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27

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 ...


13

Many older or cheaper phone cameras use a "fixed focus" lens. ie it is always set to focus a specific distance away from the camera. This is usually set to the "hyperfocal distance", ie everything from half that distance out to infinity is in focus. This depends on just what is acceptable as 'in focus'. But most photos from these cameras will be sharp ...


13

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 ...


10

Does anyone know if this software uses the Brown-Conrady model to achieve the lens correction? Yes they do use those very common camera calibration coefficients. I added some copyable text versions of the formulas to the following quote: Adobe Camera Model Geometric Distortion Model for Rectilinear Lenses xd = (1 + k1*r^2 + k2*r^4 + ...


8

The 1200mm lens you cite is something of an aberration, since it's built-to-order, not a general-market lens — see Why are some big telephoto lenses so expensive compared to telescopes? and Why are some lenses so expensive?. But the general rule holds true: lenses for DSLRs and most mirrorless cameras are gigantic compared to those in superzoom cameras. ...


7

I think that you are underestimating how bad a bad lens truly is. It is going to be very obvious if you pickup a real dud and it is acting like a $500 vs $1,600 lens. You can and should run though the related question and its recommendations for testing any new lens: How can I test a new lens to make sure it is operating correctly?. You state that you ...


7

What you are seeing in the photo is a specific type of lens flare known as ghosting. It is an inverted and reversed reflection of the brightest highlights of the scene. If you were to draw an x and y axis intersecting in the center of the photo, all of the artifacts in the photo have corresponding bright light sources at the same distance from center and at ...


7

However, someone has told me that if in both lenses I will use f/1.8 aperture, still the latter lens will have more light. It sounds illogical because it's wrong. At f/1.8, both lenses will let in (approximately) the same amount of light. I say "approximately" because the f number is derived only from the ratio of the focal length to the size of the ...


7

Why does it seem like large sensors are necessary for good low-light performance? Because for the same amount of light passing through a lens a larger sensor will collect more of it. Your tire size analogy is seriously flawed. A better analogy would be increasing the diameter of the engine's cylinders. The size of the individual molecules of the ...


6

No, this is not diffraction. Let's start by recalling how the image is formed by the lens (focused and defocused): Each point of your large aperture lens contributes to just one point of the defocused image: (by the way, this also shows why aperture size affects (de)focus) And what happens if you place an obstacle (your hands) near the lens? Not all ...


6

This isn't just one company creating their own buzz, and corresponding buzzword, for marketing purposes. This has been an important advance in optics in general over the last 15-20 years. The technology is still in its early phases, where there is a lot of proprietary knowledge being closely held by the companies that develop this. I suspect it will be ...


5

Your basic assumption about teleconverters is right. But you haven't done the math: 1/2" is 6.4mm x 4.8mm—doubled is still only 12.8mm x 9.6mm. OTOH it's not unheard-of for tiny format lenses to have image circles well larger than their specification.


5

You can try semitransparent mirror:


5

No, these are unrelated. Distortion removal is a 2D mapping which moves pixels to remove barrel and pincushion distortion. Parallax correction requires multiple images or depth information for each pixel and is performed by completely different software algorithms.


5

This reply to @Caleb's comment kept growing and growing into an off-topic answer. Maybe you still find it useful. After mounting the zoom ring gear, I'll attach a pinion gear to the stepper motor shaft to control the motion of the zoom ring. A linear zoom throw allows for smooth, consistent zooming that doesn't draw attention to itself. ...


4

They are referring to the amount of clearance between the lens rear element and the sensor. The C mount flange focal distance is 17.52mm so both of these lenses have rear elements that stick into the camera body. This fact is most relevant to SLR cameras that have a mirror which moves out of the way when a photo is taken, a lens that sticks into the camera ...


4

The fisheye "effect" is dependent only on the angle between the camera and subject, it is thus totally independent of distance. What you might be noticing is that a fisheye lens bends all straight lines unless they pass through the exact centre of the image. In some natural scenes the horizon will be the only straight line in the image, thus if you happen ...


4

A 150/4 on 35mm acts like a 150/4 on 35mm. Full-frame 35mm (43.2mm diagonal) is the default frame of reference. Equivalence is usually about referring some other sensor/film size back to that 35mm default. As in "if I use X on my camera it'll be like using Y on FF 35mm." But... the math in case you do care about the other equivalences: Diagonals are more ...


4

Mainly because every point on the front surface of the lens has light from every point in the Field Of View striking it, and other than that which is blocked by the aperture diaphragm the lens refracts all of that light to every point on the image sensor. It is the same reason reflecting telescopes (Newtonian, Maksutov, Cassegrain, Schmidt, etc.) don't have ...


4

Okay, so, the first thing to understand is that the textbook¹ is trying to get you to understand a theory put forward by Christiaan Huygens in the late 1600s. It turns out he was (generally) right about the wave nature of light, but the actual specifics are iffy. Don't get too bent out of shape trying to make everything make sense, because... well, it ...


4

The big difference between the two lenses will not be when the picture is taken. At that point both lenses will allow the same amount of light through within the limits of the accuracy of their aperture settings and transmission ratios. The big difference will be when the lenses are focused prior to stopping down. The wider aperture lens will allow more ...


4

Your last sentence gets it right. The extra light is wasted because it falls outside the sensor area. In the approximation that your lens is a single thin lens (it is not, but it is a useful way to think about it) the rays that pass through the center of the lens are not changed in direction. In full frame, you need rays that pass at a wider angle so you ...


4

The first question would be: "...a difference compared to what?" Most camera lenses have been multicoated for decades now. Before that (from around the '50s to the '70s) they were single coated. Before that, most were un-coated. Uncoated lenses typically lose around 4-8% to reflection. Single-coated lenses lose around 2-4% to reflection. Multicoated ...


3

Barrel distortion is a form of distortion (not to be confused with other aberrations). It is often found with shorter focal lengths such as the lens in a phone - especially those trying to get the wide rather than narrow angle field of view. This distortion is also often seen with a single element lens, such as those associated with magnifying glass. If ...


3

To build on the other answers, this is indeed caused by a lens with undercorrected petzval. It is also vignetted, but more in one plane than the other. Here you can see a ray intercept plot for a large format tessar lens, these are also known as RIM plots or H'-TanU' Curves. On a RIM plot of the line is clipped, it indicates vignetting. You will notice ...


3

The mount's throat diameter limits the exit pupil diameter. It also has strong control over vignetting, so it restricts the pursuit of ultra-large aperture lenses with acceptable light falloff.


3

In general: possibly yes. You actually adjust focus of your lens, not your camera. It can be an advantage1 to design a lens in a way that it changes its focal length slightly when focusing. This is not very important if you take still images. This is different for video of course and one reason why cinema lenses are so expensive But even if your lens is ...


3

All optical systems produce a blurred image as a result of diffraction. On a fundamental level, we require a ruler to measure how much blur has occurred in a system. MTF, MTF50, and other measures are all "resolved" quantities mathematically. They are produced by taking an intensity profile and performing some mathematics on it. These methods cannot tell ...


3

I can't speak specifically about LR, but many raw processing applications don't use one of several generic mathematical models (such as Brown-Conrady) that are based on an assumption of rotational symmetry at all if the lens used is a fairly popular one. Instead they use a calibrated correction profile to correct for the measured distortion of the lens at ...


3

A larger sensor requires a larger focal length to deliver the same field of view. Given the same entrance pupil size, this increases the f-number, cancelling the effect of capturing more light. This is at least part of your misunderstanding. f-number is not affected by sensor size. Field of view is, of course, because a smaller sensor sees only a part ...



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