# Advice regarding luminance and creating a domino "photo"



## JohnLofy (Dec 23, 2012)

First time poster. (Have been a reader for some time, really enjoy all of the discussions !)

I must state from the first that I'm not a terribly accomplished photographer at this time (still learning).

Ok, this is an unusual photography question. I want to make a "domino picture" of my Uncle John. This is accomplished by arranging double nine dominoes such that they represent different levels of light and dark. The guru of these types of "pictures" is Ken Knowlton. Some examples are shown at http://www.knowltonmosaics.com. 

I took a black and white picture of my Uncle John, did a quick "adjust contrast" process within Adobe Elements, and imported it into an image processing software called ImageJ (http://rsbweb.nih.gov/ij/features.html)

Using an add-in, I was able to break it down into an grid of squares (see below). Using a cursor to highlight each box, I can measure the light intensity of each box (levels from 0 to 255). I plan to convert the intensity of each box into a domino type (from NO dots to a full 9 dots).

I was thinking to measure the area ratio of an individual dot to the full area of the domino square and use this ratio to figure out how many dots to use for each square in the photo grid. But when I measured the area of a single domino, it is only about 3.3% of the total area. So even with 9 dots, the maximum area ratio (area of 9 dots/full area) is only about 31%. So how do I assign the intensity to the number of dots on the domino ? (and make it look right? 

I'm not sure how the eye perceives light intensity levels (linear?, logarithmic?). Can anyone help with this?

Also, is there an easier way to do this? (It's a LOT of grids to be manually measured !!)


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## bvukich (Dec 23, 2012)

Resize it to the number of pixels equal to the number of half dominoes, posterize to 9 colors.

See attached, I dropped out the grid as much as possible, but the cyan still wastes three of the colors... You get the point though.


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## hpmuc (Dec 23, 2012)

That's an interesting idea, however, I haven't understood whether you want to use real dominoes or images of dominoes. Anyway, before doing any calculations, I would probably take photographs of all 55 double 9 domino tiles and then hand that and your image of your uncle over to some "mosaic software", just google it. I think that will come up with a suggestion and you will see whether you can use it.


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## fpdv01 (Dec 23, 2012)

There are a number of free software programs on the net that will do what you ask.
Perform an internet search (Google, Bing etc.) for "Free Photo Mosaic Software" and a number of software options will come up.
Good luck with the execution of your idea.


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## JohnLofy (Dec 23, 2012)

Thanks, all, for the advice. (I did not expect responses so quickly!)

Yes, I do plan to make a "picture" using actual dominoes.

Didn't think about taking a picture of the actual domino to check it's gray level, but will do so. Guess I will probably have do some scaling because I expect the gray value of the "9 dots" domino will likely not be as bright as the "really white" sections of the uncle john photo.

And thanks for the advice regarding looking specifically for mosaic software on Web. Guess you can find ANYTHING on the web ! (I just thought that this idea was so specialized that not many would be doing this.)

Merry Christmas, all !

John


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