Posted by John Williams on April 15, 2010 at 9:37 AM
In one of my ESS photos, Pavel asked a follow-up question to my article about depth of field blending, and rather than end up with a technique discussion in a gallery I thought I’d post my answer here. While recognizing that everyone has a bit of a different style of photography, here’s what has worked for me when taking photos that I will blend for DOF.
First, I recommend stretching out a long tape measure, mounting your camera on a tripod at a typical height (if I remember correctly my camera was about 12” above the ground), and taking photos with the lens you are testing. Move the focus ring in small, yet recordable, increments, and make a note of which photo was focused where. You will likely need to angle the camera up and down as you work closer and farther from where you are. You can then take these photos to the computer, stack them in layers in a single file, and then align them (with Photoshop’s Auto-Align for example). By clicking these layers on and off you can get a reasonable idea of where the image will be acceptably in focus at each setting. Obviously, you will need to turn off your camera’s auto-focus. In addition, use manual settings on your camera to keep exposure consistent. In an earlier experiment, I had tested my lens in a similar way to determine that it held sharpness well at f/16, so that’s what I used to test focus in my experiment.
Second, start simple. The photo Pavel asked about in ESS was a blend of four shots. If I had started with something this complex, I would have pulled my hair out by the end. A better method would be to analyze the test shots and find a distance where two shots have a large zone of overlap. One photo should be in focus except for the very top, and the other in focus except for the very bottom, with a nice section in the middle of both photos that is in focus. Find in the notes you took what your lenses focus ring was set at for these two photos, and note in the picture at what distance on the tape measure this effect happens. Then take these numbers, your camera, and tape measure and take a “real” photo at this distance and focus settings. Try blending these two photos as a first step. Be sure to avoid close subjects that superimpose on distant subjects. For example, you don’t want a flower that is 12” away to be directly superimposed on your skyline. Rather, find a subject with a gradual and smooth transition from near to far to protect that zone where both photos are in focus. A great example would be a lawn or a field of short flowers.
Third, bracket. I always pad my odds by taking a shot focused closer than I think I will need, and another focused at infinity. Even though I usually trash these, it’s hard to impossible to go back and get an area in focus that you missed the first time. In addition, if I think there is an area that might be difficult due to the superimposition noted above, I’ll bracket a few shots in that area to try and get both close and far in the same photo. If you look closely at the photo Pavel posed the question on (try viewing it large), notice how some of the taller and closer Blue Dicks superimpose on more distant rock and grass behind. The main reason I took parts from four photos to blend this image was to compensate for this.
Hopefully the above is more helpful than confusing. To sum, find a favorable subject, get to know your particular camera and lens, and then bracket focusing just like you would exposure.
Thanks John, ive been using the advice you gave me months ago and im slowly learning. What id relaly like to know is if Helicon Focus is much better than the latest CS4 (upgrades did impriove the stacking) for landscapes? Anyone know??
My experience with this technique is that when the plane of focus is moved within a scene, the objects in the scene move their positions slightly. This has made blending many landscape images impossible because virtually nothing is lined up, or overlapped correctly. This may vary with different focal length lenses, but my experience was with wides. I finally gave up and now either stick to my large format or use the Canon 17 t-se.
Discussion
5 repliesFirst, I recommend stretching out a long tape measure, mounting your camera on a tripod at a typical height (if I remember correctly my camera was about 12” above the ground), and taking photos with the lens you are testing. Move the focus ring in small, yet recordable, increments, and make a note of which photo was focused where. You will likely need to angle the camera up and down as you work closer and farther from where you are. You can then take these photos to the computer, stack them in layers in a single file, and then align them (with Photoshop’s Auto-Align for example). By clicking these layers on and off you can get a reasonable idea of where the image will be acceptably in focus at each setting. Obviously, you will need to turn off your camera’s auto-focus. In addition, use manual settings on your camera to keep exposure consistent. In an earlier experiment, I had tested my lens in a similar way to determine that it held sharpness well at f/16, so that’s what I used to test focus in my experiment.
Second, start simple. The photo Pavel asked about in ESS was a blend of four shots. If I had started with something this complex, I would have pulled my hair out by the end. A better method would be to analyze the test shots and find a distance where two shots have a large zone of overlap. One photo should be in focus except for the very top, and the other in focus except for the very bottom, with a nice section in the middle of both photos that is in focus. Find in the notes you took what your lenses focus ring was set at for these two photos, and note in the picture at what distance on the tape measure this effect happens. Then take these numbers, your camera, and tape measure and take a “real” photo at this distance and focus settings. Try blending these two photos as a first step. Be sure to avoid close subjects that superimpose on distant subjects. For example, you don’t want a flower that is 12” away to be directly superimposed on your skyline. Rather, find a subject with a gradual and smooth transition from near to far to protect that zone where both photos are in focus. A great example would be a lawn or a field of short flowers.
Third, bracket. I always pad my odds by taking a shot focused closer than I think I will need, and another focused at infinity. Even though I usually trash these, it’s hard to impossible to go back and get an area in focus that you missed the first time. In addition, if I think there is an area that might be difficult due to the superimposition noted above, I’ll bracket a few shots in that area to try and get both close and far in the same photo. If you look closely at the photo Pavel posed the question on (try viewing it large), notice how some of the taller and closer Blue Dicks superimpose on more distant rock and grass behind. The main reason I took parts from four photos to blend this image was to compensate for this.
Hopefully the above is more helpful than confusing. To sum, find a favorable subject, get to know your particular camera and lens, and then bracket focusing just like you would exposure.
And thanks for the article too Rodney Ninow! Very interesting and amazing picture!
Sarah