to fine tune the answer a bit
Almost there - let me add my 2cents - The TV assumes that if the signal is 1080i that it must be a true HD signal, which by default is 16:9 - i think this is a flaw due to the upconversion of SD that most receivers due now, but nearly all 4:3 TVs have this detect feature built in. And this is what 4:3 option 1 on the dish 811 is. Now in addition some TV manufacturers went the other route and showed all HD content in a 4:3 window (some models from Panasonic, Toshiba, etc. - mine is a panasonic pt61hx40)- this works great for upconverted SD but it stretches a true 1080i signal. The only way to get around this one these types of TVs is to physically add black bars to the top and bottom of the picture [and since they have to add some bars, they have to take a few lines of the picture out, dropping from 1080i down to around 800 or so]. This is what 4:3 option 2 does - it allows for the letterbox of true 1080i signal, while it doesnt do anything to a SD show that it upconverts with respect to aspect ratio. So if youre tv does autodetect the HD signal and goes into a 16:9 pic then the chaning of the 4:3 option 1 or 2 shouldnt do anything on upconverted SD, but for true HD content it should show a letterbox on option 1 and what would like like a double letterbox on option 2 (short fat people).
BTW - Even though the FCC mandates that the term HD refers to 1080 or 720 in a 16:9 frame the CEA still allowed manufacturers to release some 4:3 TVs that dont have the detect featuer so it shows in the stretched 4:3 window (tall skinny people). I've actually filed complaints against panasonic about this but nobody there believes me since the CSR guys that work with HD have only ever seen a widescreen version (it just kind of puts us early adopters in a bind since only a handful of the set top boxes have that physical 4:3 letterbox option 2 mode - which is why I got dishnetwork and cancelled cable).
Also I know that some people make fun of 4:3 HDTVers but since about 80% of what I watch is upconverted SD I would still make that move if I could redo it - i can live with letterbox black bars when I do watch true HD - and since my TV is 61" 4:3 the 16:9 window is easily big enough for me. Sure in a couple of years I'll get a widescreen, but for now its been a few years and I still am happy with the 4:3 (not so happy with some of the idiots at panasonic though)