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56

The effect's name is parfocality, we are speaking of parfocal lenses. Lenses that change their focus when zooming are called varifocal lenses. Like reducing focus-breathing (change in focus also changes the focal length), parfocality is a premium-feature. Since photographers usually work with autofocus and since photographers tend to not recompose the image ...


48

You're not doing anything wrong. You're just finding the limits of the camera/lens combination you are using. The EF 50mm f/1.8 (in various versions) has been known as the "plastic fantastic" for a long time. For what it can do at what it costs, it is a fantastic value. But it isn't really a fantastic 50mm prime lens when compared to many others that, ...


40

If I have built my device with the correct distance between the flange and the optical plane, does this mean the (inexpensive) lens I am using is bad? If you had built your device using the proper specified flange distance of 17.526mm instead of rounding it off to 18mm you probably would not be asking this question. 0.474mm doesn't seem like much, but it ...


39

It depends. In many cases, it may actually be possible without any further visual aids in the picture. Many lenses, if not most, will show different longitudinal chromatic aberration in front of and behind the focus plane. If you scroll down just a little bit on the linked page, you will see this demonstrated with a picture of a focus test chart. With this ...


38

It's worth noting that sensor size plays a huge role in depth of field and behavior of the lens. A smartphone has a tiny camera sensor, often around 25 square mm. This gives the camera a crop factor of about 6. (For the Samsung S9, I'm not sure about the dimensions.) You can calculate the hyperfocal distance (or "depth of field") but you can also get a ...


37

What you are looking for is large depth of field. This is an optical property, not something applied as a special effect, so it's not something you can turn on or off. The raw image captures the light focused by the lens, and inevitably there will be parts of the scene which are either too far or too close — out of the range where the rays are tightly ...


28

It is for the same reason that chromatic aberration occurs at all: different wavelengths of light will bend at slightly different angles when passing through the same refractive medium such as a lens element. Chromatic aberration in most well designed photographic lenses will be less severe because the lens has been designed to correct for it at the various ...


27

It is not just cheaper lenses. Many modern lenses, especially Auto Focus zoom lenses have this characteristic. There are several reasons for it: Unless a lens is parfocal the exact point of infinity focus shifts as the lens is zoomed in or out, and so obviously there will be a point where infinity for one focal length is past infinity for another. As ...


27

It sounds like you're doing almost everything right, but there's one detail that caught my attention: Aperture highest the lens offers. I'm assuming that this means that you are stopping the lens all the way down. You shouldn't do that, because the small aperture results in a less sharp image overall due to diffraction. See What is a "diffraction limit&...


27

There's more depth of field behind the focus than in front of it. So focussing on the near eye gives you the best chance of getting the whole face in focus. If you can't do it focussed on the near eye, you can't do it without changing something (position, angle, aperture). In addition, you'be got a good chance of a clear view of the near eye, making ...


27

Do convex lenses make parallel light rays of different wavelength converge to different points? Yes. The separation of different wavelengths of light is called dispersion. Different wavelengths of light refract at different angles because the refractive index of a transparent medium is frequency dependent. We often describe different materials, such as ...


22

Not a digital camera/sensor, but the Contax AX film SLR was able to move its film plane forward and back via a ceramic rail and ultrasonic motor in order to be able to autofocus the normally-manual-focus-only C/Y mount Zeiss lenses. Indeed, Hasselblad V system lenses could be mounted to the Contax AX via an adapter, and the moving film plane allowed for ...


22

Fun idea. That could be called hyperlapse. If you use a specific memory card for that project, you can always switch from viewing the first photo of the project to live view. Another option is that you built a box with a grid or something and put it in front of your camera, like the old matte paint technique used in cinema. Instead of having a paint of a ...


22

You can focus manually. To do that with the Nikon AF-S DX NIKKOR 18-55mm f/3.5-5.6G VR II supplied as the kit lens with the D3300, you need to slide the switch on the lens to M for manual focus. It's the switch labeled "A-M" for "Auto Focus"/"Manual Focus". With many non-SWM lenses with an "A-M" switch (AF/M switch on non-USM Canon lenses) you should not ...


21

The twisting motions you apply to focus and zoom rings are converted to forward and backward movement by helical threads and tracks cut into the barrels inside the lens. This photo shows an example of the threads that do the focusing duties in a partially-disassembled Nikkor prime: Note the tracks cut into the inner barrel and the metal rails in the outer ...


