PDA

View Full Version : D70 strange light concentration and horizontal lines



agjell
05-13-2005, 05:16 PM
I discovered this problem the first time I took night-pictures of the sky. After shooting I went back to my computer and imported the images. I noticed a strange concentration of light located in the upper left corner of all my pictures. To better be able to see it I turned up the EV compensation and found another bothering thing; in addition to the light concentration there were lots of horizontal lines stretched across the picture. I decided to do some tests and find out where the problem lied. To eliminate the lens as a problem source I removed it and put the body-cap on the camera instead. I took a couple of pictures with different shutter speeds and ISO values. What I found was that the horizontal lines were there every time, but not in the same places, they were obviously not the same lines. Somehow they were, and still are, generated by the camera, but can only be seen on very dark pictures. The upper left light concentration occurred gradually more from about 10 seconds shutter speed and upwards, independent of ISO values. This is extremely frustrating! I included my test setup below and encourage other users to test their cameras as well.

Test setup: Remove lens. Attach body-cap to camera. Turn mode-dial to “M”. Select settings ISO 200, 30 seconds shutter. (Aperture can obviously not be set because the lens is not attached.) Take picture.

I processed the image using Photoshop CS and Camera Raw 2.4, but I’ve also verified that I got the same result with Nikon View.

My CR settings in PS were:
White balance “as shot” (4800 -4)
Exposure +4
Shadows 0
Brightness +150
Contrast +25
Saturation 0

These settings will clearly present you with the problem if you have it.

This (http://www.home.no/agjell/_DSC2826.JPG) is my test picture.

TheObiJuan
05-13-2005, 09:44 PM
I have seen this happen before, but on a canon 1D ccd.

Ant
05-14-2005, 12:58 AM
Did you have NR enabled or not?

agjell
05-15-2005, 06:56 PM
NR disabled, I don't want the camera to do any processing at all... :)

mikmac
06-06-2005, 12:58 AM
I've seen this a number of times and can tell you the glow at the top left hand corner is almost certainly amplifier noise. Maybe someone who knows more about the D70 sensor can confirm of deny this, but many such chips have an on-board amplifier which under certain circumstances can produce haloing exactly like your example. The giveaway cause of both this and the banding is the long exposures you are using, combined with featureless (or near-featureless) subjects like night sky shots. Read the D70 manual, it tells you this will happen!

Night skies are much better shot with either dedicated post-processing software (various Photoshop plug-ins available, do a Google on AstoStack for a good astro-solution) or - dare I say it - film..

With your body-cap experiment you are basically crash-testing the chip in the D70 to its extremes. It's not a particularly good camera for noise anyway; the min ISO being 200 should tell you that. However I'd like to bet the same experiment (with NR switched off!) performed on ANY digital camera will produce very similar artifacts.

Maybe some Canon and Leica owners could post some tests and prove me wrong :)

mikmac
06-06-2005, 01:03 AM
Have a look at http://www.astrostack.com/

agjell
06-06-2005, 02:41 AM
Thank you for the reply, mikmac. I actualy got the answer 2 weeks ago from another forum. You're right, it is amplifier noise. This is a known problem on CCD sensors, but not on CMOS sensors (as Canon uses). However; it can be solved by turning the internal long shutter noise reduction on. I'm not planning on doing astrophotography anyway, I just wondered if it was my camera or a genereal problem.

D70FAN
06-06-2005, 04:36 PM
Thank you for the reply, mikmac. I actualy got the answer 2 weeks ago from another forum. You're right, it is amplifier noise. This is a known problem on CCD sensors, but not on CMOS sensors (as Canon uses). However; it can be solved by turning the internal long shutter noise reduction on. I'm not planning on doing astrophotography anyway, I just wondered if it was my camera or a genereal problem.

Since you know this is a phenomena unique to CCD's without Noise Reduction turned on, I'm trying to decipher the point of your post. Is this something that the CCD camera owners need to be concerned about?

agjell
06-07-2005, 12:56 AM
Since you know this is a phenomena unique to CCD's without Noise Reduction turned on, I'm trying to decipher the point of your post. Is this something that the CCD camera owners need to be concerned about?

Not concerned, I mean it's not gonna destroy your camera. It's just that the CCD's picks up heat from the amplifier, and that it's visible on very dark images with long shutter speeds.

D70FAN
06-07-2005, 06:20 AM
Not concerned, I mean it's not gonna destroy your camera. It's just that the CCD's picks up heat from the amplifier, and that it's visible on very dark images with long shutter speeds.

What I meant was concern over photo quality.

I've worked with CCD's since 512 element single-line arrays (NEC) in the early 80's, and was just wondering what your actual point was.

Thanks.

JTL
06-07-2005, 01:56 PM
Thank you for the reply, mikmac. I actualy got the answer 2 weeks ago from another forum. You're right, it is amplifier noise. This is a known problem on CCD sensors, but not on CMOS sensors (as Canon uses). However; it can be solved by turning the internal long shutter noise reduction on. I'm not planning on doing astrophotography anyway, I just wondered if it was my camera or a genereal problem.Thanks for passing along this info (and thanks too, mikmac)! This is something that I was not aware of and I appreciate the research! :) Learning something new is always a welcomed thing!

thesween
06-08-2005, 04:01 PM
Let's see, moire, stray light, and now, at least for me, "artifacts" showing up on some D70 images. I accidentally/incidentally shot some clear sky pics yesterday, and it was just charming to find what look like small smudges just north of center in several frames. No, they ain't lens generated, I tried three seperate Nikkor lenses and they all produce the same extraneous blobs. Researching digital photography in general, and the D70 in particular, it seems that these things, "artifacts," are a way of life in our digital world. Great, just great...

