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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23
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2answers
4k views

Why is infrared light's focus point different from that of visible light?

When reading about infrared photography, it's often mentioned that IR's focus point is slightly different from visible light. Why is the focus point of infrared light point different from the focus ...
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2answers
514 views

What is the “airy disc”, in simple language?

In my understanding, this is relevant to photography because if you are shooting light of a certain wavelength (or primarily so, and such as: a blue scene), your aperture size can affect the sharpness ...
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1answer
328 views

What is the fastest T Stop available?

What is the widest T Stop possible We are having f stops of below even 0.7 NASA lenses What will be the T stop of such lenses with f stop below ONE?
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2answers
232 views

How do I design a secondary lens for my fixed-lens camera to narrow its field of view?

My goal is to put a lens or an array of lenses in front of my actioncam to use its high resolution for recording of undistorted normal-eyed footage, to avoid having to buy two cameras for the ...
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1answer
393 views

How do wavefronts/wavelets propogate in three dimensions, and why is this important for photography?

The photography book I have talks about waveforms, but it doesn't do a good job of explaining them. So, here's my understanding from the book and google searches (it could be unbelievably wrong.) In ...
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3answers
5k views

Does focal length change when I adjust the focus? [duplicate]

When I adjust the focus of my camera, in general, does this affect the focal length? I have heard that it does.
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1answer
283 views

Can a teleconverter make lenses designed for a “crop” sensor cover full frame?

I have a crop lens. Can I fill a full-frame sensor adding an appropriate tele converter (focal length extender? Specifically, I have a 1/2" C-mount lens and terrible vignetting on a full frame camera. ...
3
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1answer
551 views

Is it possible to make your own focus distance scale?

I'm using a Nikkor 18-105mm kit lens and it doesn't have a distance scale on its focus ring, is it possible to create your own distance scale by knowing the 0 and the infinity focusing points on the ...
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2answers
1k views

What could cause this visible artifact which seems to a be a glowing inverse of something outside of the frame overlayed on this photograph?

An acquaintance recently posted an image to FB from his recent trip to the JFK Historic Site asking for an explanation of a visible artifact he states was not visible to the naked eye but was visible ...
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1answer
63 views

Recommended F-Stop for older Canon 35mm F/2 [duplicate]

I have a few year old Canon 35mm F/2 lens (Here it is on Amazon). I've been shooting wide-open, but I realize that doesn't make for the sharpest photos. What would you say would get me the sharpest ...
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1answer
180 views

Is the Panasonic Leica Summilux the same quality as a non-Panasonic Leica summilux?

Is there an advantage to having a Leica Leica lens vs. a Panasonic Leica lens? To my ability to examine them, they look like the same on the inside. Would this be correct? The Leica Leicas are ...
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3answers
397 views

Why don't we have a single lens e.g. say a 18-200 f/1.2 lens for the SLR camera? [duplicate]

Right now we have multiple interchangeable lenses. So why don't we have a single lens, say a 18-200 f/1.2 lens? Are camera manufacturers deliberately avoiding that or it is that it is physically ...
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4answers
4k views

Why are superzoom lenses small but giant telephoto lenses huge?

This week I've read two news stories about two different camera lenses that can magnify things that are very far away. The first is the Nikon Coolpix P900, which is a point-and-shoot camera that ...
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4answers
595 views

What lens designs are sharper than a pinhole lens but also allow for multi-month exposures?

I have a homemade pinhole camera (film) that I use for taking super long exposures (multiple months). And while the results are fun, I would like to improve the sharpness of the image. Is diffraction ...
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2answers
3k views

Is there a formula to calculate the physical size of an image?

I'm trying to figure out the size of the physical space an image represents (IE, how many meters long/wide the real world in the image is), but I can't seem to find a formula that works with only the ...
3
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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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1answer
78 views

Why can a lens still function when subject to severe physical degradation?

Consider the following two modifications to a camera lens: Obstructing the about 75% of the lens's front element with an opaque filter as shown here: https://www.youtube.com/watch?v=43W159gPpdQ. ...
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3answers
2k views

Equivalent focal length and aperture of 150mm medium format lens on a 35mm camera

I'm mounting a Hasselblad Sonnar C 150 mm f4 on a 35mm sensor (43mm diagonal) camera. What is the calculation to get the new angle of view and equivalent focal length? Does this also affect the ...
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4answers
316 views

How can I compare different lenses in terms of quality?

I am currently looking to buy a new lens to replace with kit lens, having an extra reach, faster, better image quality and also better video quality. Without buying all the lenses I have shortlisted, ...
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3answers
755 views

Is a quartz lens necessary to prevent UV blocking on full spectrum enabled cameras?

I have read that in order to operate a "full spectrum" camera properly, so as to not block light in the ultraviolet portion of the spectrum, that one needs to acquire quartz lenses for one's camera. ...
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2answers
457 views

Projector Design and lenses

I am working on a project where I need to project a single image onto an object, Originally I was looking at the digital projector route but due to cost and complexity this has been ruled out. I found ...
5
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1answer
425 views

Background warping through foreground defocus

I came across this effect the other day, and have spent the better part of the last week trying to figure out exactly what is happening. When photographing two layers, with the foreground in front of ...
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2answers
691 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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2answers
1k views

What is the importance of the back focal length of a lens?

What is the effect and importance of the back focal length of a lens? For instance, if I look at these two lenses by Ricoh, they have the same focal length and aperture, but their back focal lengths ...
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1answer
326 views

Lenses round ..Photographs square shaped why? [duplicate]

If camera lenses are round then why is the photograph taken by the camera is square-shaped? photography
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4answers
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How can a super tiny iPhone 6 Plus lens produce significant DOF?

