Tuesday, 26 May 2015

Infrared image

Here is my first effort at an "infrared (IR)" image - taken earlier today.  

Infrared image 

This is made with a Hoya R72 infrared filter (received in this morning's post) fitted to my Canon 5D mk3. The key steps in the process for producing this image were as follows:

  1. Screw on the filter.
  2. Set the white balance. None of the "standard" white balance settings are suitable because the image will be looking at the infrared component of light. The custom white balance is set by reference to brightly lit green grass. In practice when the filter is attached the camera sensor sees only the IR light from the sun that is reflected off the green grass. The sensor does not see green.
  3. Take the shot. This is easier said than done because the filter takes out essentially all visible light; nothing is visible through either the viewfinder or the LCD screen. The easiest way to focus is to unscrew the filter, set the focus, switch to manual focus and then re-attached the filter, taking care not to move the focus setting. After some trial and error with exposures, the shot was taken at ISO3200, f/8 with a  15s exposure. The exposure time would have been even longer if I had used a lower ISO value. All IR photographs obtained the method  described here require a long exposure time - you can see that some leaves are blurred as a result of the breeze and long exposure time. (In practice I am sufficiently familiar the focus settings on the lens that I could set the focus near enough without use of viewfinder or LCD, and without unscrewing the filter. For some shots it may be important to note that IR focuses at a slightly different  point than visible light. Here the f/8 setting gave sufficient depth of focus that the different focal point for IR did not matter.)
  4. Process the raw image in Photoshop. All the visible colours in the image are "false" because the IR itself is not visible. Processing decisions are therefore based on aesthetics and what other people have discovered to produce a pleasing image. My main processing steps were as follows: 
  • Add a Channel mixer layer: Image > Adjustments > Channel mixer. For the red channel, set red to 0% and blue to 100%. For the blue channel set blue to 0% and red to 100%. This effectively swaps the red and blue channels.
  • Add a Levels layer: Image > Adjustments > Levels. Adjust the sliders for black point, white point and grey point to obtain a pleasing range of tones. I was originally advised to automate this by clicking the Auto RGB button, but a bit of trial and error showed that manual adjustment is preferable.
  • Add Hue / saturation layer: Image > Adjustments > Hue/saturation. Use the targeted adjustment control to bring the saturation of the foliage colours into an acceptable range. Similarly, make adjustments to the saturation of the sky. 

That completed 95% of the processing but here I also made some small local contrast adjustments in the long grass-like foliage at bottom-left of image, and in the tree at right.

If it's not clear from what has been said, The real colours were the colours of spring in Scotland - green grass and leaves, and a pale blue sky with white fluffy clouds. The sky was not that colour and none of the foliage was pink. All the colours in an IR image are false colours.

    Monday, 11 May 2015

    Cushnie hail

    The image of hail in an earlier blog prompted me to look again at an image of hail from a few years ago. 
    I was driving through Cushnie in Aberdeenshire in April 2012 when I spotted a hail storm. I pulled in to the side of the road and managed to get about six shots on my Canon 500D (Rebel T1i) before the hail storm fizzled out. (Hail storms really do fizzle.)  

    Original conversion using Adobe Camera Raw. 

    I reworked the original capture using Nik Silver Efex - cropping off part of the foreground, boosting contrast and working to bring out more detail and drama in the hail. I reckon it's an improvement. It's certainly different.

    New conversion using Nik Silver Efex

    Monday, 4 May 2015

    Jazz festival

    Konrad Wiszniewski (tenor saxophone) & Euan Stevenson (piano) played at Banchory's jazz festival on Friday. Last night we had Courtney Pine (bass clarinet) & Zoe Rahman (piano).  All excellent!

    I took a few pictures from a seat in the 7th row using my Sony RX100. The venue was so dimly lit I doubted there would be any usable images. I was forced to go to an uncomfortably high ISO.

    Zoe Rahman and Courtney Pine (1/50 f/4.9 ISO 3200, no flash)

    I am using the original RX100. I am told that the Mark 3 is considerably better, but my model is good enough for now. It's a nice pocket-camera.

    Sunday, 3 May 2015

    Bad weather

    The weather is so bad that I stayed indoors all day. The house is about 280m above sea level, so we sit in the clouds some days. Today we have cloud, wind and heavy rain. Here is today's view through the window.

    But when the weather is kind we can get great views even when the rest of Aberdeenshire has bad weather. Here is an image from Tuesday when large parts of Aberdeenshire were getting hail.

    Hail storms can give interesting images. Bad weather isn't necessarily bad for photography.