#1  
Old 22-03-2010, 05:33 AM
JD2439975's Avatar
JD2439975 (Justin)
Cloud hater

JD2439975 is offline
 
Join Date: Feb 2009
Location: Conondale QLD
Posts: 493
40D ISO-Exposure Noise Mosaic

I hear people say "go long on the sub exposures"...well that may be OK for those with CCD's cooled to 30 below ambient but what about us suckers with uncooled DSLR's unfortunate enough to live in the tropics?
I laugh when I hear a CCD owner worried because they can't get it under -20 C, hell I'm happy if gets below +20 C

I 'd noticed my ISO800 @ 5 min shots always seem rather noisy while the ISO800 2min & ISO1600 30sec shots seemed so much smoother, so I decided to do an ISO-exposure of my camera.
Starting with the lowest to highest ISO through the lowest to highest exposures, the lens was removed & replaced with the body cap, the viewfinder was also covered.
The whole exercise took about 7 hours with the average temp at 26 deg, dropping slightly in favour of the longer exposures, temps can be found in the second image.
The first image is a mosaic of all (RAW) darks taken, resized & saved as 16bit TIF, mosaic'd before tweaking the levels for ease of display.
The images were also feed into an online "average colour of the image" applet where I noted the black levels, ISO100 was 99% so I took the remainder 1% as noise level.
Plotting these and extrapolating for the full ISO range of the 40D I came up with a table of noise levels, note the added "missing ISO's" 2000 & 2500 that put ISO3200 in perspective.
Now this is rough & no doubt needs tweaking.

Remembering this is taken at 26 deg C does this look about right??
I was thinking...
ExtremelyLowNoise - masterpiece on bright objects...yeah right.
VeryLowNoise - ditto.
LowNoise - Lovely for that special image.
MediumNoise - a happy medium.
HighNoise - where you go for a quick snap.
VeryHighNoise - drunk or desperate or both.
ExtremelyHighNoise - noobies on a rampage.

Either I lengthen my exposure & lower my noise by lowering my ISO or I pick through Berts old posts on how he made his fridge.
Any thoughts?

Justin.
Attached Thumbnails
Click for full-size image (40D ISO-ExposureDarkMap.jpg)
184.3 KB102 views
Click for full-size image (40D Dark Temps.jpg)
180.7 KB75 views
Click for full-size image (40D ISO-Exposure Noise Mapping.jpg)
188.1 KB90 views
Reply With Quote
  #2  
Old 22-03-2010, 08:46 AM
jjjnettie's Avatar
jjjnettie (Jeanette)
Registered User

jjjnettie is offline
 
Join Date: Feb 2005
Location: Far Far Away
Posts: 16,726
That's a mammoth effort you've put into this.
And it's really put things into perspective for me.
A copy of this should be kept onsite.
Thanks
Reply With Quote
  #3  
Old 22-03-2010, 09:33 AM
Tallstock (Peter)
Registered User

Tallstock is offline
 
Join Date: Jan 2009
Location: Dungog NSW Australia
Posts: 102
Hi Justin,
Thanks for the info.
I have trouble using the small viewfinder so it is Live View for me.
Do you think it would reduce noise if the viewfinder was permanently "covered"?
Peter
Reply With Quote
  #4  
Old 22-03-2010, 11:33 AM
adman (Adam)
Seriously Amateur

adman is offline
 
Join Date: Sep 2009
Location: Brisbane
Posts: 1,279
That is fantastic Justin - could you please post the location of the 'online average colour of the image applet'?

I would love to do the same thing with my Canon 10D - it is an older chip and I think that it is quite noisy - it would be interesting to do the comparison.

Thanks
Adam
Reply With Quote
  #5  
Old 22-03-2010, 05:48 PM
JD2439975's Avatar
JD2439975 (Justin)
Cloud hater

JD2439975 is offline
 
Join Date: Feb 2009
Location: Conondale QLD
Posts: 493
Quote:
Originally Posted by jjjnettie View Post
That's a mammoth effort you've put into this.
And it's really put things into perspective for me.
A copy of this should be kept onsite.
Thanks
I was thinking of doing the full ISO scale till I worked out it would take almost 20 hours of exposures just the "classic" numbers for me thanks.
jjj I hope you & others(including me) get something out of this, makes it all worthwhile.

Quote:
Originally Posted by tallstock
Hi Justin,
Thanks for the info.
I have trouble using the small viewfinder so it is Live View for me.
Do you think it would reduce noise if the viewfinder was permanently "covered"?
Peter
Peter covering the viewfinder won't lower thermal noise but it will cut down on stray light entering the back of the camera.
I hear you on the LiveView, 10x zoom on the focus routine works a treat...but it does love to eat those batteries.

