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Messages - NormanBates

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61
Canon General / Re: DxO Mark explained
« on: December 17, 2012, 03:52:53 AM »
Comparing noise at different resolutions makes no sense whatsoever. My one pixel camera has no noise at all, even at very high ISO; will you buy it from me?

62
Lenses / Re: Which (if any) non-L lenses are enviro-sealed?
« on: December 14, 2012, 05:29:22 AM »
I would like to learn more about weather sealing. Like: what is good and what is not so good? what's the difference between o-ring and foam?
Any links? pics? threads?
Thanks

64
EOS Bodies - For Stills / Re: Would switching to FF hurt my macro??
« on: December 06, 2012, 03:56:58 AM »
OK, so it has already been established that the crop factor doesn't help the 7D, but the pixel density does.

Now, say you're worried about depth of field: when you move to FF, it will be significantly narrower than on APS-C. Can you close the iris to compensate, or will diffraction be a problem if you do? I mean: if I'm shooting f/11 on APS-C because above that I get diffraction and the image comes out soft, when I move to FF, will I want to stay at f/11, or will f/16 suddenly be acceptable?
Is the diffraction limit the same for APS-C and for FF? I'm guessing it is, since it's a characteristic of the lens, but I'm too busy today to think this through myself  ;D

65
Canon General / Re: soon to be a 'Canon/DSLR newbie' here!
« on: December 05, 2012, 04:42:27 AM »
To get an idea about how cameras and lenses work, what you need and why:
http://www.similaar.com/foto/tuten/index.html

Some recommendations of lenses for Canon, on a budget:
http://www.similaar.com/foto/equipment/us_lensc.html

66
EOS Bodies - For Video / Re: Quick help needed: Manual White Balance
« on: November 26, 2012, 04:15:09 PM »
In my case... Precisely because I want all my takes to look the same, and I know that matching them in post leads to reduced image quality --> I run this custom white balance method every time I change lenses, and every time I add or take away ND filtration.

Some lenses (specially the vintage ones I use) have a slight color tint. And my ND filters give the image a greenish tone (specially with over 3 stops of ND, be it on a single filter, or stacking several of them).

I use this custom white balance method instead of dialing in a K value because with custom white balance you not only set the K, but also the green-magenta bias (which is what my ND filters require).

67
EOS Bodies - For Stills / Re: 5D MARK III with 50 mm f/1.2 performence
« on: November 26, 2012, 09:14:15 AM »
My son, born November 14, 2012, 20 hours old, f1.2 @ 1/60, Canon 5D3, funky indoor hospital room lighting.

absolutely gorgeous pic

Quote from: jimy444
so my goal is to pick up the fastest 50mm that will focus very fast with the 5dmark III considering that he is never still!
attached a few pictures for the kind of pictures i take.

nice pics too

you are describing the 50 f/1.2L

68
EOS Bodies - For Stills / Re: Too much dynamic range?
« on: November 26, 2012, 03:27:46 AM »
Yes, that's a good example. The sun may be brighter here in southern Spain, and you may not want a wedding dress to blow up like that kid's shirt, and the broom suit may be black instead of gray (look at the shoe; that's black, the suit is not), and then you may be in trouble if your camera is DR-challenged.

Not the most common scenario, by a long shot, but I never said you always need lots of DR. Just that you may sometimes need it.

69
EOS Bodies / Re: Canon's roadmap
« on: November 26, 2012, 03:05:37 AM »
My vote:
The price of the 5D3

71
EOS Bodies - For Stills / Re: Too much dynamic range?
« on: November 24, 2012, 12:59:59 PM »
* I definitely meant stops. I chose an example with a 14-bit ADC and a sensor with 14-stops of DR to make my life easier, but I meant stops. "One stop brighter" means "twice as many photons", and the ADC is linear (it counts electrons using a linear scale), that's what makes both sides match.

* I'm talking about per-pixel DR. Matching resolution makes a lot of sense when you're comparing cameras, since it's the final image that you care about, not each individual pixel. But it makes the technical discussion a lot more complex, because you have to take into account how downsampling reduces noise. I'd rather leave that out right now.

