If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#51
|
|||
|
|||
Canon 6D
|
#52
|
|||
|
|||
Canon 6D
Robert Coe wrote:
On Thu, 20 Sep 2012 17:50:08 -0800, (Floyd L. Davidson) wrote: : Alan Browne wrote: : On 2012.09.20 02:06 , nospam wrote: : : they can skip it in the low end models, since the target market : probably doesn't care about those features. : : I disagree. There are likely a lot of people at the "lower end" who : would enjoy the GPS benefit of tagging and the WiFi benefit of quick : uploading. That would be worth a small premium in those models. : : Indeed the first cameras to sport GPS widely were P&S. : : I tend to agree with that concept. More over, I don't : think professionals will find WIFI as useful as others : expect. : : It's something that works just fine if there are only : one or two being used. But just imagine a PJ showing up : at a press conference expecting rapid transfer of : images... and discovering that there are 47 other PJ's : with wireless enabled. Oppps. : : Only 3 of the channels in the 2.4Ghz band can be used at : the same time, and all it takes is one fool choosing a : channel 3, as an example, to wipe out the entire lower : half and limit it to only two channels at a time. With : 30 or 40 users standing in line for packet time, data : transfers will be just exceedingly slow! A dialup modem : from a laptop would be way faster! It's been several years since I've been heavily involved in setting up Wi-Fi networks, but my recollection is that the client rarely gets to choose. If the access point is broadcasting on Channel n, that's what gets used. The client of course uses the channel configured at chosen AP. But the client does choose which AP, and in most cases where a camera is used with wireless the AP will in fact be specifically set up by the photographer. In a situation where there are multiple pros who might find wireless useful, it wouldn't make sense for all of them to connect to a single AP. BTW, while it's true that there are only three channels that don't bleed over onto each other, it's an exaggeration to say that only three channels can be used at the same time. Only three channels with high signal strength can be used at one time. A weaker signal will not interfere at all, but it also will not be usable itself. The point is that if multiple cameras all equipped with wireless are set up in a line, the data transfer rates can at most equal the total rate that three of them will have. If they are all on one channel, the total rate will be the same as if only one camera is there. (And will necessarily be true if they all connect to a single AP.) If the connections are spread over multiple AP's, each on different channels, the total transfer rate will never exceed the transfer rate that only 3 cameras can achieve. That can be accomplished by choosing channels 1, 6 and 11 (or 12). If a forth AP is set for channel 3, then it will necessarily share the bandwidth with units on channels 1 and 6 equally, and only 1 of those plus the unit on channel 11 can operate simultaneously. An example would be a press conference... where there might be far more than 3 or 4 photographers, but the data rate from using wireless will be limited to 3 at any one time. -- Floyd L. Davidson http://www.apaflo.com/ Ukpeagvik (Barrow, Alaska) |
#53
|
|||
|
|||
Canon 6D
On 2012.09.22 07:16 , Robert Coe wrote:
It's been several years since I've been heavily involved in setting up Wi-Fi networks, but my recollection is that the client rarely gets to choose. If the access point is broadcasting on Channel n, that's what gets used. The access point chooses. That can be automatic or set to a specific channel. BTW, while it's true that there are only three channels that don't bleed over onto each other, it's an exaggeration to say that only three channels can be used at the same time. I notice that in the homes around here there are about 8 WiFi stations and they all use one of 3 channels (1,6, 11). So I set my station to the middle of 3 unused channels (9). -- "There were, unfortunately, no great principles on which parties were divided – politics became a mere struggle for office." -Sir John A. Macdonald |
#54
|
|||
|
|||
Canon 6D
Alan Browne wrote:
