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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3answers
74 views

What techniques do higher-end lenses use to reduce astigmatism at high apertures?

I own a few lenses with a maximum aperture of f/2.8. For this question, I'll focus on two specifically: A Rokinon 14mm f/2.8, which retails around the $500 CAD mark; and A Sigma 24-70 f/2.8, which ...
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1answer
43 views

I have a Nikon D60 and two lenses: 70-300 and 18-135. Should I get a 50mm 1.8 prime?

I have a Nikon D60 and two lenses: a Tamron 70-300 mm f/4-5.6, and a Nikon 18-135 mm f/3.5-5.6. I got all of these things really cheap, and now I want to buy a prime lens. I was thinking about a 50 ...
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1answer
37 views

Are front lens focusing and unit focusing equivalent in triplet/tessar style lenses?

Some vintage tessar or triplet type lenses (eg such intended for viewfinder cameras) implement focusing by merely moving the front element or front cell. When adapting such lenses to other cameras, ...
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2answers
108 views

How can a subject stay in focus if the shot is recomposed afterwards?

I have a doubt about a procedure that I see many photographers continuously apply and they taught me. I see that, when they want to take a picture with their reflex, they do this sequence of steps: 1)...
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1answer
30 views

Lumix G85 - Black Corner regardless of lens and no hood - please help

I have owned a Panasonic Lumix G85 for about a year. This month, I've started getting a black area on the left corner of my images, which you can also see on the EVF. I can't see anything on the ...
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1answer
71 views

How to get close to 180 degrees with minimal fisheye look on iPhone X or 11?

I'm trying to film my rugby practices with my iPhone and wondering what is the best lens to use to capture the entire field without much that fish eye look? I noticed that the new iPhone 11 (Pro) ...
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2answers
49 views

How do i find the distance required to resolve a point on a page from a mobile camera?

Given all details such as focal length , aperture etc , how can i find the size of a point on a paper that is at a given distance from a mobile camera ? Or vica versa , the distance required to ...
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1answer
60 views

Ghosting artefacts in narrow DOF photographs

Snapping with a Canon EOS 600D in narrow DOF situations (for example with low f-stop numbers at long focal lenght), I get ghosting artefacts on the parts of the photograph which are out of focus. ...
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2answers
87 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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1answer
196 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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0answers
222 views

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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6answers
9k views

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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0answers
63 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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2answers
62 views

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
58 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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2answers
63 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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2answers
109 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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2answers
73 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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0answers
52 views

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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2answers
132 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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1answer
82 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
70 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
37 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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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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1answer
90 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
486 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
109 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
233 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
145 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
106 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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1answer
168 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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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
88 views

What kind of lenses with a “slightly different diffraction behaviour” were used in “large format photography in the 1980s”?

Referring to an interview with a lens expert (Krolop&Gerst Objektivreihe 17/32), discussing diffraction limits. "Es gibt ein paar Spezialobjektive die haben ein bisschen anderes Beugungsverhalten,...
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3answers
188 views

A projection of a real-image is one fixed perspective, but looking through the lens with my eye, I see many perspectives. Why?

Assume that I have a camera obscura (with a large lens - something like a magnifying glass) setup projecting an image of some still life. I look at my projection on my projection plane and I see one ...
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2answers
146 views

Why can my eye focus on the real image of a convex lens at many distances from the lens, but a projection only works at a specific distance?

Say I have a single convex lens. I set it up like a camera obscura, shine a light on my object and project the image onto a projection plane. Given the focal length of my lens, the projection plane, ...
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4answers
555 views

What is the relationship between lens diameter and exposure?

All of the online calculators for exposure, I have seen, factor in time, film speed, and aperture (which is a function of the iris diameter and the focal length of the lens). However I would have ...
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2answers
149 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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3answers
155 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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2answers
100 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 ...
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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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1answer
283 views

Is this lens decentered?

I bought a second hand lens yesterday, but I'm not sure if it's decentered or not. When buying it, I did some tests to make sure it was not decentered, but when I repeated the test at home I'm not ...
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1answer
121 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
346 views

How exactly is “flange” defined in the term ''flange distance"

The concept of a flange distance is something I understand on a theoretical level, but not so much on a practical level. It is debatably the most important measurement in the camera, determining the ...
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4answers
537 views

Why do prime lenses have multiple lens elements?

If I look up the specifications of my 50 mm lens, it says that it has 8 lens elements, in 7 groups. Why is this, why not just a single lens element with a 50 mm focal distance?
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5answers
458 views

Why use ultra-wide with short focus?

I have a Samyang F/2.0 12 mm for the Sony E Mount, so the 35-mm equivalent focal length is 18 mm (crop sensor 1.5×). I use it mainly for landscapes and architecture in order to fit more in my frame ...
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2answers
574 views

Does on-sensor phase detection autofocus need adjustment for accuracy?

Is autofocus adjustment actually no longer required with on-imaging-sensor autofocus that's phase-detection only i.e. not relying on contrast detection? If not, why? How does lens autofocus adjustment ...
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1answer
186 views

How do extension tubes affect the image circle? [duplicate]

If you abuse your lens by just stacking a bunch of extension rings one on top of the other, will this start to affect your image circle? For instance, you have a lens that can just about cover your ...
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3answers
226 views

What does the value of 'exit pupil' represent on a lens datasheet?

On this datasheet of the Kowa LM25HC lens I have access to, there is a number called exit pupil, which equals -57.9 mm. What does this number represent? This is not a question about what the exit ...