Warin
06-09-2005, 08:06 AM
Let's see, moire, stray light, and now, at least for me, "artifacts" showing up on some D70 images. I accidentally/incidentally shot some clear sky pics yesterday, and it was just charming to find what look like small smudges just north of center in several frames. No, they ain't lens generated, I tried three seperate Nikkor lenses and they all produce the same extraneous blobs. Researching digital photography in general, and the D70 in particular, it seems that these things, "artifacts," are a way of life in our digital world. Great, just great...

Try the same experiment, but shoot in NEF, then take a look at the same spot. if the blobs are still there then it could be a sensor issue. If they aren't, it is indeed an artifact of the jpeg compression.

In the grand scheme of things, digital photography is pretty dang new... so I am sure it has and will continue to have some issues. Being an early adopter means working with those issues. In the darkroom, I sometimes have to dodge and burn to get my exposure right. If there is a scratch (!) on my negative I have to do some spot toning to take care of it. The healing brush and/or clone tool within Photoshop can remove your blobs in really short order. perfection rarely occurs without at least a little fixing/post processing, whether it be photochemical or digital.

D70FAN
06-09-2005, 10:21 AM
Let's see, moire, stray light, and now, at least for me, "artifacts" showing up on some D70 images. I accidentally/incidentally shot some clear sky pics yesterday, and it was just charming to find what look like small smudges just north of center in several frames. No, they ain't lens generated, I tried three seperate Nikkor lenses and they all produce the same extraneous blobs. Researching digital photography in general, and the D70 in particular, it seems that these things, "artifacts," are a way of life in our digital world. Great, just great...

If your blobs appeared suddenly then try cleaning the sensor. This sounds like dust spots/blobs. They come and go, and sometimes require "bulbing" the sensor (blowing gently using a bulb) or actually using a sensor cleaner to remove the dust. Make sure the mirror is out of the way first. Many camera repair shops also offer cleaning for a modest fee.

erichlund
06-10-2005, 07:20 AM
Since you know this is a phenomena unique to CCD's without Noise Reduction turned on, I'm trying to decipher the point of your post. Is this something that the CCD camera owners need to be concerned about?

Look at the dates. All he was saying was that he asked the same question on another site and got a reply much sooner than he got here. Originally, when he asked the question, he didn't know the answer. Perhaps I only picked up on it because I didn't even look at this thread until today.

Cheers,
Eric

D70FAN
06-10-2005, 09:30 AM
Look at the dates. All he was saying was that he asked the same question on another site and got a reply much sooner than he got here. Originally, when he asked the question, he didn't know the answer. Perhaps I only picked up on it because I didn't even look at this thread until today.

Cheers,
Eric

Thanks Eric. I guess I sensed a "drop-in". And while it is an interesting and well known phenomena in the CCD world it is also the reason that CCD type cameras offer long exposure noise reduction.

I'm always wary of people using "subtle poisoning" in what would otherwise be an interesting discussion.

thesween
06-10-2005, 02:06 PM
Thanks for the help on this. I'll do some testing this weekend, but do believe I got the "blobs" in both JPEG and NEF. One thing worthy of a mention is that I can't duplicate them anywhere else, except when shooting a clear sky. Oddly enough, I did some googling around and discovered that clear sky artifacts are common. I didn't have time to read the articles thoroughly but did take some comfort in knowing others have the problem.

I'm learning a big lesson here. If if turns out that this is a serious sensor issue, that makes two problems so far with the D70. The initial problem was with DoF preview. I bought my D70 from a reputable dealer with a 100% return policy of seven days on all digital equipment. So, if you're going to buy a D70 I'd suggest you test it, and test it HARD, right out of the box, try everything, do everything, then do it again. That way, if you have problems, and I'd do this if I could, just return the camera and get your money back, and buy another if you like.

D70FAN
06-10-2005, 02:26 PM
Thanks for the help on this. I'll do some testing this weekend, but do believe I got the "blobs" in both JPEG and NEF. One thing worthy of a mention is that I can't duplicate them anywhere else, except when shooting a clear sky. Oddly enough, I did some googling around and discovered that clear sky artifacts are common. I didn't have time to read the articles thoroughly but did take some comfort in knowing others have the problem.

I'm learning a big lesson here. If if turns out that this is a serious sensor issue, that makes two problems so far with the D70. The initial problem was with DoF preview. I bought my D70 from a reputable dealer with a 100% return policy of seven days on all digital equipment. So, if you're going to buy a D70 I'd suggest you test it, and test it HARD, right out of the box, try everything, do everything, then do it again. That way, if you have problems, and I'd do this if I could, just return the camera and get your money back, and buy another if you like.

I'm not sure that you read the answer... so here goes again...

...it's probably dust on the sensor. Clean it.

I shoot a lot of clear blue sky and have not had any problems with artifacts, but occasionally dust spots/blobs appear. Most times, these go away on their own, but ocasionally require cleaning.