On 2012.09.22 07:16 , Robert Coe wrote: It's been several years since I've been heavily involved in setting up Wi-Fi networks, but my recollection is that the client rarely gets to choose. If the access point is broadcasting on Channel n, that's what gets used. The access point chooses. That can be automatic or set to a specific channel. The AP is not "automatic". The client can be automatic, by using a name rather than a channel. BTW, while it's true that there are only three channels that don't bleed over onto each other, it's an exaggeration to say that only three channels can be used at the same time. I notice that in the homes around here there are about 8 WiFi stations and they all use one of 3 channels (1,6, 11). So I set my station to the middle of 3 unused channels (9). The others apparently know what they are doing. The channel separation in the 2.4GHz band is 5 Mhz, but the actual bandwidth used by different authorized classes of service is often much greater. The WIFI 802.11g standard uses a 22 Mhz channel with 5 Mhz separation. Thus only 3 of the WIFI 802.11G 2.4GHz channels available in the US can be used at once on a non-interfering basis. A unit assigned to Channel 6 will interfere with any unit assigned to Channels from 2 to 9. The upper limit of bandwidth needed for a unit centered on Channel 1 is using the bandwidth of Channel 3. The lower limit of bandwith needed for a unit centered on Channel 6 is using the bandwidth of Channel 4. Here is a chart showing which channels are used by a WIFI unit assigned to a specific channel: Assigned / Used Assigned / Used 1 (-1) to 3 7 5 to 9 2 (0) to 4 8 6 to 10 3 1 to 5 9 7 to 11 4 2 to 6 10 8 to 12 5 3 to 7 11 9 to 13 6 4 to 8 12 10 to 14 Here's an ASCI graphic (that will only look right if you use a monospaced font): -15 -10 -5 0 +5 +10 +15 MHz 3 4 5 6 7 8 9 Channel | | | | | | | \__22 Mhz Used Bandwidth__/ 802.11G Bandwidth for Channel 6 \__22 Mhz Used Bandwidth__/ BW Channel 7 \__22 Mhz Used Bandwidth__/ BW, Ch 8 \__22 Mhz Used Bandwidth__/ BW, Ch 9 As you can see, the upper 7 Mhz of the bandwidth required for an AP assigned a center frequency of Channel 6 is the same as the lower 7 Mhz bandwidth used by an AP assigned to a center frequency of Channel 9. To get the 802.11G 5 Mhz spacing between channels the closest assignment above Channel 6 is at Channel 11. Extend the diagram and you'll find that Channel 9 is also sharing significant bandwidth with channels 10, 11 and barely with channel 12. Hence the use of channel 9 interferes with both channel 6 and channel 11. And they interfere with you on channel 9. When you are not using your unit, a single neighbor on channel 6 can get full time use of the bandwidth. At the same time another neighbor on channel 11 can get full time use of the bandwidth. (And if there are two units using each channel, the two share each channel equally.) But when you crank up and put traffic on channel 9 you share bandwidth with channel 6, and each of you gets half as much time. The same is true of channel 11. So if *either* of those channels is actually in use you will not get full time use of the bandwidth. If both are in use you will at most get about 1/3 of the shared time, instead of 1/2 that you'd get if you were using either channel 6 or 11. -- Floyd L. Davidson http://www.apaflo.com/ Ukpeagvik (Barrow, Alaska) |
#55
|
|||
|
|||
Canon 6D
Floyd L. Davidson wrote:
[WiFi] It's something that works just fine if there are only one or two being used. But just imagine a PJ showing up at a press conference expecting rapid transfer of images... and discovering that there are 47 other PJ's with wireless enabled. Oppps. Only 3 of the channels in the 2.4Ghz band can be used at the same time, and all it takes is one fool choosing a channel 3, as an example, to wipe out the entire lower half and limit it to only two channels at a time. With 30 or 40 users standing in line for packet time, data transfers will be just exceedingly slow! A dialup modem from a laptop would be way faster! A dialup modem manages an upload of at most 33.6 kBit/s (for a 56k modem). A WiFi (SOTA 2003) manages between 6 and 54 MBit/s on a channel. 