3/24/2011 reducing noise at physical layer cedic 2011 1 · 24.03.2011 reducing noise at physical...

3/24/2011 Reducing noise at physical layer – CEDIC 2011 1

• What is the „best“ ISO?

• ISO Amplification?

• How can mathematics help?

• Example Images


• Where does Noise and Amplification happen?

• The key point is, that most noise origins

BEFORE A/D or ISO-Amplifier


• “Does this theoretical negotiation

correspond to the reality?”

– Methods of verification

• Driving tests on deep sky objects

• Driving tests on synthetic objects

24.03.2011 Reducing noise at physical layer – CEDIC 2011 6


16 x 2 min @ ISO 1600

4 x 8 min @ ISO 400

1 x 32 min @ ISO 100

Nozzle feature

Stack of 16 x 10s @ ISO 1600




3/24/2011 Reducing noise at physical layer – CEDIC 2011 8Single 160s shot @ ISO 100


524

357

262

189

140

100

150

200

250

300

350

400

450

500

550

16 x 2 min @ISO1600

8 x 4 min @ISO800

4 x 8 min @ISO400

2 x 16 min @ISO200

1 x 32 min @ISO100

Devia

tion / N

ois

e

0°C Single Shot

0°C Stacked

Low

ISO

Stac

kin

g

• Low ISO is a great alternative

• But: You have to test your own camera to

find the best ISO settings

– Measure noise at different ISO-Settings and

different exposure times

– Find the best combination for YOUR model

– Testing will need only little time

– Testing will save a lot of observing time


• If histogram is “low”, stacking will not increase dynamic

• If histogram is “high”, separation of A – B is possible


• Long time exposures are very useful

• The higher the histogram, the better can the

image be processed by Photoshop

• You may need to do HDR

– Take short pictures to avoid saturation.

– Take long pictures to go deep.

– Combine them with software. (Photoshop, etc.)

• Question: What kind of noise will become

more and more important with long exposure

times?


• Each 6° drop - the thermal noise is divided by 2

– Surface of the Sensor heats up: 42°C – 50°C during

long time exposures. (EOS 450D, 15min - 30min)


524

357

262

189

140

719

547

433

350304

0

100

200

300

400

500

600

700

800

16 x 2 min @ISO16004 x 8 min @ISO4001 x 32 min @ISO100

Devia

tion / N

ois

e

0°C Single Shot0°C Stacked24°C Single Shot24°C Stacked


Low

ISO

Stac

kin

gco

olin

g

• EOS 450D

– Single HQ Peltier

• Power: 40W

– HQ - CPU-Cooler

– Temperature drop at

sensor: >60°

– Min. sensor temperature:

-24°C after 5 min.

– “heavy overdosed”

– The PWM reduces cooling

power to 20% in order to

avoid ice on the sensor


• EOS 1000D

– Single cheap Peltier

– Power 17W

– Cheap Chipset-Cooler

– Temperature drop at

sensor: <40°

– Min. sensor temperature:

0°C after 10 min

– “good enough”

– PWM at 80%


• There is plenty of noise that is not affected

by temperature

– Read out, random noise, fixed pattern, etc…

• If you go lower than 0°C sensor surface…

– …you may see wonderful ice flowers

– …the thermal noise is far below read out noise

• No further optimization is possible


• Abell 66, very weak PN

– 25,9 mag/sec²

– With cooling:

• More stars than in DSS

• more than 23mag of DSS

• Astroart says: 27-29vmag

• Observation

– 4 x 32min @ ISO 100

– EOS 450D @ 2°C

– Hakos, Namibia, IAS

– 50cm Newton 1500mm

focal length


• Because the sensor will heat up:

– Cooling is very effective

– It is worth to spend time on cooling projects

• On my homepage you find detailed information

about

– Used material

– Dimensions of the copper finger

– Video tutorial

• With this information, project will consume less

than 40h time.

• Visit: www.sternschnuppen.de


• Keep the well known stacking.

– Darkframes, Flats, Dithering, etc…

• Use low ISO

– Increase exposure time

– Optimize your histogram

• Cooling down the camera

– Even small effects will help


Low

ISO

Stac

kin

gco

olin

g

3/24/2011 reducing noise at physical layer cedic 2011 1 · 24.03.2011 reducing noise at physical...

Documents