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Posts Tagged ‘colour’

Processing colour C-41 films at home

August 11th, 2011 No comments

Processing black & white film at home is easy. You just need a changing bag to load the film into a tank in darkness, and the rest can be done in the bathroom with the light turned on. The chemicals for black & white are normally used at 20°C but can be used at room temperature if you compensate for the time. You could even pop the chemicals in the microwave for a few seconds.

Many amateur darkroom enthusiasts (until recently, me included) are wary about developing colour film with the C-41 process, on the assumption that it is difficult, confusing, expensive, or all three.

It is true that colour process has to be more accurately temperature-controlled, and that the development should be done at 38°C. Immediately, this conjures up images of having to buy an expensive electronic water bath, such as the Jobo CPE-2. These machines do help, and they do cost hundreds of pounds. However, they’re not necessary. The development usually takes only 3-4 minutes and the later stages do not have to be quite so accurately controlled. This means it’s possible to use a plain warm water bath.

It’s not too expensive or confusing, either. There are beginner’s kits such as the Rollei Digibase C-41 LT20 which include all of the chemicals you need, with instructions. I paid £25 for a kit that can do about 20 films. There are bigger kits which are better value too, and it’s possible to restock on the individual chemicals in future. I’m no expert on the C-41 process, so you should probably read up on C-41 chemistry yourself.

I bought a wallpaper pasting trough for £2 and made a cardboard lid with holes for my bottles and tank to stand in the water. I filled the trough with water at 50°C and stood the bottles and tank in the water to reach the right temperature. The temperature of the water bath fell rapidly at first, and then slowed down. After about 5 minutes the water bath was at about 40°C so I waited until the temperature fell to 38°C, checked the temperature of the developer as well as the water bath, and set the development process going. The thermometer still read 38°C after the development was up.

By the end of the entire process of developing, stopping, bleaching, fixing and stabilising, the temperature of the water bath had fallen to 35°C, but this is still within tolerances.

My message to photographers who are wary of processing colour film at home: don’t be. You have to be careful, but you don’t need any special equipment other than what you’ve already got for your black & white work.

Have fun!

Calibrating a TFT monitor

October 26th, 2009 No comments

I hadn’t realised how important it is to calibrate a monitor correctly.

My former method of “calibration” was simply to set the monitor’s contrast to maximum, and set the monitor’s brightness to a value that looked comfortable to me. I didn’t bother changing any settings in software.

But I got caught out.

Last night I took some photos and tweaked them on my PC so they looked OK. I published them and thought nothing of it. But several of my friends commented that they looked a bit dark, and when I checked the pictures out on two of the computers at work, they were indeed too dark.

My badly-calibrated monitors at home caused me to wrongly edit an image. So I read up on how to calibrate a monitor. There are many ways, but the method I’m writing about here is nice and simple.

  • If you have TFTs, they are sensitive to the angle you look at them. Tilt them so they face directly at you.
  • Turn the lights off in the room you are working in.
  • On the monitor, set the colour temperature to 6500K
  • On the monitor, set the contrast to 100%
  • Look at the gamma black chart below. Adjust the brightness on the monitor until:
    • Bar A is just visible at the bottom
    • Bar B is visible from the bottom to about halfway up the chart
  • Gamma black chart

    Gamma black chart

  • Absolute black on your monitor is now calibrated.
  • Find how to adjust the gamma on your computer. For example, I am running the proprietary nVidia X driver on Fedora and it comes with a convenient control panel. You can use Adobe Photo Shop to adjust the gamma, or xgamma under X Windows on Unix/Linux systems.
  • Now look at the gamma chart below. Sit as far as possible from the monitor and squint so the lines blur together.
  • Gamma chart

    Gamma chart

  • Adjust the gamma on your computer so the shade of grey completely across the gamma column is the same at 2.2.
  • The monitor is now calibrated.

References

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