HDR Test Sheets

Let's try to get this HDR thing on firmer ground.  We need a repeatable way to predict the performance of HDR for any set of parameters.  I'm going to use Dynamic Photo HDR 4 from MediaChance and I created the following simple test sheet with Photoshop CS4.  It consists of two black to white gradients at right angles.  In the dark portion of the test sheet I typed the word 'abracadabra' in black at three different locations.  In the light portion of the test sheet I typed the same word in white at three different locations.  We should be able to see, at least, some set of parameters that would let us read all six words.  Without further ado here is the test sheet (and if you can do better let me know):

I transformed this in Dynamic Photo HDR 4 using the Auto-Adaptive method of re-mapping and I selected 'Full HDR Process'.   When that was done I tone-mapped it using all seven algorithms at the default settings.  Here they are.  The first is 'Eye-Catching':

The next is 'Ultra Contrast':

Now comes the real surprise: 'Halo Matix':

I can't resist a gasp of surprise.  I would never have guessed that this algorithm (which seems to feature garish haloes and color distortions) is far and away the best at separating details from a similarly colored background.  Look how even the background tone is.  If anything it has slightly reversed the gradient.  And all six words visible as plain as day.  And notice that the white versions of 'abracadabra' are rendered in something like real white.  This distinguishes it from 'Human Eye' which picks out all three white 'Abracadabra's but in shades of gray.

Now comes 'Smooth Compressor':

What's going on with 'Smooth Compressor' also seems clear.  I believe that this algorithm simply takes the entire tonal range and compresses it into the number of output bits available (7 or 8).  We'd expect this to be a low-contrast solution which would make the words hard to read.  That's what we actually seem to see.  See this post for my ideas about reduction of contrast under some compressive HDR algorithms.

After that comes 'Auto Adaptive':

'Photographic' is next:

And, finally, 'Human Eye':

I'm going to put this on-line right now.  Next post I'll present the seven results from performing what MediaChance calls 'Eye-Catching' remapping.