems weird in my situation... I guess tomorrow I will be able to see for myself.

I have the 1.5" viewfinder and the dead pixels are just too hard to see on that. I saw them on what I was using for a field monitor, which is a
Toshiba 21 or so inch hdtv. They were very hard to see on my 8-9" sd sony field monitor until they got pretty far out of hand.

Thanks again, I guess I will investigate more tomorrow.

Black balancing will adjust gain to each pixel in total darkness to help with chroma noise. But if a pixel is truly stuck (full on all the time) due to a defect in the ccd block, black balancing will do no good and the stuck pixel has to be masked out of the image electronically by a service menu procedure.

-gb-