Questions tagged [optics]

Optics is the science of light, and in photography often refers more specifically to to the properties and construction of lenses or the technical aspects of light sensors.

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2
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4answers
340 views

Where is the aperture?

Where and how is the aperture placed inside a lens? How come the image is not affected (no obscuring) by something inside the lens literally blocking light?
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2answers
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Need help to find proper camera and lens specification

Last day I shot using an 18-135mm Nikon lens, it was barely able to capture a fly-sized point at a distance of 100m with proper details. Using a 100-400mm lens would be too expensive. Can you guys ...
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3answers
957 views

What is the (real) meaning of binocular magnification number?

This is more of an optics measurements question than a photography question, so if you don't want it on the site, just delete it. I just couldn't think of a better match. Do binoculars, loupes, ...
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2answers
255 views

Do lens optics/formulas, of the same lens model number, get updated as it is being produced?

Context I've noticed that the Nikon 105/2.5 has a long history of having many different versions from Sonnar v Gauss design to coatings and different blade counts for the aperture. Most of these ...
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3answers
1k views

Is there any physical reason a mirror lens could not have a variable aperture?

I understand that mirror lenses already have high maximum apertures and that often, the last thing one wants to do is let in less light, but is there a physical reason that one could not build a ...
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3answers
5k views

Concept of focus for a pinhole camera?

Is there a concept of "focus" and thereby defocus for a pinhole camera? If yes, then what is it? If it is assumed that only one ray of light enters in through the pinhole from every point on the scene,...
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3answers
398 views

What differences will there be when stacking add-on lenses?

I wonder what the outcome will be of stacking a lens with add-ons like these: What's the difference between stacking these on the exterior compared to actually replacing the lens?
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6answers
1k views

Why is the area in focus in front of the focus distance narrower than behind it?

I guess the title and the picture explain my question well.
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3answers
3k views

Are there any 24-70 2.8 lens with no length change in zooming?

I'm planning to buy a 24-70 f/2.8 lens for my Canon 7D. I need a lens that won't increase its length while zooming (like the Canon 70-200mm series). Is there such a lens in any brand?
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2answers
193 views

What is the light called that is outside the area of the capture medium?

Is there a name for the light that passes through a lens and does not make it to the capture medium (sensor, film, other)? I'm looking for the name of the grey area in the following image from ...
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3answers
424 views

What's the intended use of lens with f-numbers close to or “faster” than f/1?

Lens with f/1.2 are rather expensive and not very widespread. Lens with f/0.95, f/0.85, f/0.8 do exist but they are also very expensive and quite rare. Lens with f/0.7 are so rare that some of them ...
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3answers
942 views

Are thermal imagers inherently more expensive than visible-light digital cameras?

We're finally starting to see practical thermal imaging sensors (microbolometers) entering the consumer market. However, they are still vastly more expensive than comparable visible imaging sensors. ...
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2k views

What are groups and elements in lenses?

I hear people talking about groups and elements in lenses, but I am not sure what they mean. Could someone please explain?
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5answers
2k views

Is a two-prime lens possible? E.g. 35mm and 50mm

I really like prime lenses for their simplicity, zooming with my feet. I prefer it to a zoom lens because of this simplicity. But I do carry both a 35mm and 50mm because I do two different things ...
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4answers
4k views

What is the difference between perspective distortion and barrel or pincushion distortion?

I've heard of: perspective distortion barrel distortion pincushion distortion mustache distortion What are these different types of distortion, and how do they relate? What causes them, and can they ...
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5answers
499 views

How does a 'reversing adapter with automatic system' deal with the *inverseness* of the reversed lens?

First, I apologize because I don't know the exact name for this kind of adapter. (Please mention the correct term for that kind of adapters...(I mean those reversing adapters that can keep the lens's ...
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1answer
132 views

Numerical Aperture of an Inverted Webcam Lens

I have inverted the lens on a webcam to create a webcam microscope. For illumination , I am using an led array. For the project that I am doing I need to know what the NA of the lens, but I am ...
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2answers
118 views

Looking for an iPad lens that makes it possible to capture a person head to toe from up close

I am filming golfers swinging at the driving range. Due to common video standards I want to film in landscape mode instead of portrait mode. However, to fit a whole person in I need to be quite far ...
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3answers
1k views

How can I find a compact camera where I can change the lens?

