Some of the photos are just slightly out-of-focus/blurred because of camera movement. For example this one:



where the camera has chosen to focus splendidly on the box (see the writing cropped off at the bottom of the picture - perfectly sharp). Unfortunately, what we wanted was to focus on the diamond...

In some of the others I can pick a haziness which is - I'd say - exactly the way in which a diamond looks when it's in full sunlight:



Others still are perfectly crisp, and taken in slightly lower lighting or with the diamond at an angle, so that you can see there is no cloudiness in the diamond after all.



I don't think it's the fluorescence; this is what a modest "overblue" looks like. Believe it or not, this is an M colour stone.

Dear PtyMom..........a different point of view.........in some cases, the diamond may appear foggy or milky in certain lights, and in certain photos, and absolutely gorgeous in other lights (especially in real life), or in other photos.  I actually bought the diamond above for mywife, and it is a stunner in all lights.  In direct sunlight, it actually looks like a purplish blue diamond.  In fact I even mentioned to David that the photos that were posted did not do it justice.  moreover, the diamond had some dust on it because while it does have some small inclusions, the rest of the diamond is crystal clear without any of the "dusty" stuff you see.  People actually ask my wife where should would have acquired such a large blue diamond from.  It is 3.05, but looks like a 5 CT + diamond.  Anyway, here are a couple photos in direct and indirect sunlight, and it looks fab.  Also notice a 3.15 CT pear beside it.  They are good friends........;-)

You will not believe it, it is a M color stone.  I have a very strong interest in diamonds and have seen many stones from colorless (D) to fancy yellow, and this clearly looks like a J color stone, if not better.  The clarity is SI1, which I agree with.  It has some inclusions, but not at all visible to the naked eye.  The length is 11.65 mm and I cant remember the width, but I'm thinking, 9ish. 
Cheers!

One interesting aspect of diamond photos is focus- specifically where is the lens focused?
When we look at diamonds our eyes can not fix a point and freeze it the way the camera can- for this reason, I sometimes publish certain photos that may seem out of focus- but they (imo) more accurately represent what the mind perceives when the eye can not focus on the facet structure- and only sees what we call "bucket of crushed ice"

Re Diamonds in sunlight- there's no one answer that is correct here- different diamonds behave differently in different lighting scenarios.