July 28, 2014, 06:31:48 PM

Author Topic: Can Canon deliver a FF sensor that is class leading?  (Read 8036 times)

wickidwombat

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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #75 on: June 09, 2014, 07:10:24 AM »
At the extreams of contrast, yes I agree with you. But in generall use (99% of the time) I would say taht a few stops of shadow area pull ability isn't going to be a game changer. If anything, it's a just a bit more convienient when poor technique over steps it's mark.

At least for what I do I can say this is not true - I'm taking wildlife pictures at noon all the time, and 15 ev of Magic Lantern the subject can be in the shade, the sky doesn't clip and I can still get ok resolution out of the shadows with the 6d. I now also often take backlit shots with the subject on sunset, also with enough shadow resolution and no sun clipping. This is not just my subjective impression, but I can check the scene dr with ML's raw histogram.

Admittedly, you can also just use high dr as "isoless" lazy exposure and/or avoid extreme postprocessing hassle to pull up the last shadow bits or desperately try to recover the whites...

... but now that I know higher-dr capability I'd really switch systems if you'd try to take ML away from me :-). 11.5ev (6d native) and ~15ev (ML dual_iso 100/1600) is a *big* real world difference if you shoot scenes you cannot bracket-hdr.

ok how do you process a dual iso shot i took a couple to test it out and they look like junk scanlines arcade games from the 80s

 :-[
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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #75 on: June 09, 2014, 07:10:24 AM »

Marsu42

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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #76 on: June 09, 2014, 08:41:42 AM »
ok how do you process a dual iso shot i took a couple to test it out and they look like junk scanlines arcade games from the 80s


You need to run a post-processing utility "cr2hdr" over the file, it assembles the interlaced picture to a normal one. Don't be afraid to use an internet search engine or look at the ML forum :-> .. http://www.magiclantern.fm/forum/index.php?topic=7139.0

http://rohidassanap.wordpress.com/2013/08/10/guide-to-using-dual-iso-mode-on-your-canon-5d-mark-iii/

justaCanonuser

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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #77 on: June 12, 2014, 03:22:19 AM »
Pulse tube or Gifford-McMahon refrigerator. Both can reach sub-liquid He-4 temperature levels (about 1 Kelvin) and they work with a closed He gas cycle that does not need any refill. This cooling technology is already applied in satellites, low temp labs and  (I am not 100 % sure) in modern MRIs.

The chiller we use is a Gifford McMahon-type cryocooler.  It still needs occasional makeup and purging, though, so the vendor needs to bring in a dewar of LHE periodically. Good to know there are more efficient systems out there.  The 'kaboom' actually occurred during initial system charging.  Spent millions on the high T magnet and facility (copper in all the walls, extra I-beams under the floor to support the several-ton magnet, etc.), only to have it need replacement before it could be used. 

But we digress...   ;)

Sorry for the late reply, I was too busy. I remember those sorts of kabooms when I was actively researching in a lab (today I am editor of a German physics magazine and therefore sort of theoretician). But we digress indeed - good luck with your equipment!
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NancyP

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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #78 on: June 12, 2014, 10:23:49 AM »
neuroanatomist, please explain WHY someone would stick liquid helium (liquid nitrogen, liquid oxygen, etc) into a sealed and unvented container? Was there a vent that was clogged, and what could clog it firmly enough that the container blew before the clog blew? I understand that helium is getting harder to obtain, and much more expensive - true?

Liquid helium cooling is the way to go!
Liquid cooled cameras.  Sealing to keep the liquid *in* instead of out.   ;D

Nope, that's a really bad idea.  Helium used for liquid cooling does evaporate as gas, and needs to be replenished.  Know what happens when you replenish LHE into a sealed container?  I can't speak for a camera, but I know what happens when the pressure release valve on an MRI is left closed when the LHE is being refilled.  KABOOM.  Lots of structural damage.  Fortuntely it happened in the middle of the night when no one was around.

neuroanatomist

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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #79 on: June 12, 2014, 10:56:13 AM »
neuroanatomist, please explain WHY someone would stick liquid helium (liquid nitrogen, liquid oxygen, etc) into a sealed and unvented container? Was there a vent that was clogged, and what could clog it firmly enough that the container blew before the clog blew? I understand that helium is getting harder to obtain, and much more expensive - true?

Well, you'd stick it in there to keep something (super)cold.  You shouldn't keep sticking it in there after the container is full and withouth having opened the pressure relief valve, though…that's technician error and the result is an instrument that's FUBAR.
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mackguyver

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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #80 on: June 12, 2014, 11:13:26 AM »
So now we're talking about liquid nitrogen and freezing stuff.  Cool 8)
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Re: Can Canon deliver a FF sensor that is class leading?
« Reply #80 on: June 12, 2014, 11:13:26 AM »