Before the rush

Before the rush
by evan-pak

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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 ...


20

The focal length is the distance from the (theoretical) center of the lens to the image plane. On the large format camera, there's a lot more camera between the lens and the film. The lenses are also often relatively simple — there's no need for a focusing mechanism in the lens itself, for example. @osullic gives the example of the Schneider PC TS Makro-...


18

The effect is called field curvature. A good discussion comes from Nikon. It is a lens aberration that can reduce the resolution of the lens when coupled with a flat sensor. In the old days, the film could be bent a little to try to follow the image plane and reduce the effect, but our sensors today are rigid. It can be reduced with lens design.


14

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 ...


12

Unlike most other digital cameras, Panasonic micro four-thirds cameras record lens correction information (distortion and CA, iirc) into the EXIF information of their RAW files (and will bake in the correction if you shoot JPEG). Some applications recognize and apply this correction information, some don't. That's why you're seeing different results, ...


11

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 + k3*r^6)*...


8

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 ...


8

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 fuel/air ...


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

A single converging lens with real thickness has a curved focal plane. Most lenses offered by manufacturers include corrective elements to flatten the focal plane to one degree or another. There are some well known and highly desired lenses known for flattening the focal plane particularly well: The Zeiss Planar series for example. There are also lenses ...


7

More generally, why is there even a drop-down for me to choose between rectilinear and fisheye, given that it's purely a function of focal length, which is already an input? I must be missing something. Your assumption is incorrect. Rectilinear and fisheye (or curvilinear) lenses are constructed differently, with different mixes of distortions. If someone ...


6

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.


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 ...


6

The image with barrel distorsion is the actual image recorded by the camera in raw format. The corrected image on top of it is the jpeg that the camera pre-processed (with knowledge that that specific lens has that type of distorsion) and embedded into the raw file. In short, raw processors which don't have a correction profile for your specific lens with ...


6

Does sensor size impact the diffraction limit of a lens? No. Therefore, if the sensor is larger, and the photo-sites for the same resolution can also be larger, does this influence the diffraction limit of a lens? Not really. What it does affect is the sensor's (not the lens') diffraction limit. If so, how? If the size of the Airy disc caused ...


6

Short answer no - it will be approximately equivalent to the 50mm lens on a full frame camera. What you are referring to are issues of perspective. The perspective is not a property of the lens but is due to the position of the camera relative to the subject. If you are at the same distance from the subject you will get the same perspective no matter what ...


5

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 doesn'...


5

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 ...


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. "...


5

The assumption that aspheric lenses create "abnormal" projections is incorrect. There is nothing "normal" in normal spherical lenses, except that we can produce them cheaply. You don't get rectilinear projection just because you used spherical lenses, you have to struggle for accurate rectilinear projection (if that's your goal). Pinhole is automatically ...


5

One reason "professional grade" is hard to define is because it's going to get manufacturer's in trouble by setting unreasonable expectations. It's easy, for example, to say that a metal bodied lens is more durable than a plastic composite... but that's not strictly true. The metal body will show dings; the plastic composite won't. The metal body will ...


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 ...


4

With an optically perfect lens, the focal plane is parallel to your sensor, and it has the same shape as it, i.e. it is actually a plane. With a real-life lens, I guess you can get a bit of distortion of the plane, but it will essentially remain a plane. It has to be so for landscape photography where you want the whole image to be focused at infinity at the ...


4

The major manufacturers do not mark lenses as "pro" or "non pro" and they probably have a good reason for that. There are very good professionals that use cheaper "amateur grade" equipment because their back can't handle heavy expensive lenses anymore. There are professional photographers for whom top of the line lenses with latest features are not ...


4

The answer is that the pentaprism is actually a roof pentaprism. The image is laterally-inverted (left-right inverted) because the image actually bounces an additional time due to the roof of the pentaprism. Pentaprism diagram from Wikipedia: Single-lens reflex camera, CC-BY-3.0


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

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 ...



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