High ISO & Long Exposures with the D40

[psychobiologist]

hi all,

currently posting from work..

recently i visited a nearby observatory and they toned down all nearby lighting for astro purposes, had to snap at a high ISO/long exposure, and i was surprised that on a high ISO and a long exposure on my d40 (18-55II), what that was supposedly grey/white had turned out to be green

does anyone have the same experience too? is it due to the difference in camera sensitivity to certain colors?

will post the picture up when i head for lunch in abt 45 mins time

[huggable]

Did you turn on the NR?

[psychobiologist]

yup nr was on.


original w/ flash


iso1600 w/o flash

[espion]

looks like a WB issue. did u set the WB?

[Clockunder]

It's probably due to the Auto White Balance setting.

When you use Auto WB, the camera uses its "Artificial Intellligence" in its processing algorithm based on the the image captured on the sensor to guess the likely light source and then processes and compresses the data into jpeg. Apparently, your camera thought the light source was very very red and/or blue and thus have reduced the red and/blue accordingly, resulting in the grey/white turning green. Check the Red, Blue and Green channel on your software (e.g. Photoshop) and see what kind of histogram you have for each channel.

In such situations where it's not easy for you to set manual white balance on your camera, it's better to shoot in RAW and then adjust in post-processing.

I'm not sure whether the effect you get is typical of the D40.

[psychobiologist]

Originally Posted by Clockunder It's probably due to the Auto White Balance setting. When you use Auto WB, the camera uses its "Artificial Intellligence" in its processing algorithm based on the the image captured on the sensor to guess the likely light source and then processes and compresses the data into jpeg. Apparently, your camera thought the light source was very very red and/or blue and thus have reduced the red and/blue accordingly, resulting in the grey/white turning green. Check the Red, Blue and Green channel on your software (e.g. Photoshop) and see what kind of histogram you have for each channel. In such situations where it's not easy for you to set manual white balance on your camera, it's better to shoot in RAW and then adjust in post-processing. I'm not sure whether the effect you get is typical of the D40.

aah i think you are right..
they used dim red lights at the observatory to protect night vision. probably thats why.

oops. user fault i suppose.

[cichlid]

Originally Posted by psychobiologist hi all, currently posting from work.. recently i visited a nearby observatory and they toned down all nearby lighting for astro purposes, had to snap at a high ISO/long exposure, and i was surprised that on a high ISO and a long exposure on my d40 (18-55II), what that was supposedly grey/white had turned out to be green does anyone have the same experience too? is it due to the difference in camera sensitivity to certain colors? will post the picture up when i head for lunch in abt 45 mins time

Hi, just curious, where are u from?

[psychobiologist]

Originally Posted by cichlid Hi, just curious, where are u from?

i'm a singaporean but am in atlanta right now