Image strangeness. What's going on? [Archive] - Glock Talk

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JellyBelly
12-14-2006, 23:34
http://i147.photobucket.com/albums/r288/Canonista/ImageStrangeness.jpg

What's the deal with that bullseye in the middle of the picture? I went to shoot the northern lights and all of my images have that mess in them to some degree or another.

I used the XTi's kit lens and a really good Canon 24-70 lens and it happened in both. I was shooting RAW, at a few different ISO levels, f-stops, and exposures and it occurred in every one.

It's well above freezing outside so I don't think it's the cold.

What gives?

hwyhobo
12-15-2006, 03:58
Where in the world are you located? :shocked:

As for the thingie in the middle, it kinda looks to me like a processing artifact. Sometimes you may get similar patterns from overly aggressive application of median filter. Perhaps something similar is happening during conversion?

Fred
12-15-2006, 09:58
I don't have a clue what it is, but if it keeps doing it, at least you can make some targets! :tongueout:

Dandapani
12-15-2006, 10:45
http://en.wikipedia.org/wiki/Moire

http://upload.wikimedia.org/wikipedia/commons/thumb/3/31/Moire_pattern_of_bricks.jpg/150px-Moire_pattern_of_bricks.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/Moire_pattern_of_bricks_small.jpg/150px-Moire_pattern_of_bricks_small.jpg

"A moiré pattern formed by incorrectly downsampling the image above."

JellyBelly
12-15-2006, 12:11
Originally posted by hwyhobo
Where in the world are you located? :shocked:

Michigan. There was an abnormally large solar flare a couple days ago that made the news so I knew ahead of time that we'd be getting northern light activity.

I couldn't pass up the opportunity to take pictures. Only once before last night had I ever seen the Aurora Borealis, and it was never this intense.

hwyhobo
12-15-2006, 13:59
Originally posted by dmobrien2001
"A moiré pattern formed by incorrectly downsampling the image above."
So it is a processing artifact. Cool. JellyBelly, what was your process?

JellyBelly
12-15-2006, 14:56
Originally posted by hwyhobo
So it is a processing artifact. Cool. JellyBelly, what was your process?

I was using a plain-Jane 2GB SanDisk CF card.

File Name IMG_2808.CR2
Camera Model Canon EOS DIGITAL REBEL XTi
Shooting Date/Time 12/14/2006
Shooting Mode Program AE
Tv( Shutter Speed ) 30
Av( Aperture Value ) 2.8
Metering Mode Evaluative Metering
Exposure Compensation +1 1/3
ISO Speed 400
Lens EF24-70mm f/2.8L USM
Focal Length 24.0 mm
Image Size 3888x2592
Image Quality RAW
Flash Off
White Balance Mode Auto
AF Mode Manual focusing
Picture Style Landscape
Sharpness 4
Contrast 0
Saturation 0
Color tone 0
Color Space sRGB
Noise Reduction Off
File Size 8650 KB
Custom Function C.Fn:01-0
C.Fn:02-0
C.Fn:03-0
C.Fn:04-0
C.Fn:05-0
C.Fn:06-0
C.Fn:07-0
C.Fn:08-0
C.Fn:09-0
C.Fn:10-0
C.Fn:11-0
Drive Mode Single-frame shooting
Owner's Name **************
Camera Body No. **************

hwyhobo
12-15-2006, 18:34
Originally posted by JellyBelly
I was using a plain-Jane 2GB SanDisk CF card. [...]And then what happened? How did you convert it, how did you post-process it?

Dandapani
12-15-2006, 19:29
Originally posted by hwyhobo
And then what happened? How did you convert it, how did you post-process it?

He said he used RAW, but he posted a JPG, therefore there is some processing going on. Put the RAW file on www.putfile.com and provide us a link to the original to see the RAW file which is what, a BMP (bit map)?

nipperwolf
12-15-2006, 21:27
Originally posted by dmobrien2001
provide us a link to the original to see the RAW file which is what, a BMP (bit map)?

no, that would be a RAW......heeelllooooo;)


:supergrin:

JellyBelly
12-15-2006, 23:27
The bullseye pattern was visible on the camera's LCD monitor when I reviewed the image after taking the shot (before downloading the image into the computer).

sjfrellc
12-16-2006, 07:34
My theory is that because it is central and circular it is the lens filter causing artifact. You would think its not aberration in the lens.