6 MBit/s = 6144 kBit/s 6144 kBit/s / 48 PJs = 128 kBit/s (assuming there is only one single channel available and it's at it's slowest speed because the modem is far away behind thick walls. I.e. worst case) 128 kBit/s = 3.8 * 33.6 kBit/s = A dialup modem at it's best would be about 4 times slower than WiFi at it's very worst --- even worse than the scenario Floyd painted. Not that the truth or reality would have any chance against a pointless Floyd rant filled with speculation and missing basic knowledge. Since the press conference will have enough base stations at close distances to the PJs, we can assume 2-3 channels at 54 MBit/s, giving 48 PJs (wow, must be a huge press conference!) 3,3 MBit/s. (which is quite more upload per PJ than most households have, even on fast connections). A 22 MPix JPEG will take ~15 seconds, but you'll probably reduce the size anyway, and get 3 or 4 seconds/JPEG. -Wolfgang |
#56
|
|||
|
|||
Canon 6D
Alan Browne wrote:
On 2012.09.22 07:16 , Robert Coe wrote: It's been several years since I've been heavily involved in setting up Wi-Fi networks, but my recollection is that the client rarely gets to choose. If the access point is broadcasting on Channel n, that's what gets used. The access point chooses. That can be automatic or set to a specific channel. BTW, while it's true that there are only three channels that don't bleed over onto each other, it's an exaggeration to say that only three channels can be used at the same time. I notice that in the homes around here there are about 8 WiFi stations and they all use one of 3 channels (1,6, 11). So I set my station to the middle of 3 unused channels (9). Clever, then your signal interferes (and is interfered by) channels 6 and 11. There's a reason they only use 1, 6 and 11 .... as only these are fully decoupled between each other. -Wolfgang |
#57
|
|||
|
|||
Canon 6D
Wolfgang Weisselberg wrote:
Floyd L. Davidson wrote: It's something that works just fine if there are only one or two being used. But just imagine a PJ showing up at a press conference expecting rapid transfer of images... and discovering that there are 47 other PJ's with wireless enabled. Oppps. Only 3 of the channels in the 2.4Ghz band can be used at the same time, and all it takes is one fool choosing a channel 3, as an example, to wipe out the entire lower half and limit it to only two channels at a time. With 30 or 40 users standing in line for packet time, data transfers will be just exceedingly slow! A dialup modem from a laptop would be way faster! A dialup modem manages an upload of at most 33.6 kBit/s (for a 56k modem). A WiFi (SOTA 2003) manages between 6 and 54 MBit/s on a channel. 6 MBit/s = 6144 kBit/s 6144 kBit/s / 48 PJs = 128 kBit/s (assuming there is only one single channel available and it's at it's slowest speed because the modem is far away behind thick walls. I.e. worst case) 128 kBit/s = 3.8 * 33.6 kBit/s = A dialup modem at it's best would be about 4 times slower than WiFi at it's very worst --- even worse than the scenario Floyd painted. Not true. Not that the truth or reality would have any chance against a pointless Floyd rant filled with speculation and missing basic knowledge. Apparently I hit it just about on the head with the 48 PJs. If the bit rate works out to 4x, then it's probably just about the right number. There is *never* going to be a smooth transition between any two of the 48 clients. Instead there will virtually always be contention, and instead of being 4 times faster than a dialup, it would probably be about 10 times slower... at best! Since the press conference will have enough base stations at close distances to the PJs, we can assume 2-3 channels at 54 MBit/s, giving 48 PJs (wow, must be a huge press conference!) 3,3 MBit/s. (which is quite more upload per PJ than most households have, even on fast connections). A 22 MPix JPEG will take ~15 seconds, but you'll probably reduce the size anyway, and get 3 or 4 seconds/JPEG. Never tried any of this stuff, have you! :-) -- Floyd L. Davidson http://www.apaflo.com/ Ukpeagvik (Barrow, Alaska) |
#58
|
|||
|
|||
Canon 6D
Floyd L. Davidson wrote:
Wolfgang Weisselberg wrote: Floyd L. Davidson wrote: It's something that works just fine if there are only one or two being used. But just imagine a PJ showing up at a press conference expecting rapid transfer of images... and discovering that there are 47 other PJ's with wireless enabled. Oppps. Only 3 of the channels in the 2.4Ghz band can be used at the same time, and all it takes is one fool choosing a channel 3, as an example, to wipe out the entire lower half and limit it to only two channels at a time. With 30 or 40 users standing in line for packet time, data transfers will be just exceedingly slow! A dialup modem from a laptop would be way faster! A dialup modem manages an upload of at most 33.6 kBit/s (for a 56k modem). A WiFi (SOTA 2003) manages between 6 and 54 MBit/s on a channel. 6 MBit/s = 6144 kBit/s 6144 kBit/s / 48 PJs = 128 kBit/s (assuming there is only one single channel available and it's at it's slowest speed because the modem is far away behind thick walls. I.e. worst case) 128 kBit/s = 3.8 * 33.6 kBit/s = A dialup modem at it's best would be about 4 times slower than WiFi at it's very worst --- even worse than the scenario Floyd painted. Not true. In which case you would be able to show us the math and the circumstances, under which that would not be true. But you're just handwaving ... very wildly. Not that the truth or reality would have any chance against a pointless Floyd rant filled with speculation and missing basic knowledge. Apparently I hit it just about on the head with the 48 PJs. So ... which press conference was that? Or did you pull that number from your ass? If the bit rate works out to 4x, then it's probably just about the right number. There is *never* going to be a smooth transition between any two of the 48 clients. Obvious. None of the cameras are interested in talking with another camera. And that being true there will never be any kind of transaction, smooth or otherwise, between any 2 of the 48 clients. Instead there will virtually always be contention, and instead of being 4 times faster than a dialup, it would probably be about 10 times slower... at best! So 3 channels at 54 MBit/s can't keep up with 48 clients which sporadically try to pass data through them to the outside. I see. I wonder how they managed with 10 MBit ethernet and a bunch of computers on the same cable ... Since the press conference will have enough base stations at close distances to the PJs, we can assume 2-3 channels at 54 MBit/s, giving 48 PJs (wow, must be a huge press conference!) 3,3 MBit/s. (which is quite more upload per PJ than most households have, even on fast connections). A 22 MPix JPEG will take ~15 seconds, but you'll probably reduce the size anyway, and get 3 or 4 seconds/JPEG. Never tried any of this stuff, have you! :-) No, I've never been to your mythical press conference with 48 PJs all using WiFi, as one of the PJs, with a network set up as incompetently as you describe --- probably because *you* don't get to set up wireless networks at something more important than a cleaning brigade for washing the walls behind the mirrors. -Wolfgang PS: Unless you can provide proof, it's EOD. |
#59
|
|||
|
|||
Canon 6D
In article , Floyd L. Davidson
wrote: It's been several years since I've been heavily involved in setting up Wi-Fi networks, but my recollection is that the client rarely gets to choose. If the access point is broadcasting on Channel n, that's what gets used. The access point chooses. That can be automatic or set to a specific channel. The AP is not "automatic". some are. |
#60
|
|||
|
|||
Canon 6D
nospam wrote:
In article , Floyd L. Davidson wrote: It's been several years since I've been heavily involved in setting up Wi-Fi networks, but my recollection is that the client rarely gets to choose. If the access point is broadcasting on Channel n, that's what gets used. The access point chooses. That can be automatic or set to a specific channel. The AP is not "automatic". some are. Define "automatic"... -- Floyd L. Davidson http://www.apaflo.com/ Ukpeagvik (Barrow, Alaska) |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Nikon D600 | Me | Digital SLR Cameras | 4 | September 22nd 12 10:43 AM |
First images of Nikon D600 with 24 MP FX sensor | Chris Malcolm[_2_] | Digital Photography | 63 | July 10th 12 02:07 AM |
First images of Nikon D600 with 24 MP FX sensor | Wolfgang Weisselberg | Digital Photography | 0 | June 24th 12 07:27 PM |
First images of Nikon D600 with 24 MP FX sensor | Wolfgang Weisselberg | Digital Photography | 0 | June 24th 12 01:35 AM |