Quote:
Originally Posted by adman
That is fantastic Justin - could you please post the location of the 'online average colour of the image applet'?

I would love to do the same thing with my Canon 10D - it is an older chip and I think that it is quite noisy - it would be interesting to do the comparison.

Thanks
Adam
Gidday Adam, the page I used was http://www.wisegeek.com/how-can-i-fi...photograph.htm
JPG only unfortunately but good enough to get a rough numeric value on the noise.
That would be great to do the 10D, if others did thier camera they could possibly be stickied somewhere as a guide to camera noise.

Justin.
Reply With Quote
  #6  
Old 22-03-2010, 09:21 PM
dugnsuz's Avatar
dugnsuz (Doug)
to baldly go...

dugnsuz is offline
 
Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,200
I routinely image in the "drunk or desperate or both" and "noobies on a rampage" range and I don't do so badly - cheers!!

That said, my best results always coincide with lower ambient temperatures, but that would occur with all iso settings and the temperature variations of the seasons.
I can only offer an anecdotal approach (from experience) to this in that I find iso1600 the sweet spot for astro imaging with the 40D - lower temperatures and many subs being the winning factors.
My mantra is "experiment" and try to push the envelope whilst doing it! I could never go back to 400 or 800 especially with my f4 lenses.

Depends on how much time one wants to devote to an image - if you want it all done in one night, then low iso will get you a smooth image with a certain amount of data in it. I favour the 10-15min subs at high iso over multiple nights (20+ subs) approach which really opens up the capabilities of the DSLR.

Great exercise for showing the 40D noise profile, but "happy medium" isn't where I want my images to reside
All the best.
Doug

Last edited by dugnsuz; 22-03-2010 at 09:54 PM.
Reply With Quote
  #7  
Old 22-03-2010, 09:44 PM
RobF's Avatar
RobF (Rob)
Mostly harmless...

RobF is offline
 
Join Date: Jul 2008
Location: Brisbane, Australia
Posts: 5,492
Fantastic resource you've created there Justin - worthy of its own webpage or IIS write up.

One thing you may have over the rest of us "Southerners" is signal to noise remember. I suspect your skies are darker than most, so even in the higher noise cat's you have labelled, the signal to noise you collect from a dark sky site could still be very good.

With any sort of light pollution (I live in Bris Vegas ) the S:N equation quickly goes pear-shaped. It was a true revelation for me seeing the difference between ISO800 S:N at Qld Astrofest (and even better at Barambah) to the best shots I'd managed from the 'burbs. Up until that time I had been so stoked with what I could with long exposures, DSLR and pollution filter and still coming to grips with what you've done here in a FAR more piece-meal fashion.

As long as you're doing decent darks/flats/bias (or however you deem fit to calibrate your frames) and getting total exposures over a couple of hours I suspect with the S:N you'll get it won't matter if you're up in the longer exposure time for ISO 800. Suggest ISO 400 for brighter objects and avoid 1600 unless you're in a hurry.

Couple of other thoughts - perhaps consider use of external (non-battery pack) power and having a fan running on the camera if you're really pushing for a bit of advantage (must confess I've never bothered with either and Brissy nights can get pretty warm). Then again I'm not holding my breath for a David Malin either...
Reply With Quote
  #8  
Old 22-03-2010, 09:48 PM
RobF's Avatar
RobF (Rob)
Mostly harmless...

RobF is offline
 
Join Date: Jul 2008
Location: Brisbane, Australia
Posts: 5,492
Quote:
Originally Posted by dugnsuz View Post
I routinely image in the "drunk or desperate or both and "noobies on a rampage" range and I don't do so badly - cheers!!
Doug
Sounds like astronomy in the Adelaide hills is the way to go Doug!
Reply With Quote
  #9  
Old 22-03-2010, 09:55 PM
dugnsuz's Avatar
dugnsuz (Doug)
to baldly go...

dugnsuz is offline
 
Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,200
Quote:
Originally Posted by RobF View Post
Sounds like astronomy in the Adelaide hills is the way to go Doug!
Cheers Rob - my post amended (see above!!)
Reply With Quote
  #10  
Old 22-03-2010, 09:58 PM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,158
I'll continue to stand by ISO-400 as being the optimum ISO for controlling noise in your final stack.

H
Reply With Quote
  #11  
Old 22-03-2010, 10:04 PM
dugnsuz's Avatar
dugnsuz (Doug)
to baldly go...

dugnsuz is offline
 
Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,200
For DSLR owners the cooling mod looks like the most desirable upgrade in any location!
When I have a spare $1300AU I may do it!

