Monthly Archives: December 2011

Photo reconnaissance and angular size

Posted by on December 29, 2011 No comments

I went out for a scout this afternoon to find some new places to take pictures. As well as finding good locations, I needed to know which lenses to bring next time. None of the stuff in this article is ground-breaking but I think it’s a useful rule of thumb (literally).

For now, let’s forget about lens focal lengths in millimetres and think of the angular field of view of a lens. Hold your arm out straight in front of you. You can judge the angular size of a distant object by comparing it against the angular size of different parts of your hand.

Image from http://chandra.harvard.edu/photo/scale.html

Little finger, or Index fingernail 1°
Thumb at its widest part 2°
First, second and third fingers together 5°
Width of palm or knuckles 10°
Distance between index and little fingers 15°
Full handspan 25°
Double handspan 50°

So when you get home, you’ve got a list of places and the field of view you need to take each photo. Now you can use this table to figure out which lens you’ll need to give you that coverage. I’ve rounded the focal lengths to the nearest commonly-found focal lengths for APS-C DSLRs, 35mm full-frame (D)SLRs, and medium format cameras.

Field of view[1] Focal length
APS-C DSLR 35mm FF SLR 6×7 Medium Format
50° 24mm 35mm 65mm
25° 50mm 85mm 150mm
15° 85mm 135mm 300mm
10° 135mm 200mm 400mm
5° 250mm 400mm 800mm
2° 600mm 1000mm 2000mm
1° 1200mm 2000mm 4000mm

So to give a real example, if you are out on your scouting walk, and you note that you can cover part of a landscape with the palm of your hand, you know the angle subtended by the landscape is 10° and that you’ll need a 135mm lens for your DSLR when you return.

I hope this is useful to someone – I’ll certainly be using it from now on.

  1. Usually the diagonal angular value is given, but in this example I think it makes more sense to use the horizontal dimension.

Miniaturisation

Posted by on December 17, 2011 1 comment

I have a large music collection, and today I wondered how physically large it might be in various obsolete formats (not including the playback equipment).

SD card

MiniDisc

CD

Cassette

LP

1/4" tape

In its current form, it is stored on a hard disk as 59GB of MP3 and other digital compressed formats. It has a total playing time of 718 hours – just a touch under a month.

Format Weight Size
MP3s on 64GB SD memory card 0.002 kg 1.613 cm³
582 MiniDiscs 14 kg 21,338 cm³
538 audio CDs 59 kg 95,495 cm³
718 cassettes 57 kg 81,001 cm³
897 reel-to-reel tapes 449 kg 151,593 cm³
862 12″ LPs 172 kg 400,938 cm³
1724 12″ EPs 345 kg 801,876 cm³

OK, so EP was a slightly facetious choice of format for storing an entire music library, but if we compare the SD card to a stack of LPs, the LPs weighs 86,000 times more, and is 248,566 times larger. In fact, the LPs would be about the same size as a wheelie bin, and weigh as much as two people.

While the reel-to-reel tapes are a bit smaller, they also weigh almost half a ton!

If you’re curious about the definitions I’ve used in these back-of-the-envelope calculations, see the following section.

Definitions

  • Audio CD – Playing time 80 minutes, in hard jewel case with paper inlay
  • MiniDisc – Playing time 74 minutes, in hard case
  • Cassette – C60 cassette, playing time 60 minutes, in standard hard plastic case
  • Reel-to-reel – ¼” 1800′ tape on 7″ reel, 7½ips playback speed, playing time 48 minutes, in card box
  • LP – 331/3rpm 12″ vinyl, playing time 50 minutes, in thin card sleeve
  • EP – 45rpm 12″ vinyl, playing time 25 minutes, in thin card sleeve

Frickin' laser

Posted by on December 6, 2011 No comments

A friend of mine is a researcher in the field of chemical physics. This week, he invited me to his lab to take a photograph of his 5 megawatt laser, which strikes a copper target and makes a plume of plasma that lasts for just a few fleeting nanoseconds. Normally, I like taking photos of landscapes or architecture, but there’s no way a geek like me can resist the invitation to play with a frickin’ laser.

Naturally such a powerful laser is potentially rather dangerous, so I was under strict instructions not to touch anything, lest I get my hand zapped off or something. Laser safety goggles were the order of the day. As they say, “do not stare into beam with remaining eye.”

Laser sign

The laser table is large and complex. The laser itself is on the far side of the table, behind the computer screen. The beam then bounces around various mirrors and lenses in the section of the table on the left, which has black safety screens to catch any stray reflections. I am told that if any dust gets on the mirrors, it will absorb enough laser energy to become hot enough to damage the mirror.

The beam then enters the metal tube at the front of the table, and finally zaps the copper target in the square metal box in the near-left corner. The box contains a near-vacuum, with a pressure of just 3 ten-billionths of normal atmospheric pressure. The box has an observation window, and if you look carefully you can see my black camera over the hole, peering through the window.

The white box in the very foreground is a specialised laser detector, fitted out with all sorts of gizmos, including the computer on the trolley.

