Tuesday, 5 May 2009

A Gala Concert at the <i>Helix</i>, Dublin, 2009reflection

Sorry it took me so long to post some­thing new. But we’re all super busy these days, aren’t we?

I’m par­tic­u­larly excited about today’s photo; let me tell you why. When I was singing with the NUI Maynooth Gos­pel Choir(and a bunch of other choirs as well as Irish stars) was singing at a fun­drais­ing Gala Con­cert last week, I obvi­ously brought my cam­era along and shot a few pho­tos sur­round­ing the event. Unfor­tu­nately I didn’t pack my wide angle lens and was stuck with “only” 24mm (which is still quite wide, com­pared to the usual 30mm or even 35mm+ you get with com­pact cam­eras).

Being up in the choirs stalls we had this great view of the venue (the Helix in Dub­lin) and I des­per­ately wanted to cap­ture it. So I tried some­thing I haven’t done in a good while — a pan­or­ama shot. As I didn’t bring a tri­pod either, I had to do take it hand­held. So I set the cam­era to manual mode, adjus­ted the expos­ure and took 5 pho­tos (in por­trait ori­ent­a­tion in order to get as large a ver­tical field of view as pos­sible).

I then remapped the pho­tos in Hugin — a won­der­ful but slightly tech­nical open-​source, cross-​platform pan­or­ama stitch­ing soft­ware — and blen­ded them together in Pho­toshop. Basic­ally the remap­ping step “dis­torts” the images so that the over­lap­ping parts match on top of each other, and the blend­ing step, well, blends the pic­tures seam­lessly into each other.

When the whole pro­cess was done I was absol­ately amazed by the res­ult, con­sid­er­ing it was done hand held in a quite chal­len­ging light situ­ation, with people mov­ing and all. I’ve exper­i­mented with panaromas quite a while now. It star­ted on our New Zea­l­and trip five years ago, con­tin­ued in Ice­land and cul­min­ated in me buy­ing a pan­or­amic tri­pod head, which pro­duced (among oth­ers) these pan­or­a­mas (1, 2, 3). How­ever, I’ve taken less and less pan­or­a­mas lately because they are rather time con­sum­ing to make, and also hard to print.

But see­ing the con­stant pro­gress of the pan­or­ama mak­ing soft­ware and how well this latest one worked out, I’ll def­in­itely try to do more (par­tial) pan­or­a­mas in the future! Also, because of the very wide angle of view, this would hardly have been pos­sible with a tra­di­tional cam­era lens — and if so, the rec­ti­lin­ear pro­jec­tion hap­pen­ing in such lenses would have heav­ily dis­tor­ted people espe­cially in the corners of the frame, which is not the case here (thanks to the equir­ect­an­gu­lar pro­jec­tion used here). If you would like to find out more about these tech­nical term, start with this great over­view of the dif­fer­ent projections.

Focal length: 24 mm
Aperture:ƒ/4.0
Exposure:1/30 s
ISO:1250
Lens:Carl Zeiss 24-70/2.8
Location: Dublin, Ireland
Posted at 20:51

2 Comments »

  1. I love Hugin! I’m glad you also make use of it :-).

    Just one ques­tion: Why do you use Pho­toshop to blend the images, and don’t let Hugin do the Job on its own?
    Is it because you want to manu­ally choose where the junc­tions between dif­fer­ent images go?
    (This is some func­tion­al­ity which I missed in Hugin so far.)

    Ulf — 6 May 2009 @ 14:35
  2. That’s exactly right — Pho­toshop (CS3 or newer) also has an auto­matic layer-​blending func­tion­al­ity with the added bene­fit that (prior to execut­ing it) you can mask out parts in over­lap­ping areas that you don’t want included twice (like a per­son walk­ing through the pic­ture as you take the shots might appear in sev­eral images and be thus repro­duced in mul­tiple places in the stiched picture).

    How­ever, you can do this also with Gimp: first, export the pan­or­ama, but don’t blend it (i.e. only remap the images). Then, open the res­ult­ing files in Gimp and erase what you don’t want. Finally, use enblend in a sep­ar­ate step to do the blend­ing. An easy way to get the require com­mand line para­met­ers is to let Hugin blend the pic­tures and then check the logs to see how enblend was called).

    Florian — 6 May 2009 @ 15:30


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