Since there is no repeating pattern in the subject, that rules out moire effect.

Dandapani
12-16-2006, 07:42
Originally posted by nipperwolf
no, that would be a RAW......heeelllooooo;)


:supergrin:

Thanks.

http://en.wikipedia.org/wiki/RAW_image_format


There is no single RAW format: different manufacturers use their own proprietary formats, which are generically known as RAW format. Raw files contain pixel data from the image sensor usually at 12 or 14 bits per individual sensor bucket. These pixels are a mosaic of either red, blue or green values. The sensor is filtered with dye to direct the correct color of light into each bucket, this is called a Bayer filter. To retrieve an image from a RAW file this mosaic must be converted into an RGB image. This is known as Demosaicing, but this process is referred to by many manufacturers as Digital Development.

The contents of RAW files are often considered to be of 'higher quality' than the RGB converted results. Each pixel in RAW is represented by a higher range number. Transformations which affect brightness or color curve lose less information when performed on the raw data. This does not mean that an 8Mb RAW file is of higher quality than an 8Mb RGB file. It simply means that less information is lost in these particular transformations.

Other sensors, such as the Foveon X3 sensor capture information directly in RGB form.


Although the term "raw" describes files in the classical sense of "raw data" vs. "cooked data", raw files typically are slightly processed in the camera. In general, this processing is limited to algorithms that require direct access to the camera's hardware. This includes "long exposure noise reduction" (aka "dark frame subtraction") and the mapping out of "hot" (too bright) or "dead" (too dim) pixels. It also often includes rudimentary noise reduction. Noise reduces the effectiveness of compression algorithms, so files are compressed more efficiently when noise reduction is applied before compression.

Hokie
12-16-2006, 10:26
Originally posted by JellyBelly
The bullseye pattern was visible on the camera's LCD monitor when I reviewed the image after taking the shot (before downloading the image into the computer).

The image on the LCD is not the RAW file. The file has a small JPEG in it for display on the LCD.

Has it happen in any shots you taken since these?

hwyhobo
12-16-2006, 10:45
Originally posted by dmobrien2001
Thanks. http://en.wikipedia.org/wiki/RAW_image_format I think his point was that since it is RAW, it cannot be displayed directly in the browser, it would have to be processed first. However, you are right that a RAW file could be posted for download. If one had Adobe ACR (for example), one could then open it on his own computer.

DTQ
12-16-2006, 17:53
Put the RAW on an FTP or somewhere we can download it and let us take a look at it in ACR.

JellyBelly
12-16-2006, 18:28
Originally posted by Hokie
The image on the LCD is not the RAW file. The file has a small JPEG in it for display on the LCD.

Has it happen in any shots you taken since these?

I don't know how to post the RAW image here, but in Canon's software the irregularity shows up on my monitor in all the images.

I took almost 400 pictures today inside a museum with the exact same equipment and the bullseye didn't appear. Maybe my camera is haunted!:shocked:

DTQ
12-16-2006, 21:38
email one to me, send a GT message and I'll give you my email.

JellyBelly
12-16-2006, 22:48
Originally posted by DTQ
email one to me, send a GT message and I'll give you my email.

My interweb service doesn't allow it's customers to attach anyting but .gif and .jpg files to our E-mails. I couldn't send one if I wanted to.

DTQ
12-16-2006, 22:52
"if" you wanted to?


ouch...

JellyBelly
12-16-2006, 23:07
Originally posted by DTQ
"if" you wanted to?


ouch...