I would like to purchase a compact camera. But usually they are limited in optical zooming. So, I would like, if possible, to add/replace lens hardware with a different lens with better optical ...
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2answers
462 views

Point two cameras through the same lens, with the same perspective

I had an idea recently, that would involve two separate cameras, capturing at the same time, with the exact same perspective- Which I mean as, 1:1 the EXACT same perspective, as if both of the cameras ...
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2answers
333 views

Lens/Mirror system for stereo photography?

I am interested in exploring the viability of doing stereophotography using a single camera. The idea is that the camera would take images in pairs, first using one side of the lens system, then ...
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5answers
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What happens if anti-reflective coating is fully ruined or removed from lens' most outer surface?

Anti-reflective coating is sensitive to fingertips and extra care is needed when cleaning camera lens. I've heard a couple of stories where a camera owner used some organic solvents and ended up ...
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4answers
278 views

Why don't cameras ordinarily zoom by moving the whole lens as a unit?

Zoom lenses have a moving group of lenses within the whole unit. It seems to me that any lens could easily be made into a zoom lens by moving the whole lens unit towards/away from the film/sensor. ...
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1answer
358 views

Limits of camera lens capabilities [closed]

I read that the canon 35mm f/2 IS is the lowest aperture lens that also has IS. Is this because a stabilizer at any lower F-stop is not possible, or just because it is just currently outside of our ...
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3answers
381 views

Are points off-center from the lens axis out of focus? [duplicate]

If I take a picture of a flat surface perpendicular to the direction of the lens (i.e. the surface is facing directly at the camera), and I focus on the center, are the points off center in perfect ...
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3answers
1k views

Which formula for f-numbers is correct: f/D or 1/(2NA)?

I've seen two different definitions for the f-number of a general-purpose lens. Are they consistent ? I'm assuming that subjects are distant (not macro, magnification is small), and we have a lens ...
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3answers
1k views

What is the pre-computer version of Photoshop's blending modes?

Before computers, to blend two pictures into one, I'd imagine they'd have used some sort of mirror setup to reflect the one picture onto a mirror containing the reflection of the other picture. Does ...
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2answers
163 views

Clear-cut black corners with some superzoom photos

I've got a refurbished Panasonic DMC TZ40 which I consider to be very good value for money for my needs as amateur ignorant photographer. The camera is in good shape but was clearly used for some ...
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2answers
507 views

Will using a full frame lens with extension tubes on a crop sensor camera reduce the “crop”?

The question Will a macro extension tube eliminate the cropping of an APS-C lens on a full-frame sensor? is certainly related, though I'm not sure if it's a duplicate. As a follow up to my recent ...
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3answers
3k views

How can I test that the image is inverted in a pinhole camera?

I learned that a pinhole camera inverts the image on the film strip: Is it to possible to test if the image gets inverted without the film strip on which the image is projected? For example: I made ...
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2answers
628 views

Why doesn't an extension tube “crop” the picture?

Ever since I've heard of extension tubes I've been curious if they somehow crop the image that appears on the camera sensor. Based on this YouTube video, the answer is "no" (at least not that I can ...
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4answers
2k views

How to choose a good smartphone if the top priority of the user is photography?

At the current rate by which technology is improving, I believe that mobile photography is not far behind their DSLR counterparts, generally speaking. However, for amateurs like me, it is quite ...
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4answers
790 views

Why does illuminance stay the same for a given f-stop even when focal length changes?

I'm trying to wrap my head around the math/physics of how illuminance on the film/sensor plane remains equal for a given f-number regardless of the focal length of the lens. Since a longer lens will ...
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2answers
1k views

Why do modern aspherical lenses have so much coma?