* The per-pixel DR measurement that dxomark got was 13.44 stops http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/(appareil1)/834%7C0/(brand)/Nikon/(appareil2)/795%7C0/(brand2)/Canon)
I'm also puzzled at how the D800 can manage that with a 14-bit ADC. As I said above, I'd be expecting to see a lot of posterized noise in the shadows, but it's not there.

* No idea about how quantum efficiency affects all this. I never thought about it.

72
EOS Bodies - For Stills / Re: Too much dynamic range?
« on: November 24, 2012, 07:49:41 AM »

As far as I understand each camera applies it's own tone curve to the image, or am I wrong?

Initially I wanted to be brand-agnostic and instead of discussing specific sensors, I want to identify what really matters for my needs (and maybe many others). I'm not able to tell what it is right now, so everyone's input is appreciated  :)

Not really: each camera applies its own tone curve, but that happens *after* the ADC has done its job, and, as far as I know, all cameras have linear ADC (ok, some have piecewise linear, but that's actually a change for exposure, not for the ADC, which is still linear; and I'm not sure any of the ones we're talking about actually does that).

The fact that light is linear but you see it as log makes this very inefficient, and it is the reason that, for example, some Nikon cameras (low to mid-end) apply a log curve even in their RAW files: with linear, you have way more gradation than you need in the highlights, and may still be struggling in the shadows. But even this curve happens after the ADC, so it's not what we are talking about, I think.



As for the need for DR, as I said, it depends on what you do, how much time you have to do it, and how much margin of error. My friend was carrying an extra 5-year-old 12 Mpix camera just in case, because he thought he needed to do so. If you don't think you need it, well, good for you, what can I say?

Now go ask any cinematographer if they think 11 or 12 stops of DR is enough.
(hint: I hardly ever shoot stills, I'm a vidiot)

73
EOS Bodies - For Stills / Re: Too much dynamic range?
« on: November 24, 2012, 03:58:19 AM »
Is there a web-site where I can look at your friend's photos to check why someone chooses high DR cameras?

He's a wedding photographer, I don't think he publishes his pictures online, he gives them to his customers.
But the usual scenario he was referring to was: very sunny day, bride in shiny white, broom in matte black suit with subtle stripes, anything except his fuji (or, now, D800) will result in said suit looking like a black blotch, and there's nothing he can do about it.


Now, back to the technical discussion...


Let me add a twist: the ADC works linearly, but what you see is log

So, if you have a 14-bit ADC (you can count up to 16384)and can record 14 stops of DR, here is how those values will be distributed:

14th stop: 8192 to 16383
13th stop: 4096 to 8191
12th stop: 2048 to 4095
11th stop: 1024 to 2047
10th stop: 512 to 1023
9th stop: 256 to 511
8th stop: 128 to 255
7th stop: 64 to 127
6th stop: 32 to 63
5th stop: 16 to 31
4th stop: 8 to 15
3rd stop: 4 to 7
2nd stop: 2 to 3
1st stop: 0 to 1

So you may actually have very serious issues in the shadows... which I see in the Canons, but not in the D800!

* if you're going to have issues with "too much DR, not enough gradation", they'll be in the very deep shadows, which you wouldn't see anyway if you were shooting with a camera with the same ADC but less DR; your skin tones are unlikely to land anywhere below the 5th stop fro the top, so for them you have way more values than you need (anything above 50 gradations per stop is usually smooth even after heavy grading)

* how come I don't see this in samples from the D800?

75
EOS Bodies - For Stills / Re: Too much dynamic range?
« on: November 23, 2012, 09:21:54 AM »
We are saying the same, I guess I didn't make myself sufficiently clear.

What I mean is that if you add 1 bit to your ADC and instead of having

00 = 0-100 photons in a pixel
01 = 100-200 photons in a pixel
10 = 200-300 photons in a pixel
11 = 300-infinity photons in a pixel

You now have:

000 = 0-42 photons in a pixel
001 = 42-84 photons in a pixel
010 = 84-126 photons in a pixel
011 = 126-168 photons in a pixel
100 = 168-210 photons in a pixel
101 = 210-252 photons in a pixel
110 = 252-294 photons in a pixel
111 = 294-infinity photons in a pixel

...and you have the same read-out noise, you still have the same DR, because neither your full-well capacity nor your read-out noise have changed.

<----- is writing the VHDL code for the FPGA of a motion picture camera

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