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Old 07-09-2008, 10:39 AM
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g__day (Matthew)
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Canon DSLR 12 vs 14 bit A/D Convertors - Query?

Guys I am pondering how easy it is to see the difference between a shot of say a planetary nebulae take with a 10mega pixel DSLR with 12 vs 14 bit analogue to digital converters.

Could someone who has both post a shot or two please. I presume the extra 2 bits giving you 2^2 = 4 four more levels of shade will produce some nice results - I am wondering how nice!

Anyone that could help - greatly appreciated!

Thanks,

Matthew
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Old 07-09-2008, 12:30 PM
Ian Robinson
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power(2,12)=4096 bits
power(2,14)=16384 bits
difference = 12288 bits

It comes down to alliasing , and how well the digital conversion represents the analog signal. Obviously 14 bit is a lot better than 12 bit.
The link below explains the idea of aliasing - http://www.dsptutor.freeuk.com/aliasing/AD102.html

This might illustrate the advantage of 14 bit cf 12 bit : http://www.earthboundlight.com/photo...us-12-bit.html

Last edited by Ian Robinson; 07-09-2008 at 01:36 PM.
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Old 07-09-2008, 01:26 PM
Craig_L
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Hi Mathew,

I have both the 400D and the 450D, 12 and 14 bit but the 450 is modded and not the 400 so I don't know how good the comparison would be.

Any targets in mind?

Craig
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Old 07-09-2008, 02:20 PM
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RB (Andrew)
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Quote:
Originally Posted by g__day View Post
I presume the extra 2 bits giving you 2^2 = 4 four more levels of shade will produce some nice results - I am wondering how nice!

Anyone that could help - greatly appreciated!

Thanks,
Matthew
Quote:
Originally Posted by Ian Robinson View Post
power(2,12)=4096 bits
power(2,14)=16384 bits
difference = 12288 bits
LOL Matt, 4 four more levels of shade won't make much of a difference at all !!

A 14 bit A/D converter gives you 14 bits per channel (RGB channel) shades of grey.

Ian is correct in what he posted but he means levels not 'bits', so a difference of 12288 levels.

Technically 14-bit A/D conv, means the camera records up to 16,384 grey shades per channel and allows the camera to record images with better and more accurate gradations of tones and colours.
What this means is basically you have a wider dynamic range to play with and ability to stretch the data.

Whether it will make a difference in your astro images in the end basically depends on your skills in processing and the ability of your monitor and printer to display the difference but 14 bits will give you a wider dynamic range to manipulate the data that's for sure.
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Old 07-09-2008, 02:23 PM
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g__day (Matthew)
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Thanks guys - good thought. On showing a side by side comparison - I'd suggest a target with alot of faint detail or High Dynamic range. So several suitable targets leap to mind - M16, M20 or M42 (Eagle, Triffid or Orion nebulae). A shots between 6 - 12 minutes on each camera would be ideal (so long as light pollution doesn't ruin things) - I'd love to see the difference of 12 vs 14 bit RAW (both before and after image processing). To me the extra stops could be very useful to an astro-photographer dealing with many interesting things that are very faint.
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Old 07-09-2008, 02:46 PM
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Look at this page
http://www.astrosurf.com/buil/eos40d/test.htm
He compares the 12 to 14 bit converters. The english version is spread through the page.
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Old 08-09-2008, 12:28 PM
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g__day (Matthew)
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Very nice find - thank you!
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