Not what I meant at all, although I see now how it could easily be read that way...:shocked:

I do want to. I can't.:thumbsup:

I started a thread at DP Review. I think it's been answered.

http://forums.dpreview.com/forums/read.asp?forum=1010&message=21291465

It's the filter, but not from it touching anything. It's interference in the filters coating due to the particular wavelength of light that ionized atomic oxygen emits, and has bit many an aurora photographer.

DTQ
12-16-2006, 23:20
That's it! I had never heard of that before...

http://www.eaglestation.com/dick/aurora.html

hwyhobo
12-16-2006, 23:51
Interesting. I might suspect interference with electronics, but not with the filter.

I guess that just confirms again my old argument of not using filter on a digital camera. ;)

hwyhobo
12-16-2006, 23:54
Wait, that wouldn't be a gel filter, would it? Gel filters will produce that effect sometimes with a sudden change in temperature (taking it out into cold weather and not giving it enough time to settle).

JellyBelly
12-17-2006, 12:07
Originally posted by hwyhobo
Wait, that wouldn't be a gel filter, would it? Gel filters will produce that effect sometimes with a sudden change in temperature (taking it out into cold weather and not giving it enough time to settle).

No, it was a Tiffen screw in filter.

nipperwolf
12-17-2006, 14:37
Originally posted by hwyhobo
I guess that just confirms again my old argument of not using filter on a digital camera. ;)

I learned that lesson the hardway, too. remember that thread, hobo?

No, it was a Tiffen screw in filter.

IF you are going to use a filter, buy the best you can; B&W, Hoya UMC, Nikon Clear.....

don't buy a fine,$1400 lens, and then slap on a cheap Tiffen filter.;) (I'm guessing it was a UV)

not only will they produce some weird effects
http://img.photobucket.com/albums/v605/nippr/mine/DSC_1426vw.jpg

they will also affect sharpness

http://img.photobucket.com/albums/v605/nippr/mine/compare2.jpg

hwyhobo
12-17-2006, 16:02
Originally posted by nipperwolf
I learned that lesson the hardway, too. remember that thread, hobo?
You bet. Threads like that can also be found all over dpreview and other boards.

MrsKitty
12-17-2006, 17:42
I have noticed that the use of filters are as debated as the 9mm v. 45 issue here :supergrin:

sjfrellc
12-17-2006, 18:03
Originally posted by sjfrellc
My theory is that because it is central and circular it is the lens filter causing artifact.


I resemble that diagnosis.:banana:

nipperwolf
12-17-2006, 20:19
Originally posted by misskitty5077
I have noticed that the use of filters are as debated as the 9mm v. 45 issue here :supergrin:

luckily, our quite, little, friendly, forum isn't as heated as dpreview. ;)

:supergrin: :supergrin:

:wavey:

but then again, Jelly Belly hasn't replied yet....:)

:supergrin:

:tongueout:

:wavey:

:supergrin: :supergrin: :supergrin:

nipperwolf
12-17-2006, 20:22
Originally posted by sjfrellc
I resemble that diagnosis.:banana:

VIOLATOR!!!!!

no fair quoting your own posts.

even if you might be correct. ;)

alphacat
12-17-2006, 20:40
Man I don't see no targets but that is the greatest picture.

Sun flair ups are whats causing it.
Don't you watch the news?

Watch out next time it does it, I might just show up in your driveway.

Way cool picture, made my chin drop.



Hey, I made it my desktop wallpaper and now I can see the target rings.

JellyBelly
12-17-2006, 22:00
Originally posted by nipperwolf
luckily, our quite, little, friendly, forum isn't as heated as dpreview. ;)

:supergrin: :supergrin:

:wavey:

but then again, Jelly Belly hasn't replied yet....:)

:supergrin:

:tongueout:

:wavey:

:supergrin: :supergrin: :supergrin:

10mm beats em' all!!!!!:thumbsup:

MrsKitty
12-18-2006, 07:34
Scattergun. ;)

MrsKitty
12-18-2006, 07:35
Originally posted by nipperwolf
VIOLATOR!!!!!

no fair quoting your own posts.

even if you might be correct. ;)

Quoting yourself confuses me so bad I forget who was debating what and how and why :rofl: