DOF2. Testing The Theory Most photographers accept the common belief that short focal length lenses have greater depth of field than do long lenses. A wide angle lens, in other words, will give greater depth of field than will a telephoto. Right? Sounds about right, but it's not the case. In fact, if the subject image size remains the same, then at any given aperture all lenses will give the same depth of field. Because this is such a controversial statement, and because it initially flies in the face of common experience, I have created the following set of example images. The set-up for it was as you see below.
Each of the frames below was taken so that the gremlin doll is exactly the same size in each frame. Focal lengths from a 400mm telephoto down to 17mm ultra-wide were used. The Depth of Field is Essentially The Same As you can see, the degree to which the tower and the hand puppet are out of focus is essentially identical in each frame regardless of focal length. 400 mm 200 mm 100 mm 50 mm. Focus and Recompose. • You are here --> BobAtkins.com > photography > technical > This Page Before the days of cameras with multiple focus points, it was common to focus on the object of interest, lock focus and then recompose. However from time to time you see comments in photography forums that this process can lead to focus errors. So what's the truth? Does focusing and recomposing lead to focusing errors? The answer is yes...and no!
To explain this I'll use the diagram below which shows how a rectilinear lens (and most photographic lenses that aren't fisheye lenses are rectilinear) forms an image on a sensor. If the distance at which the lens is focused on "C" is given by "d" as shown in the figure, then the distance to the points "R" and "L" will be given by x = d/cos(theta), where theta is the angle between "C" and "R" (or "L"). So let's take an example. But will it matter? So when won't it be OK? Let's look at a 20mm f2.8 lens on a full frame 35mm camera and focused at a distance of 1m.
How to do AF Microadjustment (50D) - Digital Grin Photography Fo. Lovin' It Join Date: Feb 2006 Location: Newport News, VA Posts: 6,510 How to do AF Microadjustment (50D) You have this beautiful camera (the 50D) and a host of lenses. But, you mount a lens and take a picture. And you're a pixel-peeper (like me ) and the image doesn't have that stellar sharpness you were hoping for.
In the past is was the whole send the lens in for calibration, get it back, still not sharp, complain, "Oh, you need to send in the lens and the camera" .... Not any more. The following are the steps I've arrived at to get the job done in the quickest time possible. Note: In these images, the focus point is on the center of the nearly healed over know near the center of the crops. The steps: Mount your lens.Set your camera to Av mode, RAW only, and set the aperture to the maximum provided by your lens.
Hyperfocal Distance and Depth of Field Calculator - DOFMaster. Why Focus-Recompose Sucks. In most modern SLR cameras, the autofocus sensor located at the center of the frame is generally designed to be more sensitive and more accurate than most or all of the camera's other AF sensors. In low-light situations, it is possible for the center AF sensor to be the only one that will reliably lock on to the subject and achieve focus lock. This has given rise to the technique of center point focus-recompose, which involves placing the center AF sensor on the portion of the subject that needs to be the most clearly focused, and activating autofocus.
Once focus has been achieved, then the camera is reoriented until the desired framing is achieved, and then the shutter is released. There's just one problem with this idea: it is 100% guaranteed to cause focus to be behind the intended center of focus. To understand why, one needs to understand some basics of modern lens design. In this example, the correct distance setting is 6.456 feet, represented by the horizontal green line.