Light Trails

Use Back Button Focus to Pre Focus

Sometimes it’s useful if the shutter button doesn’t focus. Instead you press another button to focus. I’ve used it in the past when shooting street photography (focus on the ground and I know anything a metre away will be in focus), and at night on a tripod when taking long exposure shots of moving lights.

Back button focus is when you don’t use your shutter button to focus the camera. Instead you’ll use a button on the back of your camera. Not every camera can do it but check your manual or use Google to search for your camera name and “back button focus”. Here are two good videos describing why it’s good for sports photography:

Here’s a video I found to get it working on the Canon 6D using the AF-On button. I usually use the Q menu now to disable focusing on the shutter button.

The beauty of back button focusing is that you can focus your camera before the proper shoot and then take as many photographs as you want of the scene, often when the lighting has changed and focusing is impossible. This is especially important at night, but it also lets you shoot faster as the lens is already focused. This may just mean the difference between a great street photo and a missed opportunity.

Finally, here’s a photo I shot last night using back button focus to set up the shot. I could as easily have manually focused the lens but this worked just as well.

Light Trails

Aperture ƒ/4.5
Camera Canon EOS 6D
Focal length 17mm
ISO 100
Shutter speed 10s
Sensor dust

How to clean your camera sensor

One of the horrors of owning a DSLR and using multiple lenses is the dread of getting dust on the camera sensor. In small amounts it’s visible whenever you shoot using a small aperture like f/22 but if you leave it go too long you’ll see round smudges show up on your every day snaps at f/8 or f/4 too.

This video describes part of the process I go through when I clean my camera lens. A Nikon body is used in the video but the method is similar for Canon and other manufacturers. I only have a blower and soft brush but they have served me well over the course of the last decade.

Cleaning the sensor is risky. It’s a sensitive piece of electronics but there’s an infrared filter in front of it and that’s what you’re really cleaning. It’s sturdy and tough but if you pushed too hard on it you will scratch it. I’ve never scratched the sensors of any of my cameras though so I don’t worry too much about it as long as I’m careful.

After blowing and wiping the dust away you should do the same with the inside glass of your lens. It’s likely that’s where the dust came from in the first place.

Once I’ve rebooted my camera I’ll test the sensor by doing the following:

  • Grab a sheet of clean white paper.
  • Set the lens to manual focus, the camera to shoot RAW, and change it to aV (or A) mode to change the aperture to f/22. If you use any exotic shooting styles reset them to standard.
  • Prop the paper on a shelf in clear light.
  • Shoot the paper. You don’t have to worry about it being a long exposure and camera shake. The dust on the camera sensor won’t move!
  • Examine the picture on the camera LCD, zoom in and you’ll see any remaining dust particles as black dots. They’ll look like the images below.
  • Repeat the “mirror lockup, clean, check” cycle until you’re happy with how much dust is left.

dust on the sensor

dust on the sensor

Aperture ƒ/22
Camera Canon EOS 6D
Focal length 24mm
ISO 100
Shutter speed 1.3s

Long Exposure Photography through Stacking

The usual way of taking long exposure photos is by leaving the shutter open for a long time. This requires either a dark location or ND filters of some sort on the end of your lens. There is another way and that’s called image stacking.

In a nutshell, you take a series of well exposed photos of short exposure for the same duration you’d use for a long exposure shot. Then in development you create a number of images files which are then merged together to create a final “averaged” image. You can use Photoshop, GIMP, Imagemagick or I presume many other apps to create this image. I used Imagemagick here as I don’t have Photoshop and didn’t want to load all those images into GIMP and I had read that “convert” would do a good job.

Here’s one I created earlier today in the slightly shady but bright gardens of Blarney Castle:


The images that went into creating that image all look like this. They were shot at f/4, mostly shot at 1/80 of a second and ISO 100. I wanted fast images with minimal noise and the scene is mostly flat so I wasn’t too worried about depth of field.


To make this image I took 27 photos of the scene. I imported them into Lightroom (didn’t do much apart from applying my default settings) and exported Jpeg files. In the directory where I exported them I ran the convert programme from ImageMagick like this:

convert *.jpg -average average.jpg

That command was used by Luis Argerich, the author of this post who created a simulated 4 hour exposure of the sky and went on to say:

Averaging can be used in static scenes to create a new photo with less noise. Noise is reduced in the function of the square root of the number of images. So if you average 25 shots you have 5 times less noise than in a single image.
Averaging can also be used in non-static scenes to simulate a long exposure.

Patrick David in this post suggests a slightly different command which I tried and it created a similar photo.

If your exposure somehow went wildly different with some images bright, some dark, use the “Match Total Exposures” feature in Lightroom to pull them back.

ImageMagick is fairly easy to install. If you are using Linux you probably already have it installed. You can download it from this site or if you use Mac OS X, install Homebrew and then it’s as simple as this to install:

brew install imagemagick

Here are a few more examples:


This one didn’t work out. I was trying to capture the swirling of the bubbles on the water.


This one works better. The source photos are all around 1/25th of a second which is certainly not fast enough to freeze the water.


Almost happy with this one. The source photos go from 1/60th to 1/100th of a second.


I like this. It was created from ten photos shot at f/4, 1/60th sec, ISO 100.

I didn’t try very hard to make the images here pretty. They’re purely experimental and done with minimal effort but I’m very happy with most of the results. In shaded daylight I was able to take the equivalent of five to ten second exposures without ND filters or reducing the size of the aperture. It would have been easier to make the aperture smaller and add an ND filter but that’s not the point of this exercise.

