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Messages - noisejammer

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106
EOS Bodies / Re: Need seasoned advice - keep 5D Mark II or NO?
« on: February 09, 2013, 09:19:44 AM »
I'm something of a luddite - I figure that as long as my camera isn't the determining factor in my image quality, it doesn't need upgrading. Although I own a 1D4, my 5D2 gets far more use.

Beside this, after deducting the price of your 24-105 the 5D2 effectively cost you $1300... it isn't going to depreciate more than $300 over then next couple of years. Let's say you decide to upgrade then - you get the use of an excellent camera for 40 cents a day.... How can you go wrong? (I'm guessing here but I really expect the 6D and 5D3 to loose half their value over then next year or so - it happens when you buy things that are close to the bleeding edge.)

107
Canon General / Re: Why did you choose Canon?
« on: January 27, 2013, 09:29:46 PM »
I purchased a 40D several years ago with the intention of using it for astrophotography. Although Nikon had similar offerings, the wisdom was that Canon's in-camera processing was gentler which would mean faint stars were less likely to be nailed.

As things turned out, I only used the 40D for lunar shots - I bought a cooled CCD camera for faint object astrophotography. Of course, I bought a couple of lenses which more or less cemented the relationship and five years down the line, here I am.

It has occurred to me that the reason Nikon systems have better out-of-camera noise remains the same - Nikon is more aggressive with the in-camera processing.

108
EOS Bodies - For Stills / Re: Too much dynamic range?
« on: November 24, 2012, 11:31:32 AM »
...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
...

This is incorrect - if you replaced "bit" with "stop" then it is correct (and it's then obvious why ETTR works too.)

It's easier to consider a 3- or 4-bit digitiser. Let's say it offers 4 bit resolution then the possible counts are 0000 through 1111. This translates to 2^4 or 16 levels. Written the way that Norman stated it, there would only be four distinct levels - this is incorrect (but I understand he meant there would be 16 levels.)

Some things appear to have been glossed over in the discussion. First, the ADC operates on a per-pixel basis.

I've read the DxO tests on various sensors. It is important to remember that the notional dynamic range is referred back to an 8 mp standard. This means that the D800's quoted 14 bits dynamic range is significantly less than 14 bits at a per-pixel level. The 36 mp > 8 mp conversion gains the sensor sqrt(4.5) = 2.1x notional improvement in dynamic range. The 2.1x is slightly more than 1 stop in quoted dynamic range. This means that the true per-pixel dynamic range is about 12.9 stops.

In order to read those 12.9 stops, the ADC needs a bit more resolution than the 13 bits required by the pixel. I'm quite surprised because the 14 bits in the ADC suggests that the entire detection chain has ~1 bit of noise.... It sounds improbable.

Photon shot noise has been commented on briefly. If we assume 13 bits dynamic range and (say) 10% quantum efficiency (pidooma), then the number of photons required to fill a pixel is 10 x 2^13 or 80k. Since shot noise varies with the square root of the number of photons, the pixel could have shot noise of up to 280 photons (rms).

Since 1 bit translates to 80k/8192 = 10 photons and we must have about 6 bits of photon noise at the upper end of the sensor's dynamic range. At the bottom end, the quantum efficiency sets the performance and there must be ~3 bits of noise.

Shot noise alone suggests that the true dynamic range of an image cannot be more than about 8-10 bits. It seems that the only way to improve on this is by greatly enhancing the sensor's quantum efficiency.

To answer the OP's question - photon noise alone suggests that there's not a whole lot of benefit to high resolution ADC. It does allow for more sophisticated noise filtering - presumably at the expense of resolution.

<---- physicst / astronomer

109
Lenses / Re: Your technique for switching lenses in the field?
« on: October 27, 2012, 03:22:00 PM »
I mostly use primes so I do the lens shuffle all the time.
My second set of hands is the protective pouch that came with my RRS ballhead. I usually have a Think Tank pouch mounted outside my rucksack, so the drill goes something like this
1. Put the new lens in the tripod pouch
2. Remove the rear lens cap from my pocket
3. Remove the lens, cap it's rear surface and drop in in the TT pocket
4. Remove the rear cap from the new lense, install it and drop the rear cap in my pocket.

I chose pockets that are big enough so that the lens hoods stay on facing the direction they are used in. The lens goes in front element first but the hood prevents any chance of damage to the front element.

