I doubt you'll find any detailed information on the differences between iTTL and D-TTL as Nikon has never divulged (to my knowledge) how either of them work (trade secret). All we really know is that they both use preflashes to calculate the exposure prior to taking a picture. I believe the intensity of the preflashes may be different (with i-TTL being brighter); but, that's about all we know. Apparently, D-TTL was not as reliable as iTTL which is why Nikon abandoned it and developed iTTL.
There is also regular TTL which is used by film SLR's. TTL doesn't use preflashes. It measures the light reflecting off of the film plane during the actual exposure and turns the flash off once it determines enough light was received. Apparently, light doesn't reflect off of digital sensors the same way it reflects off of film which is why Nikon (and others) have resorted to preflashes.
The important thing to know is that the camera body determines which is used. Nikon Film SLR's use TTL (with the exception of the F6 which, I believe, also supports iTTL), older Nikon DSLR's (e.g. D100) use D-TTL, and all of the current DSLR's (e.g. D50, D70/s, D80, D200, D2x, etc.) use iTTL. To my knowledge, there are no DSLR's that support both D-TTL and iTTL. I don't know about the D2h; although, I suspect it supports D-TTL.
Older Nikon flashes (e.g. SB-24/25/26/27/28) only support TTL; although, they can be used on your D2h in manual mode. There are a couple of flashes (e.g. SB-28DX, SB-80DX) which support both TTL and D-TTL. The SB-600/800 support TTL, D-TTL, and iTTL. If your D2h supports D-TTL then there really shouldn't be much difference between the SB-80DX and a SB-800. The fact that the SB-800 also supports iTTL is irrelevant since your D2h doesn't support it.
What I don't know is if you'll be able to use the wireless capability (I believe that is one of the enhancements they added with iTTL). The SB-800 also has a SU-4 mode; however, that might be tricky to use because it seems like the D-TTL preflashes would cause it to fire prematurely. However, you should be able to connect them together via sync cords. I believe both the SB-80DX and SB-800 have 3-pin TTL sync ports (via a SC-18/19/26/27 sync cord) and standard PC sync ports (via SC-11/15 sync cords). Although, I suspect you would only be able to use the remote flash in manual (or possibly Auto) mode.
Yes, in manual and non-ittl auto.
intelligent through-the-lens (flash control)
Yes, in manual and non-ittl auto modes and as a non-ittl slave using its built in slave mode and using the camera flash on manual to trigger it.
Yes, in non i-ittl auto and manual.
Yes in non-ittl auto and manual flash modes, manual flash power zoom and no af assist illuminator.
The SB-20 is an older model flash, and is not intended to function with the iTTL/CLS system on the D40x. It would have to be used manually, with guide numbers. Otherwise it will not provide proper exposures. Keep in mind that we managed with guide numbers for many years and got great results. Sometimes I wish we still did. The equipment was much cheaper and more durable. However, it did require a knowledge of basic photography that digital cameras allow people to avoid most of the time. It doesn't just have to be used manually, it can also be used in non-ittl auto mode.
My personal opinion is the D40, although it has less pixels it produces less image noise than the D3000 i.e. you could be using the D40 at twice the iso of the D3000 for the same amount of image noise. There are a number of differences that could be a deal breaker to some. The D3000 has better autofocus. The D40 has higher flash sync 1/500 using ITTL and 1/4000 when not.
just add cold water and ittl do the job
the nikon d7200 and the nikon d 750
The Nikon D800 is Nikon's latest and top camera.
The first Nikon camera was the Nikon F camera in 1959.
A Nikon is actually a intelligent black gurilla
The Nikon D90 is one of the newer Nikon cameras. It comes with a detachable lens that is compatible with other Nikon lenses.
Nikon all the way, bro.
The Finepix range is made by Fuji, not by Nikon.
i prefer nikon
The population of Nikon is 31.
Nikon's population is 2,011.
nothing will get stuck ittl be fine no chicken tho
Nikon or Nikor
Nikon vision and mission
The best source to find out more about what Nikon offers is to go directly to the official Nikon site. Here is the website for Nikon: www.nikonusa.com/
You may either send your camera back to Nikon directly or you must take it to a Nikon authorized repair station. To determine which Nikon repair dealers are located in your area contact Nikon directly.