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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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2answers
71 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 ...
2
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0answers
29 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
66 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
159 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 ...
4
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1answer
76 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
90 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 ...
8
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4answers
275 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?
4
votes
5answers
419 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
189 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 ...
0
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1answer
104 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 ...
1
vote
3answers
91 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 ...
12
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4answers
3k views

How do manufacturers get to high (83x) zoom levels on hybrid cameras?

Obviously the biggest hybrid zoom on the market (Nikon Coolpix P900 I think) does not range from actual 24 mm to 2 meters in physical length, but what kind of optical systems do manufacturers use to ...
4
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3answers
532 views

Can I force the aperture to stay open on macro lens?

I have a sigma 180mm f/2.8 lens, which I bought because it was the largest aperture I could find that focuses around 0.5m See this question for why this was important.. Upon arrival, however, the lens ...
2
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2answers
206 views

Is this a bubble in my lens element?

Both images show the same artifact.
6
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2answers
321 views

What is the cause of inclusions in my bokeh?

I was doing a lens review an two of my lenses showed these rather unsightly inclusions in their bokeh. There are two different lenses. EDIT: The third lens I have tested also seems to have this ...
1
vote
3answers
574 views

How to calculate stops of light lost from a teleconverter?

How would I be able to take the multiplication value of a teleconverter (1.7, 1.4, 2, etc) and find out how many stops of light are lost when using it just based on that number?
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0answers
32 views

Finding X,Y,Z values in an image by knowing the focal length and apeture [duplicate]

What is the systematic procedure to find x,y,z values of an image by knowing the focal length of the camera lens ?
7
votes
2answers
181 views

Why is the aperture of this old lens showing as centered blue glare?

I just bought a old Minolta MD Zoom 35-135mm 1:3.5-4.5 lens together with two old Minolta SLRs to get into film photography. Before using actual film I adapted it to my Canon 600D (using a no-name MD-...
4
votes
4answers
173 views

Does a macro lens have a smaller DOF in 'real-world' distances at the same focal length and aperture as other primes, why?

This question IS about: Does a macro lens have a shallower DOF at the same settings and focal length as another prime? If so, what in the optics is responsible for this? Using a Macro lens as a ...
5
votes
3answers
203 views

Why would lens be much longer than its focal length?

I accidentally saw Nikon 17-35mm f/2.8 lens and noted that it is rather large for its focal length. Here's the first review of this lens search offered - looks like it's 107 millimeters long. Given ...
1
vote
2answers
281 views

What function does C1, C2, and Off mean on Sigma 120-300mm f/2.8 Sports lens?

I am using a Sigma f/2.8 120-300mm lens. How does the C1 and C2 affect pictures? Also, what about the Off, 1, and 2 switch on the OS feature?
5
votes
1answer
78 views

Are focus and resolving power optically equivalent?

Limited "resolving power" or "sharpness" is a problem one can see with many lower-quality lenses, especially with higher-resolution camera bodies. Playing with my cheap 500mm mirror lens, I often get ...
1
vote
1answer
163 views

What causes this pattern? [closed]

What causes the pattern seen on the image (it is a still from a video)? This doesn't seem to be a Moiré. It seems to be largely related to the camera or the filter (the pattern is fixed and aligned ...
5
votes
4answers
254 views

A thin camera and a thin lens with a large glass element

After seeing these 3D designs, I was wondering if a camera that is thin could possibly have such a large piece of glass in the lens (given the lens piece doesn't expand when powered on). As far as I ...
4
votes
4answers
222 views

Is there an optical filter that reduces the film's contrast?

As far as I know, the change of the exposure moves the negative' density curve left or right only (moves the objects to the different zones), and to shrink or enlarge overall contrast, one has to ...
5
votes
1answer
167 views

Is there an easy way to tell the size of an image circle a lens has?

I know that lens can come in many formats, e.g. crops vs. full frame. However, someone recently told me that the Zeiss Otus has an image circle that is larger than the intended format. This is one ...
-3
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3answers
143 views

If a camera has two lenses, where is the focal plane? In the sensor or in the second lens?

For example, this exercises asks where is the focal plane. Is in the sensor or in the second lens?
2
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3answers
120 views

What limit do lens manufactures come upon first when making a wide range lens with large aperture (besides economics)? [duplicate]

Economies of selling such a lens would be my first guess to why a lens doesn't exist but I am more interested in the physical characteristics of a lens. How do the characteristics of a lens affect ...
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3answers
863 views

Understanding focus distance of Nikon f/1.8D lens with D5600 Camera

I took some sample photos using my Nikon D5600 camera with Nikon f/1.8D lens. I had to set the focus manually since this lens doesn't provide AF with my camera. My Question: The album of my sample ...
2
votes
1answer
93 views

How do phone attachment lenses affect depth of field?