Once everything's settled, I may remove the rear cap from the old lens and give it a blast with a rocket blower - this depends on conditions.

When it's very dusty, you can pretty much do the job inside a plastic bag but it's easier if you sit down. If it's raining, I don't change lenses unless I can get shelter and dry the camera and lens before removing the lens.

110
EOS Bodies / Re: 1dmk4 vs 5d3
« on: September 11, 2012, 11:49:13 PM »
I have a 5D2, 1D4 and have used a 5D3 quite a bit.
On the whole, the per pixel noise is quite similar. Of course, the 5D3 produces higher resolution images but this is at the expense of image scale. If you compare like with like, the noise is similar.

The big thing that the 1D4 can do is shoot all day. I recently ran 2200 frames at an airshow and there was still plenty of juice in the battery. Weather sealing is good to have but I don't like getting rained on. 10 fps is good to have if you need it (and sometimes I do.) A deep buffer just means you need to time your button presses :D

It helps to be able to autofocus at f/8. I've only used it once but when I needed it I could do it.

From an economic point of view, I expect that the 1D4 is going to drop less in value than the 5D3. This may be significant when you decide to upgrade, be it 2 or 3 models down the road.

111
Lenses / Re: What lenses do you own?
« on: September 11, 2012, 11:36:53 PM »
Hmm lots of lenses, 35 years and some tips.

1. Lenses that I use a lot...

Zeiss - 21/2.8, 25/2, 28/2, 35/1.4, 50/2 MP, 100/2 MP.

Canon - TS-E 17, 70-200 II, 400/4 DO

Occasional use - OM 55/1.2, 8-15L, OM 16 FE

2. Time behind the eyepiece - 35 years.

3. Tips

a. Get a full frame camera
b. Get a 28mm manual focus lens (say an OM 28/2.8 ) and a really good adapter. Fotodiox Pro is the one to spring for.
c. Learn to visualise what's going to be in the field of view, how to estimate your exposure and how to position yourself to get the best composition. Once you can do these things without thinking, you are ready for a second lens. I'd get a really good 50mm - Zeiss are bringing one out in about a year - that's about the right time frame.

d. It takes time to learn what a lens can do. DONT buy too many lenses at one go, even if you can afford it. One or two lenses a year is probably about right.
e. Take lots of pictures, take notes too, read them from time to time.
f. ETTR about 1 stop and pull it back in post.

g. Start a flickr page and use it to see how your technique is improving.
h. Look at other photographers images and see whether you know how to do what they've presented.
i. Learn to use Lightroom, buy the Nik Software bundle.

j. PRACTICE and HAVE FUN.

Oh yes.... FART before you press the button...

F ind a subject that catches your eye
A nalyse why it works for you
R efine your composition, exclude the garbage
then Trip the shutter.

:D

112
Software & Accessories / Re: Photoshop CS6 on sale
« on: September 02, 2012, 10:07:30 PM »
B&H offered a single-shot promo code to people who had purchased an Adobe product from them in the past. I jumped at the chance and now have and received CS6 on Thursday. $400 savings are not to be sniffed at :)

113
Software & Accessories / Re: ND Filters for Photography
« on: September 02, 2012, 09:36:58 PM »
OP - Since you're after an 8x, I assume it's 3 stops you want.

If you're going for a Lee filter, be wary that they specify their filters in terms of optical density. So 0.3 = 1 stop, 0.6 = 2 stops, 0.9 = 3 stops etc.

The Lee Big Stopper (mentioned above) has an optical density of 10 (give or take) which equates to 10 stops. 10 stops means your shutter is open for 1000x longer than it would be without the filter... This can be a help or a hindrance.

On colour cast - up to 3  stops, colour cast is not much of a problem (except with Cokin) but my experience has been that all filters exhibit some colour cast. The solution is to make a test image using something like a X-rite Color Checker. As a rule, you can get away with somewhat higher ISO so the photographic process doesn't need to take forever.

114
EOS Bodies / Re: 5D3 Viewfinder vs LiveView
« on: August 23, 2012, 08:20:00 PM »
Lloyd Chambers commented on having difficulty using the lcd to focus accurately. He put it down to a change in the way the lcd image is processed. Apparently, the 5D2 used alternating lines which enhanced the contrast while the 5D3 does not.

It's likely that Magic Lantern will be released for the 5D3 next. (sorry - I have no idea when.) When it is, you will be able to use the built in focus peaking with live view.

