30 March 2009

prn to pdf

Lets say that you work in an environment where you occasionally have to deal with Microsoft Office documents. You need to convert these to .pdf's so everyone can read them. Openoffice does the job admirably most of the time but sometimes it crashes or just messes up the layout. There is a (slightly circuitous) way of converting any printable windows document to a pdf file that doesn't require having to install any special dodgy PDF converter software.

You will need:
  • A Windows installation that can read & print the document
  • A postscript printer driver for the Windows install (see below)
  • A linux installation with ps2pdf installed
If you don't already have one installed, you can get postscript printer drivers here or you can try following the steps here. Once you have the drivers installed, the steps are:
  • On windows, go to print your document
  • When the print dialog comes up, make sure you select your postscript printer

  • Also select the 'print to file' option
  • Hit print; a dialog will come up specifying the file you want to write to. For arguments sake, lets call it wombat.prn
  • Copy this file to somewhere you can get to on linux
  • On linux, open up a terminal where wombat.prn lives, and run:
ps2pdf wombat.prn wombat.pdf

...and now you have a shiny new .pdf. There are a ton of options you can use in ps2pdf to tweak document size and quality - see here.

23 March 2009

building a tilt-shift plungercam lens for less than $25

New visitors: the updated DIY tilt-shift lens tutorial is here: http://cow.mooh.org/projects/tiltshift.

In it, I've got a comprehensive guide to how tilt-shift works, along with a guide to using existing 35mm lenses to build DIY tilt-shift lenses.

On the weekend I finally got organized and with some help from Briony we finished attaching a male EOS adapter on to a toilet-plunger - because, lets face it, there isn't any more productive activity than affixing low-end plumbing equipment to high-end optics :P From certain angles, it looks totally badass. From most angles, it looks like a toilet plunger. The whole thing was built for less than US$25, so I can't really complain.

My previous attempts at tilt-shift have ranged from pure fakery to some fairly decent results achieved by holding a prime lens a little away from the camera body and simply just tilting it. However, this was a fast path to getting dust and grime in the camera body, so I started to seek out a closed solution.

One key disadvantage of using a 35mm prime lens for tilt-shift is that the flange focal depth of the lens means that it has to sit right next to or even slightly inside the camera body to get a picture. However, by using a medium format lens, which has a longer flange focal depth and a bellows arrangement, you can afford to move the lens about a bit more. Two people who've championed this technique (and used a plunger as bellows) have been Dennison Bertram and Keith Loh, from whom I draw my inspiration for this project.

For this particular implementation, I wanted a fairly strong, permenant solution that would still allow me to swap out the lens at end of the bellows. My materials list was:

Canon EOS body cap

I first used a hobby knife to make an aperture as large as possible in the body cap; this was going to be the EOS mount for the plungercam.

Attaching the EOS body mount

I lopped the head and tail off the plunger; the smaller end had a diameter to match that of the body cap, and the larger end that of the lens. Here you can see where the male EOS adapter was attached. I was aiming to do this completely without screws or glue, but I ended up needing to glue the adapter into place to make a secure fit.

lens attachment

The lens is held into place by slotting into the end of the plunger, into a flange made up of tabs cut from the end of the plunger plastic. A screw-clamp is put around the lens and the tabs so it all holds together, which is seems to do quite securely.

Completed plungercam

I was a bit worried that the lens would bend the plastic and would need constant holding. However, the plunger is relatively stiff, and I feel fairly confident that the lens mechanism holds up under its own weight without flopping about dangerously. And there you have it - probably one of only a few toilet plungers in the world that come with an EOS mount.

Once you work out a way of holding the lens comfortably, it's pretty easy to tweak the focus of the lens. It's quite sensitive to position, and the rubber is fairly stiff, so I it's not advisable to use it for long-exposure shots. Also, the lens completely and utterly throws out spot metering. The fix is to switch back to evaluative metering (bah! humbug!) and underexpose the image a little (one f-stop seemed to work for me); this way you can merrily shoot in aperture priority mode without having to constantly tweak the shutter speed.

But does it take decent pictures? I did a field test with it yesterday, and I've included some highlights below (click on the images to see larger versions). It's still early days yet with this lens, but I'll leave the quality judgement up to you.

plungercam test 03
Here the lens really shows its lovely shallow depth of field. From the tests so far, I really do think it's ideal for portrait and macro shots as opposed to trying to miniaturise cities.

plungercam test 04

plungercam test 02
Later on in the day, after a bit of practice, it became pretty easy to select a target to focus on in the image.

plungercam test 01
Another tilt-shift artifact - bright lights (see reflection of tail-lights in the window on the right) become big, fuzzy bokeh highlights. This might be a boon for some, but maddening for others.

plungercam test 05
I really love what real tilt-shift does to parallel lines in the image - what seems to happen is that the blur increases as you move away from the focal plane.

See some of my other DIY projects (plungercam 2, iPhone SLR lens adapter, papercraft etc) here.