*ist D bad pixels


malcolmk

Link Posted 18/10/2003 - 11:20
Hi Lurach,

I too gave the 'first generation' issue some thought but I decided Pentax were not new to digital and not new to SLRs either so the problem might be small if there was one at all. I remember my LX was 'first generation' back in nineteen eighty whatever it was and after fewer than 12 months the shutter failed and I took it back to Pentax UK. The technician said something along the lines of 'they don't make them like this any more, all this has been integrated'. But the old one looks exactly the same externally as newer production and worked just as well so it didn't matter to me, and the *ist D supposedly has user upgradable firmware.

There is a danger of dud pixels in CCDs but it's not a problem encountered so often as it was. I've heard of a *ist D being exchanged because of bad pixels in the USA but my recently purchased Sony 17" LCD monitor has got none.

Yesterday I was speaking to an engineer who works for a company that make 35mm cinema cameras (Arri) and they have developed a prototype 'video' camera that uses a full frame sensor. I mentioned my dud pixels and he thought the number I had was 'totally unacceptable'. He also said his new camera produced 6 gigabytes of data a second. No, they hadn't solved the data storage problem yet.

MattMatic

Link Posted 18/10/2003 - 22:09
Malcolm,

Glad that Park have come up trumps. They've always seemed a perfectly reasonable company to deal with

Sorry I misunderstood your troubles - yes digital is a fast moving technology, and I doubt anything will become a "classic" in the ways the old LXs and the like did (even my Z1 is still a dream to use). What I can say about digital is that it's great for improving composition skills. I have taken over 4500 images on a Canon S30 in 18 months, and already the *istD has done nearly 600 frames. Of some of the good *istD shots I have, I took maybe 10 duds. There's nothing like that for just trying things out (wonder if this lighting will work... nope... try again). I feel I have learned more in my digital times than all the years I took film - mainly because I couldn't accurately remember the situations and learn from them. Even after the S30 I approached 35mm film in a different way, with different "eyes" you could say.
Lurach, I didn't mean "first generation", I meant first production run. Pentax have some really nice digital cameras now (like the Optio 550 etc). In any production run you learn the little slip ups, improve, and the subsequent batches should yield fewer duds. The *istD behaves impeccably, and from what I've read on the 'net has a larger and clearer view finder than any other DSLR. That can't be bad
Also, Lurach, the 500 and 360 do not share the same feature set with the *istD. Only the 360 does P-TTL flash and high speed wireless flash. However, the 500 has a higher power and can do multiple flash - if that's your thing (the 360 is a newer flash).

Well, hope you all manage to resolve your issues and get some really great images
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

malcolmk

Link Posted 19/10/2003 - 16:01
Hi Matt, have you any views on this?

I have seen the red/blue/green pixels enough times to have a pretty good idea about the sort of scene that reveals them, so I set up a suitable one indoors. I have been shooting it repeatedly (tripod mounted) at a range of speeds (1 to 1/125 second) at a variety of apertures and ISO settings but always contrived to be correctly exposed plus shots at one and two stops under and ditto over.

The over exposed shots don't appear to have any bad pixels. I know exactly where to look and they are simply not there. However three bad areas are visible on the correctly exposed shots (irrespective of shutter speed, aperture, ISO) and one or two more dependent on the degree of under exposure. However if underexposed to the point of complete blackness they disappear again.

I can't quite get my head around a situation where no light or too much light gives the correct result, but anything close to the norm is a problem.

There may also be ISO related factors. Although consistent pixel problems are present at all ISO ratings, additional problem areas show up at higher ISOs. These extra areas are smaller than the others and I expect more problems at high ISOs. However the clusters visible at 200 ISO (given correct or underexposure) are a different matter.

MattMatic

Link Posted 20/10/2003 - 13:36
Malcolm,

I'll try and add some insight into the behaviour you describe... CCDs in digicams are not what you might expect. Each 'site' in the CCD measures only light level, so a filter is placed over the CCD. Typically the filter is configured as a 2x2 square with RGBG - Red, Green, Blue, Green. Two sites measure green (because the human eye is most sensitive to green), while two other sites measure red and blue. There are variations on the theme (Nikon generally use CYMK style separations, while the Sigma SD9 uses the Foveon chip that has red, green, and blue as layers in silicon so that each site does all three colours.)

When the data is processed, they fill in the missing colours using complex algorithms (ie the Red site had no green or blue - these colour components are interpolated, etc). This is why moire is sometimes a big problem.

I guess what you are seeing is a frisky site that is excessively noisy and outputting a larger signal for the light. Hence, when the surrounding sites represent 50%, say the red site is reporting 90% - and produces a red-ish pixel. (Similar things happen when the site affected is blue or green.)

There's nice explanation with graphics on DPReview: http://www.dpreview.com/learn/Glossary/Camera_System/Sensor_01.htm

Hope that clears things (Including the "blooming" pixels )
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

malcolmk

Link Posted 21/10/2003 - 20:54
I took a CD of test pics down to Park Cameras today. For all I knew they might have told me that my collection of red green blue pixels was fairly normal. However I needn't have worried. "Totally unacceptable" was the verdict and we then spent best part of two hours with a new camera (their second batch, delivered today I believe) testing out a variety of things.

