Contrast, color temperature, and saturation

We've released several iPhone photo apps with what I tell nerds is a divide and conquer among 64 choices interface.  (go buy them and rate them please!).   The main one is SimplePic which has changed completely since we first released it.  Our big question all along was "what dimensions of an image are most fundamental".  We have arrived at an answer that will surprise nobody, but the ordering has a nuance.

What the app does is give you four choices and you pick the one you like.  Our premise is that humans are terrible at looking at thumbnails of images, but very good at looking at a few images and picking their favorite.    We chose four because a perfect square lays out well, and nine is in our opinion too many (and they get too small) Here is the first screen.

First screen of SimplePic   Contrast

You graphics types can probably tell the first screen is messing with contrast (upper left screen is original image).

Second Screen of SimplePic  Color Temperature

The second screen messes with color temperature (two warmer and one cooler).

Third screen of SimplePic.  Saturation.

The final screen messes with saturation (one up too down).

All of you technical types can see that we are really just providing 64 choices in a 3-step process.  We could really provide any set of 64 choices as we don't expect the user to see structure here (that is the whole point of the interface-- naive users still have strong visual opinions).  However, having one intuitive dimension for each screen in our opinion makes the task more intuitive.   WHAT dimenions to use didn't seem that hard-- some variation on hue/saturation/value and we came up with what is above.  More interesting was how to vary those dimensions and what order to present the variations.  I, and almost everybody I know, first messes with gamma/contrast/luminance when they hand edit an image.  Then they fix the white point.  Then maybe they mess with the saturation.  This is what we tried.    Other orders empirically have not worked as well.  Another issue is **how** to vary those parameters.  We spent a ton of time on that, and the most industrious can reverse engineer what we did.

If you try the app, let us know when it fails to produce a better image!  Also note that these all run as photo app extensions.  I am a huge fan of the extension concept-- give it a try!