Can someone explain what is meant by well depth?

h0ughy (David) · #1 17-07-2013, 11:41 AM

this "new" nightscape camera i bought says it has a well capacity of 25000 -e. i am assuming thats not high end

, but i will be using a hyperstar setup SO my question is really what is the level to obtain images at in order to process in colour?

and no only used DSLR's and i havent the faintest

avandonk · #2 17-07-2013, 12:31 PM

Quote:

Originally Posted by h0ughy

this "new" nightscape camera i bought says it has a well capacity of 25000 -e. i am assuming thats not high end

, but i will be using a hyperstar setup SO my question is really what is the level to obtain images at in order to process in colour?

and no only used DSLR's and i havent the faintest

It is quite simple. Well depth is the maximum signal that can be recorded without saturating. You will find it is far higher than most DSLR's apart from most top end Canons.

Well depth is proportional to pixel size. The larger the pixel the greater the well depth. Signal to noise can be considered as a ratio of maximum well depth to all the other factors that contribute to noise inherent in the detector or sensor pixels.

Bert

h0ughy (David) · #3 17-07-2013, 12:36 PM

Quote:

Originally Posted by avandonk

It is quite simple. Well depth is the maximum signal that can be recorded without saturating. You will find it is far higher than most DSLR's apart from most top end Canons.

Bert

thanks Bert, so the aim of the game is to approach the limit and stop just short, like 24500 etc?

RickS (Rick) · #4 17-07-2013, 12:46 PM

Quote:

Originally Posted by h0ughy

thanks Bert, so the aim of the game is to approach the limit and stop just short, like 24500 etc?

When you start getting up near full well the response typically becomes non-linear so ideally you want to stay a fair bit lower.

In practice you'll almost always reach full well depth with your bright stars. Just make sure the rest of your data doesn't get too close. The conservative advice for flats is typically to target half well depth.

If you're really keen you can run a photon transfer curve and find out exactly how far you can push your sensor.

avandonk · #5 17-07-2013, 12:48 PM

Very bright stars and not so very bright will always saturate within a few seconds. The dim stuff takes a lot longer. It is all a matter of balance.

Bert

h0ughy (David) · #6 17-07-2013, 01:10 PM

thanks guys - steep learning curve

Bassnut (Fred) · #7 17-07-2013, 06:35 PM

Quote:

Originally Posted by h0ughy

thanks Bert, so the aim of the game is to approach the limit and stop just short, like 24500 etc?

When you go over full well (saturation) then you get blooming on some cameras, the excess photons spill into adjacent wells (messy)That's why most chips have anti blooming gates, they skim off spilled over photons so you can keep exposing after saturation. It's safe to continue exposing on an ABG chip so you can get faint stuff, it just means stars have no colour (rgb all saturated =white stars).