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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Can a smaller sensor's “crop factor” be used to calculate the exact increase in depth of field?
If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame ...
32
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6answers
3k views
What is a “diffraction limit”?
I've seen the term used, but what is a "diffraction limit", when should I worry about it, and what undesirable effects are a result of it ?
82
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6answers
6k views
What is bokeh, exactly?
I understand that "bokeh" refers to out-of-focus areas of an image — but there is obviously more to it than that. What does the term mean exactly? How well is bokeh really understood? Is it purely ...
7
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6answers
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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 ...
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4answers
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Why do light sources appear as stars sometimes?
See for example this photo:
From my experience, the longer the exposure the stronger can this effect be observed. Is this correct? Are there any other factors that influence the creation of these ...
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2answers
1k views
Why do zoom lenses and compact cameras have varied maximum aperture across the zoom range?
Why does a camera's maximum (allowed) aperture get smaller when you increase its zoom?
14
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3answers
2k views
What causes lens flare?
I heard a couple of years ago that only certain types of lens caused flare to appear, something related with the material and/or quality of the lens. Is this true? Which material/quality caused flare? ...
12
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3answers
367 views
What is Chromatic Aberration?
What is Chromatic Aberration? Is it a physical part of the lens, or just an optical illusion?
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3answers
3k views
How does the human eye compare to modern cameras and lenses?
A goal in most photography is to present a scene which resembles what a person who had been there at that moment would have seen. Even when intentionally working outside of that, human vision is the ...
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Does changing the focal length change focus?
When using manual focus or back focus on D60, I sometimes zoom in the lens, set the focus, and then zoom out. Does changing the focal length (zooming out), also change the focus?
In case the answer ...
26
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4answers
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How does aperture work without “cropping” the image hitting the sensor?
I've been teaching myself the various settings in cameras and now have a much fuller understanding of how to use my camera effectively, but one thing is still bugging me.
When the aperture size is ...
19
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4answers
1k views
What is focal length and how does it affect my photos?
What is focal-length? Are focal-length and zoom synonymous? How does the focal length of a photo affect it?
27
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5answers
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How do constant aperture 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 ...
21
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2answers
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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
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How do I interpret an MTF Chart?
As part of how Canon (and other lens makers) give technical information about their lenses, they supply an MTF (Modulation Transfer Function) chart. How do I read and interpret what the chart is ...
12
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2answers
1k views
What is the “Circle of Confusion?”
I know that when I want to calculate Depth of Field by hand one of the variable elements in that equation is the Circle of Confusion. In layman's terms, what is the "Circle of Confusion," how do I ...
7
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2answers
1k views
How can a prime lens focus on more than one plane?
By definition, a prime lens is a fixed lens system with a fixed focal length.
Then, simple physics tells us that it should be able to focus only on one plane (at a fixed distance) in front of it. But ...
2
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3answers
2k views
What is the technical difference between focus and zooming?
This may look like a silly question but I don't know what the difference between zooming and focusing is. Zooming in will usually let me have fewer subjects in the scene while zooming out will allow ...
44
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4answers
2k views
Why aren't all viewfinders 100%?
We often see that a manufacturer's high-end (D)SLR models offer a "100% viewfinder," which shows the entire exposed frame, and allows precise composition with regard to objects near the edge of the ...
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11answers
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How does the lens diameter influence photo quality?
I have tested two different 50mm lenses in my camera. One was a Nikkor 50mm ∅52mm. The other one was a Sigma 50mm ∅72mm. I took some pictures with both lenses using the same setup for aperture and ...
33
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2answers
9k views
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 ...
6
votes
2answers
536 views
How are neutral density filters in compact cameras implemented?
I've read here on this very site that some compact cameras don't use aperture blades to stop down the lens and limit the amount of light hitting the sensor. Stopping down increases diffraction. ...
44
votes
5answers
885 views
Is there development in the world of lenses?
Now, I'm not an expert, so if this post makes you laugh, you're welcome. Still, as far as I know there are basically two components that determine the potential quality of a camera's photos:
Sensor
...
23
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3answers
5k views
What does the number of elements and groups in a lens mean?
All lens specifications include a statement of how many elements the lens contains, and in how many groups, for example:
Nikon AF-S VR Zoom-NIKKOR 70-300 mm 1:4,5-5,6G: 17 elements in 12 groups (two ...
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6answers
748 views
Is there an easy way to force chromatic aberration?