The Nikon Noct 58mm f/1.2 from 1997 is famous for having excellent coma control wide open. Sources generally credit this to its being one of the first lenses that used an aspherical element, which had ...
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2answers
628 views

Why do mirrors give less sharpness, gamut, and contrast than lenses?

What is the scientific reason mirrors give less sharpness, gamut, and contrast compared to lenses? Ex. Is it an inherent property where light dissipates more when scattered compared to going through a ...
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3answers
593 views

How can I experimentally determine the size of my lens’s aperture?

I have a Canon FD 28mm f/2.8 that I shoot on my entry-level Canon DSLR using an adapter. You have to set the aperture manually, but only every second aperture is marked: between ƒ/2.8 and ƒ/4, for ...
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3answers
3k views

What causes lens flare along specific axes?

When photographing bright objects, what causes lens flare along specific axes? First two images captured from Reds Rhetoric & Vincent Jones's video, last from SpaceX's feed. In reflecting ...
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1answer
1k views

Mirror vs Lens: do either or both invert the image?

Answers to this other Question on photo stackexchange have prompted me to seek clarification on this. consider for example the following images: Original scene How a mirror "sees" it (flipped ...
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2answers
2k views

How many times is the image inverted inside a DSLR camera?

How many times is the image flipped (inverted) inside a standard Digital Single Lens Reflex camera?
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2answers
148 views

What is the most general theoretical reason images out of focus appear blurry?

Don't know if I should ask here or physics for optics. But I am wondering how come images out of focus appear blurry? It seems to me that if a given lens geometry has a given focal length, then ...
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2answers
1k views

Does say a 35mm on an APS-C camera have the same facial/other deformations as a 35mm? [duplicate]

I am about to purchase a 35mm (Nikon 35mm F1.8 DX) for my APS-C camera, to get the equivalent of a 50mm lens. I want to use it for portraiture a bit, but I'm worried the facial deformations will ...
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3answers
1k views

What exactly “professional-grade” means in Nikon line of lenses?

I was researching a bit on Nikon 16-35mm f/4 lens. Both Nikon USA and India websites are silent about the build material of the lens barrel. There are a class of people, who either out of "frustration"...
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4answers
2k views

How can I increase the flange focal distance (back focal length) of DSLR lens?

I am working on a custom setup where I am using a DSLR lens (Canon 50mm f/1.8) to project an image onto an image sensor (image plane). For my application, I require a very large distance between the ...
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3answers
1k views

What determines whether chromatic aberration will be purple/green or red/cyan?

In my experience, both with my own photography and looking online, chromatic aberration is usually purple on one end and green on the other. However, I have also seen the same effect with red and cyan,...
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4answers
2k views

Why is my large format lens so much smaller (in length) than my 35mm-format lens?

In general I have found that as the focal length of 35mm (or APS-C) lenses increases, the physical length of the lens increases as well. However, my large format lens is much thinner than other 35mm ...
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1answer
261 views

Can you build a camera obscura indoors, to watch a play upside-down as it's performed? [closed]

I've seen Youtube videos of people who have converted a room into a camera obscura to capture images of skyline/trees/clouds, but couldn't you capture indoor scenes too? Or would you need bright ...
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1answer
101 views

What are the (dis)advantages of moving the entire lens for focusing vs. only parts of it?

There's a lens adapter available that adapts Leica lenses to Sony mirrorless cameras. It's called TECHART PRO. The key feature is that it allows to use autofocus with the manual lenses. This works by ...
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5answers
855 views

Aperture iris in front of lenses (in object space)

This question discusses the iris placed in camera body and this question does not reveal too much details about external iris. I recall from scattered information that I have read that iris placed in ...
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1answer
197 views

How is a lens distortion model performed? [duplicate]

So, as the title suggests, how is a lens distortion model (e.g. Brown-Conrady or pinhole camera model) applied on an image? I know it uses some calibration parameters (principal point's coords,focal ...
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2answers
765 views

How do lenses control “projection”?

How is a fisheye lens made differently from a normal ortholinear projection lens? How are real lenses acting differently from the ideal "thin lens" or pinhole, in terms of how the 3D scene in front ...