One issue that may bite you is the speed of your media. My camera quite often flashed a “busy” notice because it was writing to the SD card. Then again, I was shooting 20MP images and my card says it’s rated at 30MB/second which is a problem as each image is around 20MB. As they’ll only ever be viewed online that’s probably not really needed. I might try the half-size option next time.

One nice bonus to this method is that Google Photos will generate nice animated GIFs from your image stack. I posted mine here. I won’t embed them as the files are huge!

I’m definitely trying this out again!

Aperture ƒ/4
Camera Canon EOS 6D
Focal length 24mm
ISO 100
Shutter speed 1/60s
San Francisco, 2007

Shoot … in the Style of Garry Winogrand

Tomorrow I’ll be braving the streets with Cork Streetphotography taking photos in the style of Garry Winogrand.

I’d never heard of Garry but a quick Google brought me plenty of digest. First this documentary, filmed in 1982, that showed his technique and friendly nature:

Then I came across this excellent blog post about the man. To summarise his technique:

  • Shoot, shoot, shoot.
  • Garry Winogrand shot with a 28mm lens. That’s fairly wide, so he was always in the thick of the action. No telephoto lens allowed.
  • He would frame his shot by looking through the viewfinder, so no shooting from the hip.

You can see in the video above how he fiddles with his camera to distract the people around him. That’s not a bad idea, especially when you have a wide lens!

Camden Wharf, Cork

The tips from that post, which I urge you to read:

  • Shoot, a lot
  • Don’t hesitate and follow your gut
  • Smile when shooting on the streets
  • Don’t shoot from the hip
  • Don’t crop
  • Emotionally detach yourself from your photographs
  • Look at great photographs
  • Focus on form and content
  • Become inspired by things outside of photography
  • Love life

Camden Quay, Cork

I’ll be only using my wide angle (17-40mm) lens so I won’t be tempted to zoom in too much. Tomorrow will be challenging.

The photos in this post are mine, just in case you’re not familiar with Cork. I shot the first photo in San Francisco in 2007. You can find many images by Garry Winogrand on Google Images.

Aperture ƒ/8
Camera Canon EOS 6D
Focal length 24mm
ISO 100
Shutter speed 1/200s
We love WordPress

Use Lightroom Collections to Publish Photos

Since I started posting photos online I’ve always created two images:

  1. A web sized version to go online.
  2. A full size version for my archive.

This has served me well as I have from time to time changed the software I use to develop photos. Otherwise, I might have the web version and not be able to recreate a full size version for printing or other uses.

Up until very recently after I worked on an image I would add it to an “inphotos” default collection (press B), then right-click and export twice. Once for web, once for full size. I had to do this for each image. Sometimes I could select a bunch of them and export if I knew I had a number of “keepers” from a shoot but otherwise it was tiresome.


I’m now experimenting with smart collections in a Hard Drive Publish Service. I still have an collection, but I added another one called, “Published inphotos”. That’s a smart folder that contains all the published photos that have already gone up on the site. That folder contains every image that comes from the collection and is labelled Yellow.

Aside: I also added a “Potential” smart folder for photos I’d like to work on. Labelling a photo RED will put it in this folder.


Obviously I haven’t added every published photo to it and I probably won’t. I don’t have time to, but I will fill in older photos when I have a spare moment.

If you’re not familiar with collections here are two videos from Adobe on ordinary collections and smart collections that are worth watching:


Publish Services

I then created two publish services. One for full size images, the other for web images.


The 00-inphotos and 00-Large smart folders initially contained every image that is in the collection. I soon realised I’d have a problem with the web sized 00-inphotos folder. If I published a photo how would I remember that event easily? In the past I moved the file into a different physical folder, but I wanted Lightroom to track this. To do this I decided to add a yellow label to every photo I published. I created a new “00-published” smart folder. This folder collects every image that is labelled Yellow from the collection.inphotos_published_smart_folder_settingsI modified the 00-inphotos smart folder so it contained every image except those labelled Yellow.inphotos_smart_folder_settings

So, when I published an image I went into the collection in Lightroom and labelled the image yellow by pressing “7”. This would cause the 00-inphotos smart collection to delete the image, and the image would be added to the 00-published smart collection. I just had to hit Publish on each of them and the file would be “moved” from one physical folder to the other.

It’s early days yet and I’ve only posted a few photos using this method but it works well. Editing photos and adding them to the collection is a breeze but this is a process that’s not set in stone and will be refined with time. If it’s too awkward I’ll move on to something else.

I use the WordPress “new post” interface to make new posts, or if I have time to do so, I’ll schedule a number of posts using Postbot.

How do you use Lightroom to post to your blog or social media site?

The Brenizer Method – shallow DOF and wide angle

I love shallow depth of field and the Brenizer Method (or bokeh panorama) is an intriguing way of achieving that in a wide angle shot.

Basically, with your lens zoomed in you take many overlapping photos of your scene like you would a panorama but you don’t go for the traditional 360 degree image. It’s more like 50-90 degrees, or what a “normal” lens would see. The beauty of the technique is achieving a very shallow depth of field because your lens is zoomed in and the DOF is shallower still than it would be wide open, or so I’ve read. I haven’t managed to take such a photo yet!

Here’s a great video showing how to do it with Photoshop, but you could use Hugin or Microsoft Ice as well.

Take a look at the stunning photos here, here and here. Beautiful.

Quickly Match Exposures in Lightroom

I had no idea this existed, but then I’ve rarely had to match the exposures of multiple files. When I used the GIMP to edit photos I would play around with multiple exposures more often but Lightroom can extract so much information from RAW files it covers 99% of my image development.

tl;dr – fix the exposure of one image, select other relevant images and click on Settings->Match Total Exposures.