#1  
Old 03-06-2013, 04:28 PM
Wavytone (Nick)
BigBanger

Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 3,996
Game-changer: How about 8 stops faster ?

Saw this the other day: http://www.extremetech.com/extreme/1...ht-photography

If it makes it to production, it will revolutionise astrophotography but I'm not sure how the mass camera market will react.

1000x better is 8 stops. OK, so we could shoot landscapes by starlight at f/8 using ISO100.

For astrophotography, you won't really need to worry about PE as your exposures are only going to be a couple of seconds or less. Even tracking might be unnecessary, so even a dob could do astrophotography.

Conversely slow scopes like my f/15 Mak could do astrophotography (!) Hmmm....

But if you want to use long exposures to get the silky water look will need around 11-12 stops of ND filter... comparable to shooting through a solar filter (!).

And it poses problems for bokeh, where a fast lens around f/2 or 1.4 is needed... either the shutter speeds will have to be around a microsecond, or we'll have to learn to shoot portraits by moonlight.

Anyway seems like I'll forget about DSLR bodies until this happens.
Reply With Quote
  #2  
Old 03-06-2013, 05:06 PM
Shiraz's Avatar
Shiraz (Ray)
Registered User

Shiraz is offline
 
Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,787
Interesting link, but sorry to be a wet blanket - its only 1000x better than previous graphene detectors.

Modern affordable cmos/ccd detectors are now so efficient that they are detecting 7-8 out of every 10 photons that fall on them. That is almost as good as it can ever get (which is 100% detection), so don't expect huge breakthroughs in visible band detection capability with any new devices - that is now physically impossible. However, if the graphene technology has stable gain, it may be effective in reducing the read noise, the last area where affordable cooled visible band detector technology can be improved significantly. In that case the technology would be competing with at least three other low read noise technologies, although none of those is low cost at present.

EDIT: did some more looking and it seems with with these "major breakthrough" press releases, the devil is always in the detail. From a more measured source:

"Graphene also shows great promise for photonics applications because it has an ideal "internal quantum efficiency" – almost every photon absorbed by the material generates an electron–hole pair that could, in principle, be converted into electric current. Thanks to its "Dirac" electrons, it can also absorb light of any colour.
However, all is not perfect because graphene's "external quantum efficiency" is low – it absorbs less than 3% of the light falling on it. "

ie, it is currently useless as a visible band photodetector.

reckon you should buy a modern CMOS DSLR body - not much point in waiting for graphene technology.

Ref:http://physicsworld.com/cws/article/...tector-a-boost

Last edited by Shiraz; 06-06-2013 at 12:34 AM.
Reply With Quote
  #3  
Old 04-06-2013, 02:39 PM
gregbradley's Avatar
gregbradley
Registered User

gregbradley is offline
 
Join Date: Feb 2006
Location: Sydney
Posts: 15,409
Quote:
Originally Posted by Shiraz View Post
Interesting link, but sorry to be a wet blanket - its only 1000x better than previous graphene detectors.

Modern affordable cmos/ccd detectors are now so efficient that they are detecting 7-8 out of every 10 photons that fall on them. That is almost as good as it can ever get (which is 100% detection), so don't expect huge breakthroughs in visible band detection capability with any new devices - that is now physically impossible. However, if the graphene technology has stable gain, it may be effective in reducing the read noise, the last area where affordable cooled visible band detector technology can be improved significantly. In that case the technology would be competing with at least three other low read noise technologies, although none of those is low cost at present.
It sounds interesting but there are other characteristics that it needs to have. One is low noise. Perhaps it is 10X more sensitive to heat as well making it very noisy.

Greg.
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 08:06 PM.

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