A couple of months ago I was playing with my camera and a magnifying glass and I noticed that this glass produced a very soft chromatic aberration. Here's an example:
(Here is the full size, 18mp ...
26
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3answers
2k 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
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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 ...
6
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4answers
508 views
Is it possible for a lens to produce too much contrast?
I came across a complaint that a certain lens produces too much contrast. The lens was described as rendering "cartoonish" contrast when shooting a portrait with diffused light from a window, where ...
11
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3answers
4k views
How does a spherical lens differ from an aspherical lens?
Many lenses (like the Pentax DA 15mm f/4 Limited, or the Nikon AF-S 35mm f/1.4G) are described as having "aspherical lens elements". Does this mean that regular lenses are spherical lenses? What's the ...
10
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1answer
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What are Barrel and Pincushion distortion and how are they corrected?
I have some questions regarding Barrel distortion and pincushion distortion. Since they are related I have put them in single post.
I am aware that barrel distortion
occurs more in wide-angle
...
7
votes
5answers
427 views
Why not have the diaphragm in camera body instead of the lens?
Why is the diaphragm to control the amount of light entering the camera typically in the lens and not the camera body itself?
4
votes
2answers
634 views
Is it normal for focal length to change while focusing?
When I change the focus distance on my Pentax 55-300mm lens, the focal length appears to change. More specifically, the lens appears to zoom in as I focus towards the minimum focusing distance. This ...
2
votes
2answers
668 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 ...
11
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5answers
2k views
What is “infinity focus”?
I have been reading a bit about astrophotography and the term infinity focus keeps coming up. What is infinity focus and how do you set the camera to infinity focus?
15
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5answers
690 views
How do I find the aperture that produces the highest-quality images for a given lens?
I'm not talking about large aperture (f/1.8, f/2.8...), rather, about small apertures (f/18, f/20, f/23...). I read somewhere (actually I think it was on this site, but I don't exactly remember which ...
11
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4answers
1k views
What is the reference point that the focal length of a lens is calculated from?
I understand the idea of a focal length for a single lens, i e the distance from the lens to the point at which parallel rays of light converge. However, in the case of a photographic lens with ...
9
votes
2answers
1k views
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.
3
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2answers
108 views
What's the difference between real and effective aperture?
I understand that the simple idea that f-stop is focal length divided by aperture really applies to a simple single-glass lens, not the compound lens systems used to provide good image quality in ...
16
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3answers
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What makes a Carl Zeiss lens so special in a smartphone?
There are smartphones on the market that have a focus towards photography. Some are equipped with a Carl Zeiss lens. I have looked into Wikipedia, which tells me that they are a brand who produces ...
15
votes
2answers
530 views
Do rounded edges on aperture blades improve image sharpness, and how?
In the description for the XF lenses for its new X-Pro system, Fujifilm crows:
The [XF lenses] all offer precise control over depth-of-field and deliver excellent out-of-focus bokeh thanks to the ...
11
votes
3answers
371 views
How does the D800E reverse the effect of an antialiasing filter by adding another filter?
According to http://mansurovs.com/nikon-d800-vs-d800e the D800E differs from the D800 in that one of the layers of the filter reverses the effect of the initial low-pass filter. How does this work?
...
7
votes
3answers
331 views
What are ED elements?
I find that some lenses are indicated with the letters "ED", referring to some special type of lens element. What are ED elements, and what advantages do they bring?
Note that this question isn't ...
7
votes
1answer
380 views
How is Bokeh created?
I am not asking how to create a bokeh effect. I found the answer to that quesiton here: Best way to get shaped bokeh?
The answers on that question say you basically cut out an image from a piece of ...
4
votes
1answer
220 views
What's the history of neutral density filters instead of aperture diaphragms in compact cameras?
Some compact cameras use neutral density filters to control light rather than aperture blades, to avoid the effects of diffraction in tiny sizes.
I first heard of this as a feature of the Nokia N8 ...
2
votes
3answers
494 views
How does a short flange back distance improve image quality?
In the description for the new lens mount for their X-Pro series, Fujifilm says:
1: Specifically designed to maximize the mirrorless design of the body, the X-Mount has a short flange back ...
2
votes
1answer
590 views
How does the quantity of elements and blades in a lens affect the optics?
I am trying to get a greater understanding of how lenses work. Basically I bought this lens, the Sigma 10-20 f4-5.6:
The construction has really fascinated me. 14 Elements in 10 Groups?! What ...
