Comparing depth of field: iPhone 6 vs camera

▼ In my post about the iPhone 6 as a camera, I talked about how phone cameras have extensive depth of field (objects near and far are both in focus) compared to regular cameras because their sensors are so small. This is even more pronounced in the iPhone 6 because it has a wide angle lens.

So I thought I'd do some comparisons. This is a photo taken with the iPhone 6. The camera is focussed at a distance of maybe 30 centimeters, so the parliament buildings in the distance are out of focus.

This is the same image taken with a Canon SX280 compact camera with a 20x zoom lens. At this wide angle, the minimum aperture of the zoom lens is f/3.5, which lets in only half of the light that the iPhone's f/2.2 lens lets in. The focal length of the lens is just under 6 mm, while that of the iPhone is just over 4 mm. So the sensor of the Canon camera is 1.4 times larger than that of the iPhone. The depth of field looks a bit larger than that of the iPhone.

Last but not least, the same image taken with a Nikon D7100 with an 18-55 mm lens at 18 mm, resulting in an image that's a bit wider than that of the iPhone and the SX280. The aperture is also f/3.5. The sensor of the Nikon is about 4.5 times larger than that of the iPhone, so even though the lens is a bit wider and the aperture a stop smaller, the depth of field is a lot smaller.

Here's two 100% zooms of the middle of the image. Click on the links to load the specified version of the image: iPhone 6, Canon SX280 or Nikon D7100. The ones with the ∞ symbol are focussed at infinity and should provide a sharp image, the others are focussed at 30 cm and should be more or less blurry. I've also included Nikon versions at f/8 and f/22, so you can see the effect of a smaller aperture on depth of field. Select two images of your choice to compare them.

If you compare the f/22 ∞ version to the f/3.5 ∞ or f/8 ∞ version, you'll see that the sharpness actually goes down at very small aperture sizes. Also, the f/8 ∞ is somewhat sharper than the f/3.5 ∞ version—f/8 is usually the sharpest aperture for most DSLR lenses. However, the SX280 already starts to suffer from the diffraction effect at f/8, so the f/8 ∞ version isn't quite as sharp as the f/3.5 ∞ version, and f/8 is the smallest aperture.

Permalink - posted 2015-01-10

IPv6 addresses and AS numbers in 2014

▼ After yesterday's final yearly IPv4 address report, I thought that today, I'd look at the other numbers the five Regional Internet Registries give out: IPv6 addresses and autonomous system (AS) numbers.

I have pages that show the latest numbers for these based on the most recently imported RIR data: IPv6 and AS numbers.

On January first, 2015, the total number of IPv6 addresses given out was 12626804692343330164921678734295040. The number of IPv6 addresses that are currently set aside for regular "global unicast" use is 42535295865117307932921825928971026432, so 0.0296% of the IPv6 address space has been used up so far. (And we can increase the global unicast space by at least a factor six if we need to.)

Of course the number of individual IPv6 addresses is rather meaningless, as each Ethernet or Wi-Fi network uses up 18446744073709551616 of those, even if there's only a single IPv6 system connected to that network. A more meaningful number is the number of /32s given out. A /32 is the size of the address block given to small-to-mediumsize ISPs. The equivalent of 159,372.68 /32s had been given out on January first, 17,916.90 of which in 2014. That number varies a bit from year to year, as some large ISPs or government entities happen to get particularly large blocks of addresses. However, the number of IPv6 address blocks has been growing fairly steadily from 2510 in 2010 to 4536 in 2014, with a total of 22,118 given out on January first. (For IPv4 the total is 145,917, which is 9039 higher than the total on January first, 2014.) Split out per RIR region:

              2014              Totals
RIR      Blocks   In /32s   Blocks   In /32s
 
AfriNIC     62      51.00     449    4617.00
APNIC      528    2663.00    3730   46210.15
ARIN       512    5232.68    4193   41465.94
LACNIC    1208    1363.20    3370    7989.54
RIPENCC   2226    8607.00   10376   59090.03

As every BGP expert knows, in order to advertise those IPv4 and IPv6 address blocks into the global routing system, you need an autonomous system number. Originally, those were 16 bits, allowing for 64512 usable AS numbers. 58,800 of those had been given out by January first, 2015, with the yearly rate being between 3500 and 4000 in recent years and 3056 in 2014.

However, BGP has been modified to work with 32-bit AS numbers. 9475 of those have been given out; 2052 in 2011, 1706 in 2012, 1577 in 2013 and 2988 in 2014. So the total number of AS numbers given out went pas 6000 for the first time last year. The mix is rather different at the different RIRs (ASNs given out in 2014):

RIR        16+32      32    % 32
 
AfriNIC      141     114     81%
APNIC       1299     722     56%
ARIN        1587     421     27%
LACNIC       964     570     59%
RIPENCC     2053    1161     57%

Unlike with the transition from IPv4 to IPv6, where you need to adopt IPv6 in order to talk to other IPv6 users, existing 16-bit AS numbers can be used to talk to routers that have a 32-bit AS number, making for a much easier transition.

Permalink - posted 2015-01-09