Some of this is rambling, wry, and droll—actually it's not, I just said that for no reason at all. What follows is a slightly edited version of an internal report I wrote. It's from an earlier build so some of this may no longer apply. I'm sharing it because this communicates exactly what I go through when I feel—and experience—the excitement of a new feature. Maybe it'll show Lindens think more about these things than seems to be the case sometimes. Mad props to Richard Linden for working the magic on da photoz 
After vocally hoping for this for so long, it's finally arrived!Seeing the new Snapshot Preview floater caught me by surprise. A little background: let's just say I'm am an enthusiastic shutterbug. For a long time, I've lamented that the JPEG output quality when sending a postcard couldn't be changed, and thus, sucked a lot! It ruined a lot of good pictures, especially those with flat or subtlely-gradiated tones like certain texture swatches, hills, and even water. Oddly enough, I soon found myself counteracting this by deliberately taking very detailed images crammed with tonnes o' stuff so the compression wouldn't be as noticeable. Still, not an overall solution.
I've taken tens of thousands of snapshots and archived many of them. 4,000+ can be seen on my Snapzilla collection: http://www.sluniverse.com/pics/Default.aspx?Name=Torley+Linden
The first few minutes of looking at this new Snapshot Preview floater had me poking around, trying to figure out how to use it.
Instant thought: I LOVE how it asks me questions, e.g. "What would you like to do?" This is very human, very friendly, and puts weight to my choices. Wish we had more of this in the interface.
Layout looks very clean and understandable for the most part. I have no idea why "File size:" is always in bytes, tho–very longwinded and hard to read for big images in the millions of bytes. :p Wish it could show the size in KB or even MB for larger images!
After taking my first snapshot, I was distracted because I expected there to be a preview thumbnail. Then, I realized: the screen IS the preview and I'm frozen in place! So… uh… why can I rez prims? That's exactly what I tried doing.
After taking a snapshot, I noticed thin white verical fringes appear at the edges of the screen. Intentional?
I clicked the "Save snapshot to hard drive" button and closed the floater, and opened it again–it had reseted to the default, "Send a postcard". I think this should stick with whatever you set last. Some of the settings don't appear to, like image size.
I also noticed that at 1600×1200, any preview I did at "Current Window" size looked very pixelated and rough, which looks kind of like an old Sierra or LucasArts game and made it difficult for me to discern some finer details. Is the lower resolution being displayed for speed?
A really cool thing that made me jump out of my seat at first was how each picture "falls" away like old Polaroids after "Refresh Snapshot" is clicked. That's an awesome transitional effect! However, upon taking each snapshot, there's another shiny "wipe" which travels from the top left to the bottom right and is pretty jerky. I wonder why? Anyway, I hope some creative SL moviemaker finds a way to incorporate the this falling effect into their film.
Playing around with Debug, I noticed I could use Alt-Ctrl-1 to hide the full-screen preview overlay.
I wanted to send some hi-res, as well as terribly low-quality postcards to myself. Unfortunately, it didn't work, and the pictures appeared the same they always do, despite the Send Postcard preview looking as expected.
I notice under the Image Quality slider (all the XUI sliders seem a little chunky and the black bars are about a pixel thicker in height than what I'm used to) there's another pop-up menu with "Colors", "Depth, and "Object Id" as choices. What do these do? "Color" appears to be the normal default, "Depth" seems to always gives me a blank white screen, and "Object Id" gives me a cool, almost retro-vision that reminds me of those classic flight sim games.
I didn't have much success taking pictures in high resolution. I tried to take a picture with a resolution of 3200×2400, and ended up with a preview that looked like multiple tiled copies of the same image. After repeating the steps and seeing this several times, I relogged and tried again. Saved it to disk… and no matter what, I kept ending up with a "3200 x 1174" snapshot! Technically, I'm running SL in a window with a resolution of 1600×1174.
I also wonder why JPEG images can't be saved directly to hard drive? For example, "Image Quality" would be enabled for "Save snapshot to hard drive" and setting it to less than 100 would automatically make it a JPEG. 100 would leave it as BMP. I understand postprocessing (which I currently do) is useful, but for the spontaneity of quickly snapping something and uploading it to a site like Flickr, JPEG saves some steps. Altho, I suppose you could email postcards to yourself and access them that way–which still seems a bit longwinded.
Another oddity: I took a snapshot at 320×240 and then changed it to 640×480 from the pop-up menu. The snapshot preview squashed in half vertically and left black space on the right of the screen, instead of shrinking to 1/4 the size with correct aspect ratio. (I can make a movie of this if needed.)
I can't seem to upload textures at larger sizes. Uploading one at 1024×1024 and 2048×2048 came out as 512×512. The spinners for "Upload a texture"'s Width and Height should also go up and down in power-of-two increments. Instead, what happened was I selected "Medium (256×256)" and pushed up on the Width spinner. It went up to 306 instead of 512. Looks like the spinners are meant to go up/down by 50 with each click on all modes.
Will "What size image do you need?" show resolutions with the proper aspect ratios if I'm on a widescreen monitor?
I wondered for a moment why my cursor always looked like it was going to alt-zoom–I soon found out this is the default behavior. I wish there was still a way I could walk around freely and take pictures, though: this is going to be a real pain for a model switching between poses, because you have to keep opening and closing the Snapshot Preview floater on each pose. Even with pressing ` (or Shift-` as it'll be), changing options necessitates opening the floater, freezing yourself again. So could a way to continue moving inworld with the floater still open–e.g., the old behavior–PLEASE be added?
Also really importantly in the community, is the feature to NOT show HUDs in snapshots by default (and saving repeated trips to View menu > Show HUD Attachments), going to be added soon? I don't see an option for it here.(We're almost out of the water on this. The checkbox has been added and it's going to work… soon!)All in all, this is a really refreshing addition and I'm happy to see it at last!