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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 ...


52

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, ...


44

A focus rail + stacking software will help you achieve deeper depth of field. However, if you don't have a focus rail (or time to set one up), try to pick an optimal angle to capture as much of your subject as you can. This can mean using an interesting angle (e.g. focusing on the eyes), or using an angle that captures a lot of detail despite the shallow ...


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'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 ...


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 ...


31

Yes of course it can be post processed. It might make it “better.” But it will never make it the picture you wish it was. The good news is that there will be other snakes on other days. Plenty of chances to make better snake pictures lie in the future if you want. There are good reasons to work on pictures that probably can’t be saved. One is to practice ...


29

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 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 ...


23

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

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

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 ...


22

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 ...


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

Several possibilities: In the examples shown, it could be a problem with the subject. The center of the picture is a rather fuzzy plumage for the dove and sharp lines for the white-eye. Your 55-250mm is not so sharp at the long end. Decent lens, but not built/checked to stringent specs like a L series. Only way to tell is to try another lens. Your camera's ...


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

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 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

Focal length is the distance between the lens and the sensor when the subject is in focus, not the distance to the subject. The term for the distance to the subject in focus is the focus distance and is measured from the image plane (sensor/film plane). The distance from the lens to the subject is called the working distance which can be significantly less ...


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

Three things: Film is relatively lenient, and exposure variations are handled in the printing. The lens has a relatively small fixed aperture and focus is set at a reasonable distance to get a lot of depth of field. Finally, prints from these things are usually 4×6, and not subjected to a high degree of scrutiny — we basically expect them to be relatively ...


15

The first image was shot wide open with what is essentially the lowest cost Canon lens (50mm f/1.8), in demanding low light conditions, and at ISO 1600. I'd say your results are exactly what I would expect. The second image, I don't see anything wrong with. My best guess is that you are overly concerned with the quality of each pixel viewed at 100% to a ...


14

For focusing on stars, I suggest using a Bahtinov mask, which uses purposely-created diffraction spikes to determine correct focus. Bahtinov mask by Justin Dolske, from Flickr. CC BY-SA-2.0 This image montage is an example of a Bahtinov mask on a telescope focusing on the star Betelguese. The center image is correctly focused; the other two images are ...


14

Because the way human vision perceives a two dimensional representation of the three dimensional human face if the nearest eye is in focus it looks to us more like the whole face is in focus. Even if the question is regarding group portraits (the question is rather nebulous at this point) it still holds true. A group portrait with the front person(s) in ...


14

You are just too close to your subject. Cell phone cameras and "Point and Shoot" cameras can take photos from very close distances. DSLR cameras can not. It is actually the lens that determines how close you can shoot. Most general purpose lenses have a minimum focus distance of about 9-12 inches. If you need to focus closer you can buy a specialty "Macro" ...


13

Yes, it's possible With the focus stack you could estimate a depth map of the scene. Then this map is used to selectively blur the image to emulate the effect of shallower depth of field. See for example: https://graphics.stanford.edu/papers/focalstack/ You could of course use other methods to generate the depth map, such as moving the camera (as the ...


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