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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42 views

Proof of the relationship between the image area and focal length of a lens [duplicate]

It is a well-known fact that image area is directly proportional to the square of focal length of the lens. Is there any mathematical proof to it? (Possibly starting out with the lens equation and ...
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1answer
100 views

What is a good reference for the technological aspects of modern digital photography? [closed]

What is a good readable, technically detailed reference on the technology involved in modern digital cameras, raw file conversion, and digital image processing? (Possibly a complete a complete answer ...
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What is the farthest a camera can see?

At what distance can a face no longer be identified using a camera? At what distance can a figure of a person no longer be captured?
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2answers
71 views

Is it possible to get green and red chromatic aberration?

In one of the hallucinating scenes in a video I have played. The vision is blurry and objects nearer the edges of the screen are green and red Now the usual chromatic aberration patterns are purple/...
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6answers
10k views

How do constant aperture zoom lenses work?

Cheaper zoom lenses usually are faster at the wide end and slower at the long end (for example, the $150 Canon EF-S 18-55mm f/3.5-5.6). More expensive constant-aperture zoom lenses have the same ...
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1answer
188 views

Can a camera be a mile long?

Could parts of a camera be spaced out over a distance rather then together to work in a way a normal camera cannot? What characteristics would this camera have over a normal camera? In the picture ...
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What causes this repetition pattern in a picture? (when re-arranging its pixels by their intensity - code included) [closed]

Just out of curiosity, I was playing with RGB coordinates and pixels of pictures. Then for some reason I decided to get all pixels of a picture, get the RGB coordinates/values of each pixel (eg. RGB(...
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0answers
62 views

How did technicians individually hand-shim each Pentax/Konica 35mm slr lens mount?

I just received a Konica Autoreflex T and I found out that the lens mount is individually hand shimmed. How did the technicians determine if the lens mount is correctly parallel to the focal plane?
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1answer
116 views

Why do CCTV and pro camcorder lenses often have vignettes, and apertures that can be fully closed?

I noticed this on both CCTV and "TV lens" C-mount lenses. Is this for manual black level calibration, or protecting some early sensor or *icon tube style from wear, or entirely another reason? It ...
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3answers
14k views

What is a zone plate?

I was looking into alternative methods of photography and I happened upon something called a 'zone plate.' Three questions: What is a zone plate? How does it work? What can I do with it?
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2answers
526 views

Is this a bubble in my lens element?

Both images show the same artifact.
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Determine the effective aperture size by f-stop/sensor size/focal length/Size of CoC [duplicate]

Is it possible to calculate the effective aperture size by the parameters below? f-stop sensor size focal length of lens size of circle of confusion If yes, what is the equation? If no, what are ...
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1answer
54 views

Is there an online lens diffraction and maximum sharpness table?

I simply want to see an table that lists the lens diffraction limit of each camera. I have came across this well done answer with animated PNG and I realized there i also the perfect sharpness ...
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6answers
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Why is depth of field affected by focal length?

As the focal length decreases, the depth of field increases as well. Why is this? I'm not so much interested in a physics lesson as I am interested in a simple, down-to-earth explanation.
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2answers
62 views

Relationship between f-number and amount of light being let into the lens system [duplicate]

Why does smaller f-number imply greater aperture diameter and consequently, greater amount of light entering the lens of a camera? As evidenced from my study across a number of resources, an absolute ...
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1answer
162 views

How do focal distance reductors affect image quality?

I have a bunch of lovely old full frame K mount lenses (like the 50mm f1.2 and the 135mm f2.5) and the idea of using them in a proper mirrorless body (I have the K-01 and that's a hell of a brick) ...
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2answers
107 views

DSLR lens image inversion?

 Out of simple curiosity, do DSLR cameras produce an inverted image on the sensor, with the image being flipped by software?  I've dabbled with astronomy prior to my current interest in ...
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3answers
3k views

What causes barrel distortion?

Here are some scenarios for barrel distortion: When a target is too close to a camera, the photo will show barrel distortion. My flip cell phone's camera often produces barrel distortion. Some lenses ...
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2answers
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What is the difference between a pentaprism and a pentamirror?

Higher-end SLR cameras include a pentaprism to transmit the image from the lens to the viewfinder, whereas lower-end SLR cameras use a pentamirror to accomplish the same task. What are the ...
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52 views

What's the actual physics behind the optical apodization? [duplicate]

Canon seems to plan to introduce a 50mm with apodization for a more natural bokeh [1], but it is not the first in photography [2]. Wikipedia article is only an introduction [2], and does not develop ...
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What creates a calisson-like shaped light bokeh ? How to craft this aspect of the bokeh? [duplicate]

What creates a calisson-like shaped light bokeh such as this one (made with Arri signature T/1.9) ? The further from the center the more present are the angles, why ? Another lens (Zeiss Supreme T/1....
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1answer
157 views

How wide does the front element of a lens have to be, given the focal length and the aperture?

Clearly, a lens with focal length F and aperture 1/f has to be at least F/f mm wide. Maybe a little more to accommodate the angle of view. However, lenses tend to have wider front elements than F/f. ...
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3answers
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What is the cause of this non-uniform bokeh effect?

A friend of mine is thinking of buying a used medium-format film TLR camera (a Mamiya C330), and he showed me some of the test shots he'd taken with it. I was struck by the curiously non-uniform ...
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2answers
126 views

What useful information can one gain from a lens element diagram?

On many photo gear review sites, cutaway diagrams of lenses are featured which show the layout of the elements in each lens. Here's the style of diagram I'm talking about, taken from Nikon's website ...
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2answers
138 views

Is it theoretically possible to use a mirrorless lens for a smartphone camera?

