Photography Travelogues by Peter Eastway – Karijini National Park 2/3

June 7, 2011 by 8 Comments

Dales Gorge, But Not Sunset

Things are not always what they seem! The strong reds and oranges in the photograph of Dales Gorge in Karijini National Park, Western Australia are not from an early morning sunrise or a late sunset. Rather they are from sunlight reflected off red canyon walls.

Australia’s ‘Red Centre’ is at its reddest in Western Australia and there are few places I have visited that are as colourful as Karijini. As you walk down into the gorges, steep textured cliffs rise above you and if they catch direct sunlight, it is reflected strongly into the water pools and cascades below.

It might seem like a relatively straightforward matter to walk along the base of the gorge, looking for reflections – and to a certain extent it is. But those reflections don’t stay in the one place for long and so you can find yourself constantly moving your camera angle to retain the light and the colour. For images like this, mid morning and mid afternoon are usually the best times because this is when the sun is strongest on the gorge walls, but the gorge itself is still in shadow. The dim surroundings contrast wonderfully with the rich colours reflected from the cliffs up high.

This image is taken with a mid-telephoto lens, ideal for the angle I wanted, but challenging in terms of depth-of-field. To make the most of the location, I wanted sharp focus all the way from the bottom of the frame up to the top. A small aperture (like f22) almost gave me what I wanted, but as you stop down a lens (use a smaller aperture), diffraction increases. Diffraction reduces image clarity and occurs when light is forced through a small aperture, so while a smaller aperture is increasing image quality with more depth-of-field, at the same time you’re losing image clarity through diffraction.

My solution is to use a wider aperture – such as f8 or f11 – and shoot a series of images, each focused at slightly different points.

This series is then ‘stacked’ together. A popular program for ‘focus stacking’ is called Helicon Focus (www.heliconsoft.com) and while originally designed for scientific applications, it can work wonders for landscape photography as well.

To get the best results from focus stacking, you need to ensure your camera is locked off on a sturdy tripod. Although the light was changing quickly, I forced myself to slow down and ensure I had a good camera angle. I use an Arca Swiss Cube head on my tripod and it allows very precise positioning and once set, the camera won’t move. With the camera ready, I switched to manual focus and took a series of six images with different focus settings, beginning close to the camera and extending out to infinity. It’s a good idea to use manual exposure mode as well to ensure the exposures are consistent.

In Capture One Pro, turning on the Focus Mask quickly shows you where each image is correctly focused, the green ‘mask’ covering the areas of critical focus. If you’ve focused accurately, you can determine which frame gives you best focus in the foreground, and then follow the exposures through until you find the one with the best focus in the background.

Once I had selected the five files I needed, I refined the exposure, colour and tonal settings on the first frame. Then I copied up these adjustments (using the upward sloping arrow icon) and applied them to the other four images (using the downward sloping arrow icon). The images were then output – I produced full size 16-bit TIF files.

With my five files processed, I then opened Helicon Focus, selected the files and further processed them into a single file where the small curve of rock in the bottom left of the frame is just as crisp and sharp as the small cascade in the middle up the top of the frame.

The result is an image with more clarity and sharpness than a single frame taken at f22, both in terms of the extent of focus, and the lack of any diffraction.

To see more of Peter Eastway’s photography techniques, including his Landscape Photography MasterClass, please visit http://www.betterphotography.com/.

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Achieve sharp images with wide angle lenses

March 31, 2011 by 40 Comments

With today’s high-resolution cameras, you are required to pay much more attention to how you shoot in order to get sharp images.

Focusing is harder than ever:

For wide angel lenses, the tolerance for when the lens is properly focused is extremely narrow. Often the tolerance for the autofocus system is not tight enough to get the most out of modern lenses.  When using wide angle lenses, you can easily achieve extreme wide depth of field reaching from infinity to a few meters in front of the lens. The focusing just needs to be perfectly right – I call it the focusing sweet spot.

Use manual focus:

Test your lens to find and mark your focusing sweet spot. This will give you sharper and more consistent images.  In doing this, you will sometimes find that the lenses you previously found disappointing now give you exactly what you want.

The examples above is a 200 % zoomed view of an image which was shot from my office window, and you can see just how big a difference it makes when you use the lens focusing sweet spot compared to just using the autofocus system. This example is made with a Canon Zoom at 17 mm. but could have been made with most other wide angle, primes as well as zoom lenses.

  

Find your focusing sweet spot

The easiest way to find the focusing sweet spot is to shoot tethered, as you get immediate feedback on how well you are focusing. With Canon and Nikon cameras, you will have tethered functionality directly in Capture One 6 Pro. With other camera brands, you can use Capture One´s hot folder functionality to get your images into Capture One by using a vender specific program for shooting tethered.

Steps for finding the focusing sweet spot:

  • Ideally, find a location where you can focus on infinity where you have objects all the way from infinity to a few meters from the camera.
  • Place your camera on a steady tripod
  • Make sure to turn off any image stabilization as this may influence the sharpness from shot to shot.
  • Set camera on manual focus
  • Set the lens to full open.
  • Shoot a series of images where you sweep through a range of focusing positions near the focusing point for infinity. For each image, check if you have better sharpness in the center of the image at a zoom level of 200-400 %. Once you have achieved maximum sharpness mark this point on the lens with a pen.

On this zoom lens, I have marked the position for the best focus on infinity.

Steps for finding the aperture that gives you the best compromise between sharpness and depth of field:

  • Set focus on the marked position for maximum focus on infinity
  • Take an image at each aperture step. 
  • Compare the images side by side to see the effect of stopping the lens down.  In Capture One Pro 6, you can simultaneously zoom into a maximum of 12 images. Doing so is a big help for this analysis

Typically, you will see that you get the best sharpness at 1-2 f-stops from full open.   Stopping further down may lead to softer images in the center. You should also check the edges and objects closer to the camera. For very vide angle lenses like 10-20mm, the depth of field is extremely deep even for apertures like 5.6 and 8 and stopping further down may not give you an increased depth of field as the whole image may just become softer.

With the lens set at best focus for infinity, I shot at each full aperture step.  Above are a 200 % zoomed view of the centers of the images.  At f5.6, the image is at its sharpest, but the range from f4-11 also works well.  At f16 and f22, the image sharpness decreases dramatically.

 The images above show a 200 % zoomed view of a car half way between “infinity” and the camera. Contrary to what one might expect, the increased f-stops doesn’t give a greater depth of field. As the lens is stopped down it just becomes softer and softer. Again the image is actually most sharp at f5.6.

Setting the sweet spot – Optimizing focusing for the best aperture:

My goal is to be able to achieve the sharpest possible image from infinity to as close to the camera as possible. With the lens stopped down will my initial focus mark on the lens still be the best compromise? My experience is that for most wide-angle lenses, primes as well as zooms this is actually the best compromise, but to be absolutely sure, we need to check it out.

Set the lens at your mark for the best focus for infinity.

  • Take some shots where you focus slightly closer than infinity.
  • For each shot, check if you get a better compromise between best sharpness at infinity and the deepest depth of field.
  • Mark the lens with a pen at the point where you have the best compromise.  

Now you have found the focusing sweet spot for the lens. Next time you need maximum sharpness and maximum depth of field, set your camera to manual focus and use your sweet spot mark on your lens. Doing this, you may achieve sharpness you may not have thought possible.

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