Back when I was playing GT4 on a TV, I would curse the difference in appearance of the photos I'd taken in the game after transferring them to my PC. The lighting was all wrong by comparison, all over-exposed.
Now, with GT5 and GT6, I've never played either for any length of time on a TV screen, instead using a PC monitor, and I don't recall having any issues with visibility. I recently did a lap of Streets of Willow at midnight with no headlights on and could see plainly where I was going, even with bright lights on in the room. To test that I didn't have the brightness too high on the display, I changed time to midday; whilst some of the colour was bleached out (due to an obvious screen-space "bloom" effect), there was still a full range of on-screen levels (black to white), and I still had no "visibility issue".
So I wonder if the game's visuals are tuned on decent displays instead of "limited gamut" TVs. Possibly an error given the audience, but it does look good as a result, provided you have the right display. Unfortunately, I can't get the exposure control in GT6's photomode to behave as well as it did in GT5, it just seems to do as it pleases sometimes - that possibly compounds the issue.
The square sun is the result of a low-res "bloom buffer" (as I call it), which shimmers a lot, too (aliasing), e.g. glare on car bodies. That resolution has been reduced from GT5, and the dithering that was applied in GT5 to soften the blockiness of that buffer is also missing now. Probably because dithering itself is gone (except in the alpha / transparency stuff, which is different anyway, I think) thanks to a higher colour count used in the game outright (for HDR purposes).