A example situation. I want to take photo of a far away text for identification but my camera has a dead battery! If I decide to use my phone (Just another 1/2.55 smartphone) and a RF (Or a EF-S) ...
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6answers
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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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2answers
689 views

Why does the same f-number mean same amount of light? [duplicate]

Intuition tells me that a bigger lens will collect more light with the same f-number than a small lens. But photographers tell me I am wrong. I cannot understand why. There are quite a few posts both ...
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In what way does the lens mount limit the maximum possible aperture of a lens?

In many answers to questions about different aspects of really large aperture lenses it's pointed out that the lens mount sets a hard limit on the maximum possible aperture of the lenses to that ...
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5answers
7k views

What does a hexagonal sun tell us about the camera lens/sensor?

In this picture, we see that the sun comes out as a hexagon. I am sure it is not arbitrary. What does the hexagon tell us about the instrument that captured the image?
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3answers
154 views

Can too-tight lens hoods become accidental apertures?

There is frequently the suggestion to use tighter lens hoods than specified for some lenses when they are used with smaller sensors than they are designed for. The idea is that the vignetting ...
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6answers
3k views

What is the Leica look?

What is the Leica look that fans of the company claim is unique to them? What concrete differences are there that are most obvious to a layman?
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1answer
80 views

Is there theoretical limit on the minimal focal length for a given sensor size?

There seems to be a limit, around 0.33, on the fastest possible aperture. Is there a theoretical limit on how wide a non-fisheye lens can be? That is, what is the minimal possible focal lens for a ...
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1answer
69 views

What defines an “objective”?

I'm not experienced in photography and would like to get some knowledge about the terminology. My question is: What defines an objective? Or: When would you define something as an objective? I mean, ...
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1answer
33 views

Focus Issues Using a C mount Filter on a CS Lens

I'm trying to use the Arducam 8mp with CS mount with a 25.4 C-Mount Filter, but I am unable to focus the picture. The filter fits perfectly and still leaves room for the lens to screw in. It says in ...
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3answers
4k views

When you zoom in with a lens on an SLR why does the lens go in then out?

I guess this is more a question of optics than photography but I just got an SLR with a basic 18-55 lens. I noticed that when going from 18 to 55 or 55 to 18 the lens physically comes back in and ...
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4answers
6k views

Do lenses affect color fidelity?

It seems to me that my costlier (Tamron 90 f/2.8 macro) lens gives better colors than my cheap Canon 18-55 IS kit lens. So does lens matter for color quality? What physical processes are involved in ...
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4answers
2k views

Is camera lens focus an exact point or a range?

I have often wondered if the focus of a lens at a particular focal length is an exact point or a range within a few millimeters. This becomes all the more important when manually focussing. How far ...
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8answers
20k views

Technically, why is the out of focus area blurred more when using a bigger aperture?

I'm wondering, technically, why and how does the out of focus areas blur more when using a bigger aperture. I think it'd help a lot if I presented a problem that's been driving me nuts for a long time:...
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2answers
2k views

Is the size of the entrance pupil the same as the size of the effective aperture?

I understand that the entrance pupil is the image of the aperture as seen from the front of the lens. However, is the size of the entrance pupil the same as the size of the effective aperture? In ...
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1answer
81 views

Rainbow flare effect on Industar 50-2

I am reproducibly getting the kind of rainbow-streak flare seen in the attached image on my copy of the Industar 50-2 (a russian 50mm f3.5 tessar-ish M42 pancake). The pattern does rotate when ...
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2answers
454 views

Camera image in pixel to real image in meters size relation [closed]

first post so please be nice. I am doing an image processing project and my problem is now that I would like to know how big my digital image is in the real world. I have: digital image: 336x256 ...
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3answers
101 views

Does field of view change for different lens model for the same focal length?

I am using two lenses - Tamron 75-250mm F/3.8-4.5 Model 104A and AF-P DX NIKKOR 70-300mm. When shot with lenses set to 250mm of focal length, the field of view for the Tamron lens is greater than the ...
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5answers
760 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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5answers
222 views

Why is low chromatic aberration considered important in the digital era?

I have read many lens reviews. It seems that low chromatic aberration is considered an important property of lenses. However, film is a dead dinosaur today. Practically everyone is using digital ...
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2answers
84 views

Does the T-number account for lens vignetting, or only for glass/coating transmission?

Surprsingly I could not find information on this. Many lenses have vignetting profiles available. Vignetting changes if you use a cropped sensor, or, in case of zoom lenses, can change with zoom. ...
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1answer
126 views

What is lens astigmatism?

Can someone simply explain astigmatism and its different types? How are they caused in lenses, and how can they be identified in images? I'm looking for a simple, understandable explanation. I've ...
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3answers
102 views

Light falloff - until lens surface, focal center, or camera sensor?

Preface: if there is a better-suited forum for this question, please direct me. I figured it'd be better to post into Photography and not Physics as some of you might have already examined this ...
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2answers
139 views

Taking Photograph Through Beamsplitting Glass so the object photographed cannot see camera lense back

I am new to beam splitting glass & its properties and possibilities, but I would like to think that it should be possible for me to some sort of beam splitting glass in order to be able to take a ...
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2answers
65 views

Does adding a lens with a higher MTF50 in front of a lens with a lower MTF50 increase the MTF50 of the entire system?

I know that the MTF of an entire imaging system can be modeled by multiplying the MTF of each component (possibly because multiplication in spatial frequency domain is convolution in space?) So, let'...
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2answers
96 views

Are bokeh (ball) shapes a result of vignette or aperture action?

The effect of getting shaped out-of-focus highlights (bokeh balls) from both non-circular apertures inside the lens, and masks applied in front of it (where an external aperture would presumably also ...