Let's take, for example, the Moment Tele Lens. This lens is pitched as a 60mm lens that allows you to get 2x "closer" to the subject. The iPhone 6s uses a f/2.2 lens. Does the mounting of the tele ...
0
votes
3answers
113 views

Design and Fabricating My Own Lens

I have a small business (just me) selling an inspection machine. The camera and lens work well, but I've had to print my own camera mount to get the lens further away from the CCD to get a good focus....
0
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2answers
267 views

Does the sensor size matters in the size and weight of an equivalent lens? Why?

In other words, does the size of projected image circle matters in the size and weight of two lenses with the same aperture/DOF (different f-number) and field of view (different mm)? All other things ...
21
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3answers
5k views

Why is the hole in a pinhole camera usually a circle?

I know that for pinhole cameras and camera obscuras the holes are usually round (they are circular). But I don't see the link between the shape of the hole and the formation of the image.
2
votes
4answers
514 views

Do convex lenses make light from different points converge to different points?

I'm starting to study camera and lenses. Most of the sources online introduce you to the concept of convex lenses, with pictures similiar to this: This picture just show you that parallel rays (of ...
12
votes
3answers
2k views

Do convex lenses make parallel light rays of different wavelength converge to different points?

I'm starting to study cameras and lenses. By reading explanations and watching videos on convex lenses, I learnt that they make parallel light rays converge to a single point called the focal point. ...
1
vote
2answers
293 views

What does lens flare from a catadioptric (mirror) lens look like?

Can one get lens flare with a mirror lens? What does it look like?
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0answers
79 views

How to know if a lens will work for my camera [closed]

I've a camera like a FLIR Blackfly C and CS mount camera and I want to buy a new lens for it from a vendor such as IDS Imaging Development Systems GMBH, for example, which has a fixed parameters (...
6
votes
1answer
175 views

Determining the size of the smallest resolvable detail for a given camera

My generic question: Given camera specifications, e.g: sensor resolution, sensor image area, pixel size (area), optical size, focal length (ratio), fov (horizontal and/or vertical) and ...
0
votes
2answers
134 views

Confused about different optical zoom on different lens [duplicate]

I'm looking at 3 different lens mainly for distance shots but with a bit of Macro occasionally. Tamron AF 70-300mm F/4-5.6 Nikon AF-S DX NIKKOR 55-300mm f/4.5-5.6G Sigma 70-300mm f4-5.6 The bit ...
1
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2answers
135 views

Color consistency across equal cameras but different lenses

I want to stitch images using equal cameras(Point Grey GS3-U3-41C6C-C) but with different lenses. One lense is a wide-angle lense (Sunex DSL318B-650-F2.4) and the other is a fish-eye lens (Fujinon ...
1
vote
2answers
181 views

How would apodization impact landscape photography?

I'm considering purchasing the Sony FE 100mm f2.8 STF GM OSS which just looks and feels incredible to me. I haven't been able to find any reviews, articles, or conversations though discussing the ...
1
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3answers
261 views

Is focal length internal or external? [duplicate]

I just wanted to check because I've encountered various distinctly different assertions. I was originally taught that focal length referred to the optimum distance from subject| ←→|lens, where ...
2
votes
1answer
378 views

How to measure field-of-view of a camera with fisheye Lens? [duplicate]

For a camera with a rectilinear lens a simple measurement would consist of taking images from known distance of an object of known size. For example using a sheet of paper as an object set on a wall ...
2
votes
1answer
374 views

What are these vertical light lines on pictures taken with my smartphone?

We are back from holidays and we notice many photos with strange vertical lines, see photos below. Can someone explain this optical effect to me, please? How can I avoid it in future? The pictures ...
0
votes
1answer
567 views

How do I clean a Yashica Mat-124g taking lens?

I have disassembled the taking lens of my Yashica Mat-124g and tried to clean it. First, I used 99% isopropyl alcohol and it didn't help. Then I used a 1:1 solution of hydrogen peroxide and ammonia ...
1
vote
6answers
455 views

Lens equivalent depth of field [duplicate]

This question is ported directly from Physics SE, because the guys there believe this is the right place for it. In digital photography, there's the principle of lens equivalency, according to which, ...
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2answers
404 views

How to prevent fringing? [duplicate]

When using my Tamron 16-300mm lens I frequently experience chromatic aberrations in my photos. how so I prevent this?
1
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1answer
283 views

Why might focus fall off at the edges?

In the John Wayne movie Rooster Cogburn (1975), there is a dramatic focus fall off at least 10% of the vertical height at both the top and bottom of the lens. Why does this happen?
3
votes
4answers
246 views

How do catadioptric camera systems show the whole frame despite mirror obstructing the center?

I am a beginner and I recently started reading about catadioptric systems. While I understand how they can be used to simulate longer focal lengths, I am still confused as to how the entire frame is ...
2
votes
0answers
106 views

What is a Proj.-Tessar lens?

I recently picked up a lens and an estate sale. "Carl Zeiss Jena No907646 proj-tessar 1:4,5 f=13,5cm." The 'proj' prefix led me to believe that it's a projector lens, but I'm not sure what kind of ...