21

Light from a far distance object, like a star, arrive at the lens, as parallel rays. As they transverse the lens, they are forced to change their direction. They bend inward, we call this refraction from the Latin to bend backwards. We can draw a trace of these rays; they trace out the shape of a cone. What we find is, the apex of the violet cone of light ...


20

If by "landscape" you mean something like this: then the answer is simple: at very large distances, depth of field is extremely large even at large apertures. That is, at any aperture if you focus at infinity, objects 20m, 200m, and 2000m from you will be sharp. However, focal length of the lens also influences depth of field, see answers below. Smaller ...


20

When the aperture is positioned to minimize vignetting, the bokeh shapes for objects that are too far is rotated by 180° compared with objects that are too near. (The aperture image is reflected through its center point.) If the arrangement of your aperture blades is not symmetric around the center point, you can try finding "reference bokeh" that are ...


20

There's only one distance that is in sharpest focus. Everything in front of or behind that distance is blurry. The further we move away from the focus distance, the blurrier things get. The questions become: "How blurry is it? Is that within our acceptable limit? How far from the focus distance do things become unacceptably blurry?" What we call depth of ...


19

The two generally control two different aspects of the image projected by the lens. Focusing sometimes has the effect of changing "zoom" a little as well, however its purpose is different. To keep it simple: Focus adjusts the Focal Plane The focal plane is the thin plane of reality that is focused clearly on the imaging medium Focusing moves this plane ...


19

The reason tilt-shift "sells" the miniature effect to the eye is that it allows both the foreground and background to be out of focus. We are accustomed to seeing images of city scenes, for example, where the foreground is a bit blurry, or the distant background is out of focus, but not both. Normal lenses shooting these scenes near infinity focus will ...


18

Hitting the DOF preview with a stopped down aperture should make it obvious: what you see can be very dim, dim enough it can be very difficult to compose and focus. That's why cameras have the lens wide open until actually taking a picture, so you can get the brightest image by which to setup your shot.


17

Have you tried the High Pass Filter in Photoshop? Make a selection around the area of the image you need better focus on, press ctrl-J to jump this to a new layer. Then, in the Filter menu, scroll down to Other, and choose High Pass. Depending on how large your photo is, you might want to choose from 1-6 pixels. You will probably have to ...


17

Rachael, it sounds like your aperture is set to a wide aperture (low f-number), allowing lots of light in, but at the expense of a very narrow 'depth-of-field'. This creates a thin slice of focus where anything before or after is blurry. Let's assume you're 2 feet away from your subject when taking a photo with your 50mm lens. Most common SLR 50mm lenses ...


17

I don't have Photoshop, but there's an ancient open source project called refocus-it (for iterative refocus), which uses some of the same techniques as Photoshop's new-in-CS6 deblur feature. This should give better results than sharpening with unsharp mask or a high-pass filter. Below, I chose (after some experimentation) a radius of 3.1 and (since the image ...


16

The lens is not parfocal in either direction. What you have discovered is the difference between narrow Depth of Field (DoF) at longer focal lengths and deeper Depth of Field at wider focal lengths. The focusing error you introduce when you focus at 18mm and then zoom to 105mm is greater than the shallow DoF at 105mm even at f/8, so you notice how out of ...


16

The ideal lens would cause light beams of every color to come to a focus at the same distance from the lens. That would be the focal length of the lens when the lens is imaging at infinity (∞ as far as the eye can see. When we image objects that are closer than infinity, they come to a focus further away from the lens. That is why we must cause the camera ...


16

The use of a large diameter, f/3.2 aperture allowed you to set the shutter at ½ second. You captured snow as it tumbled down. The shutter speed is insufficient to freeze the falling snow. The flakes you captured were moving, thus the camera recorded them as streaks. More importantly, the f/3.2 aperture yields a shallow depth-of-field. If you look closely, ...


15

This is called focus breathing. With some lenses, especially macro lenses such as the Canon EF 100mm f/2.8 Macro USM, this effect can be substantial—at the minimum focusing distance, the focal length becomes about 70mm. While this is not normally an issue in still photography, it can pose a problem in video shooting as it can cause the angle of view ...


15

The simple recipe is to convolve with a Laplacian of Gaussian kernel (3x3, with 8 in the middle surrounded by -1 and take the abs(result)) . After this you get some artifacts if it is a jpeg image, and out of focus borders that have a high intensity difference will also "ping". The result you can threshold to detect the strongest edges and remove teh ...


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