Laser table

Finally, the image we’ve been waiting for. This picture shows the inside of the box. The green laser beam enters the picture from the right, but you can’t see it because there is no mist or smoke for it to reflect from. The centre of the bright flash is where the beam strikes the copper, and you can see a bit of green in there. The plume of plasma then spreads back along the beam, heading right. It isn’t also going left – what you can see there is a reflection of the plume on the shiny copper surface. Not sure what else I can say about this. I’m no expert! :)

Laser plume

Crowds

Posted by on December 5, 2011 No comments

For this week’s Photo Challenge, crowds, I took this composite picture of students coming and going from the chemistry department at the University of Bristol.

ABBA – The Day Before You Came

Posted by on December 2, 2011 No comments

This week, I was contacted by Dutch producer Matt Pop who asked if he could use some of my photographs of Stockholm in the video for his remix of ABBA‘s The Day Before You Came.

Who am I to say no? I like ABBA and I like dance remixes. See if you can spot my pictures in the video.

If you like club-style remixes of pop music, be sure to check out Matt Pop’s YouTube channel.

My new darkroom

Posted by on December 1, 2011 No comments

Last year I wrote about the darkroom I had set up in my loft. Since then I’ve moved house, so I need to build the darkroom again. This time I have a windowless utility room on the ground floor, with running water and a worktop, so it’s already better than what I had before. Here’s how I’ve set it up.

Click for a larger version, and see below for a bit more explanation. Apologies for the poor quality of this picture – I used my phone as my DSLR is currently tied up in a laser lab at Bristol university’s chemistry department. Hopefully photos to follow!

  1. Safelight. This is a very old Paterson safelight, emitting just a dim red glow. Note that this is only suitable for black & white paper – all films must still be handled in total darkness.
  2. Liquid concentrates – Various Ilford products, (including Multigrade developer, Ilfostop and Ilfotol), Rollei Digibase C41 chemicals and a bottle of Agfa Viradon New sepia toner.
  3. Powdered concentrates – At the moment, just Ilford Microphen. Usually I would choose to use ID-11, but someone gave me 15 litres  of Microphen powder, so who am I to complain!
  4. Universal film tanks. These are Paterson tanks and can take 35mm, 120 or 127 film.
  5. Graduates, or as most people call them, measuring cylinders. I don’t know why the photography word is different. I also have some funnels for getting stuff back into bottles and some measuring jugs.
  6. B&W film chemistry, diluted and ready for use in processing black & white films.
  7. Gloves. Developer is quite alkaline and can make your hands sore if you handle it too much. Wearing gloves also helps prevent getting fingerprints on the film.
  8. Colour C41 film chemistry – in this case, Rollei Digibase C41. It is diluted and ready for use.
  9. Paper squeegee for getting most of the water off finished prints.
  10. Film squeegee for getting most of the water off processed negatives. Seems that most people are divided on squeegees for film – they avoid water drying marks, but can cause scratches. Always clean your squeegee!
  11. Scissors for cutting film up.
  12. Pop-up drying rack for hanging prints over the sink to drip dry.
  13. Rinsing tray. This is a normal paper tray, but I made some holes at one end so water trickles in from the tap, over the prints, out of the holes and down the drain. It’s an effective way of washing prints and saves buying an expensive print washer.
  14. Paper processing trays for developing, stopping and fixing prints. There are extra trays in the cupboard under the sink for occasions where I also want to tone prints. I also have other sizes.
  15. Paper easel. This one is a Durst 8×10″ but there is plenty of room for a larger easel on the baseboard.
  16. Dust blower for getting dust off negatives before printing from them. It’s a Giottos Rocket Blower, and works well.
  17. Focus finder for inspecting the magnified grain in the negative before printing.
  18. Warm water bath. C41 colour processing must be done at 38°C, so I fill this wallpaper pasting trough with warm water and place the bottles of chemicals and the film tanks in it.
  19. Thermometers & pencils, also some stirring rods. The thermometers are used to check temperatures of chemicals (20°C for black & white, 38°C for colour). The pencils are essential for making notes about the prints I make, so I can make more copies the same way in the future.
  20. Enlarger. Mine is an LPL C7700 medium format enlarger, and can make prints from negatives as large as 6×7cm. I have 50mm and 75mm lenses for 35mm and 120-format negatives.
  21. Work light, because sometimes you need to see what you’re doing :)

Not pictured:

  • A clock that ticks loudly so I can time things in the dark
  • A room thermometer so I can estimate how warm the chemicals on the shelves might be without having to check.
  • A place to hang films to dry. A 36-exposure film is about six feet long, and obviously won’t fit on my print drying rack above the sink!

Most of the photography-specific equipment was purchased either from FirstCall Photographic or second-hand from eBay. Most of the more generic fixtures and fittings were bought from Ikea or other DIY shops.

If you are a darkroom enthusiast, buy Ilford film, paper and chemistry! It might not be the cheapest brand but it’s probably the best and it’s good to support a British company. Too many traditional photographic companies have discontinued products, changed focus or shut down entirely. Support traditional photography, and buy more film! :D