Playing with Sauroposeidon photos

January 30, 2014

Following on from Matt’s post about the difficulty of photographing big specimens without distortion, I thought I’d have a play with our best Sauroposeidon C8 photo, which I think is this one:

sauroposeidon-c8-alone

(That’s been the basis for classic SV-POW! posts such as Your neck is pathetic and Darren’s new indeterminate Wealden maniraptoran is inadequate.)

I was motivated by Andy Farke’s comment:

Another–and perhaps more important–area where surface models excel is when you can remove colors on the original specimen that wash out relevant details…I bet this is probably the case for the example vertebra of Sauroposeidon. How many fossae and foramina just don’t show up well on the photos above?

Andy was talking about completely colourless 3d surface models, in which the 3d shape allows a render to make shadows that bring out the subtle shapes. But it made me wonder whether we could get anywhere just by washing out the most prevalent colour in the photo.

I started by doing a big, fat Gaussian blur on a duplicate layer — 500 pixels in each direction — and sampling the colour in the middle, to get a rough-and-ready average. (There may be a better way — please shout if you know one.) That average colour was#7e6b2f. I used it to run Colour To Alpha on another duplicate of the original layer, so that we’d be left with only residual colours. Here’s the result:

sauroposeidon-c8-alone-colour-completely-removed

I’m in two minds about this. It may be informative, but it sure is ugly. To compromise, I reinstated the original layer underneath this mostly-transparent one, and turned its opacity down to 75%. Here’s the result — a nice compromise:

sauroposeidon-c8-alone-colour-removed

Of course, there are endless other approaches you can take — that’s the blessing and the curse of image-editing programs like GIMP. For example, here’s what I got doing a simple Colours → Auto → White Balance:

sauroposeidon-c8-alone-whitebalanced

I’m not sure that isn’t the best of the bunch, in terms of informativeness.

I also tried something else — not amazingly successfully, but I think it’s worth seeing. Since the two photos that Matt showed in the previous post were evidently taken from somewhat different angles, I thought I’d have a go at compositing them into a red-cyan anaglyph. Because the variation in camera position is mostly dorsoventral rather than anteroposterior, the vert has to be pointed upwards for the two eyes to see the two versions from different horizontal points. Here’s the best I could do:

c8-anaglyph

I would say this is of some value; but it’s nowhere near as good as, for example, the anaglyph of Cervical S of the Archbishop. I could sit and look at that one all day. The problems with this one arise for three reasons.

First, I had to reduce both parts of the Sauroposeidon anaglyph to monochrome (since one was already in that form), so all colour information was lost.

Second, I had to scale the high-resolution picture to the same size as the lower-resolution one, throwing away more detail.

Finally, and most important, the two photos were not taken with the intention that they should be used to make an anaglyph. To work well, this has to be done with the images taken under the same lighting conditions, at the same distance from the specimen, from perspectives differing by about the distance between the pupils of the viewer, and with the camera-position difference being perfectly in the plane of the specimen. Needless to say, none of these conditions was met in this case, so it’s actually quite impressive that it works as well as it does.

We have a lot of options for illustrating specimens these days. Postage-stamp-sized greyscale photos really don’t cut it any more.

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One Response to “Playing with Sauroposeidon photos”

  1. Matt Wedel Says:

    Speaking of dropping color, has anyone played with the method described by Hammer and Spocova in PE last year (link)?


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