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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4answers
238 views

Why is there an air gap between lenses and digital sensors, as opposed to continuous glass-like higher refractive index?

Thinking about ultra-fast lenses (ƒ<1), it would seem useful to have a solid+liquid medium between lens and sensor. This wouldn't have been very practical (presumably) at the time of film, but with ...
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0answers
45 views

prime lens has auto focus but it has fixed “focal length” [duplicate]

I am so lost. Focal length in physics is the distance at which focus is achieved when rays are parallel. Clear! "focal length" in photography videos (shown below) always talks about sensor ...
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0answers
85 views

Would you consider this lens (Samyang 8mm CS II) defective?

I purchased a new Samyang 8mm F3.5 UMC Fish-eye CS II today. After I made my first shot with it I immediately noticed a flaw. At f/3.5 the flare of bright objects is shifted towards the bottom (and ...
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2answers
208 views

How are wide angle lenses able to project an image onto a sensor?

The Nikon F-mount has a flange distance of 46.5mm. A 14mm lens for example has an horizontal angle of view of about 104°. How is a lens able to project an image from the rear element onto the sensor ...
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4answers
148 views

Seeming contradiction on wikipedia about rear nodal points and how the principal plane is related to focal length

There are two lines on the wikipedia pages for "cardinal points" and "focal length" that seem to contradict each other, and I would be extremely grateful if someone could explain ...
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2answers
77 views

Estimating the optical resolution of a lens

In Tony & Chelsea Northrup's recent video titled 5 Lies Camera Companies Tell You, they mention that the optical resolution of a kit lens is often lower than the resolution of the sensor at around ...
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2answers
96 views

What means lens optical characteristics?

I have 12-60 Panasonic lens for mft system. I'm about to buy 12-60 Leica for the same camera, because the photos I do with my current lens feel, smartphone-ish. Depite the lenses are similar in ...
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1answer
131 views

Can you calculate lens thickness from knowing focal length and diameter?

I'm not the best at math, but I'm wondering if there is a formula to figure out the thickness of a lens from only knowing the focal length and diameter.
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159 views

Lens Magnification vs Pixel Magnification

Scenario: I take a picture with a camera that has a crop factor of 3.19. I use a 55 mm focal length equivalent for taking the photo. In the resulting image file header, it says a magnification of 0....
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3answers
419 views

What is the necessary recess on an enlarger lens board?

I have recently acquired a Meopta Belar 75mm/f4.5, to use with my Durst M605 enlarger. I was remiss in not checking the mount of this lens (M23.5) before I bought it, and have therefore ended up with ...
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2answers
94 views

No more turn left to get focus at infinity (hit the lens limit) [duplicate]

Academic question: If I run out of turn attempting to achieve an infinity focus (close, but no cigar) would I: Move the lens away from the sensor? OR Move the lens closer to the sensor?
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201 views

What's the best choice of lens from an optics surplus shop to get a Stanhope Lens-like magnifying function?

I am looking to do some experiments with my cellphone and a lens, holding the lens in contact with my cellphone lens. I'm looking for a lens that has the shortest back focal length length possible, so ...
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3answers
420 views

Why are adapters for slightly too-short backfocus lens mounts not made with just a thick glass window instead of a lens element?

Infinity-correcting adapters tend to incorporate a weak teleconverter usually. It would appear that a thick, planar optical glass window is also capable of lengthening back focus - and would probably ...
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1answer
343 views

How can i calculate the direction vector of a pixel? [closed]

So if you take a pinhole camera and make it as the origin of our plane(3D) and a pixel from the image plane and connect the two with a straight line it should make a vector, which has direction and a ...
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1answer
237 views

Why is there a maximum focus distance when using an extension tube? [duplicate]

I am using the Nikon D850 together with the Sigma 50mm/1.4 Art and the MEIKE MK-N-AF1-A extension tube(s). During first shots I found out that the combination not only has a minimum focus distance (...
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2answers
124 views

Which is better in lens hoods, felt-like material or sawtooth surface?

I have noticed that many1 Canon lens hoods contain a felt-like matte black material designed to reduce reflections. The material probably does so admirably, but tends to get dusty over time. On the ...
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1answer
93 views

What explains a lens flare “streak” on only one side of light source?

We know than an axial streak can be caused by a smudged lens that has been wiped in one direction. The following image shows both lens flare and a lens "streak." But what could explain the one-sided ...
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5answers
4k views

Why can't my custom camera body focus to far distances?

I have built a custom optical device that uses a standard C-mount lens as found on CCTV cameras. Wikipedia states that the flange-to-film distance of a C-mount lens is 17.526 millimetres. I have ...
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3answers
108 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
63 views

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

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
109 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
118 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
65 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
202 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
54 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
73 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
136 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
211 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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6answers
11k 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
75 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
93 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
99 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
177 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
115 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
228 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 ...
3
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0answers
65 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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3answers
194 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
142 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
116 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
81 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
66 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
3k 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
133 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
838 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
199 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
308 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
112 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
184 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
179 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
261 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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