What is going on here

USAIR · January 28, 2006

This seems to happen in very cold weather when I am out shooting.
And also does not happen when I am shooting in daylight in same conditions.
It does go away but almost missed a shot because of this
And very hard to see on lcd too

20D 3sec @ f/8 70-200 f/2.8 lens iso 100 shot in RAW

Thanks
Fred

Khaos · January 28, 2006

It kind of looks like electrical interference.

DavidTO · January 28, 2006

It's been discussed here.

USAIR · January 28, 2006

DavidTO wrote:

It's been discussed here.

Holy Cow its RAW doing this never would have thought this.
If I un check everything in RAW it should go away right...
Well just glad its not my sensor

It only happens at night and...in cold I think

Thanks David I will read this again tommorrow...it just never sinks in after one reading

Fred

pathfinder · January 28, 2006

As discussed in the previous thread, this occurs when ACR is presented an image with large areas that are vastly underexposed and should appear as a deep black. ACR moves the exposure corrections strongly to the + compensatoin side, and random noise appears in the image from noise in the sensor's circuitry.

Rutt asked if the image can be helped with a blend. My first suggestion is to return to the RAW files and push the shadow slider much further to the right. A second alternative would be to shoot two exposures - one for the forground building and a second exposure for the sky and then blend them in PS> OR even create two exsposures from the same RAW file.

I pulled down Fred's image in the 800x600 pixels and used the SUrface blur filter on each of the R,B,G channels to blur the dark areas without affecting the straight lines and form, I then selected the sky, and painted in some blue from the sky in the color blend mode and obtained this image with less striations, but still with some variation in the sky.

USAIR · January 29, 2006

Thanks Jim
I will have to try this on the orginal and see what I can come up with.

One question...on some of these I do see those noise lines in the 20D lcd and thats before ARC gets into the picture right ?
Most photos like this you cant see it on the cameras lcd but this photo you could see it.

Fred

DavidTO · January 29, 2006

USAIR wrote:

One question...on some of these I do see those noise lines in the 20D lcd and thats before ARC gets into the picture right ?

It depends. CS2 will auto correct in Bridge, unless you change your prefs. So you would most likely see it there.

pathfinder · January 30, 2006

Fred, what you see on the LCD on the 20D IS an in-camera derived jpg. You do not see the RAW data on the LCD - it has already been through the 20D algorithm for creating a jpg.

SO, the noise is from the camera's attempt to create image data from a large underexposed area - ergo - noise. Just like when you accept the default settings in ARC, but done by the camera and sent to the LCD.

I think this is the explanation.:):

USAIR · January 30, 2006

pathfinder wrote:

Fred, what you see on the LCD on the 20D IS an in-camera derived jpg. You do not see the RAW data on the LCD - it has already been through the 20D algorithm for creating a jpg.

SO, the noise is from the camera's attempt to create image data from a large underexposed area - erg - noise. Just like when you accept the default settings in ARC, but done by the camera and sent to the LCD.

I think this is the explanation.:):

Makes sense to me
I dont see it too often but enought to make me wonder
Just glad it not the camera going south

Thanks
Fred

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