This evening I've repeated shots of my test scene which so clearly showed the traffic light effects of the previous body and I've not yet seen anything wrong, in fact they look slightly sharper to me but that may be due to the artificial light instead of daylight. So that's a big thank you to Matt and the chaps at Park Cameras who couldn't have been more helpful and didn't suggest I was an old fuss-pot as I'd half feared.

Now I'd better whisper this bit because it wouldn't do for too many people to know...

The third camera, never before unpacked, that they'd put on one side for me was faulty too (**).

A few phone calls to Pentax UK to see if there was any way to fix this particular fault without returning it revealed that I had single handedly been responsible for a high proportion of *ist D returns (three). Obviously I shouldn't be allowed out with hi-tech products.

** It refused to recognise any memory card, apparently not the first UK unit to fail in that way

Anonymous

Link Posted 05/11/2003 - 16:24
Hi,
I had exactly the same problem, hot pixels appeared in more or less the same place as in your camera. I returned the camera back.
Regards,
Ivan, Moscow

Anonymous

Link Posted 27/11/2003 - 14:12
I too know the headaches of bad pixels. I realize it's not the same camera, but I bought a pentax optio 33L about six months ago, after the first week I noticed 2 bad pixels, so I took it to Pentax Canada, which is convieniently down the street from where I work. They fixed it no problem. 4 months later I was browsing through some pictures when I noticed another bad pixel so I returned to Pentax who told me they didn't understand what was wrong but they would replace the camera. They brought out my new camera and gave it to me but before I left I thought I would give it a try. I took the camera out and took a picture of a dark area in the room. Then in preview mode I zoomed in on the picture and scrolled around the screen. In a matter of minutes I was looking at another bad pixel. So I showed the guy who was helping me. He started talking about how less than 5 bad pixels was considered acceptable by Pentax standards. I told him that 0 bad pixels was acceptable to me. After a bit of talking he finally got me another replacement. I tested this one......another bad pixel. I showed the guy and he started getting mad. He went into the back room and brought out a technician and another replacement. The technician refused to believe that these camera's were bad and that I was finding pixels that easily. He gave me another replacement but this time put in his own batteries and card and this time he took the picture then shoved the camera over to me and told me to find any problems. I found 3 bad pixels on that camera. After I showed it to him, he agreed there was a problem. They told me to come back in a couple of days. I went back later and they gave me a properly working replacement. I also demanded a new 1 year warranty which I had to fight for.
I have 2 pentax SLR camera's which I love, I really like the design of this camera and it was really affordable. I'm not sure if my next digital will be a pentax though.


Shawn

http://www.geocities.com/swancustomphoto

MattMatic

Link Posted 27/11/2003 - 16:44
Shawn,

Sounds like the Pentax guys gave you a hard time.
However, all in all, it's not really Pentax that's at fault (just the fact they didn't recognise the problem). Any manufacturer of digital camera will have the same problems - and the response from each company will certainly vary

Hot/bad pixels are a fact of life - the sensor is a grown crystal of silicon onto which the electronics are etched (like any semiconductor). It is similar with memory cards and flash memory technology - they [a]all[/b] have dud memory cells, it's just that the software maps them out without you knowing about them

If you were to purchase a digital back for medium format or large format, there will be a ton of hot pixels. They need to use cooling to keep the physical temperature down, and therefore reduce the problems of electronic noise Just as well we don't need to resort to that in compact digitals!

As I mentioned in previous posts, there are several post-shoot solutions to hot pixel removal. Maybe Pentax need to address the issue in the camera firmware a little better - like optionally detecting the hot pixels and mapping them out before JPG encoding.

Personally, I have found Pentax's response to issues and suggestions regarding the *ist-D very positive indeed. As their user base is more intimate, it seems you have more chance of getting heard

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

Anonymous

Link Posted 27/11/2003 - 21:52
Thanks for the info Matt.

I just figured out how to make a batch file in photoshop that will go through multiple photo's and fix the dead pixels automatically. Photoshop RULES!!! If anyone wants to know how to make the batch file, let me know. I'll post a site that goes through it step by step.

Shawn

MattMatic

Link Posted 28/11/2003 - 07:11
Nice one Shawn

Yes, Photoshop rules
(Especially the new Photoshop CS - it's blown me away along with the whole Creative Suite!)

Could you post the link, or email it?

Thanks,
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

Anonymous

Link Posted 28/11/2003 - 14:38
Alright, here's a very descriptive way to fix dead pixels in Photoshop. I think you need to have photoshop 5 or greater to run a batch.

Here's the link:
http://www.geocities.com/swancustomphoto/pixelfix.htmL

Try it and let me know how it works for you.


Shawn
http://www.geocities.com/swancustomphoto

Anonymous

Link Posted 23/02/2004 - 22:12
Just wondering if anyone tried my Pixel Fix with photoshop?

MattMatic

Link Posted 25/02/2004 - 07:06
Shawn,

Thanks for the PS action. However, I feel that it is not quite automated enough. I generally use the healing brush tool in PS-CS which does a great job (I seem to have 3 hot pixels at ISO 1600).

I did find a fully automated tool, though. The author is pretty reputable, also producing the PTAssembler tool for stitching panoramas together using Panorama Tools. Here's the reference for the thread:
https://www.pentaxuser.com/forum/ftopic448.html

Happy zapping
Thanks!
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
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