Problem with my istDS?

[BT*ist]

Hi there,

I've recently found that most of the photos I've been taking on my Pentax istDS are looking fine on the back of the camera when I'm chimping, and looking okay when I pass a cursory glance at the histogram that's popping up, but a problem is evident whenever I look at the full size image on a CRT monitor. The image looks a little something like this (and no, it was not taken in near darkness):


All the data is still there, because an ext.reme levels/midtones adjustment shows to me that the detail is still being recorded as bringing out a decent(ish) shot (note : no flash, ISO1600, yellow/tungsten lighting, automatic white balance, and some deliberate desaturation. But bottom line, it wasn't taken in near or total darkness):


And yet, twice now the shot has been accompanied by some bands on the image, which is again something I don't like one little bit (there's also some across Puppy Dog's head, evident in the preceeding picture):


Does anybody have any experience with this sort of thing that you could provide? Is it the camera's sensor? The SD card? sunspots, voodoo dolls, etc? The problem first came up a couple of months ago, but it seems to have gotten steadily worse. I don't mind doing a minor midtones adjustment to shots, but obviously this is more wholesale image reconstruction... The problem is happening across all modes.

I'm about 38 days away from going on a 3 week US holiday with this camera and I'm wondering to what extent I should be panicking hysterically at this point.. The camera is almost 1 year old (yeah.. I'll be looking for that receipt)

[gstark]

I chimp to see composition and lighting effects, rather than exposure or colour related items.

Chimping rarely tells you what you need to know about exposure, wb, exposure, or anything like that. Does the Pentax have a histogram function? That's far more usable.

[moz]

istDS are looking fine on the back of the camera when I'm chimping, and looking okay when I pass a cursory glance at the histogram that's popping up, but a problem is evident whenever I look at the full size image on a CRT monitor

Have you gamma calibrated the monitor? Even the test strip at the bottom of DPreview's reviews will be better than nothing. You might just find that the CRT is quite dark. I know my 17" LCDs are lifeless next to the new toy (20" LCD), so I try to avoid C&C except on that monitor.

[avkomp]

no experience with pentax digital, but trying to exclude obvious stuff like you didnt recently clean your sensor or something??

Steve

[DionM]

Ummm ... guys ... can you see the banding? Using a histogram and calibrating your monitor won't get rid of those bands!

BT*ist ... I would perhaps go looking for a firmware update or the like? What lens were the shots taken with?

The reason you won't see the bands on the LCD preview monitor is that it is too small to resolve that detail. Does your *ist have a TV-out function? Try playing back that way - that may give us some indication as to where the banding is coming in.

Also what type of shot are they - RAW or JPEG? Maybe a problem with JPEG compression (again, have a look for updated firmware).

[avkomp]

the monitor calibibrate issue came to mind also when I saw the post but forgot to mention it when I got to the banding also.

I wonder if you revisit some older images that used to look ok and see now.
It seems to me that if the histograms appear ok and the preview, it may be you monitor

Steve

[moz]

Ummm ... guys ... can you see the banding? Using a histogram and calibrating your monitor won't get rid of those bands!

I see them but fixing them is beyond me. I thought I'd point out the obvious thing and let someone who's actually seen a Pentax comment on the banding.

Hey, they don't use Nikon sensors do they?

[DaveB]

FWIW, I believe the DS uses the same Sony sensor as the D70 (or at least one very similar).

The banding and general darkness does seem to indicate gross underexposure, but that should be visible in a histogram as data being bunched up to the left. If the histogram on the camera doesn't match the histogram being shown in Photoshop then there's definitely something weird going on!
As others have asked: are these RAW or JPEG shots? (although I would have to assume RAW: the JPEG quality from the DS is weird so I don't know why anyone would try to use it). If they're RAW, what converter are you using?

The latest f/w for the DS is 2.00, BTW.
I have a DS, but right now it's in pieces on my workbench so I can't check anything for you at the moment.

[MattC]

Are all shots coming out the same?

Exposure? D70 can do the same (the banding) when an image is underexposed... but I have never seen it quite like that.

Another thing is streaks left behind after a wet clean, which btw, are more obvious with under exposure.

Cheers

[DaveB]

These bands seem to be perfectly horizontal and consistent across the entire frame. They do not look like muck on the sensor filter.

[gstark]

Ummm ... guys ... can you see the banding? Using a histogram and calibrating your monitor won't get rid of those bands!

Dion.

The first thing to do is to ensure that he has correct exposure. For that you cannot rely uponchimping, because the in-camera display settings may be set to bright to permit vieiwin in high ambient light scenarios (bright sunlight, for instance) and thus an underexposed image may appear ok in that display, but it will still be underexposed.

And if an image is underexposed, then banding becomes more of a probability, rather than a possibilty.

So, let's make sure that we're talking about a well exposed image before we tackle the banding, which may be a symptom, rather than a problem.

[BT*ist]

Photos were taken as JPGs (blush), on an 18-55mm kit lens (widest angle I have).

What's confounding me is that while the issue with darkness is more or less universal, the banding is rare> I took a series of about 70 shots of Puppy Dog that afternoon and only three appeared to have banding. Another batch of 100 I took at a work event a week earlier were also all dark (not this dark, but somewhat) and there were no banding issues on any of them, and a different lens was used for some of those.

The sensor on the camera has not recently (or ever) been cleaned, wet or dry. The work monitor I use hasn't been calibrated, but the image darkness I'm facing is much greater than anything that would make me say "wow, that's dark" on any photo I see on dslrusers....

I'll get more data once I'm back home with the camera and original files in hand. I'll take some random shots under 'easy' conditions tomorrow and post those...

[Flyer]

My cousin had exactly the same problem after he updated the firmware to ver.2.00.
He tried the update again - still same problem.
He then downloaded firmware again from Pentax UK & after reinstalling that the issue disappeared.

As for banding I believe DaveB is correct in saying that it is due to gross underexposure.
I see sometimes on my D70 when playing with levels in greatly underexposed photos.

Cheers.

[DionM]

Ah okay, didn't realise the banding was a trait of underexposure. The original didn't look that underexposed.

[BT*ist]

Okay, had another look at various components of what may be the problem.

Firstly, I think that my work monitor is part of the issue, and the fact that I'm finding my photos have become darker over time suggests that my monitor is fading and may need to be replaced soon.

I've also had a look at the histogram of the puppy dog shot I posted up top, and it is under-exposed: that is, the graph, while not entirely stacked to the left, has a dual-peaked bell-shaped curve that entirely inhabits the leftmost quarter of the histogram display (The attached diagram approximates it).


As for the banding, there I'm a little more concerned. I had another look at the shots on either side and recalled that I was using rapid-fire mode when taking these photos, although at each of the three instances of banding, the shots on either side were similarly exposed but with no banding. In another sequence of shots, the histogram was a neat bell-shape entirely occupying the left half of the histogram display, even on the one with bands, eg:


I've taken a photo with my camera just now at work, and per the histogram other than the dark area on the bottom right, the bell-shaped curve is pretty much centre of the display.


I 'll see if I can induce some banding next...

Thanks for all your help so far!

[Big Red]

have you formatted the SD card lately?
update to version 2:00 if that doesn't work.
try another SD card ?

haven't heard of your problem before but it is the same sensor as the D70 so its could be the same thing.