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Archive 2012 · Quite a challenge
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p.1 #1 · p.1 #1 · Quite a challenge


I am shooting several huge wall murals that consist of a number of rectangular ceramic tiles. Actually, I am shooting them one tile at a time, because the tiles are pretty complicated: reflective gold and silver and glossy surfaces. As a side note, the customer requires gold and silver to look like gold and silver, but there must be absolutely no direct reflection from glossy surfaces. Anyway, I shoot these murals one at a time and here's what I get:

Naturally, the tiles are lit somewhat irregularly. There is zero chance I can get them lit uniformly. So all I can hope for is post-processing. Doing it by hand (curves adjustments over gradient masks) works to a certain extent, but I feel there should be some better solution. By the way, the "auto-blend layers" in photoshop CS3 fails miserably at this task.

Anyway, has anybody had any experience with third-party plugins that could make these tiles fit better together exposure-wise? Perhaps PTGui in some weird mode?


Jan 23, 2012 at 01:48 PM
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p.1 #2 · p.1 #2 · Quite a challenge

the latest version of PTgui does have an 'align to grid' function that seems like it'd be almost tailor made for this. It's specifically for images like featureless sky or ocean where there isn't enough detail to generate control points. I think it'd be worth a try at the very least.

Jan 23, 2012 at 02:39 PM
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p.1 #3 · p.1 #3 · Quite a challenge

I tried PTgui, but even though the tiles align well, I can't pick a suitable projection. But even in other projections the blending is not so good.

Jan 23, 2012 at 04:18 PM
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p.1 #4 · p.1 #4 · Quite a challenge

Here is a way to deal with the background tiles.

Add a white layer on top and set the blend mode to Difference. What you see is a pretty good "mask" for the white tiles, showing the difference in tones. Load that as a mask (go to any channel and ctrl-click) and then delete the white "difference" layer.

Next, add an adjustment layer with that mask and start tweaking. In a brief experiment, I found that a Selective Color adjustment worked best, by subtracting Black from the White and/or Neutral elements of the Selective Color adjustment. Levels and Curves might work, but seemed more difficult. Selective Color with the mask makes the white tiles much more even in tone, and retains their faint texture. Not perfect, but close. By tweaking the mask itself with a Levels adjustment you can vary the effect.

Put that Selective Color adjustment layer in a Group and add a mask to the Group that blacks out the car itself, leaving the Selective Color Adjustment effecting only the white tiles. You can then add a Levels or Curves adjustment in the Group (on top of the Selective Color layer) and move the overall tone of the white tiles up or down to taste.

Jan 23, 2012 at 08:11 PM
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p.1 #5 · p.1 #5 · Quite a challenge

The masking works like a charm:

Now, on to the big version of the mural!

Jan 24, 2012 at 09:15 AM

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