I still love the simplicity of my DSLR and LiveView over the (perceived - as I have no hands-on exp) CCD learning curve right now - perhaps I'm wussing out, but I enjoy the challenge of extracting the best results from my "amateur" gear right now - and this is why Justin's efforts are appreciated.
Reply With Quote
  #12  
Old 22-03-2010, 10:05 PM
dugnsuz's Avatar
dugnsuz (Doug)
to baldly go...

dugnsuz is offline
 
Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,200
Quote:
Originally Posted by Octane View Post
I'll continue to stand by ISO-400 as being the optimum ISO for controlling noise in your final stack.

H
Live a little H
Reply With Quote
  #13  
Old 22-03-2010, 10:07 PM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,158
I am, Doug. The STL-11000M will be here within two weeks.

H
Reply With Quote
  #14  
Old 22-03-2010, 10:09 PM
dugnsuz's Avatar
dugnsuz (Doug)
to baldly go...

dugnsuz is offline
 
Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,200
Also, in a rare moment of self awareness/self reflection I realise indeed I am desperate, drunk and a noobie on a rampage!!!!

All the best...good job Justin
Doug
Reply With Quote
  #15  
Old 22-03-2010, 10:10 PM
dugnsuz's Avatar
dugnsuz (Doug)
to baldly go...

dugnsuz is offline
 
Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,200
Quote:
Originally Posted by Octane View Post
I am, Doug. The STL-11000M will be here within two weeks.

H
OUCH!!!!
Go for it son!!!!
Reply With Quote
  #16  
Old 22-03-2010, 11:34 PM
JD2439975's Avatar
JD2439975 (Justin)
Cloud hater

JD2439975 is offline
 
Join Date: Feb 2009
Location: Conondale QLD
Posts: 493
Quote:
Originally Posted by Octane View Post
I am, Doug. The STL-11000M will be here within two weeks.

H
Oh that's rubbing salt.

Doug as you say experimentation is the key...now if those damn clouds would just clear.
Kind of happy with the DSLR myself, sure it has limitations but still a flexible camera for both terrestrial & astro use, besides all that swapping filters would drive me mad.
Drunk & desperate I can relate but to baldy go where no noobie has rampaged before...

Rob I'm looking forward to those dark skies returning, well & truly over these clouds.
I was just thinking of getting external power for the 40D, getting a little tired of swapping out batteries a couple of times a night & there's nothing worse than forgetting to check the battery only to find it cut out as you walked away.

$1300AU for a cooling mod!! think I'll stick with the ambient system for now.

Justin
Reply With Quote
  #17  
Old 23-03-2010, 12:01 AM
JD2439975's Avatar
JD2439975 (Justin)
Cloud hater

JD2439975 is offline
 
Join Date: Feb 2009
Location: Conondale QLD
Posts: 493
One thing I would like to do is capture another set of darks at say 10-15 deg lower temp to see just how far the graph moves down & to the right.
Reply With Quote
  #18  
Old 23-03-2010, 12:08 AM
kinetic's Avatar
kinetic (Steve)
ATMer and Saganist

kinetic is offline
 
Join Date: Jun 2008
Location: Adelaide S.A.
Posts: 2,260
Justin,

excellent work.
Kinda goes against the mantra that 400-800 ASA is the
zone for DSLR LX though, doesn't it.

However, as Doug and Humi have mentioned, the next step
in your research is to so a stack set of multiple subs.

The S/N ratio of any stack will alter your outcomes significantly.
Also, the number of frames in a sub set will as well.

We all benefit from this stuff, great work.
A bit of education, theory and experimenting never hurt
any of us
Does the type of alcohol used affect the outcome BTW?

Steve
Reply With Quote
  #19  
Old 23-03-2010, 12:21 AM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,158
It's all built into the camera. Set and forget.

Quote:
Originally Posted by JD2439975 View Post
besides all that swapping filters would drive me mad.
Do yourself a favour and get the AC battery adapter. They're an absolute rip-off for what they are, but, you'll never be left wanting for power. You can go all night!

H
Reply With Quote
  #20  
Old 23-03-2010, 01:09 AM
JD2439975's Avatar
JD2439975 (Justin)
Cloud hater

JD2439975 is offline
 
Join Date: Feb 2009
Location: Conondale QLD
Posts: 493
Quote:
Originally Posted by Octane View Post
Do yourself a favour and get the AC battery adapter. They're an absolute rip-off for what they are, but, you'll never be left wanting for power. You can go all night!

H
Don't know the details but these things look like 240v to 7.4v that the camera battery plug unit plugs into.
Is there a 12v to 7.4v transformer available? if not commercial then DIY, I'm trying to get the whole scope both 240/12v friendly.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 08:45 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Lunatico Astronomical
Advertisement
NexDome Observatories
Advertisement
OzScopes Authorised Dealer
Advertisement
SkyWatcher Australia
Advertisement
Meade Australia
Advertisement
Celestron Australia
Advertisement
Astronomy and Electronics Centre
Advertisement