According to Apple specs the iPhone 6 Plus thickness is 0.28 inch (7.1 mm) and the lens length is only a part of that. And according to an article I found, Depth of Field is a function of "aperture (i....
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2answers
2k views

What do resolution figures mean in lens specifications?

I'm working in computer vision and choosing the right lens is obviously as critical as having a good sensor if you're going for quality inspection (for example). Sadly I have very little experience ...
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2answers
3k views

How to determine if a new lens is a subpar copy?

I have read some posts like the ones below about testing a lens to determine how well it performs optically. What I didn't see was anything on determining whether the lens performs as it should and is ...
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1answer
266 views

Why does the “fisheye effect” look stronger or weaker with different scenes taken with the same lens?

It seems that the fisheye effect can look different with the same lens. So I want to understand how it works. For example, I use a Dji Phantom vision 2 drone to take pictures, all of my pictures have ...
7
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1answer
956 views

How is Nikon's PF optics different from and similar to Canon's DO optics?

Nikon has just announced a new 300 mm lens featuring a new technology called "PF" or "Phase Fresnel." This has been compared to Canon's existing DO (Diffractive Optics) lenses such as the 400 mm f4 DO....
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1answer
1k views

How can I calculate the effect of a supplementary close-up lens (a.k.a macro filter)?

If I have a +1, +2, +4, or +10 close-up lens which attaches to the front of my regular lens, how can I calculate its effect on close focusing distance, figure out how much magnification I can get from ...
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1answer
469 views

How do add on macro smartphone lenses allow you to take macro photos?

It may sound obvious, but how exactly does an add on macro lens allow you to take close up photos? Can someone give technical reasons? I'd like to know the physics behind add on macro lenses and how ...
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1answer
144 views

Why do I need an add-on lens to take smartphone macro photos?

Why do you need an external macro lens for a smartphone to take macro photos. Why can't the smartphone lens itself take macro photos?
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1answer
336 views

Where do rays of light from one point strike the film?

I am a programmer and I am doing a camera simulation, I am stuck in a matter of how to know where does every ray of light incident after traveling through the lens, every point of the object will give ...
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0answers
67 views

Where is the focal point of a camera lens? [duplicate]

If the distance between the center of the lens and the film is called Focal length, does that mean the focal point of the camera lens is located on the film?
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3answers
392 views

How to estimate the minimum magnification to capture features of a certain size?

What is the correct way to estimate the minimum magnification (maximum subject distance) at which features of a certain size are resolved? My thinking is that given a system capable of resolving a ...
4
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3answers
1k views

How can the focal length of a lens be many times greater than the lens's physical length?

I bought a Tamron 16-300. Question is: how can it have a focal length 0f 300 mm when it is only about 30 mm long? Doesn't the lens have to be 300 mm from the sensing element?
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2answers
1k views

Why are large zoom ratio constant apertures lenses not generally available?

I know about 17-55 f2.8 and the likes of it, but I am talking about something say 18-135 f2.8. There exists 70-200mm f2.8 and the range (200-70 = 130mm) is much bigger than in 18-135. I am aware of ...
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4answers
2k views

Why Isn't This Photograph Pin Sharp?

I Have Been Trying Out My New Canon EF 24-70mm and I'm pretty underwhelmed by its sharpness. Here is a RAW file shot from a solid tripod on an (almost) windless day using a remote. Obviously it isn'...
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4answers
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Why does crop factor apply with APS-C lenses, and why aren't these brighter than FF ones at same aperture?

I know that the image circle of FF-lenses is bigger than it needs to be on APS-C sensors, thus the FOV spears narrower. I've heard that APS-C lenses sit closer to the sensor, thus projecting a smaller ...
2
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2answers
221 views

Pentax k-30: can i buy all lens not stabilized?

I'm interested to buy a Pentax K-30. I'm wondering : can I buy not stabilized optics because of body' stabilized sensor ? Is the overall image quality comparable to an optic with stabilizer (like ...
14
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3answers
9k views

How does an apodization filter improve bokeh?

The new Fujifilm Fujinon XF56mmF1.2 R APD has an "apodization" filter, which Fujifilm says "smoothes the outline of the subject to create a more natural bokeh effect". The Wikipedia article on ...
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1answer
1k views

How does a focus ring bring a subject in or out of focus?

When you manually adjust your focus ring on the lens, what actually happens inside the lens? Is this changing simply the point at which the lens is focusing, so that anything at this distance away ...
4
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2answers
523 views

What is the maximum aperture consistent with the Nikon F-mount?

In a related thread, it's been debated whether there is a hard limitation to maximum possible lens aperture; it seems there is none. However, using the example of the nikon F mount, this technical ...
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6answers
277 views

Should lenses of equal quality for smaller sensors be cheaper?

In theory do we expect lenses of identical specs and quality to be cheaper when designed for smaller sensors? My expectation is that the answer is yes, because all of the things that lenses struggle ...
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2answers
2k views

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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1answer
76 views

Is there an “optimal” background distance when striving for a minimally distracting background?

Let's assume a thin lens and an object O in focus at a distance of dO from the lens. Further, let's assume there's a large out-of-focus background object B at a distance of dB. Now, we know ...
6
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2answers
445 views

Use of DOF adapters in stills photography

The camcorder guys figured out long ago how you can get the shallow DOF of a larger sensor system (typically full frame) on a camcorder equipped with a much smaller sensor (typically 1/2.8") by doing ...
2
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1answer
817 views

How to find numerical aperture of lens

I need to find the precise collection cone angle of an arbitrary objective at an arbitrary (but known and finite) object-side focal length. This is typically given as the "numerical aperture", defined ...
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3answers
1k views

Why do circular fish eye lenses create circular images?

I'm trying to understand the physics of circular fish eye lenses. As far as I can see circular fish eye lenses create an circular image because the area of the sensor is larger than the projected ...