115
Lenses / Re: Zeiss 2/25 or 2/35 for everyday use in APS-C?
« on: July 26, 2012, 11:24:26 PM »
Given the investment you're looking to put in to Zeiss glass you'd be well served to subscribe to DigiLloyd.  He has extensive reviews of every lens you've discussed.

I'll second that suggestion. Lloyd's "Zeiss Guide" has some good insight into all the ZE / ZF lenses.
IMO, it's well worth the fee.

116
Third Party Manufacturers / Re: 3rd Party ... Bodies??
« on: July 26, 2012, 11:17:36 PM »
I'm depressed at the low-ISO performance offered by Canon's latest. Since there's no improvement, I'm stuck with a 1D4/5D2 combination for at least the foreseeable future. Canon doesn't care - I have too many EF bayonet lenses to really give a lot of thought to jumping ship.

Because of this, I'd be quite interested but also cautious. Assuming the camera offered what I want and had reasonable ergonomics, I'd give it a go.... but since I don't trust Canon's marketing department (let alone Sigma's) I would want to see the performance before I put my money down.

I think the problem is that there's a lot more to making a usable camera than just obtaining a decent sensor and building a box around it.... witness the SD1 or M9 to which you refer. Leica can get away with it, a third party supplier can't.


117
Lenses / Re: Zeiss 2/25 or 2/35 for everyday use in APS-C?
« on: July 26, 2012, 08:28:49 AM »
I'm also inclined to think you should sit back until you have a ff camera... but that's not what you asked. Bear in mind that my comments refer to their use on a 5D2, principally using live view. I do not believe it's possible to achieve accurate focus (that does justice to these lenses) using the viewfinder.

Among others (you have these), I own the the 2/25, the 1.4/35 and the 2/35. I find each is different.

The 2/35 has a wonderful 3D-like image. The 1.4/35 has spherical aberration when wide open (this produces a glow around your subject and is probably why you found it difficult to focus.) It's the equal of the 2/35 at f/2.8 and is considerably sharper at f/8 - f/11. The 2/25 is the sharpest of the bunch - if anything it's at least as sharp as my 2/50.

If I was buying one Zeiss for a full frame camera, it would be the 1.4/35. For a 1.6 crop, I think the 2/25 might be a slightly better choice however you're going to need a Zacuto Z-finder Pro 3x and a ff camera to get the most from it.

Edit - Just a comment to BozillaNZ... it's easy to outperform autofocus if you spend the time learning the technique. Of course, the point-and-grunt interface has it's place... you're welcome to it.

118
At low speed and reasonable ISO, the 5D3 has essentially the same image performance as the 5D2... so why not continue offering a 5D2 at $2k... perhaps migrate to a 60D style body and cut the production cost.... add some arbitrary firmware, a tilt screen and built in flash to make it more attractive.

Maybe in a year you can offer a plastic model using the 5D3's sensor (but that strikes me as improbable.)

The thing is to sell lenses not bodies. It's lenses that keep your customers loyal.

119
EOS Bodies / Re: 2023: a look into Canon's flagship body
« on: July 16, 2012, 11:12:14 PM »
Of course it's a joke thread but how about some serious ideas...

1. The viewfinder will stay but it's likely to be electronic, it will out-resolve the eye and and its sensor will get light through a pellicle.

2. There will be an electronic shutter using something like a Pockel's cell.

3. The sensor will be a flip chip which will improve sensitivity by about two stops.. so 102k ISO will be usable.

4. The dynamic range will be slightly better but unless Bayer masks are abandoned it'll probably not be more than 1 stop. If they are abandoned - say for a true 3- or 4-channel system - you can add another 2 stops immediately... this interacts with point 3 so that 102k would have the noise of about current 6400 ISO.

5. Resolution will be matched to lens performance... so perhaps about 8 microns resolution in the image (equivalent to 54 mp today.)

6. Pixels will not be square... I'm thinking hexagons or maybe the interlaced octagon / square arrangement that Fuji had years ago.

7. Battery life will be 30% better.

8. Lenses will focus in an blink of the eye and autofocus will still get it wrong.

9. f/1.2 lenses might actually offer some benefit.

10. I will still ditch 99% of my images.

120
Animal Kingdom / Re: Ribit!
« on: July 08, 2012, 07:38:31 AM »
I'll play.... I found this pair in Tobermory


POG Frog by NoiseJammer, on Flickr

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